Najafpour, M. M., Salimi, S., Zand, Z., Hołyńska, M., Tomo, T., Singh, J. P., Chae, K. H., Allakhverdiev, S. I., "Nanosized manganese oxide/holmium oxide: a new composite for water oxidation ", New Journal of Chemistry, 41: (22), 13732-13741, (2017).
Abstract:
Herein, holmium oxide as a support for nanosized Mn oxide was used toward the synthesis of a new catalyst for water oxidation. A composite of Mn and Ho oxide was synthesized by a simple hydrothermal procedure and characterized by scanning electron microscopy, extended edge X-ray absorption fine structure, transmission electron microscopy, powder X-ray diffraction and electrochemical methods. The effect of calcination temperature on the composite performance for the water-oxidation process was examined in the range of 100–600 °C. The turnover frequencies for the catalyst toward water oxidation in the presence of cerium(IV) ammonium nitrate and photo-produced tris(2,2′-bipyridyl)ruthenium(III), [Ru(bpy)3]3+ are 0.12 and 0.04 (mmol O2 per mol Mn s), respectively. In addition, the catalyst shows self-healing in the presence of cerium(IV) ammonium nitrate and under the water-oxidation conditions.
Najafpour, M. M., Madadkhani, S., Akbarian, S., Hołyńska, M., Kompany-Zareh, M., Tomo, T., Singh, J. P., Chao, K. H., Allakhverdievf, S. I., "A new strategy to make an artificial enzyme: photosystem II around nanosized manganese oxide ", Catalysis Science & Technology, 7: (19), 4451-4461, (2017).
Abstract:
Herein we report a new strategy to disperse Mn oxide into the apoenzyme of photosystem II. The compound was characterized by scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction and some electrochemical methods. Under electrochemical conditions, the peaks attributed to Mn(II)/(III), Mn(III)/(IV) and Mn(II)/(IV) were assigned and compared with other manganese oxides. Linear sweep voltammetry shows that water electro-oxidation occurs at 80 mV less than that for the apoenzyme of photosystem II. Thus, Mn oxide maintains its water-oxidizing activity under these conditions. The compound is a new type of structural and functional model for the water-oxidizing complex in photosystem II.
Najafpour, M. M., Madadkhani, S., Tomo, T., Allakhverdiev, S. I., "A nanosized Mn oxide/boron nitride composite as a catalyst for water oxidation ", New Journal of Chemistry, 41: (19), 10627-10633, (2017).
Abstract:
Herein, a nanosized Mn oxide/boron nitride composite is reported as a catalyst for water oxidation. This study is interesting because nanosized boron nitride is one of the most stable and inert compounds and can form a new composite with Mn oxides. The composite was synthesized using a straightforward and simple procedure and characterized, showing that the composite is a supported Mn(III,IV) oxide on boron nitride. The water-oxidizing activity of the composite was studied in the presence of cerium(IV) ammonium nitrate and photoproduced Ru(bpy)33+ as oxidants. The optimized catalyst calcined at 200–300 °C showed a turnover frequency of 0.15 (mmolO2/s−1 molMn−1) in the presence of cerium(IV) ammonium nitrate.
Najafpour, M. M., Jameei Moghaddam, N., Hosseini, S. M., Madadkhani, S., Hołyńska, M., Mehrabani,, S., Bagheri, R., Song, Z., "Nanolayered manganese oxides: insights from inorganic electrochemistry ", Catalysis Science & Technology, 7: (16), 3499-3510, (2017).
Abstract:
Nanolayered Mn oxides are among the important Mn-based catalysts for water oxidation. Mn(II), (III) and (IV) ions are present in the structure, and, thus, the electrochemistry of the solid is very complicated. Herein, the cyclic voltammetry of nanolayered Mn oxides in the presence of LiClO4 at pH = 6.3, under different conditions, was studied using scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray diffraction and visible spectroelectrochemistry. The scan rates, calcination temperatures and the range of the cyclic voltammetry have very important effects on the electrochemistry of nanolayered Mn oxides. The effect of the use of D2O instead of H2O on the electrochemistry of nanolayered Mn oxides was also considered. Such nanolayered Mn oxides were reported as water-oxidizing catalysts in the presence of cerium(IV) ammonium nitrate. As a next step, we studied the cyclic voltammetry of nanolayered Mn oxides under acidic conditions and in the presence of cerium(IV) ammonium nitrate.
Najafpour, M. M., Zarei Ghobadi, M., Hosseini, S. M., Chae, K. W., Mehrabani, S., Rafighi, P., Bagheri, R., Song, Z., "Rethink about electrolyte: Potassium fluoride as a promising additive to an electrolyte for the water oxidation by a nanolayered Mn oxide", International Journal of Hydrogen Energy, 42: (22), 15160-15166, (2017).
Abstract:
Water oxidation is a bottleneck of the hydrogen production through the water-splitting reaction. Herein, the promising role of fluoride on the water-oxidizing activity of a nanolayered Mn oxide under the electrochemical condition is reported. The experiments show the increase of the water-oxidizing activity of the nanolayered Mn oxide under an electro-water oxidation circumstance in the presence of potassium fluoride as a promising additive to an electrolyte. As a result, the required overpotential is decreased and the yield of oxygen evolution raised in the water-oxidation reaction.
Najafpour, M. M., Kaboudin, B., Mostafalu, R., Shahbazy, M., Safdari, R., Kompany-Zareh, M., "A proposed mechanism to form nanosized Mn oxides from the decomposition of β-cyclodextrin-Mn complex: Toward nanosized water-splitting catalysts with special morphology", International Journal of Hydrogen Energy, 42: (16), 11187-11198, (2017).
Abstract:
Metal oxides are promising compounds for water-splitting systems toward hydrogen production. One of the most important methods to prepare nanosized metal oxides is the decomposition of metal complexes. Herein, different Mn oxides from the decomposition of β-cyclodextrin-Mn complex in different calcined temperatures were studied by scanning electron microscopy, thermal gravimetric analysis, X-ray diffraction and a few electrochemical methods. Using scanning electron microscopy, we propose a mechanism to answer to the question that how is Mn oxide formed by the decomposition of β-cyclodextrin-Mn complex. In the next step, usual chemometric methods, principal component analysis (PCA) and multivariate curve resolution-alternating least squares (MCR-ALS), were used to not only determine the number of components and data visualization, but also examine the square wave voltammograms of obtained Mn oxides from the decomposition of β-cyclodextrin-Mn complex. Water-oxidizing activities of the compounds under the presence of photo-produced Ru(bpy)33+ were also considered.
Akbarian, S., Najafpour, M. M., Kompany-Zareh, M., "PARAFAC study of bovine serum albumin conformational changes in the interaction with nanosized manganese oxide as a biomimetic model for water-oxidizing complex", International Journal of Hydrogen Energy, 42: (15), 9733-9743, (2017).
Abstract:
Water splitting toward hydrogen production is an important step and a bottleneck for large-scale energy storage in artificial photosynthesis. The effect of metal oxide nanoparticles on the biopolymers behavior and their properties is important in designing new catalysts for water-splitting reaction. Herein, the interaction of bovine serum albumin (BSA) and MnOx nanoclusters is studied for the first time, exploiting the intrinsic excitation-emission (EEM) fluorescence of tryptophan and tyrosine residues. As the conformation of BSA changes as a function of pH and temperatures, three-way fluorescence data were recorded for BSA and BSA/MnOx. Then, the obtained profiles from parallel factor analysis (PARAFAC) were interpreted. Generally, the results from fluorescence spectroscopy showed that the MnOx nanoparticles cause some changes in the structure of BSA conformation as a function of pH and temperature. Also, the denaturation pathway of the BSA molecule is significantly different in the presence of MnOx nanoclusters. Moreover, the same result is acquired by augmentation of pH and temperature data for BSA and BSA/MnOx, which confirms that the fluorescence changes due to considered components during the processes. Although the EEM fluorescence spectra of similar proteins are almost identical, the cube of spectra measured during their conformational changes can be significantly different and applicable in rapid and low cost investigation of proteins. Spectral change and selectivity for similar proteins can be achieved without labeling with fluorophore molecules.
Najafpour, M. M., Amini, M., Ashrafi, M., "Lessons from metal oxides to find why Nature selected manganese and calcium for water oxidation", International Journal of Hydrogen Energy, 42: (12), 8539-8544, (2017).
Abstract:
The problem of finding a way to store energy from abundant sources such as sunlight, wind or geothermal heat is critical. Water splitting toward hydrogen production is a very promising way for the goal. Although the cathodic reaction is of major interest in hydrogen production, the concurrent anodic water oxidation, which provides cheap electrons for the cathodic reaction, is a limitation for hydrogen formation. The best water-oxidizing catalyst was found by Nature million years ago and used in plants, algae and cyanobacteria. We believe learning from the natural system is very promising, because Nature has been successfully splitting water for millions of years, using an inexpensive and environmentally friendly Mnsingle bondCa oxido cluster. Herein we study the phenol oxidation by some nano-sized metal oxides in the presence of H2O2. As metal oxides are functional and structural models for the water-oxidizing complex in Photosystem II, the results can be expanded for the natural site. We suggest that low organic compound oxidation under water oxidation is an important issue to select manganese and calcium ions for water oxidation.
Najafpour, M. M., Shirazi Amin, A., Balaghi, S. E., Deljoo, B., Mousazade, Y., Jafari, T., Aindow, M., Suib, S. L., "Transformation of La0.65Sr0.35MnO3 in electrochemical water oxidation", International Journal of Hydrogen Energy, 42: (12), 8560-8568, (2017).
Abstract:
One of the most promising approaches to produce sustainable energy is hydrogen evolution by water splitting. Since water electrolysis is limited by the high overpotential required for the water oxidation reaction, electrocatalysts are applied to reduce the activation energy necessary for this reaction. However, primary catalysts may chemically convert to other compounds during the reaction. Therefore, the physicochemical and electrochemical changes of catalysts used over a long time need to be investigated in detail to understand the real operating catalyst. In this work, we have observed long-term microstructural changes and amorphization of La0.65Sr0.35MnO3 when used as a catalyst in water-electrolysis at near neutral pH. Microscopic and electrochemical analyses show that the catalyst changed at the molecular level. This study revealed that an entirely different catalyst evolved from the original material over the course of the water oxidation reaction. This observation revealed the importance of the study of the long-term stability and reactivity of La0.65Sr0.35MnO3 toward the water oxidation reaction.
Khatamian, M., Heidari, S., Najafpour, M. M., "Mn-containing ZSM-5 type zeolite as a water-oxidizing catalyst: New findings and current controversies", International Journal of Hydrogen Energy, 42: (12), 7938-7950, (2017).
Abstract:
Water-splitting for H2 and O2 production is a key reaction toward a clean energy future. However, the water-oxidation is one of the major limiting factors affecting the efficiency of this important reaction. Thus, the development of low-cost and efficient water-oxidizing catalysts is a key challenge in the artificial photosynthesis field. In this work, Mn-containing ZSM-5 type zeolite was synthesized using silicic acid, manganese(II) chloride tetrahydrate, potassium carbonate and tetrapropylammonium bromide (TPAB). Samples were characterized by different methods. The water-oxidizing activity of the catalysts were studied in the presence of cerium(IV) ammonium nitrate (Ce(IV)) and in the electrochemical water-oxidation condition. The effect of K+ ions on the structural properties and the catalytic performance of the compounds was also investigated. It was observed that after treating of manganosilicate with a Ce(IV) solution or applying a 2 V constant potential to the sample, in a convective–suspension–collision system, framework located Mn ions completely leaked. These results are important to reconsider the true catalysts in the different catalytic reactions in the presence of manganosilicates.
Najafpour, M. M., "From manganese complexes to nano-sized manganese oxides as water-oxidizing catalysts for artificial photosynthetic systems: Insights from the Zanjan team", Comptes Rendus Chimie, 20: (3), 243-260, (2017).
Abstract:
On the occasion of the international year of light and light-based technologies, I provide a short overview of our recent findings and personal view on the Mn-based water-oxidizing catalysts and the related sophisticated strategies toward water oxidation, which are promising in the artificial photosynthetic systems.
Najafpour, M. M., Jameei Moghaddam, N., "Iron oxide deposited on metallic nickel for water oxidation", Sustainable Energy Fuels, 1: (3), 658-663, (2017).
Abstract:
Solar energy is too intermittent to be directly used on a large scale, and thus, a large energy storage system should be developed. One interesting approach is the use of sunlight to perform water splitting for hydrogen production. For such systems, developing an efficient and stable water-oxidizing catalyst is an essential task. Using K2FeO4, we report a simple method to deposit iron oxide on metallic nickel for water oxidation. The Fe/Ni-based electrode, at pH = 13, shows a current density of 1.9 mA cm−2 at an overpotential of 250.0 mV, making it a promising anode for use in water-splitting systems. At a higher overpotential (700.0 mV), a current density of 23.5 mA cm−2 was observed.
Najafpour, M. M., Jameei Moghaddam, N., "An efficient nickel oxides/nickel structure for water oxidation: a new strategy", New J. Chem., 41: (5), 1909-1913, (2017).
Abstract:
A very simple method to synthesize an efficient and stable Ni-based water-oxidizing electrode was reported from the reaction of metallic nickel foam and Oxone (2K2SO5·K2SO4·KHSO4). The Ni-based electrode at pH = 13 yields current densities of at least 4.5 mA cm−2 at an overpotential of 450 mV, which is promising for use as an anode in water splitting systems. After 10 h, not only did the electrode not show a decrease in water oxidation, but an increase in water oxidation was also observed (∼6.0 mA cm−2). At a higher overpotential (837 mV), a current density of 24.3 mA cm−2 was observed, which was approximately 5 times larger than that of pure Ni foam in a similar condition
Najafpour, M. M., Heidari, S., Balaghi, S. E., Hołyńska, M., Hossaini Sadr, M., Soltani, B., Khatamian, M., Larkum, A. W., Allakhverdiev, S. I., "Proposed mechanisms for water oxidation by Photosystem II and nanosized manganese oxides", BBA Bioenergetics, 1858: (2), 156-174, (2017).
Abstract:
Plants, algae and cyanobacteria capture sunlight, extracting electrons from H2O to reduce CO2 into sugars while releasing O2 in the oxygenic photosynthetic process. Because of the important role of water oxidation in artificial photosynthesis and many solar fuel systems, understanding the structure and function of this unique biological catalyst forms a requisite research field. Herein the structure of the water-oxidizing complex and its ligand environment are described with reference to the 1.9 Å resolution X-ray-derived crystallographic model of the water-oxidizing complex from the cyanobacterium Thermosynechococcus vulcanus. Proposed mechanisms for water oxidation by Photosystem II and nanosized manganese oxides are also reviewed and discussed in the paper.
Najafpour, M. M., Madadkhani, S., Tavahodi, M., "Manganese oxides supported on nano-sized metal oxides as water-oxidizing catalysts for water-splitting systems: 3-Electrochemical studies", International Journal of Hydrogen Energy, 42: (1), 60-67, (2017).
Abstract:
Hydrogen formation by water splitting is very promising to store energy. Water oxidation in water splitting significantly affects the efficiency of hydrogen generation due to the need to apply high overpotential. Among of different compounds, Mn oxides are promising water-oxidizing catalysts. Herein we study the electrochemistry of Mn oxide supported on KAl3(SO4)2(OH)6, Co3O4, CuO, Fe3O4, MgO, NiO, SiO2, SnO2, TiO2, WO3, Zeolite, ZnO or ZrO2. The electrochemical studies showed that redox-active supports such as NiO, Co3O4, Fe3O4 and CuO could significantly change characteristic of Mn oxides. In our experimental conditions, cyclic voltammograms for Mn oxide supported on these redox active supports are significantly different from pure Mn oxides. We found that the effect of support on the water oxidation depend on the conditions of water oxidation. The pure redox-inactive supports such as SiO2, zeolite, MgO and KAl3(SO4)2(OH)6 without Mn oxide showed similar potential to start water oxidation. However, ZnO showed better activity toward water oxidation than other redox-inactive supports. Among pure redox active supports, Co3O4 is excellent for water oxidation. After the deposition of Mn oxides on the supports, the formed compounds showed complicated effect toward water oxidation.
Najafpour, M. M., Salimi, S., Safdari, R., "Nanosized manganese oxide supported on carbon black: A new, cheap and green composite for water oxidation", International Journal of Hydrogen Energy, 42: (1), 255-264, (2017).
Abstract:
Water splitting is a very promising method to produce hydrogen. However, water oxidation is a crucial step for hydrogen production since it can provide cheap electrons for proton reduction. Herein a nanosized Mn oxide immobilized on carbon black as a reasonable catalyst for water oxidation is reported. The composites were synthesized by a simple, low-cost procedure using different ratios of carbon black and Mn oxide. Catalysts were characterized by scanning electron microscopy, energy-dispersive spectroscopy (EDX), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electronic spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS). In the next step, the water-oxidizing activities of the composites were observed in the presence of cerium(IV) ammonium nitrate. The composites were reasonable catalysts with turnover frequencies of ∼0.07 (mmol O2/mol Mn s). In addition to the water-oxidizing activity, the self-healing for this composite in the experimental condition was also studied.
Najafpour, M. M., Amini, E., Madadkhani, S., "Nano-sized manganese oxide coated sea sand: A new water-oxidizing catalyst", International Journal of Hydrogen Energy, 41: (48), 22866-22875, (2016).
Abstract:
H2 production by water splitting is a promising fuel to store the intermittent energies. However, water splitting is limited by water oxidation. Herein for the first time we used sea sand for support of nano-sized Mn oxide to obtain a new water-oxidizing catalyst. The compound was synthesized by a simple method and characterized by some methods. The water-oxidizing activities of the compound were also studied under cerium(IV) ammonium nitrate and photochemically produced Ru(bpy)33+. The results showed that the nano-sized manganese oxide coated sea sand is a good manganese-based water-oxidizing catalyst.
Najafpour, M. M., Hosseini, S. M., "Toward a nanosized iron based water-oxidizing catalyst", International Journal of Hydrogen Energy, 41: (48), 22635-22642, (2016).
Abstract:
Water oxidation is a key step and a bottleneck for large-scale energy storage in artificial photosynthesis. Herein Fe oxide on the surface of fluorine-doped tin oxide electrode was synthesized by a very simple, new and low-cost method, using the reduction of K2FeO4 in water. The electrode was characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy and Raman spectroscopy. Such fluorine-doped tin oxide electrode could be used as stable water-oxidizing anodes at pH = 13 to yield current densities of 1 mAcm−2 at an overpotential of 550 mV.
Najafpour, M. M., Salimi, S., Madakhani, S., Hołyńska, M., Tomo, T., Allakhverdiev, S., "Nanostructured manganese oxide on silica aerogel: a new catalyst toward water oxidation", Photosynth Res., 130: (1), 225-235, (2016).
Abstract:
Herein we report on the synthesis and characterization of nano-sized Mn oxide/silica aerogel with low density as a good catalyst toward water oxidation. The composite was synthesized by a simple and low-cost hydrothermal procedure. In the next step, we studied the composite in the presence of cerium(IV) ammonium nitrate and photo-produced Ru(bpy)33+ as a water-oxidizing catalyst. The low-density composite is a good Mn-based catalyst with turnover frequencies of ~0.3 and 0.5 (mmol O2/(mol Mn·s)) in the presence of Ru(bpy)33+ and cerium(IV) ammonium nitrate, respectively. In addition to the water-oxidizing activities of the composite under different conditions, its self-healing reaction in the presence of cerium(IV) ammonium nitrate was also studied
Najafpour, M. M., Hosseini, S. M., Zarei Ghobadi, M., Rafighi, P., Bagheri, R., Song, Z., "Treated nanolayered Mn oxide by potassium fluoride: An improvement for nanolayered Mn oxide toward water oxidation", International Journal of Hydrogen Energy, 41: (46), 21203-21211, (2016).
Abstract:
Water splitting can store sustainable energies in the form of fuel (H2) and oxidant (O2). However, the efficiency of H2 production from the reaction is limited by the slow kinetics of the water oxidation. Herein the promising role of fluoride on water-oxidizing activity of nanolayered Mn oxide is reported. The effects were studied for water oxidation in the presence of cerium(IV) ammonium nitrate. These experiments showed that the treatment of nanolayered Mn oxide by potassium fluoride increases water-oxidizing activity of these oxides in the presence of cerium(IV) ammonium nitrate approximately two times.
Najafpour, M. M., Madadkhani, S., "Nano-sized Mn oxide/agglomerated silsesquioxane composite as a good catalyst for water oxidation", Photosynthesis Research, 130: (1), 73-81, (2016).
Abstract:
Water splitting to hydrogen and oxygen is an important reaction to store sustainable energies, and water oxidation is identified as the bottleneck for water splitting because it requires the high activation energy to perform. Herein a nano-sized Mn oxide/agglomerated silsesquioxane composite was used to synthesize an efficient catalyst for water oxidation. The composite was synthesized by a straightforward and simple procedure and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, dynamic light scattering, X-ray diffraction spectrometry, and electrochemical methods. Silsesquioxane causes good dispersion of Mn in the composite. The water-oxidizing activity of this composite was studied in the presence of cerium(IV) ammonium nitrate. The composite at the best calcination temperature (300 °C) shows a turnover frequency 0.3 (mmol O2/mol Mn.s). Regarding the low-cost, environmentally friendly precursors, simple synthesis, and efficiency for water oxidation, the composite is a promising catalyst that can be used in artificial photosynthetic systems for water splitting.
Najafpour, M. M., Ebrahimi, F., Abasi, M., Hołyńska, M., Hosseini, S. M., "Manganese oxides supported on nano-sized metal oxides as water-oxidizing catalysts for water splitting systems: 1-synthesis and characterization", International Journal of Hydrogen Energy, 41: (41), 18465-18471, (2016).
Abstract:
Water splitting to produce H2 is an important procedure for the conversion of intermittent energies. However, the reaction is energetically limited by the water-oxidation process. Herein, we report the synthesis of Mn oxide on nanoparticles of KAl3(SO4)2(OH)6, Co3O4, CuO, Fe3O4, MgO, NiO, SiO2, SnO2, TiO2, WO3, zeolite, ZnO and ZrO2 by a simple, low-cost and green procedure aiming at obtaining a good water-oxidizing catalyst. The obtained materials are characterized by high-resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction studies.
Najafpour, M. M., Ebrahimi, F., Abasi, M., Hosseini, S. M., "Manganese oxides supported on nano-sized metal oxides as water-oxidizing catalysts for water splitting systems: 2-Water-oxidizing activities", International Journal of Hydrogen Energy, 41: (41), 18472-18477, (2016).
Abstract:
Synthesis and characterization of Mn oxides on the surface of nanoparticles such as KAl3(SO4)2(OH)6, Co3O4, CuO, Fe3O4, MgO, NiO, SiO2, SnO2, TiO2, WO3, zeolite, ZnO, and ZrO2 have been reported previously. Herein, we reported the effect of support on the water-oxidizing activity of amorphous Mn oxides in the presence of cerium(IV) ammonium nitrate. We found that the efficiency of systems toward water oxidation depends on the nature of the support, and a significant effect was observed in the case of redox-active supports.
Najafpour, M. M., Madadkhani, S., Zand, Z., Hołyńska, M., Allakhverdiev, S., "Engineered polypeptide around nano-sized manganese–calcium oxide as an artificial water-oxidizing enzyme mimicking natural photosynthesis: Toward artificial enzymes with highly active site densities", International Journal of Hydrogen Energy, 41: (40), 17826-17836, (2016).
Abstract:
The solar energy is intermittent, and thus, to be practical at a huge scale, will require a large capability for energy storage. One approach involves artificial photosynthesis to drive solar energy for water splitting into hydrogen or to reduce CO2 to reduced carbon fuels. In such reactions, cheap electrons from water oxidation are critical. Herein we aim to design and synthesize an artificial water-oxidizing enzyme with highly active site densities, report on nano-sized Mn–Ca oxide in two engineered polypeptides (Arg-Arg-Glu-Glu-Glu-Glu-Arg-Arg and Tyr-Tyr-Tyr-Glu-Glu-Glu-Glu-His-Tyr-Tyr-Tyr) as structural models for biological water-oxidizing site in plants, algae, and cyanobacteria. The compounds were synthesized by a simple procedure and characterized with multiple methods. Using Nafion, electrochemical studies show the peptide has an important effect on the potential for Mn(III)/Mn(IV) oxidation on Mn–Ca oxide and it is decreased in the presence of the polypeptide. We also found that the peptide has an important role on morphologies of Mn–Ca oxide.
Najafpour, M. M., Hosseini, S. M., "An efficient and inexpensive water-oxidizing manganese-based oxide electrode", Dalton Trans., 45: (42), 16948-16954, (2016).
Abstract:
Using inexpensive and environmentally friendly Mn oxide, a very simple method to synthesize an efficient and stable water-oxidizing electrode on the surface of a fluorine doped tin oxide electrode was reported. The electrode at pH = 13 yields a current density of 1 mA cm−2 at an overpotential of 450 mV, which is promising to be used as an anode in water-splitting systems. In higher overpotential (800 mV), a current density of 7 mA cm−2 was observed. Proposed different states of the growth of layered Mn oxide on the surface of FTO based on SEM images were also discussed
Khatamian, M., Heidari, S., Najafpour, M. M., "Water-oxidizing activity of ZSM-5 type manganosilicate: The importance of the Mnsingle bondOsingle bondMn bonds", International Journal of Hydrogen Energy, 41: (32), 14088-14100, (2016).
Abstract:
Water-splitting into O2 and H2 is a promising way to prepare eco-friendly fuels in the future. However, the water-oxidation is the bottleneck for this important reaction. Thus, finding more details of water-oxidation mechanism leads to design more efficient water-splitting catalysts for the hydrogen evolution reaction. Herein, an aluminum-free manganese incorporated ZSM-5 type zeolite is synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy (DRS), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic absorption spectroscopy (AAS), Transmission electron microscopy (TEM) and N2 physical adsorption analysis. The water-oxidizing activity of the synthesized sample is studied in the presence of ammonium cerium(IV) nitrate as an oxidant. Water-oxidation experiments confirm that direct cooperation between Mn ions is one of the most important factors for the water-oxidation by Mn oxides.
Najafpour, M. M., Jafarian Seddigh, D., Hosseini, S. M., Zaharieva, I., "Treated Nanolayered Mn Oxide by Oxidizable Compounds: A Strategy To Improve the Catalytic Activity toward Water Oxidation", Inorg. Chem., 55: (17), 8827-8832, (2016).
Abstract:
Herein, we investigate the effect of post-treatment of nanolayered manganese oxide by different inorganic and organic compounds. We use the fact that nanolayered manganese oxides are among the strongest naturally occurring oxidants, capable of oxidizing a wide range of organic molecules. Post-treatment of the synthetic Mn oxides with oxidizable compounds increases the cerium(IV)-driven water oxidation catalyzed by treated layered manganese oxides more than 25 times. On the basis of X-ray absorption investigations, we attribute this effect to the increased amount of manganese(III) ions. This finding can explain some puzzles in water oxidation by manganese oxides and may help to advance toward an efficient design strategy of water-oxidizing catalyst in artificial photosynthetic systems
Najafpour, M. M., Hosseini, S. M., Tavahodi, M., Zarei Ghobadi, M., "The conversion of CoSe2 to Co oxide under the electrochemical water oxidation condition ", International Journal of Hydrogen Energy, 41: (31), 13469-13475, (2016).
Abstract:
Hydrogen production by water electrolysis is a very promising way to store sustainable energies. In practice, however, large-scale electrochemical production of hydrogen from water splitting is greatly limited by water-oxidation reaction. CoSe2 and its composites with other compounds are efficient catalysts for water oxidation. Herein for the first time, we report that CoSe2 is converted to cobalt oxide when is used as a water-oxidizing catalyst under the electrochemical water oxidation condition at pH = 13. The results are very important for water-splitting systems, which use CoSe2 as a water-oxidizing catalyst.
Najafpour, M. M., Hosseini, S. M., Zand, Z., "Manganese oxide supported on gold/iron as a water-oxidizing catalyst in artificial photosynthetic systems ", Dalton Trans., 45: (22), 9201-9208, (2016).
Abstract:
Herein, we reported that KMnO4 with iron nanoparticles coated with gold layers was a promising catalyst for water oxidation. The compound was characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic absorption spectroscopy and electrochemistry. The new compound was a conductive, recyclable, highly dispersible, magnetically separable, environmentally friendly, and nano-sized catalyst for water oxidation via cerium(IV) ammonium nitrate or Ru(bpy)33+ and electrochemical water oxidation. The turnover frequency of Mn oxide/gold/iron for water oxidation via cerium(IV) ammonium nitrate is 0.4 mmol O2 per mol Mn per second, which shows that this catalyst is among the best Mn-based catalysts for water oxidation. We also showed a strategy for placing this catalyst on the surface of an electrode without adding any other compounds.
Najafpour, M. M., Hosseini, S. M., "Highly dispersed PtO2 on layered Mn oxide as water-oxidizing catalysts", International Journal of Hydrogen Energy, 41: (16), 6798-6804, (2016).
Abstract:
Herein we report a new method to synthesize highly dispersed PtO2 on layered Mn oxide. The compound was characterized by scanning electron microscopy, energy dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic absorption spectroscopy. Then, we investigated the role of PtO2 on the water-oxidizing activity of nanolayered Mn in the presence of cerium (IV) ammonium nitrate as a non-oxo transfer oxidant. The water-oxidizing activities of these composites with other previously reported Mn oxides are compared and also the important factors influencing the water-oxidizing activities of Mn oxides are discussed.
Najafpour, M. M., Abasi, M., Hołyńska, M., Pashaei, B., "Manganese oxides as water-oxidizing catalysts for artificial photosynthetic systems: The effect of support", International Journal of Hydrogen Energy , 41: (12), 5475-5483, (2016).
Abstract:
Herein the effect of support on water-oxidizing activity of amorphous Mn oxides was investigated. We used nanoparticles of CuO, NiO, MgO, SiO2 or ZrO2 as support and placed Mn oxides on these oxides. The compounds were synthesized by a simple procedure and characterized by high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray diffraction spectrometry. In the next step, the water-oxidizing activities of these compounds were considered in the presence of cerium(IV) ammonium nitrate. We found that the efficiency of Mn oxide toward water oxidation depends upon the nature of the support. A turnover frequency ∼5 based on Mn was observed for Mn oxides on NiO.
Najafpour, M. M., Zarei Ghobadi, M., Sarvi, B., Madadkhani, S., Jafarian Seddigh, D., Rafighi, p., Tavahodi, M., Shen, J.- R., Allakhverdiev, S., "Polypeptide and Mn–Ca oxide: Toward a biomimetic catalyst for water-splitting systems", International Journal of Hydrogen Energy, 41: (12), 5504-5512, (2016).
Abstract:
Water oxidation is the bottleneck for hydrogen production by water-splitting systems using sunlight or other sustainable energies. Herein we report nano-sized Mn–Ca oxide in an engineered polypeptide (Glu-Glu-Glu-Glu-Glu-Glu-Glu-His-Val-Val-Val-Val-Val-Val-Val-Val) as a structural model for biological water-oxidizing site in plants, algae, and cyanobacteria. The compound was synthesized by a simple procedure and characterized by transmission electron microscopy, atomic absorption spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction spectrometry, UV–Visible spectroscopy, dynamic light scattering, and some electrochemical methods. Using hydrogen to store sustainable energies is a promising strategy in near future and such nano-sized Mn–Ca oxide/polypeptide is a promising strategy in water-splitting systems to provide cheap electrons from water toward hydrogen production.
Najafpour, M. M., Salimi, S., Hołyńska, M., Allakhverdiev, S., "A highly dispersible, magnetically separable and environmentally friendly nano-sized catalyst for water oxidation", The International Journal of Hydrogen Energy, 41: (8), 4616-4623, (2016).
Abstract:
The reaction of KMnO4 with cobalt nanoparticles coated with SiO2 layers forms a highly dispersible, magnetically separable and environmentally friendly catalyst toward water oxidation. The compound was characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray Photoelectron Spectroscopy, X-ray diffraction, electron spectroscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The nano-sized catalyst shows self-healing in the presence of cerium(IV) ammonium nitrate and under the water-oxidation conditions. The turnover frequencies for the catalyst toward water oxidation in the presence of cerium(IV) ammonium nitrate and [Ru(bpy)3]3+ are 0.15 and 0.25 (mmol O2/mol Mn·s), respectively.
Najafpour, M. M., Safdari, R., Ebrahimi, F., Rafighi, p., Bagheri, R., "Water oxidation by a soluble iron(III)–cyclen complex: new findings", Dalton Trans., 45: (6), 2618-2623, (2016).
Abstract:
Herein, the role of iron oxide in the electrochemical water oxidation of an iron cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) is considered using scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, nuclear magnetic resonance spectroscopy, chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy.
Najafpour, M. M., Ebrahimi, F., Hołyńska, M., "Nanolayered Mn oxide obtained in the reaction of KMnO4 and Mn2CO10: Conflict between extremes toward an efficient water-oxidizing catalyst", International Journal of Hydrogen Energy, 41: (4), 2583-2591, (2016).
Abstract:
Using sustainable energies, large-scale electrochemical and photochemical hydrogen production from water splitting are greatly limited by water-oxidation reaction. Herein we report that nanolayered Mn oxide obtained in the reaction of KMnO4 and Mn2CO10 is a good catalyst toward water oxidation. The Mn oxide was synthesized by a simple method and characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activity of the oxide was considered in the presence of cerium(IV) ammonium nitrate. The compound shows good water-oxidizing activity with turnover frequencies of ∼0.5 (mmol O2/(mol Mn·s)) toward water oxidation.
Najafpour, M. M., Salimi, S., Balaghi, S. E., Hołyńska, M., Tomo, T., Hossaini Sadr, M., Soltani, B., Shen, J.- R., Veziroglu, T. N., "Nanostructured manganese oxide on frozen smoke: A new water-oxidizing composite", International Journal of Hydrogen Energy, 41: (4), 2466-2476, (2016).
Abstract:
The water-oxidizing complex or oxygen-evolving complex in plants, algae and cyanobacteria is an Mn4CaO5 cluster catalysing light-induced water oxidation. Herein we report that nano-sized Mn oxide/carbon aerogel is an active and low-density catalyst toward water oxidation. The composite was synthesized by a simple, low-cost procedure with different ratio of carbon aerogel to Mn oxide and characterized by scanning electron microscopy, energy-dispersive spectroscopy, high resolution transmission electron microscopy, X-ray diffraction, electronic spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. Then, the water-oxidizing activity of this composite was considered in the presence of cerium(IV) ammonium nitrate. The composites with a high ratio of Mn oxide to carbon aerogel are good Mn-based catalysts with turnover frequencies of ∼0.33 (mmol O2/(mol Mn·s)). In addition to the water-oxidizing activities of these composites under different conditions, their self-healing reaction in the presence of cerium(IV) ammonium nitrate was studied. We also compare the composite with graphene quantum dots/Mn oxide, which is not stable under these conditions. Using hydrogen to store sustainable energies is a promising strategy in the near future and our results show that nano-sized Mn oxide/carbon aerogel is a promising catalyst for water-splitting systems toward hydrogen evolution.
Najafpour, M. M., Renger, G., Hołyńska, M., Nemati Moghaddam, A., Aro, E.- M., Carpentier, R., Nishihara, H., Eaton-Rye, J. J., Shen, J.- R., "Manganese Compounds as Water-Oxidizing Catalysts: From the Natural Water-Oxidizing Complex to Nanosized Manganese Oxide Structures", Chem. Rev., 116: (5), 2886-2936, (2016).
Abstract:
All cyanobacteria, algae, and plants use a similar water-oxidizing catalyst for water oxidation. This catalyst is housed in Photosystem II, a membrane-protein complex that functions as a light-driven water oxidase in oxygenic photosynthesis. Water oxidation is also an important reaction in artificial photosynthesis because it has the potential to provide cheap electrons from water for hydrogen production or for the reduction of carbon dioxide on an industrial scale. The water-oxidizing complex of Photosystem II is a Mn–Ca cluster that oxidizes water with a low overpotential and high turnover frequency number of up to 25–90 molecules of O2 released per second. In this Review, we discuss the atomic structure of the Mn–Ca cluster of the Photosystem II water-oxidizing complex from the viewpoint that the underlying mechanism can be informative when designing artificial water-oxidizing catalysts. This is followed by consideration of functional Mn-based model complexes for water oxidation and the issue of Mn complexes decomposing to Mn oxide. We then provide a detailed assessment of the chemistry of Mn oxides by considering how their bulk and nanoscale properties contribute to their effectiveness as water-oxidizing catalysts.
Najafpour, M. M., Abbassi Isaloo, M., Hołyńska, M., Shen, J.- R., Allakhverdiev, S., "The effect of lanthanum(III) and cerium(III) ions between layers of manganese oxide on water oxidation", Photosynth. Res., 126: (2), 489-498, (2015).
Abstract:
Manganese oxide structure with lanthanum(III) or cerium(III) ions between the layers was synthesized by a simple method. The ratio of Mn to Ce or La in samples was 0.00, 0.04, 0.08, 0.16, 0.32, 0.5, 0.82, or 1.62. The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction studies, and atomic absorption spectroscopy. The compounds show efficient catalytic activity of water oxidation in the presence of cerium(IV) ammonium nitrate with a turnover frequency of 1.6 mmol O2/mol Mn.s. In contrast to the water-oxidizing complex in Photosystem II, calcium(II) has no specific role to enhance the water-oxidizing activity of the layered manganese oxides and other cations can be replaced without any significant decrease in water-oxidizing activities of these layered Mn oxides. Based on this and previously reported results from oxygen evolution in the presence of H 2 18 O, we discuss the mechanism and the important factors influencing the water-oxidizing activities of the manganese oxides.
Najafpour, M. M., Allakhverdiev, S., "Recent progress in the studies of structure and function of photosystems I and II, Editorial", Journal of Photochemistry and Photobiology B: Biology, 152, 173-175, (2015).
Najafpour, M. M., Mostafalou, R., Kaboudin, B., "Nano-sized Mn3O4 and β-MnOOH from the decomposition of β-cyclodextrin–Mn: 1. Synthesis and characterization", Journal of Photochemistry and Photobiology B: Biology, 152: (P.A), 106-111, (2015).
Abstract:
Nano-sized Mn oxides contain Mn3O4 and β-MnOOH have been prepared by a simple and high-yield method using β-cyclodextrin as a ligand for Mn ions, and decomposition of this Mn complex. Scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and X-ray diffraction spectroscopy have been used to characterize morphologies and the phases of these prepared nano-sized Mn oxides.
Najafpour, M. M., Carpentier, R., Allakhverdiev, S., "(Guest Editors) Special issue on Artificial Photosynthesis", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 1-172, (2015).
Najafpour, M. M., Allakhverdiev, S., "(Guest Editors) Special issue on Recent progress in the studies of structure and function of photosystems I and II", Journal of Photochemistry and Photobiology B: Biology, 152: (P. B), 173-175, (2015).
Najafpour, M. M., Salimi, S., "Carbon for engineering of a water-oxidizing catalyst ", Dalton Trans., 44: (48), 20991-20998, (2015).
Abstract:
Herein we report that the reaction of KMnO4 with cobalt nanoparticles coated with multiple graphene layers forms a promising catalyst toward water oxidation. The compound was characterized by scanning electron microscopy, energy-dispersive spectroscopy, high resolution transmission electron microscopy, X-ray diffraction, electronic spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In addition to the Mn oxide-based characteristics of the catalyst, it is a conductive, self-healing, recycling, highly dispersible, magnetically separable, environmentally friendly, and nano-sized catalyst for water oxidation. The turnover frequency for the catalyst toward water oxidation is 0.1 and 0.05 (mmol O2 per mol Mn s) in the presence of cerium(IV) ammonium nitrate and photo-produced Ru(bpy)33+
Najafpour, M. M., Carpentier, R., Allakhverdiev, S., "Artificial photosynthesis Editorial", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 1-3, (2015).
Najafpour, M. M., Mostafalou, R., Holynska, M., Ebrahimi, F., Kaboudin, B., "Nano-sized Mn3O4 and β-MnOOH from the decomposition of β-cyclodextrin-Mn: 2. The water-oxidizing activities", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 112-118, (2015).
Abstract:
Nano-sized Mn oxides contain Mn3O4, β-MnOOH and Mn2O3 have been prepared by a previously reported method using thermal decomposition of β-cyclodextrin-Mn complexes. In the next step, the water-oxidizing activities of these Mn oxides using cerium(IV) ammonium nitrate as a chemical oxidant are studied. The turnover frequencies for β-MnO(OH) and Mn3O4 are 0.24 and 0.01–0.17 (mmol O2/mol Mn s), respectively. Subsequently, water-oxidizing activities of these compounds are compared to the other previously reported Mn oxides. Important factors affecting water oxidation by these Mn oxides are also discussed.
Najafpour, M. M., Allakhverdiev, S., "Nano-sized Mn oxide: A true catalyst in the water-oxidation reaction", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 127-132, (2015).
Abstract:
The short perspective highlights new results by water-oxidizing Mn-based catalysts in artificial photosynthetic systems.
Najafpour, M. M., Abbassi Isaloo, M., "The mechanism of water oxidation catalyzed by nanolayered manganese oxides: New insights", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 133-138, (2015).
Abstract:
Herein we consider the mechanism of water oxidation by nanolayered manganese oxide in the presence of cerium(IV) ammonium nitrate. Based on membrane-inlet mass spectrometry results, the rate of H218O exchange of μ-O groups on the surface of the nanolayered Mn–K oxide, and studies on water oxidation in the presence of different ratios of acetonitrile/water we propose a mechanism for water oxidation by nanolayered Mn oxides in the presence of cerium(IV) ammonium nitrate.
Shahbazy, M., Kompany-Zareh, M., Najafpour, M. M., "QSAR analysis for nano-sized layered manganese–calcium oxide in water oxidation: An application of chemometric methods in artificial photosynthesis", Journal of Photochemistry and Photobiology B: Biology, 152: (P. A), 146-155, (2015).
Abstract:
Water oxidation is among the most important reactions in artificial photosynthesis, and nano-sized layered manganese–calcium oxides are efficient catalysts toward this reaction. Herein, a quantitative structure–activity relationship (QSAR) model was constructed to predict the catalytic activities of twenty manganese–calcium oxides toward water oxidation using multiple linear regression (MLR) and genetic algorithm (GA) for multivariate calibration and feature selection, respectively. Although there are eight controlled parameters during synthesizing of the desired catalysts including ripening time, temperature, manganese content, calcium content, potassium content, the ratio of calcium:manganese, the average manganese oxidation state and the surface of catalyst, by using GA only three of them (potassium content, the ratio of calcium:manganese and the average manganese oxidation state) were selected as the most effective parameters on catalytic activities of these compounds. The model’s accuracy criteria such as R2test and Q2test in order to predict catalytic rate for external test set experiments; were equal to 0.941 and 0.906, respectively. Therefore, model reveals acceptable capability to anticipate the catalytic activity.
Najafpour, M. M., Zarei Ghobadi, M., Larkum, A. W., Shen, J-R., Allakhverdiev, S., "The biological water-oxidizing complex at the nano–bio interface", Trends in Plant Science, 20: (9), 559-568, (2015).
Abstract:
Photosynthesis is one of the most important processes on our planet, providing food and oxygen for the majority of living organisms on Earth. Over the past 30 years scientists have made great strides in understanding the central photosynthetic process of oxygenic photosynthesis, whereby water is used to provide the hydrogen and reducing equivalents vital to CO2 reduction and sugar formation. A recent crystal structure at 1.9–1.95 Å has made possible an unparalleled map of the structure of photosystem II (PSII) and particularly the manganese–calcium (Mn–Ca) cluster, which is responsible for splitting water. Here we review how knowledge of the water-splitting site provides important criteria for the design of artificial Mn-based water-oxidizing catalysts, allowing the development of clean and sustainable solar energy technologies.
Najafpour, M. M., Hosseini, S. M., Hołyńska, M., Tomo, T., Allakhverdiev, S., "Platinum/manganese oxide nanocomposites as water-oxidizing catalysts: New findings and current controversies", International Journal of Hydrogen Energy, 40: (34), 10825-10832, (2015).
Abstract:
Herein we consider the role of platinum nanoparticles on water-oxidation catalyzed by manganese oxide. The nanocomposites were synthesized by two different methods and characterized by scanning electron microscopy, energy dispersive spectrometry, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. Then, the water-oxidizing activities of these composites in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant were studied. We compare these composites with other previously reported Mn oxides and also discuss the important factors influencing the water-oxidizing activities of Mn oxides.
Najafpour, M. M., Ebrahimi, F., Safdari, R., Zarei Ghobadi, M., Tavahodi, M., Rafighi, P., "New findings and the current controversies for water oxidation by a copper(II)-azo complex: homogeneous or heterogeneous? ", Dalton Transactions , 44: (35), 15435-15440, (2015).
Abstract:
In this paper, new findings for the water-oxidizing activity of [(L)CuII(NO3)], (L = (E)-3-(pyridin-2-yldiazenyl)naphthalen-2-ol (HL)) under both electro-water oxidation conditions and in the presence of cerium(IV) ammonium nitrate are reported.
Najafpour, M. M., Amini, E., "Nano-sized Mn oxides on halloysite or high surface area montmorillonite as efficient catalysts for water oxidation with cerium(IV) ammonium nitrate: support from natural sources ", Dalton Transactions , 44: (35), 15441-15449, (2015).
Abstract:
We used halloysite, a nano-sized natural mineral, and high surface area montmorillonite as supports for nano-sized Mn oxides to synthesize efficient water-oxidising catalysts. The composites were synthesized by an easy and simple procedure, and characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectrometry. Halloysite has low amounts of hydroxyl groups on its surface, thus it causes better dispersion of Mn oxides. The water-oxidising activities of these composites were also measured in the presence of cerium(IV) ammonium nitrate. Considering the low-cost, environmentally friendly precursors, simple synthesis and efficiency for water oxidation, the composites are promising catalysts in artificial photosynthetic systems.
Najafpour, M. M., Hosseini, S. M., Malgorzata, H., Tomo, T., Allakhverdiev, S., "Gold nanorods or nanoparticles deposited on layered manganese oxide: new findings ", New J. Chem., 39, 7260-7267, (2015).
Abstract:
Herein we consider the role of gold nanorods, with a diameter of ∼ 10 nm or nanoparticles (size < 100 nm), deposited on nanolayered Mn oxide in water oxidation. The catalysts were synthesized by simple methods and characterized by scanning electron microscopy, energy dispersive spectrometry, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activities of these composites were studied in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. A comparison with other previously reported Mn oxides and important factors influencing the water-oxidation activities of Mn oxides are also discussed. Our results show that gold has no significant effect on the water-oxidizing activity of the Mn oxide phase at least in the presence of Ce(IV).
Najafpour, M. M., Hosseini, S. M., Hołyńska, M., Tomo, T., Allakhverdiev, S., "Manganese oxides supported on gold nanoparticles: new findings and current controversies for the role of gold", Photosynth. Res., 126: (2), 477-487, (2015).
Abstract:
We synthesized manganese oxides supported on gold nanoparticles (diameter <100 nm) by the reaction of KMnO4 with gold nanoparticles under hydrothermal conditions. In this green method Mn oxide is deposited on the gold nanoparticles. The compounds were characterized by scanning electron microscopy, energy-dispersive spectrometry, high-resolution transmission electron microscopy, X-ray diffraction, UV–Vis spectroscopy, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water-oxidizing activities of these compounds in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant were studied. The results show that these compounds are good catalysts toward water oxidation with a turnover frequency of 1.0 ± 0.1 (mmol O2/(mol Mn·s)). A comparison with other previously reported Mn oxides and important factors influencing the water-oxidizing activities of Mn oxides is also discussed.
Najafpour, M. M., Zarei Ghobadi, M., Sarvi, B., Haghighi, B., "An engineered polypeptide around nano-sized manganese–calcium oxide: copying plants for water oxidation ", Dalton Transactions, 44: (34), 15271-15278, (2015).
Abstract:
Synthesis of new efficient catalysts inspired by Nature is a key goal in the production of clean fuel. Different compounds based on manganese oxide have been investigated in order to find their water-oxidation activity. Herein, we introduce a novel engineered polypeptide containing tyrosine around nano-sized manganese–calcium oxide, which was shown to be a highly active catalyst toward water oxidation at low overpotential (240 mV), with high turnover frequency of 1.5 × 10−2 s−1 at pH = 6.3 in the Mn(III)/Mn(IV) oxidation range. The compound is a novel structural and efficient functional model for the water-oxidizing complex in Photosystem II. A new proposed clever strategy used by Nature in water oxidation is also discussed. The new model of the water-oxidizing complex opens a new perspective for synthesis of efficient water-oxidation catalysts.
Najafpour, M. M., Ebrahimi, F., Amini, M., Rahimi, M., El-Sawy, A., Suib, S L., "Nano-sized Mn oxides as true catalysts for alcohol oxidation by a mononuclear manganese(II) complex ", Dalton Transactions, 44: (34), 15121-15125, (2015).
Abstract:
Herein new findings on the alcohol-oxidizing activity of a mononuclear manganese(II) complex are reported. We propose that nano-sized Mn oxides are true catalysts for the oxidation of some alcohols to aldehydes in the presence of Oxone (2KHSO5·KHSO4·K2SO4) as an oxidant.
Nath, K., Najafpour, M. M., Voloshin, R. A., Balaghi, S. E., Tyystjärvi, E., Timilsina, R., Eaton-Rye, J. J., Tomo, T., Nam, H. G., "Photobiological hydrogen production and artificial photosynthesis for clean energy: from bio to nanotechnologies", Photosynth Res., 126: (2), 237-247, (2015).
Abstract:
Global energy demand is increasing rapidly and due to intensive consumption of different forms of fuels, there are increasing concerns over the reduction in readily available conventional energy resources. Because of the deleterious atmospheric effects of fossil fuels and the uncertainties of future energy supplies, there is a surge of interest to find environmentally friendly alternative energy sources. Hydrogen (H2) has attracted worldwide attention as a secondary energy carrier, since it is the lightest carbon-neutral fuel rich in energy per unit mass and easy to store. Several methods and technologies have been developed for H2 production, but none of them are able to replace the traditional combustion fuel used in automobiles so far. Extensively modified and renovated methods and technologies are required to introduce H2 as an alternative efficient, clean, and cost-effective future fuel. Among several emerging renewable energy technologies, photobiological H2 production by oxygenic photosynthetic microbes such as green algae and cyanobacteria or by artificial photosynthesis has attracted significant interest. In this short review, we summarize the recent progress and challenges in H2-based energy production by means of biological and artificial photosynthesis routes.
Najafpour, M. M., Hołyńska, M., Salimi, S., "Applications of the “nano to bulk” Mn oxides: Mn oxide as a Swiss army knife", Coordination Chemistry Reviews, 285, 65-75, (2015).
Abstract:
Mn oxides are inexpensive, environmentally friendly, stable and redox-active compounds. Thus, they are among the most promising compounds for different applications. In this short review we discuss the importance of Mn oxides in different catalytic reactions, such as alcohol, sulfide and water oxidations, and also promising applications of these compounds as supercapacitors, in batteries and water treatment.
Najafpour, M. M., Zarei Ghobadi, M., Haghighi, B., Tomo, T., Shene, J. R., Allakhverdiev, S. I., "Comparison of nano-sized Mn oxides with the Mn cluster of photosystem II as catalysts for water oxidation", Biochimica et Biophysica Acta (BBA) - Bioenergetics , 1847, 294-306, (2015).
Abstract:
“Back to Nature” is a promising way to solve the problems that we face today, such as air pollution and shortage of energy supply based on conventional fossil fuels. A Mn cluster inside photosystem II catalyzes light-induced water-splitting leading to the generation of protons, electrons and oxygen in photosynthetic organisms, and has been considered as a good model for the synthesis of new artificial water-oxidizing catalysts. Herein, we surveyed the structural and functional details of this cluster and its surrounding environment. Then, we review the mechanistic findings concerning the cluster and compare this biological catalyst with nano-sized Mn oxides, which are among the best artificial Mn-based water-oxidizing catalysts.
Najafpour, M. M., Amini, E., "A very simple and high-yield method to synthesize nanolayered Mn oxide ", Dalton Trans, 44, 1039-1045, (2015).
Abstract:
Nanolayered Mn oxides have been prepared by a very simple, low-cost and high-yield method using soap, KOH, MnCl2 and H2O2. Scanning electron microscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction spectrometry have been used to characterize the phase and the morphology of the nanolayered Mn oxide. The nanolayered Mn oxide shows good catalytic activity toward water oxidation in the presence of cerium(IV) ammonium nitrate.
Najafpour , M. M., Fekete, M., Jafarian Sedigh, D., Aro, E. M., Carpentier, R., J. Eaton-Rye, J., Nishihara, H., Shen , J. R., Allakhverdiev, S. I., Spiccia, L., "Damage Management in Water-Oxidizing Catalysts: From Photosystem II to Nanosized Metal Oxides", ACS Catal, 5, 1499-1512, (2015).
Abstract:
Current energy resources largely rely on fossil fuels that are expected to be depleted in 50–200 years. On a global scale, the intensive use of this energy source has resulted in highly detrimental effects to the environment. Hydrogen production by water splitting, with sunlight as the main energy source, is a promising way to augment the production of renewable energy; however, the development of an efficient and stable water-oxidizing catalyst remains a key task before a technological breakthrough based on water splitting can be realized. A main issue hampering the development of commercially viable, non-precious-metal-based catalysts is their susceptibility to degradation. To efficiently address this major drawback, self-healing catalysts that can repair their structure without human intervention will be necessary. In this review, we focus on water oxidation by natural and artificial Mn-, Co-, and Ni-based catalysts and then discuss the self-healing properties that contribute to sustaining their catalytic activity.
Najafpour, M. M., Khoshkam, M., Jafarian Seddigh, D., Zahraei, A., Kompany-Zareh, M., "Self-healing for nanolayered manganese oxides in the presence of cerium(IV) ammonium nitrate: new findings ", New J. Chem., 39: (4), 2547-2550, (2015).
Abstract:
The self-healing reactions for metal oxides are among the most important reactions. For Mn oxides in the presence of cerium(IV) ammonium nitrate, Mn(II) and MnO4− combine and heal the Mn oxide. In the reaction, Mn(II) is formed from the reductive dissolution of the Mn oxide or by disproportionation of Mn(III) on the surface of the oxide. This Mn(II) is then oxidized by cerium(IV) ammonium nitrate to MnO4−. The MnO4− in the presence of Mn oxide oxidizes water or in a second pathway is reduced by Mn(II) to form Mn oxide. Here, we use the multivariate curve resolution-alternative least squares method for the first time to analyze spectroscopic data and obtain concentration profiles of cerium(IV) ammonium nitrate and MnO4− during the reaction under different conditions.
Najafpour, M. M., Zahraee, A., Amini, E., Ahari-Mostafavi, M. M., Kompany-Zareh, M., "Antimicrobial effects of silver deposited on nanolayered manganese oxide ", RSC Adv, 4, 64688-64691, (2014).
Abstract:
Silver deposited on layered manganese oxide was synthesized by a simple method, and characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy, and energy-dispersive X-ray mapping. In the next step, antimicrobial effects of the compound for Escherichia coli and Staphylococcus aureus were considered.
Amini, M., Najafpour, M. M., Zare, M., Amini, E., "Nanolayered manganese-calcium oxide as an efficient and environmentally friendly catalyst for alcohol oxidation", Journal of Molecular Catalysis A: Chemical, 394, 303-308, (2014).
Abstract:
Here, we report that nanolayered Mn-Ca oxide is an efficient catalyst toward alcohol oxidation in the presence of O2.
Najafpour, M. M., Abbasi Isaloo, M., Zarei Ghobadi, M., Amini, E., "The effect of different metal ions between nanolayers of manganese oxide on water oxidation ", J. Photochem. Photobiol. B, 141, 247-252, (2014).
Abstract:
Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides.
Amini, M., Najafpour, M. M., Zare, M., Hołyńska, M., Nemati Moghaddam, A., Bagherzadeh, M., "A water-oxidizing dinuclear iron complex as an efficient catalyst toward organic sulfide oxidation", Journal of Coordination Chemistry, 67: (18), 3026-3032, (2014).
Abstract:
In this paper, we report that a known dinuclear Fe complex, [tpa(H2O)FeOFe(H2O)tpa](ClO4)4 (tpa: tris(2-pyridylmethyl)amine), is an efficient catalyst toward organic sulfide oxidation in the presence of urea-hydrogen peroxide.
Najafpour, M. M., Abbasi Isaloo, M., J. Eaton-Rye, J., Tomo, T., Nishihara, H., Satoh, K., Carpentier, R., Shen, J. R., Allakhverdiev , S. I., "Water exchange in manganese-based water-oxidizing catalysts in photosynthetic systems: From the water-oxidizing complex in photosystem II to nano-sized manganese oxides", Biochimica et Biophysica Acta , 1837, 1395-1410, (2014).
Abstract:
The water-oxidizing complex (WOC), also known as the oxygen-evolving complex (OEC), of photosystem II in oxygenic photosynthetic organisms efficiently catalyzes water oxidation. It is, therefore, responsible for the presence of oxygen in the Earth's atmosphere. The WOC is a manganese–calcium (Mn4CaO5(H2O)4) cluster housed in a protein complex. In this review, we focus on water exchange chemistry of metal hydrates and discuss the mechanisms and factors affecting this chemical process. Further, water exchange rates for both the biological cofactor and synthetic manganese water splitting are discussed. The importance of fully unveiling the water exchange mechanism to understand the chemistry of water oxidation is also emphasized here. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: Keys to Produce Clean Energy.
Najafpour, M. M., Amini, M., Hołyńska, M., Zare, M., Amini, E., "A hexanuclear manganese(II) complex: synthesis, characterization and catalytic activity toward organic sulfide oxidation ", New J. Chem, 38, 5069-5074, (2014).
Abstract:
Herein we report on the synthesis and characterization of a hexanuclear [MnII6] wheel-like assembly with naphthalene-1,8-dicarboxylate and 1,10-phenanthroline as ligands. Overall antiferromagnetic behavior of the magnetic properties is observed. The complex acts as a catalyst toward organic sulfide oxidation in the presence of H2O2 with good selectivity (98–100%).
Najafpour, M. M., Zarei Ghobadi, m., Haghighi, b., Tomo, T., Carpentier, R., Allakhverdiev, S. I., "A nano-sized manganese oxide in a protein matrix as a natural water-oxidizing site", Plant Physiology and Biochemistry, 81, 3-15, (2014).
Abstract:
The purpose of this review is to present recent advances in the structural and functional studies of water-oxidizing center of Photosystem II and its surrounding protein matrix in order to synthesize artificial catalysts for production of clean and efficient hydrogen fuel.
Najafpour, M. M., Zarei Ghobadi, M., Jafarian Sedigh, D., Haghighi, B., "Nano-sized layered manganese oxide in a poly-L-glutamic acid matrix: a biomimetic, homogenized, heterogeneous structural model for the water-oxidizing complex in photosystem II ", RSC Adv, 4, 39077-39081, (2014).
Abstract:
We, for the first time, report a nano-sized layered Mn–Ca oxide in poly-L-glutamic acid as a structural model for biological water-oxidizing sites in plants, algae and cyanobacteria. The compound was synthesized by a simple method and characterized by transmission electron microscopy, atomic absorption spectroscopy, scanning electron microscopy, UV-Visible spectroscopy, dynamic light scattering, Fourier transform infrared spectroscopy and electrochemistry. The results show the important effect of PGA on the electrochemistry of a Mn–Ca oxide.
Najafpour, M. M., Hołyńska, M., Shamkhali, A. N., Kazemi , S. H., Hillier , W., Amini , E., Ghaemmaghami , M., Jafarian Sedigh, D., Nemati Moghaddam, A., Mohamadi, R., Zaynalpoor, S., Beckmann , K., "The role of nano-sized manganese oxides in the oxygen-evolution reactions by manganese complexes: towards a complete picture", Dalton Trans, 43: (43), 13122-13135 , (2014).
Abstract:
Eighteen Mn complexes with N-donor and carboxylate ligands have been synthesized and characterized. Three Mn complexes among them are new and are reported for the first time. The reactions of oxygen evolution in the presence of oxone (2KHSO5·KHSO4·K2SO4) and cerium(iv) ammonium nitrate catalyzed by these complexes are studied and characterized by UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy, membrane-inlet mass spectrometry and electrochemistry. Some of these complexes evolve oxygen in the presence of oxone as a primary oxidant. CO2 and MnO4(-) are other products of these reactions. Based on spectroscopic studies, the true catalysts for oxygen evolution in these reactions are different. We proposed that for the oxygen evolution reactions in the presence of oxone, the true catalysts are both high valent Mn complexes and Mn oxides, but for the reactions in the presence of cerium(iv) ammonium nitrate, the active catalyst is most probably a Mn oxide.
Najafpour, M. M., Abasi, M., Hołyńska, M., "Nanolayered manganese oxides as water-oxidizing catalysts: the effects of Cu(II) and Ni(II) ions ", RSC Adv, 4, 36017-36023, (2014).
Abstract:
We synthesized nanolayered manganese oxides by the reaction of Mn(CH3COO)2·4H2O and KMnO4 in the presence of copper(II) or nickel(II) ions. The compounds were synthesized, and characterized by scanning electron microscopy, transmission electron microscopy, powder diffractometry and atomic absorption spectroscopy. Water-oxidizing activities of these oxides in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant are reported. The results and proposed important factors influencing the water-oxidizing activities of these oxides are also discussed.
Najafpour, M. M., Abasi, M., Tomo, T., Allakhverdiev, S. I., "Mn oxide/nanodiamond composite: a new water-oxidizing catalyst for water oxidation ", RSC Adv, 4, 37613-37619, (2014).
Abstract:
Herein, we report nanosized Mn oxide/nanodiamond composites as water-oxidizing compounds. The composites were synthesized by easy and simple procedures by the reaction of Mn(II) and MnO4− in the presence of ND (1), the reaction of MnO4− and ND at different temperatures (2 and 4) and by the simple mixing of Mn–Ca oxide and ND (3). The compounds were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The water-oxidizing activities of these compounds were also considered in the presence of cerium(IV) ammonium nitrate. A Mn oxide/nanodiamond resulting from the reaction of MnO4− and ND shows a turnover frequency of 1 (mmol O2/mol Mn.s). However, other Mn oxide/nanodiamond composites show lower activity toward water oxidation.
Najafpour, M. M., Abasi, M., Tomo, T., Allakhverdiev, S. I., "Nanolayered manganese oxide/C60 composite: a good water-oxidizing catalyst for artificial photosynthetic systems ", Dalton Trans, 43, 12058-12064 , (2014).
Abstract:
or the first time, we considered Mn oxide/C60 composites as water-oxidizing catalysts. The composites were synthesized by easy and simple procedures, and characterized by some methods. The water-oxidizing activities of these composites were also measured in the presence of cerium(IV) ammonium nitrate. We found that the nanolayered Mn oxide/C60 composites show promising activity toward water oxidation.
Hou, H. J. M., Allakhverdiev, S., Najafpour, M. M., Govindjee, ., "Current challenges in photosynthesis: from natural to artificial", Front. Plant Sci., 5, 231-1-232-3, (2014).
Najafpour, M. M., N. Moghaddam, A., Dau, H., Zaharieva, I., "Fragments of layered manganese oxide are the real water oxidation catalyst after transformation of molecular precursor on clay", J Am Chem Soc, 136, 7245-7248, (2014).
Abstract:
A binuclear manganese molecular complex [(OH2)(terpy)Mn(μ-O)2Mn(terpy)(OH2)](3+) (1) is the most prominent structural and functional model of the water-oxidizing Mn complex operating in plants and cyanobacteria. Supported on montmorillonite clay and using Ce(IV) as a chemical oxidant, 1 has been reported to be one of the best Mn-based molecular catalysts toward water oxidation. By X-ray absorption spectroscopy and kinetic analysis of the oxygen evolution reaction, we show that [(OH2)(terpy)Mn(μ-O)2Mn(terpy)(OH2)](3+) is transformed into layered type Mn-oxide particles which are the actual water oxidation catalyst.
Najafpour, M. M., Rahimi, F., Fathollahzadeh, M., Haghighi, B., Hołyńska, M., Tomode , T., Allakhverdiev, S. I., "Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis", Dalton Trans, 43, 10866-10876, (2014).
Abstract:
Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) [similar] 2.6.
Wiechen, M., Najafpour, M. M., Allakhverdiev, S. I., Spiccia, L., "Water oxidation catalysis by manganese oxides: learning from evolution ", Energy Environ. Sci, 7, 2203-2212, (2014).
Abstract:
The Oxygen Evolving Complex (OEC) in photosystem II, a cluster that contains four manganese and one calcium ions bridged by five oxygen atoms in a distorted chair like arrangement, carries out the biological oxidation of water during photosynthesis. Since this is the only cluster established in biological water oxidation catalysis, efforts have been made to develop synthetic systems that mimic its structure, properties and water oxidation activity. This perspective provides a brief overview of the current structural and mechanistic understanding of the OEC in photosystem II. It then compares the structural features of this complex with those of manganese oxide water oxidation catalysts and discusses structure–function relationships that inform the development of new catalysts. The identified features should be considered when endeavouring to design manganese oxide, and other metal oxide, catalysts with optimal activity that can ultimately be integrated into photo-electrochemical devices to achieve solar water-splitting.
Najafpour, M. M., Heidari, S., Amini, E., Khatamian, M., Carpentier, R., Allakhverdiev, S. I., "Nano-sized layered Mn oxides as promising and biomimetic water oxidizing catalysts for water splitting in artificial photosynthetic systems", Journal of Photochemistry and Photobiology B: Biology, 133, 124-139, (2014).
Abstract:
One challenge in artificial photosynthetic systems is the development of artificial model compounds to oxidize water. The water-oxidizing complex of Photosystem II which is responsible for biological water oxidation contains a cluster of four Mn ions bridged by five oxygen atoms. Layered Mn oxides as efficient, stable, low cost, environmentally friendly and easy to use, synthesize, and manufacture compounds could be considered as functional and structural models for the site. Because of the related structure of these Mn oxides and the catalytic centre of the active site of the water oxidizing complex of Photosystem II, the study of layered Mn oxides may also help to understand more about the mechanism of water oxidation by the natural site. This review provides an overview of the current status of layered Mn oxides in artificial photosynthesis and discuss the sophisticated design strategies for Mn oxides as water oxidizing catalysts.
Najafpour, M. M., Z. Ghobadi, M., Haghighi, B., J. Eaton-Rye, J., Tomo, T., J. -R, Shen., Allakhverdiev , S. I., "Nano-sized manganese-calcium cluster in photosystem II", Biochemistry (Moscow) , 79: (4), 324-336, (2014).
Abstract:
Cyanobacteria, algae, and plants are the manufacturers that release O2 via water oxidation during photosynthesis. Since fossil resources are running out, researchers are now actively trying to use the natural catalytic center of water oxidation found in the photosystem II (PS II) reaction center of oxygenic photosynthetic organisms to synthesize a biomimetic supercatalyst for water oxidation. Success in this area of research will transcend the current bottleneck for the development of energy-conversion schemes based on sunlight. In this review, we go over the structure and function of the water-oxidizing complex (WOC) found in Nature by focusing on the recent advances made by the international research community dedicated to achieve the goal of artificial water splitting based on the WOC of PS II.
Amini, M., Najafpour, M. M., Naslhajian, H., Amini, E., F. Farnia, S. M., "Nanolayered manganese–calcium oxide as an efficient catalyst toward organic sulfide oxidation ", RSC Adv, 4, 10851-10855, (2014).
Abstract:
We for the first time report that nanolayered Mn–Ca oxide in the presence of H2O2 is an efficient catalyst toward sulfide oxidation to sulfoxide. We characterized the catalyst by DLS, UV-Vis, diffuse reflectance infrared Fourier transform spectroscopy, SEM, TEM and HRTEM. We also considered different parameters of the sulfide-oxidation reaction.
Najafpour, M. M., Abbasi Isaloo, M., "Mechanism of water oxidation by nanolayered manganese oxide: a step forward", RSC Adv, 4, 6375-6375, (2014).
Abstract:
We, for the first time, estimate the rate of H218O exchange for μ-O groups on the surface of nanolayered Mn–K oxide by diffuse reflectance infrared Fourier transform spectroscopy. These results, in addition to results from previously reported membrane-inlet mass spectrometry, provide new insights into the mechanism of water oxidation by nanolayered Mn oxide.
Najafpour, M. M., Abbasi Isaloo, M., Abasi, M., Hołyńska, M., "Manganese oxide as a water-oxidizing catalyst: from the bulk to Ångström-scale ", New J. Chem, 38, 852-858, (2014).
Abstract:
Ångström-scale particles of Mn oxide within the HY zeolite were synthesized and characterized. The compound shows water-oxidizing activity in the presence of cerium(IV) ammonium nitrate as an oxidant. However, the rate of decomposition to MnO4− for the compound is also high and stability is low in the presence of high (>0.2 M) concentrations of cerium(IV) ammonium nitrate. On the other hand, separated Mn ions incorporated in a tungstate cluster (molecular dimensions of [similar]7 × 9 × 4 Å) show no water oxidation in the presence of cerium(IV) ammonium nitrate. These experiments confirm the importance of the size of the catalyst and also cooperation among Mn ions for water oxidation.
Najafpour, M. M., N. Moghaddam, M., Jafarian Sedigh, D., Hołyńska, M., "A dinuclear iron complex with a single oxo bridge as an efficient water-oxidizing catalyst in the presence of cerium(IV) ammonium nitrate: new findings and current controversies ", Catal. Sci. Technol (Invited paper) , 4, 30-33, (2014).
Abstract:
In this paper a dinuclear Fe complex, [tpa(H2O)FeOFe(H2O)tpa](ClO4)4 (tpa: tris(2-pyridylmethyl)amine) is reported as an efficient catalyst for water oxidation in the presence of cerium(IV) ammonium nitrate. The turnover frequency of this dimer is 6 times greater than the turnover frequency reported for the [Fe(OTf or Cl)2(tpa)] complex (OTf: trifluoromethanesulfonate). The role of FeO42− ions in the water oxidation reaction is also discussed.
Najafpour, M. M., "An approach for catalyst design in artificial photosynthetic systems: focus on nanosized inorganic cores within proteins", Photosynth. Res. (Invited Review) , 117, 197-205, (2013).
Abstract:
Some enzymes can be considered as a catalyst having a nanosized inorganic core in a protein matrix. In some cases, the metal oxide or sulfide clusters, which can be considered as cofactors in enzymes, may be recruited for use in other related reactions in artificial photosynthetic systems. In other words, one approach to design efficient and environmentally friendly catalysts in artificial photosynthetic systems for the purpose of utilizing sunlight to generate high energy intermediates or useful material is to select and utilize inorganic cores of enzymes. For example, one of the most important goals in developing artificial photosynthesis is hydrogen production. However, first, it is necessary to find a “super catalyst” for water oxidation, which is the most challenging half reaction of water splitting. There is an efficient system for water oxidation in cyanobacteria, algae, and plants. Published data on the Mn–Ca cluster have provided details on the mechanism and structure of the water oxidizing complex as a Mn–Ca nanosized inorganic core in photosystem II. Progress has been made in introducing Mn–Ca oxides as efficient catalysts for water oxidation in artificial photosynthetic systems. Here, in the interest of designing efficient catalysts for other important reactions in artificial photosynthesis, a few examples of our knowledge of inorganic cores of proteins, and how Nature used them for important reactions, are discussed.
Najafpour, M. M., Amouzadeh Tabrizi, M., Haghighi, B., J. Eaton-Ry, J., Carpentier, R., Allakhverdiev, S. I., "Imidazolium or guanidinium/layered manganese (III, IV) oxide hybrid as a promising structural model for the water-oxidizing complex of Photosystem II for artificial photosynthetic systems", Photosynth. Res, 117, 413-421, (2013).
Abstract:
Photosystem II is responsible for the light-driven biological water-splitting system in oxygenic photosynthesis and contains a cluster of one calcium and four manganese ions at its water-oxidizing complex. This cluster may serve as a model for the design of artificial or biomimetic systems capable of splitting water into oxygen and hydrogen. In this study, we consider the ability of manganese oxide monosheets to self-assemble with organic compounds. Layered structures of manganese oxide, including guanidinium and imidazolium groups, were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, and atomic absorption spectroscopy. The compounds can be considered as new structural models for the water-oxidizing complex of Photosystem II. The overvoltage of water oxidation for the compounds in these conditions at pH = 6.3 is ~0.6 V. These compounds may represent the first step to synthesize a hybrid of guanidinium or imidazole together with manganese as a biomimetic system for the water-oxidizing complex of Photosystem II.
Najafpour, M. M., Rahimi, F., Jafarian Sedigh, D., Carpentier, R., J. Eaton-Rye, J., Shen, J.R., Allakhverdiev, S. I., "Gold or silver deposited on layered manganese oxide: a functional model for the water-oxidizing complex in photosystem II", Photosynth. Res, 117, 423-429, (2013).
Abstract:
In this report, gold or silver deposited on layered manganese oxide has been synthesized by a simple method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy, and energy-dispersive X-ray mapping. The gold deposited on layered manganese oxide showed efficient catalytic activity toward water oxidation in the presence of cerium(IV) ammonium nitrate. The properties associated with this compound suggest it is a functional model for the water-oxidizing complex in photosystem II.
Najafpour, M. M., Haghighi, B., Jafarian Sedigh, D., Zarei Ghobadi, M., "Conversions of Mn oxides to nanolayered Mn oxide in electrochemical water oxidation at near neutral pH, all to a better catalyst: catalyst evolution ", Dalton Trans, 42, 16683-16686, (2013).
Abstract:
Here, for the first time, it is reported that some Mn oxides after a few hours convert to a nanolayered Mn oxide when the compounds are used as water-oxidizing catalysts in a water electrolysis device at near neutral pH and in the presence of LiClO4. The new nanolayered Mn oxide is more active than other Mn oxides toward water oxidation. This result is very important for artificial photosynthetic systems that use Mn oxides as water-oxidizing catalysts.
Najafpour, M. M., Amini, M., Jafarian Sedigh, D., Rahimi, F., Bagherzadeh, M., "Activated layered manganese oxides with deposited nano-sized gold or silver as an efficient catalyst for epoxidation of olefins", RSC. Adv, 3: (46), 24069-24074, (2013).
Abstract:
Activated layered manganese oxides with deposited nano-sized gold or silver were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy and energy-dispersive X-ray mapping. Here, we report that Au or Ag nanoparticles deposited on layered Mn oxides improve the catalytic activity of the Mn oxides toward the epoxidation of olefins in the presence of H2O2 and NaHCO3.
Najafpour, M. M., Haghighi, B., Zarei Ghobadi, M., Jafarian Sedigh, D., "Nanolayered manganese oxide/poly(4-vinylpyridine) as a biomimetic and very efficient water oxidizing catalyst: toward an artificial enzyme in artificial photosynthesis", Chem Commun, 49: (78), 8824-8826, (2013).
Abstract:
Nanolayered Mn oxide/poly(4-vinylpyridine) as a model for Mn cluster in photosystem II was synthesized and characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy (UV-Vis). The compound is a very efficient water oxidizing catalyst, and sizable oxygen evolution was detected at 50 mV overpotential at near neutral pH. The number is as low as the overpotential is used by nature in photosystem II of cyanobacteria, algae and green plants for similar reactions.
Najafpour, M. M., Kompany-Zareh, M., Zahraei, A., Jafarian Sedigh, D., Jaccard, H., Khoshkam, M., Britt, R. D., H. Casey, W., "Mechanism, decomposition pathway and new evidence for self-healing of manganese oxides as efficient water oxidizing catalysts: new insights ", Dalton Trans, 42, 14603-14611, (2013).
Abstract:
The electrochemical water-oxidation reaction usually requires a catalyst to reduce the overpotential and Earth-abundant catalysts, like MnO2, are attracting much attention. Here we use chemometric analysis, EPR and UV-Vis spectroscopies to track Mn(II) and MnO4− byproducts to the reaction of a MnO2 film in the presence of cerium(IV) ammonium nitrate. Permanganate ion is involved in at least two key reactions: it may oxidize water to O2 or can combine with Mn(II) to remake MnO2 solid. We propose mechanisms for water oxidation and present a self-healing process for this reaction.
Najafpour, M. M., Abasi, S., Allakhverdiev, S. I., "Recent Proposed Mechanisms for Biological Water Oxidation", Signpost Open Access J. NanoPhotoBioSciences (REVIEW ARTICLE), 1, 79-92, (2013).
Abstract:
Photosystem II (PSII) drives life on our planet by capturing sunlight and extracts electrons from H2O to reduce CO2 into sugars while releasing the O2 we breathe. In this review, the important proposed mechanisms of water oxidation by the water-oxidizing complex (WOC) of PSII are discussed and the structure of the WOC and its ligand environment are described with reference to the 1.9-Å resolution X-ray-derived crystallographic model of PSII from the cyanobacterium Thermosynechococcus vulcanus.
Najafpour, M. M., Jafarian Sedigh, D., "Water oxidation by manganese oxides, a new step towards a complete picture: simplicity is the ultimate sophistication", Dalton Trans, 42, 12173-12178, (2013).
Abstract:
We, for the first time, report that many Mn oxides (Mn3O4, α-Mn2O3, β-MnO2, CaMnO3, Ca2Mn3O8, CaMn3O6 and CaMn4O8) in the presence of cerium(IV) ammonium nitrate, in the water oxidation, convert to layered Mn oxide. This layered Mn oxide is an efficient water oxidizing catalyst.
Birkner, N ., Nayeri, S., Pashaei, B., Najafpour, M. M., H. Casey, W., Navrotsky, A., "Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation", PNAS, 110: (22), 8801-8806, (2013).
Abstract:
Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.
Najafpour, M. M., N. Moghaddam, A., Sakha, Y., "A simple mathematical model for manganese oxide-coated montmorillonite as a catalyst for water oxidation: from nano to macro sized manganese oxide ", Dalton Trans, 42, 11012-11020, (2013).
Abstract:
Here, we propose a mathematical model that gives a good fit to the experimental data for water oxidation by Mn oxide-coated montmorillonite with different Mn content. Our data show that the water oxidation may progress by cooperation among only neighbor Mn ions on montmorillonite. It is a promising model for finding more about the mechanism of multi-electron reactions.
Najafpour, M. M., Jafarian Sedigh, D., Pashaei, B., Nayeri, S., "Water oxidation by nano-layered manganese oxides in the presence of cerium(IV) ammonium nitrate: important factors and a proposed self-repair mechanism ", New J. Chem, 37, 2448-2459, (2013).
Abstract:
Nano-sized layered cadmium, magnesium and potassium–Mn oxides were synthesized and characterized by scanning electron microscopy, energy-dispersive X-ray mapping, transmission electron microscopy, X-ray diffraction spectroscopy, and atomic absorption spectroscopy. These oxides showed water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. The formulae of the best catalysts are Cd0.16MnO2, Mg0.16MnO2 and K0.25MnO2 with an average oxidation state of [similar]3.7–3.8 for the Mn ions in the birnessite structure. We also prepared a mixture of redox-active metal ions containing Fe(II), Cu(II), Co(II), and Ni(II) instead of inert redox ions. Important factors and a proposed self-repair mechanism for the layered Mn oxides in the water oxidation reaction are reported.
Najafpour, M.M., Pashaei, B., Zand, Z., "Photodamage of the manganese–calcium oxide: a model for UV-induced photodamage of the water oxidizing complex in photosystem", Dalton Trans, 42, 4772-4776, (2013).
Abstract:
The Mn-Ca cluster is proposed to play an important role in the ultraviolet (UV) photoinhibition of photosystem II, but the mechanism is still unknown. Here, we used Mn-Ca oxide as an important structural and functional model for the Mn-Ca cluster in photosystem II, and report the effect of UV radiation on the decomposition of the structure in the presence of organic groups. Our results show similarities between the reactions of the Mn-Ca oxide and the WOC of PSII in the presence of UV radiation.
Machura , B., Palion , J., Mrozin´ ski, J., Amini, M., Najafpour , M.M., Kruszynski, R., "Manganese(II) complexes of 2,3,5,6-tetra-(2-pyridyl)pyrazine – Syntheses, crystal structures, spectroscopic, magnetic and catalytic properties", Polyhedron, 53, 132-143, (2013).
Abstract:
A systematic studies on complex formation between Mn(II) ions, 2,3,5,6-tetra(2-pyridyl)pyrazine and halide or pseudohalide (N3−, NCS− and N(CN)2−) ligands have been carried out and the following complexes [Mn2(μ-Cl)2Cl2(tppz)2] (1), [Mn2Cl2(μ-N3-κN1)2(tppz)2] (2), [MnCl(SCN)(tppz)(H2O)]·H2O (3), [MnCl(dca)(tppz)(H2O)0.57(MeOH)0.47] (4), [Mn(NO3)2(tppz)(H2O)] (5), [Mn(N3)(NO3)(tppz)(H2O)] (6), [Mn(SCN)2(tppz)] (7) and [Mn(NO3)(dca)(tppz)]n (8) have been obtained. The compounds were characterized by elemental analysis, IR, EPR, magnetic measurements and X-ray analysis. Two of them (5 and 6) have been tested as catalysts in oxidation of alcohol to aldehydes/ketones using oxone (2KHSO5·KHSO4·K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature and as catalysts in oxidation of sulfides to sulfoxides with UHP (urea hydrogen peroxide) as oxidant.
Najafpour, M.M., C. Leonard, K., F. Fan, F. R., Amouzadeh Tabrizi, M., J. Bard, A., K. King’ondu, C., L. Suib, S., Haghighi, B., Allakhverdiev, S. I., "Nano-size layered manganese-calcium oxide as an efficient and biomimetic catalyst for water oxidation under acidic conditions: comparable to platinum.", Dalton Trans, 42, 5085-5091, (2013).
Abstract:
Inspired by Nature's catalyst, a nano-size layered manganese-calcium oxide showed a low overvoltage for water oxidation in acidic solutions, which is comparable to platinum.
Najafpour, M. M., Amouzadeh Tabrizi, M., Haghighi, B., Govindjee, ., "A 2-(2-hydroxyphenyl)-1H-benzimidazole–manganese oxide hybrid as a promising structural model for the tyrosine 161/histidine 190-manganese cluster in photosystem II ", Dalton Trans, 42, 879-884, (2013).
Abstract:
In this communication, we report the synthesis, characterization, and electrochemistry of a 2-(2-hydroxyphenyl)-1H-benzimidazole–manganese oxide hybrid. Our results suggest that this compound is a promising model for the manganese cluster together with tyrosine-161 and histidine-190 in photosystem II of plants, algae and cyanobacteria.
Najafpour, M.M., Barber,, J., Shen, J.R., Moore, G., Govindjee, ., "Running on sun", Chemistry World, 11, 43-43, (2012).
Abstract:
On the centenary of Giacomo Ciamician’s paper predicting a solar-fuelled future, five experts discuss the promise and challenges of artificial photosynthesis.
Najafpour , M. M., J. Sedigh, D., L. Suib, S., "Nano-sized manganese oxide-bovine serum albumin as a promising and biomimetic catalyst for water oxidation", RSC. Adv , 2, 11253-11257, (2012).
Abstract:
Nano-sized manganese oxide–bovine serum albumin was synthesized and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-vis, X-ray diffraction (XRD), infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), elemental mapping and transmission electron microscopy (TEM). The oxide shows water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. We used bovine serum albumin in the compound as a promising model for stabilizing proteins in photosystem II.
Najafpour, M. M., N. Moghaddam, M., "Amorphous manganese oxide-coated montmorillonite as an efficient catalyst for water oxidation", New J. Chem, 36, 2514-2519, (2012).
Abstract:
Amorphous manganese oxide-coated montmorillonite hybrids were synthesized and characterized by SEM, N2 adsorption–desorption isotherms, TEM, EDX, XRD, FTIR and AAS. The compounds show efficient water oxidation activity (0.22 mmol O2/mol Mn.s) with a turnover number of [similar]3 in 1 h in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Effects of manganese oxide content, calcination temperature, concentration of oxidant on the water oxidation activity of the compounds were studied and compared with other manganese oxides. The O2 evolution was analyzed by Yagi's kinetic model. The activation energy parameter, leaking of manganese ions into solution, and a cooperatively proposed mechanism for manganese oxide toward water oxidation were also reported for the hybrid.
Najafpour , M. M., N. Moghaddam, A., Yang, Y. N ., Aro , E. M., Carpentier , R., J. Eaton-Rye, J., Lee , C. H., Allakhverdiev, S. I., "Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.", Photosynth Res , 114, 1-13, (2012).
Abstract:
The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 Å resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.
Najafpour, M. M., "Biomineralization: a proposed evolutionary origin for inorganic cofactors of enzymes", Theory Biosci, 131, 265-272, (2012).
Abstract:
In this paper, three different reactions of nanoparticles and proteins are explained. As a model system, the interactions of birnessite, which is a common manganese oxide in the environment, and bovine serum albumin, as a protein that has a strong affinity for a variety of inorganic molecules, are studied. The author proposes that the cofactor-formation in particular enzymes may be considered as a biomineralization in the presence of the protein. One of the numerous and very small nanoparticles produced in the presence of protein could be formed in an appropriate location in proteins and be used as a primitive inorganic core (cofactor) of enzyme.
Najafpour, N. N., Hillier, W., Shamkhali, A. M., Amini, M., Beckmann, K., Jagličić, Z., Jagodič, M., Strauch, P., N. Moghaddam, A., "Synthesis, characterization, DFT studies and catalytic activities of manganese(ii) complex with 1,4-bis(2,2':6,2''-terpyridin-4'-yl) benzene.", Dalton Trans, 41, 12282-12288, (2012).
Abstract:
A new di-manganese complex with "back-to-back" 1,4-bis(2,2':6,2''-terpyridin-4'-yl) benzene ligation has been synthesized and characterised by a variety of techniques. The back-to-back ligation presents a novel new mononuclear manganese catalytic centre that functions as a heterogeneous catalysis for the evolution of oxygen in the presence of an exogenous oxidant. We discuss the synthesis and spectroscopic characterizations of this complex and propose a mechanism for oxygen evolution activity of the compound in the presence of oxone. The di-manganese complex also shows efficient and selective catalytic oxidation of sulfides in the presence of H(2)O(2). Density functional theory calculations were used to assess the structural optimization of the complex and a proposed reaction pathway with oxone. The calculations show that middle benzene ring is distorted respect to both of metallic centers, and this in turn leads to negligible resonance of electrons between two sides of complex. The calculations also indicate the unpaired electron located on oxyl-ligand emphasizes the radical mechanism of water oxidation for the system.
Najafpour, M. M., Rahimi, F., Aro, E. M., Lee, C. H., Allakhverdiev, S. I., "Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review ", J. R. Soc. Interface, 9, 2383-2395, (2012).
Abstract:
There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese-calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.
Najafpour, M. M., Pashaei, B., "Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst", Dalton Trans, 41, 10156-10160, (2012).
Abstract:
Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant.
Najafpour, M. M., Rahimi, F., Amini, M., Nayeri, S., Bagherzadeh, M., "Avery simple method to synthesize nano-sized manganese oxide: an efficient catalyst for water oxidation and epoxidation of olefins", Dalton Trans, 41, 11026-11031, (2012).
Abstract:
Nano-sized particles of manganese oxides have been prepared by a very simple and cheap process using a decomposing aqueous solution of manganese nitrate at 100 °C. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction spectrometry have been used to characterize the phase and the morphology of the manganese oxide. The nano-sized manganese oxide shows efficient catalytic activity toward water oxidation and the epoxidation of olefins in the presence of cerium(IV) ammonium nitrate and hydrogen peroxide, respectively.
Najafpour, M. M., N. Moghaddam, A., "Nano-sized manganese oxide: a proposed catalyst for water oxidation in the reaction of some manganese complexes and cerium(IV) ammonium nitrate", Dalton Trans, 41, 10292-10297, (2012).
Abstract:
According to UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy, nano-sized manganese oxides are proposed as active catalysts for water oxidation in the reaction of some manganese complexes and cerium(iv) ammonium nitrate.
Najafpour, M. M., Pashaei, B., Nayeri, S., "Nano-sized layered aluminium or zinc–manganese oxides as efficient water oxidizing catalysts", Dalton Trans , 41, 7134-7140, (2012).
Abstract:
Nano-sized layered aluminium or zinc–manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed.
Najafpour, M. M., N. Moghaddam, A., Allakhverdiev, S. I., Govindjee, ., "Biological water oxidation: Lessons from Nature (Invited Review)", BBA-Bioenergetics , 1817, 1110-1121, (2012).
Abstract:
Hydrogen production by water splitting may be an appealing solution for future energy needs. To evolve hydrogen efficiently in a sustainable manner, it is necessary first to synthesize what we may call a ‘super catalyst’ for water oxidation, which is the more challenging half reaction of water splitting. An efficient system for water oxidation exists in the water oxidizing complex in cyanobacteria, algae and plants; further, recently published data on the Manganese–calcium cluster have provided details on the mechanism and structure of the water oxidizing complex. Here, we have briefly reviewed the characteristics of the natural system from the standpoint of what we could learn from it to produce an efficient artificial system. In short, to design an efficient water oxidizing complex for artificial photosynthesis, we must learn and use wisely the knowledge about water oxidation and the water oxidizing complex in the natural system. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
Najafpour , M. M., Allakhverdiev, S. I., "Manganese compounds as water oxidizing catalysts for hydrogen production via water splitting: From manganese complexes to nano-sized manganese oxides", Int J Hydrogen Energ , 37, 8753-8764, (2012).
Abstract:
For hydrogen production by water splitting, the water oxidation half reaction is overwhelmingly rate limiting and needs high over-voltage (w1 V), which results in low conversion efficiencies when working at current densities required. At this high voltage, other chemicals will be also oxidized and this would be environmentally unacceptable for large-scale H2 production. In past few years, there has been a tremendous surge in research on the synthesis of various metal compounds aimed at the simulating water oxidizing complex of Photosystem II. Particular attention has been given to the manganese compounds not only because manganese has been used by Nature to oxidize water but also because manganese is cheap and environmentally friendly. In this review, we focus on manganese compounds as functional models of the water oxidizing complex of Photosystem II for hydrogen production via water splitting.
Amini, M., Najafpour, M. M., Nayeri, S., Pashaei, B., Bagherzadeh, M., "Nano-layered manganese oxides as low-cost, easily synthesized, environmentally friendly and efficient catalysts for epoxidation of olefins", RSC. Adv, 2, 3654-3657, (2012).
Abstract:
ncorporation of calcium( II ), zinc(II )andaluminium(III)to manganese oxides greatly improved the activity of manganese oxide towards the epoxidation of olefins in the presence of anhydrous tert -butyl hydroperoxide as an oxidant.
Najafpour, M. M., Pashaei, B., Nayeri, S., "Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation", Dalton Trans, 41, 4799-4805, (2012).
Abstract:
CaMnO3 and Ca2Mn3O8 were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H2O2. Oxygen evolution from water during irradiation with visible light (λ > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2′-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO3 and Ca2Mn3O8 in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered.
Najafpour, M. M., Amouzadeh Tabrizi, M., Haghighi, B., Govindjee, ., "A manganese oxide with phenol groups as a promising structural model for water oxidizing complex in Photosystem II: a ‘golden fish ", Dalton Trans, 41, 3906-3910, (2012).
Abstract:
We describe here the ability of manganese oxide monosheets to aggregate to form layered structures with 4-aminophenol molecules. These aggregated monosheets could be considered as the first step to synthesize a self-assembled layered hybrid of phenol–manganese ions with phenol and manganese(III) and (IV) as exists in the water oxidizing complex of Photosystem II.
Najafpour , M. M., Hołyn´ska, M., Shamkhali, A. N., Amini, M., Kazemi , S. H., Zaynalpoor , S., Mohamadi , R., Bagherzadeh , M., Lis , T., "New mononuclear manganese(II) complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) – selective catalyst in UHP oxidation of sulfides", Polyhedron, 34, 202-209, (2012).
Abstract:
A new manganese complex of the formula [Mn(tptz)(OH2)3](CF3SO3)2_EtOH, (1, where tptz = (2,4,6-tris(2- pyridyl)-1,3,5-triazine) is presented, exhibiting an excellent catalytic activity and selectivity in oxidation of various sulfides to the corresponding sulfoxides with UHP (urea hydrogen peroxide) as oxidant under air at room temperature. A modified preparation procedure produces another new manganese complex of the formula [Mn(tptz)(CH3COO)(OH2)2](CF3SO3)_3H2O (2). X-ray structures of both Mn(II) complexes, properties (elemental analysis, electrochemistry, EPR, IR, Raman, and UV–Vis spectra), as well as DFT studies results are reported.
Najafpour, M .M., "Hollandite as a Functional and Structural Model for the Biological Water Oxidizing Complex: Manganese-Calcium Oxide Minerals as a Possible Evolutionary Origin for the CaMn4 Cluster of the Biological Water Oxidizing Complex", Geomicrobiol J , 28, 714-718, (2011).
Abstract:
Oxygen evolution was observed upon mixing either hollandite, which has been proposed as a structural model for the biological water oxidizing complex, or hausmannite with an aqueous solution of cerium (IV) ammonium nitrate. Oxygen evolution from water during irradiationwith visible light (λ>400 nm) was also observed upon adding either hollandite or hausmannite to an aqueous solution containing tris (2,2_-bipyridyl)ruthenium(II) chloride and chloro pentaammine cobalt(III) chloride in acetate buffer. These experiments showed that hollandite is a good catalyst for oxygen evolution in presence of cerium (IV) ammonium nitrate or tris (2,2_-bipyridyl)ruthenium (III). Thus, hollandite is not only a structural but also a functional model for the biological water oxidizing complex. Supplemental materials are available for this article. Go to the publisher’s online edition of Geomicrobiology Journal to view the free supplemental file.
Najafpour, M .M., "Self-assembled layered hybrid [Ru(bpy)3]2+/manganese(III,IV) oxide: a new and efficient strategy for water oxidation", Chem. Commun, 47, 11724-11726, (2011).
Abstract:
For the first time, a self-assembled layered hybrid [Ru(bpy)3]2+/manganese(III,IV) as a water oxidizing system is reported.
Najafpour, M. M., Nayeri, S., Pashaei, B., "Nano-size amorphous calcium–manganese oxide as an efficient and biomimetic water oxidizing catalyst for artificial photosynthesis: back to manganese ", Dalton Trans, 40, 9374-9378, (2011).
Abstract:
A nano-size amorphous calcium–manganese oxide shows efficient water oxidation activity in the presence of cerium(IV) ammonium nitrate.
Zaharieva, I., Najafpour, M. M., Wiechen, M., Haumann, M., Kurz, Ph., Dau, H., "Synthetic manganese–calcium oxides mimic the water-oxidizing complex of photosynthesis functionally and structurally", Energy Environ. Sci., 4, 2400-2408, (2011).
Abstract:
In theworldwide search for sustainable energy technologies,water oxidationby abundant low-cost materials is of key importance. In nature, this process is efficiently catalyzed by an intricatemanganese–calcium (Mn4Ca) complex bound to the proteins of photosystem II (PSII). Recently synthetic manganese–calciumoxides were found to be active catalysts of water oxidation but at the atomic level their structure has remained elusive. To investigate these amorphous catalysts, extended-range X-ray absorption spectroscopy (XAS) at the K-edges of both manganese and calcium was performed. The XAS results reveal! striking similarities between the syntheticmaterial and the naturalMn4Ca complex. The oxidation state ofmanganese in the active oxides was found to be close to+4, butMnIII ions are present as well at a level of about 20%. NeighboringMn ions are extensively interconnected by two bridging oxygens, a characteristic feature of layered manganese oxides. However, the oxides do not exhibit long-range order, as opposed to canonical, but catalytically inactiveMnIII- or MnIV-oxides. Two different Ca-containing motifs were identified. One of them results in the formation of Mn3CaO4 cubes, as also proposed for the natural paragon in PSII. Other calcium ions likely interconnect oxide-layer fragments.We conclude that these readily synthesized manganese–calcium oxides are the closest structural and functional analogs to the native PSII catalyst found so far. Evolutionary implications are considered. From the differences to inactive manganese oxides, we infer structural features facilitating the catalysis of water oxidation in both the protein-boundMn4Ca complex of PSII and in the synthetic oxides.
Najafpour, M. M., Hillier, W., Lashgari, M., Matloubi, D., "Oxygen Production of Peroxomomosulphate Induced by Cobalt(II)", Int. Rev. Biophys. Chem. (IREBIC)(Invited paper), 2: (1), 9-14, (2011).
Najafpour, M. M., Govindjee, ., "Oxygen evolving complex in Photosystem II: Better than excellent ", Dalton Trans (PERSPECTIVE), 40, 9076-9084, (2011).
Abstract:
The Oxygen Evolving Complex in photosystem II, which is responsible for the oxidation of water to oxygen in plants, algae and cyanobacteria, contains a cluster of one calcium and four manganese atoms. This cluster serves as a model for the splitting of water by energy obtained from sunlight. The recent published data on the mechanism and the structure of photosystem II provide a detailed architecture of the oxygen-evolving complex and the surrounding amino acids. Biomimetically, we expect to learn some strategies from this natural system to synthesize an efficient catalyst for water oxidation, that is necessary for artificial photosynthesis
Najafpour, M. M., "Calcium-Manganese Oxides as Structural and Functional Models for Active Site in Oxygen Evolving Complex in Photosystem II: Lessons From Simple Models", J. Photochem. Photobio. B: Biology (Invited Paper), 104, 111-117, (2011).
Abstract:
The oxygen evolving complex in photosystem II which induces the oxidation of water to dioxygen in plants, algae and certain bacteria contains a cluster of one calcium and four manganese ions. It serves as a model to split water by sunlight. Reports on the mechanism and structure of photosystem II provide a more detailed architecture of the oxygen evolving complex and the surrounding amino acids. One challenge in this field is the development of artificial model compounds to study oxygen evolution reaction outside the complicated environment of the enzyme. Calcium-manganese oxides as structural and functional models for the active site of photosystem II are explained and reviewed in this paper. Because of related structures of these calcium-manganese oxides and the catalytic centers of active site of the oxygen evolving complex of photosystem II, the study may help to understand more about mechanism of oxygen evolution by the oxygen evolving complex of photosystem II.
Shevela, D., Koroidov, S., Najafpour, M. M., Messinger, J., Kurz, Ph., "Calcium Manganese Oxides as Oxygen Evolution Catalysts: O2 Formation Pathways Indicated by 18O-Labelling Studies", Chem. Eur. J., 17, 5415-5423, (2011).
Abstract:
Oxygen evolution catalysed by calcium manganese and manganeseonly oxides was studied in 18O-enriched water. Using membrane-inlet mass spectrometry, we monitored the formation of the different O2 isotopologues 16O2, 16O18O and 18O2 in such reactions simultaneously with good time resolution. From the analysis of the data, we conclude that entirely different pathways of dioxygen formation catalysis exist for reactions involving hydrogen peroxide (H2O2), hydrogen persulfate (HSO5) or single-electron oxidants such as CeIV and [RuIIIACHTUNGTRENUNG(bipy)3]3+. Like the studied oxide catalysts, the active sites of manganese catalase and the oxygen-evolving complex (OEC) of photosystem II (PSII) consist of moxido manganese or m-oxido calcium manganese sites. The studied processes show very similar 18O-labelling behaviour to the natural enzymes and are therefore interesting model systems for in vivo oxygen formation by manganese metalloenzymes such as PSII.
Najafpour, M.M., "A Soluble form of Nano-Sized Colloidal Manganese(IV) Oxide as an Efficient Catalyst for Water Oxidation†", Dalton Trans., 40, 3805-3807, (2011).
Abstract:
A soluble form of colloidal manganese(IV) oxide showed efficient oxygen evolution or water oxidation in presence of oxone, H2O2, cerium(IV) ammonium nitrate and tris(2,2¢- bipyridyl)ruthenium(III).
Najafpour, M. M., "Mixed-Valence Manganese Calcium Oxides as Efficient Catalysts for Water Oxidation", Dalton Trans., 40, 3793-3795, (2011).
Abstract:
Incorporation of calcium to mixed-valencemanganese oxides improved the water oxidation activity of these manganese oxides
Bagherzadeh, M., Amini, M., M. Boghaei, D., Najafpour, M .M., McKee, V., "Synthesis, X-ray structure, characterization and catalytic activity of a polymeric manganese(II) complex with iminodiacetate", Appl. Organometal. Chem., 25, 559-563, (2011).
Abstract:
A polymeric manganese(II) complex with the general formula [Mn(O2CCH2NH2CH2CO2)2(H2O)2]n from reaction of iminodiacetatic acid and manganese(II) perchlorate under nitrogen in water, was synthesized and characterized. The structure of the complexwas determined using single-crystalX-ray diffraction, elemental analysis, IR andUV-vis spectra. This complex exhibited excellent catalytic activity and selectivity for oxidation of various alcohols and sulfides to the corresponding aldehydes/ketone and sulfoxides using urea hydrogen peroxide and oxone (2KHSO5·KHSO4·K2SO4), respectively, as oxidants und! er airat room temperature. The easy preparation,mild reaction conditions, high yields of the products, short reaction time, no over-oxidation products, high selectivity and inexpensive system make this catalytic system a useful method for oxidizing various alcohols and sulfides. Copyrightc 2011 JohnWiley & Sons, Ltd.
Najafpour, M. M., Kozlevčar, B., McKee, V., Jagličić, Z., Jagodič, M., "The First Pentanuclear Heterobimetallic Coordination Cation with CeIII, CeIV and MnII", Inorgan. Chem. Commun., 14, 125-127, (2011).
Abstract:
[Mn2(μ-dipic)2(H2O)6]·2H2dipic (dipic=dipicolinate) reacts with (NH4)2[Ce(NO3)6] to produce the pentanuclear coordination species in [MnCe4(μ-dipic)6(H2O)20] Ce(dipic)3]2·11H2O (1). The coordination anion [Ce(dipic)]2− is formed by three tridentate O,N,O dipicolinate(2−) anionic ligands around the metal CeIV cation. The same pattern is found for two CeIV in the pentanuclear CeIII/CeIV/MnII/CeIV/CeIII chain-like coordination cation [MnCe4(μ-dipic)6(H2O)20]4+. The CeIV(dipic)3 moieties in the cation coordinatively bridge the terminal CeIII(H2O)8 with the central MnII(H2O)4 units. Each manganese(II) ion is thus 6-coordinated and each cerium(III, IV) ion is 9-coordinated. During the synthesis of 1, the gaseous dioxygen is evolved, due to water oxidation that is attributed to the presence of Ce and Mn in different oxidation states.
Najafpour, M. M., "Amorphous Manganese-Calcium Oxides as a Possible Evolutionary Origin for the CaMn4 Cluster in Photosystem II", Orig Life Evol Biosph, 41, 237-247, (2011).
Abstract:
In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation. The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of edge-sharing Mn3+ in a distorted octahedral environment and eight-coordinate Ca2+ centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus, the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally. Also in this paper, oxygen evolution is studied with marokite (CaMn2O4), pyrolusite (MnO2) and compared with hollandite 0.2Ca0.15K0.3Mn6.9Al0.2Si0.3O16), hausmannite (Mn3O4), Mn2O3.H2O, CaMn3O6.H2O, CaMn4O8.H2O, CaMn2O4.H2O and synthetic marokite (CaMn2O4). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10. As reported in this paper, amorphous calcium-manganese oxides with different ratios of anganese and calcium are effective catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II.
Najafpour, M. M., Hołynska, M., Amini , M., Kazemi, S. H., Lis, T., Bagherzadeh , M., "Two New Silver(I) Complexes with 2,4,6-Tris(2-pyridyl)-1,3,5-Triazine (tptz): Preparation, Characterization, Crystal Structure and Alcohol Oxidation Activity in the Presence of Oxone", Polyhedron, 29, 2837-2843, (2010).
Abstract:
Two new silver(I) complexes ((tptz)Ag2(NO3)2 and [Ag5(tptz)4](NO3)5) with 2,4,6-tris(2-pyridyl)-1,3,5- riazine (tptz) have been synthesized and characterized by X-ray diffraction, elemental analysis, 1H NMR, IR, fluorescence, UV–Vis spectroscopy and electrochemistry. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted with one of the Ag complexes as a catalyst, soluble enough in organic solvent, using oxone (2KHSO5KHSO4K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature.
Najafpour, M. M., M. Boghaei, D., McKee, V., "Synthesis, Characterization, Crystal Structure and Oxygen-Evolution Activity of a Manganese(II) Complex with 2,4,6-Tris (2-pyridyl)-1,3,5-Triazine", Polyhedron, 29, 3246-3250, (2010).
Abstract:
The title complex [Mn(tptz)(CH3COO)(OH2)2]NO3 was synthesized through the reaction of tptz (2,4, 6-tris(2-pyridyl)-1,3,5-triazine), nitric acid and manganese(II) acetate. The molecular structure was characterized by X-ray diffraction, elemental analysis, electrochemistry, EPR, IR, fluorescence and UV–Vis spectroscopy and its oxygen evolving activity has been studied. X-ray structure analysis shows that each Mn(II) ion is seven coordinated by a bidentate acetate, three nitrogen atoms of tptz and two oxygen atoms from two water ligands, which are coordinated in axial positions. The complex acts as an oxygen evolving complex with oxone (2KHSO5KHSO4K2SO4) as primary oxidant in aqueous solution with a turnover number of 1 (mol of O2/mol of the complex). Kinetic studies revealed a first-order dependence on the complex and oxidant. The EPR spectrum shows that the mononuclear complex oxidize to a MnIII,IV 2 di-l-oxo by oxone.
Najafpour, M. M., McKee, V., "A dinuclear manganese(II) complex with 2,6-pyridinedicarboxylate: Preparation, crystal structure and oxygen evolution activity in the presence of oxone", Catal. Commun., 11, 1032-1035, (2010).
Abstract:
A dinuclear complex of Mn(II) with 2,6-pyridinedicarboxylate, [Mn2(dipic)2(H2O)6].2H2dipic, where dipic=2,6-pyridinedicarboxylate, has been synthesized and characterized by elemental analysis, IR, EPR, electronic absorption spectroscopy, electrochemistry and single-crystal X-ray diffraction. The complex acts as an oxygen evolving complex with oxone (2KHSO5.KHSO4 .K2SO4) as primary oxidant in aqueous solution with a turnover number of ∼5 (mol of O2/mol of the complex).
Najafpour, M. M., Ehrenberg, T., Kurz, M. W. P., "Calcium-Mangan(III)-Oxide (CaMn2O4·xH2O) Als Biomimetische Katalysatoren fur Die Sauerstoffbildung", Angew. Chem., 2281 -2285, (2010).
Najafpour, M. M., Ehrenberg, T., Wiechen, M., Kurz, P., "Calcium Manganese(III) Oxides (CaMn2O4·xH2O) as Biomimetic Oxygen-Evolving Catalysts", Angew. Chem. Int. Ed,(Hot Paper), 49, 2233-2237, (2010).
Najafpour, M. M., M. Boghaei, D., Sjöberg, J. R., "Solution Structure of a Seven Coordinated Manganese(II)Complex Via Electrospray Ionization Mass Spectrometry", Spectrochimica Acta Part A, 75, 1168-1170, (2010).
Abstract:
The mononuclear complex [Mn(tptz)(CH3COO)(OH2)2]NO3 (1) was investigated by electrospray ionization mass spectrometry in aqueous solution at pH 4.5. Electrospray ionization mass spectrometry shows that mononuclear and dinuclear manganese cationic species are present in solution, probably in equilibrium with neutral 1. An experiment showed that the most important reaction in the presence of oxone (2KHSO5·KHSO4·K2SO4) is decoordination.
Najafpour, M. M., Amini, M., Bagherzadeh, M., M. Boghaei, D., McKee, V., "Synthesis, Structural Characterization and Alcohol Oxidation Activity of a New Mononuclear Manganese(II) Complex", Transition Met. Chem., 35, 297-303, (2010).
Abstract:
A manganese(II) complex of 2,4,6-tris(2-pyridyl)- 1,3,5-triazine (tptz) has been synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR, and UV–Vis spectroscopic techniques. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this catalyst using oxone (2KHSO5KHSO4 K2SO4) as an oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature. Easy preparation, mild reaction conditions, high yields of the products, short reaction times, no further oxidation to the corresponding carboxylic acids, high selectivity and inexpensive reagents make this catalytic system a useful oxidation method for aliphatic and benzylic alcohols.
Hou, H. J. M., Najafpour, M. M., Moore, G. F., Allakhverdiev, S. I (Editors)., "Photosynthesis: Structures, Mechanisms, and Applications", Springer, ISBN: 978-3-319-48871-4, 1-424, (2017).
Najafpour, M. M., Hou, H. J. M., Allakhverdiev, S. I ., "Photosynthesis: Natural Nanomachines Toward Energy and Food Production", Springer, ISBN: 978-3-319-48871-4, Chapter 1, 1-9, (2017).
Najafpour, M. M., Salimi, S., Holynska, M., Rahimi, F., Tavahodi, M., Tomo, T., Allakhverdiev, S. I., "Nanostructured Mn Oxide/Carboxylic Acid or Amine Functionalized Carbon Nanotubes as Water-Oxidizing Composites in Artificial Photosynthesis", Springer, ISBN: 978-3-319-48871-4, chapter 15, 321-332, (2017).
Najafpour, M. M., Balaghi, S. E., Hossaini Sadr, M., Soltani, B., Sedigh, D. J., Allakhverdiev, S. I., "Self-Healing in Nano-sized Manganese-Based Water-Oxidizing Catalysts", Springer, ISBN: 978-3-319-48871-4, chapter 16, 333-341, (2017).
Najafpour, M. M., "Applied Photosynthesis: New Progress", INTECH, ISBN 978-953-51-2267-8, 1-219, (2016).
Poudyal, R. S., Tiwari, I., Najafpour, M. M., Los , D. A., Shen, J.- R., Allakhverdiev, S., "Current Insights to Enhance Hydrogen Production by Photosynthetic Organisms in Hydrogen Science and Engineering", Wiley, ISBN: 978-184-80-0392-7, Chapter 20, 461-487, (2016).
Najafpour, M. M., Heidari, M. M., Abasi, S., Khatamian, M., Allakhverdiev, S. I., "Layered Manganese Oxides as Water-Oxidizing Catalysts for Hydrogen Production via Water Splitting—An Aid to Environmental Protection, CRC Concise Encyclopedia of Nanotechnology", CRC Press, ISBN: 97-814-665-8034-3, Chapter, 1121-1131, (2015).
Poudyal, R. S., Tiwari, I., Koirala, A. R., Masukawa, H., Inoue, K., Tomo, T., Najafpour, M. M., Allakhverdiev, S., Veziroglu, T. N., "Hydrogen production using photobiological methods", Compendium of Compendium of Hydrogen Energy, Elsevier, ISBN: 978-1-78242-361-4, Chapter 10 , 289-317, (2015).
Abstract:
Production of photobiological hydrogen by microorganisms has been an active field of research for many years. The experimental process for generating photobiological hydrogen from water using solar energy has become a major novel source of sustainable and renewable production of hydrogen gas without greenhouse gases emissions or environmental pollutants. Hence, this method is considered a future alternative source of energy. Several methods have been developed to generate hydrogen gas; among them, the generation of photobiological hydrogen is one of the most important and easy methods. In addition, photobiological methods easily achieve the efficiency of solar energy conversion, which may be economically feasible in the future. As we know, several microorganisms such as algae, cyanobacteria, bacteria, and even higher plants have the capacity to produce biohydrogen in the presence of sunlight. Hence, based on current and previous research, we briefly review the different strategies for renewable photobiological and artificial hydrogen production as well as its significance for a multidisciplinary approach.
Najafpour, M. M., J. Sedigh, D., J. Eaton-Rye, J., Allakhverdiev, S. I., "The Water-Oxidizing Complex in Photosystem II", Photosynthesis: Open Questions and What We Know Today: Vol. I / Eds. S. I. Allakhverdiev, A. B. Rubin, V. A. Shuvalov.— Moscow–Izhevsk: Izhevsk Institute of Computer Science, Chapter 10, (Book Chapter), 1, 325-341, (2014).
Abstract:
Life on our planet is driven by PhotosystemII (PS II) that captures sunlight and extracts electrons from H 2O to reduce CO2 into sugars while releasing the O we breathe In this chapter the origin of the water-oxidizing complex (WOC) of PS II is discussed and the structure of the WOC and its ligand environment are described with reference to the 1.9-2˚ A resolution X-ray- derived crystallographic model of PS II from the cyanobacterium Thermosynechococcus vulcanus (Umena et al., Nature, 2011, 473: 55-61). Throughout key advances and outstanding questions regarding the structure and mechanism of the WOC are emphasized.
Hou, H. J. M., Allakhverdiev, S. I., Najafpour, M. M., Govindjee, ., "Current challenges in photosynthesis: from natural to artificial (Book Chapter) ", 1st ed.; Edited by Hou, H. J. M., Allakhverdiev, S. I., Najafpour, M. M., Govindjee, Chapt. 1, FRONTIERS, 5, 5-7, (2014).
Najafpour, M. M., "NaNomaterials for eNviroNmeNtal ProtectioN", Edited by Boris I. Kharisov, Oxana V. Kharissova, H. V. Rasika Dias,ISBN 978-1-118-84535-6– ISBN 978-1-118-84554-7 (epub) – ISBN 978-1-118-49697-8 John Wiley & Sons, Inc., Hoboken, New Jersey , Chapter 25, 429-442, (2014).
Najafpour, M.M., N. Moghaddam, A., Shen, J. R., Govindjee, ., "Water Oxidation and Water Oxidizing Complex in Cyanobacteria, Stress Biology of Cyanobacteria: Molecular Mechanisms to Cellular Responses ", Editors: A. Kumar Srivastava, A. Nath Rai, B. A. Neilan, ISBN-13: 978-1466504783, Chapter 2, (Invited Book Chapter)., 41-59, (2013).
Najafpour, M. M. (Editor)., "APPLIED PHOTOSYNTHESIS ", In Tech Publications, Hard cover, ISBN: 978-953-51-0061-4, 1-422, (2012).
Najafpour, M. M., "Manganese Compounds as Water Oxidizing Catalysts in Artificial Photosynthesis Book Chapter in Artificial Photosynthesis ", In Tech Publications, ISBN: 978-953-307-966-0. Chapter Three, 37-52, (2012).
Najafpour, M. M., Nayeri, S., "Gathering Light: Artificial Photosynthesis Book Chapter in Artificial Photosynthesis ", In Tech Publications, ISBN: 978-953-307-966-0. Chapter one, 3-10, (2012).
Najafpour, M. M. (Editor)., "Artificial Photosynthesis", In Tech Publications, Hard cover, ISBN: 978-953-307-966-0, 1-288, (2012).
Najafpour, M. M., Pashaei, B., "Photosynthesis: How and Why? Book Chapter in Advances in Photosynthesis- Fundamental Aspects (Book)", In Tech Publications, ISBN: 978-953-307-928-8.Chapter one., 3-12, (2012).
Abstract:
The total solar energy absorbed by Earth is approximately 3,850,000 exajoules per year. This was more energy in one hour than the world used in one year! Nature uses very wonderful and interesting strategies to capture the energy in an interesting process: Photosynthesis. To know more about photosynthesis, the first we should know about phototrophy. Phototrophy is the process by which organisms trap photons and store energy as chemical energy in the form of adenosine triphosphate (ATP). ATP transports chemical energy within cells for metabolism. There are three major types of phototrophy: Oxygenic and Anoxygenic photosynthesis, and Rhodopsin-based phototrophy. Photosynthesis is a chemical process that converts carbon dioxide into different organic compounds using solar energy. Oxygenic and anoxygenic photosynthesis undergo different reactions in the presence and absence of light (called light and dark reactions, respectively). In anoxygenic photosynthesis, light energy is captured and stored as ATP, without the production of oxygen. This means water is not used as primary electron donor. Phototrophic green bacteria, phototrophic purple bacteria, and heliobacteria are three groups of bacteria that use anoxygenic photosynthesis. Anoxygenic phototrophs have photosynthetic pigments called bacteriochlorophylls. Bacteriochlorophyll a and b have maxima wavelength absorption at 775 nm and 790 nm, respectively in ether. Unlike oxygenic phototrophs, anoxygenic photosynthesis only functions using a single photosystem. This restricts them to cyclic electron flow only, and they are therefore unable to produce O2 from the oxidization of H2O. In plants, algae and cyanobacteria, the photosynthetic processes results not only in the fixation of carbon dioxide (CO2) from the atmosphere but also release of molecular oxygen to the atmosphere. This process is known as oxygenic photosynthesis.
Najafpour, M. M. (Editor)., "Advances in Photosynthesis: Fundamental Aspects (Book)", In Tech Publications, Hard cover, ISBN: 978-953-307-928-8, 1-598, (2012).
