Download or read book Elucidation of Photoinduced Energy and Electron Transfer Mechanisms in Multimodular Artificial Photosynthetic Systems written by Gary Lloyd Nogra Lim and published by . This book was released on 2017 with total page 361 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multimodular designs of electron donor-acceptor systems are the ultimate strategy in fabricating antenna-reaction center mimics for artificial photosynthetic applications. The studied photosystems clearly demonstrated efficient energy transfer from the antenna system to the primary electron donor, and charge stabilization of the radical ion pair achieved with the utilization of secondary electron donors that permits either electron migration or hole transfer. Moreover, the molecular arrangement of the photoactive components also influences the route of energy and electron transfer as observed from the aluminum(III) porphyrin-based photosystems. Furthermore, modulation of the photophysical and electronic properties of these photoactive units were illustrated from the thio-aryl substitution of subphthalocyanines yielding red-shifted Q bands of the said chromophore; hence, regulating the rate of charge separation and recombination in the subphthalocyanine-fullerene conjugates. These multicomponent photosystems has the potential to absorb the entire UV-visible-NIR spectrum of the light energy allowing maximum light-harvesting capability. Furthermore, it permits charge stabilization of the radical ion pair enabling the utilization of the transferred electron/s to be used by water oxidizing and proton reducing catalysts in full-scale artificial photosynthetic apparatuses.
Download or read book Molecular Level Artificial Photosynthetic Materials Volume 44 written by Gerald J. Meyer and published by John Wiley & Sons. This book was released on 2009-09-17 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discover the exciting, promising field of molecular level artificial photosynthesis This special volume of Progress in Inorganic Chemistry presents the theory and practice of molecular artificial photosynthesis-a field holding tremendous promise now that molecular solar energy materials are fast becoming competitive with their solid-state counterparts. The only book on the market to address this important area of inorganic research, Molecular Level Artificial Photosynthetic Materials shows us, in effect, how to imitate the complex natural processes of photosynthesis-featuring state-of-the-art strategies and techniques for creating artificial photosynthetic devices at the molecular level. It takes a multidisciplinary approach, drawing on materials science techniques used in the design of solar energy devices, examining the molecular nature of the chemistry involved, and applying existing knowledge in inorganic photochemistry and photophysics to the growing pool of molecular photonic materials. Composed of seven superbly crafted contributions by leading experts in the field, this comprehensive work * Describes molecular components integrated within nanophase materials, gels, zeolites, thin films, and layered solids * Uses novel time resolved vibrational spectroscopies to elucidate fundamental electron and energy transfer mechanisms in complex supramolecular compounds * Highlights practical applications such as the conversion of light into electricity, solar detoxification of pollutants, and the production of useful fuels-including the splitting of water into hydrogen and oxygen * Points to areas of future research and usefulness for inorganic photochemists, as well as for students, chemists, material scientists, physicists, and engineers in a wide range of fields
Download or read book Molecules for Energy and Charge Transfer for Biomimetic Systems written by Marely Tejeda Ferrari and published by . This book was released on 2016 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sunlight, the most abundant source of energy available, is diffuse and intermittent; therefore it needs to be stored in chemical bonds in order to be used anytime. Photosynthesis converts sunlight into useful chemical energy that organisms can use for their functions. Artificial photosynthesis aims to use the essential chemistry of natural photosynthesis to harvest solar energy and convert it into fuels such as hydrogen gas. By splitting water, tandem photoelectrochemical solar cells (PESC) can produce hydrogen gas, which can be stored and used as fuel. Understanding the mechanisms of photosynthesis, such as photoinduced electron transfer, proton-coupled electron transfer (PCET) and energy transfer (singlet-singlet and triplet-triplet) can provide a detailed knowledge of those processes which can later be applied to the design of artificial photosynthetic systems. This dissertation has three main research projects. The first part focuses on design, synthesis and characterization of suitable photosensitizers for tandem cells. Different factors that can influence the performance of the photosensitizers in PESC and the attachment and use of a biomimetic electron relay to a water oxidation catalyst are explored. The second part studies PCET, using Nuclear Magnetic Resonance and computational chemistry to elucidate the structure and stability of tautomers that comprise biomimetic electron relays, focusing on the formation of intramolecular hydrogen bonds. The third part of this dissertation uses computational calculations to understand triplet-triplet energy transfer and the mechanism of quenching of the excited singlet state of phthalocyanines in antenna models by covalently attached carotenoids.
Download or read book Dynamics and Mechanisms of Photoinduced Electron Transfer and Related Phenomena written by N. Mataga and published by Elsevier. This book was released on 2012-12-02 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains papers which examine fundamental aspects of photoinduced electron transfer reactions, an area in which a number of breakthroughs have recently occurred. The book is divided into four parts. Parts I and II are mainly concerned with the fundamental aspects of the inter- and intra-molecular charge transfer, electron transfer and related phenomena such as solvent effects, solvation dynamics, energy gap dependences and radical pair dynamics. Part III is concerned with electron transfer and energy transfer phenomena in polymers, films, crystals, and other confined systems. In Part IV, the mechanisms of the energy and electron transfer in biological photosynthetic systems, proteins and reaction center systems are discussed.
Download or read book Molecular Level Artificial Photosynthetic Materials Volume 44 written by Gerald J. Meyer and published by Wiley-Interscience. This book was released on 1996-10-16 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discover the exciting, promising field of molecular level artificial photosynthesis This special volume of Progress in Inorganic Chemistry presents the theory and practice of molecular artificial photosynthesis-a field holding tremendous promise now that molecular solar energy materials are fast becoming competitive with their solid-state counterparts. The only book on the market to address this important area of inorganic research, Molecular Level Artificial Photosynthetic Materials shows us, in effect, how to imitate the complex natural processes of photosynthesis-featuring state-of-the-art strategies and techniques for creating artificial photosynthetic devices at the molecular level. It takes a multidisciplinary approach, drawing on materials science techniques used in the design of solar energy devices, examining the molecular nature of the chemistry involved, and applying existing knowledge in inorganic photochemistry and photophysics to the growing pool of molecular photonic materials. Composed of seven superbly crafted contributions by leading experts in the field, this comprehensive work * Describes molecular components integrated within nanophase materials, gels, zeolites, thin films, and layered solids * Uses novel time resolved vibrational spectroscopies to elucidate fundamental electron and energy transfer mechanisms in complex supramolecular compounds * Highlights practical applications such as the conversion of light into electricity, solar detoxification of pollutants, and the production of useful fuels-including the splitting of water into hydrogen and oxygen * Points to areas of future research and usefulness for inorganic photochemists, as well as for students, chemists, material scientists, physicists, and engineers in a wide range of fields
Download or read book Photoinduced Electron Transfer III written by Marye Anne Fox and published by Springer. This book was released on 1991 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultrafast Photoinduced Energy and Electron Transfer Studies in Closely Bound Molecular and Nanocarbon Donor Acceptor Systems written by Habtom Berhane Gobeze and published by . This book was released on 2018 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of the study, photosynthetic system constructs based on BF2-chelated dipyrromethene (BODIPY), BF2-chelated azadipyrromethene (AzaBODIPY), porphyrin, phthalocyanine, oxasmaragdyrin, polythiophene, fullerene (C60), single-walled carbon nanotube and graphene are investigated. Antenna systems of BODIPY dyads and oligomers having BODIPY as an excitation energy donor connected to different acceptors including BODIPY, azaBODIPY, oxasmaragdyrin and aluminum porphyrin are studied. Different synthetic methodologies are used to afford donor-acceptor systems either directly linked with no spacer or with short spacers of varying length and orientation. The effect of donor orientation, donor optical gap as well as nature of donor-acceptor coupling on the donor-acceptor spectral overlap and hence the rate of excitation energy transfer is investigated. In all these systems, an ultrafast energy transfer followed by electron transfer is observed. In particular, in a directly connected BODIPY-azaBODIPY dyad an unusually ultrafast energy transfer (̃ 150−200 f̧ ' ) via F©œrster mechanism is observed. The observation of energy transfer via F©œrster instead of Dexter mechanism in such closely coupled donor-acceptor systems shows the balance between spatial and electronic coupling achieved in the donor-acceptor system. Moreover, in donor-acceptor systems involving semiconducting 1D and 2D materials, covalently functionalized single-walled carbon nanotubes via charge stabilizing (TPA)3ZnP and noncovalently hybridized exfoliated graphene via polythiophene chromophores are studied for their charge transportation functions. In both cases, not only an ultrafast charge transfer in the range of (̃ 2−5 p̧ ' ) is observed but also the charge-separated states were long lived implying the potential of these functionalized materials as efficient charge transporting substrates with organic chromophores for photovoltaic and optoelectronic applications where ultrafast intercomponent charge transfer is vital. In addition, as a final part of this dissertation, the mechanisms of electron injection and back electron transfer in heterogeneous systems involving supramolecularly anchored high potential chromophores on TiO2 film are studied by femtosecond transient absorption spectroscopy. In this study, not only are important insights gained on the utilization of supramolecular anchoring of chromophores such as porphyrins, phthalocyanines, and their perflorinated high potential analogues, chromophores currently showing promise as highly efficient sensitizers in dye sensitized solar cells, on TiO2 film but also on the effect of anchor length and sensitizer orientation on the rates of electron injection and back electron transfer at the sensitizer-TiO2 interface.
Download or read book High Energy Long Lived Charge Separated States Via Molecular Engineering of Triplet State Donor Acceptor Systems written by Christopher O. Obondi and published by . This book was released on 2018 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an 'antenna' system causing an electron transfer into the 'reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy. In this dissertation, we report on the design and synthesis of donor-acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the greatest amount of energy but must be fast to out compete intersystem crossing. To address this limitation, we have designed novel donor -acceptor conjugates that use high-energy triplet sensitizers in which electron transfer is initiated from the long lived triplet state of the donor. The triplet photosensitizers used were palladium(II) porphyrin and platinum(II) porphyrin. Heavy metal effect in these porphyrins promoted intersystem crossing and the energies of their excited state was quite high. For the case of palladium (II) porphyrin the energy stored was found to 1.89 eV and that of platinum(II) porphyrin 1.84 eV. In addition to using triplet photosensitizers as donors, we have used donors that are difficult to oxidize and hence producing long lived charge separated states with adequate amount of stored energy. The system that was used for this study is zinc porphyrin with meso-aryl pentafluorophenyl substituents and fullerene, C60 as the acceptor. The presence of fluorine substituents on zinc porphyrin makes it harder to undergo oxidation. When this high potential donor-acceptor system undergoes a photoinduced charge-separation, the estimated energy stored was found to be 1.70 eV, one of the highest reported in literature so far. To further extend the lifetime of the charge separated states generated in this high-potential zinc porphyrin-fullerene dyad a pyridine functionalized tetrathiafulvalene was axially coordinated to the Zn metal producing a supramolecular triad capable of producing long-lived charge separated state. In a subsequent study, a multi-modular donor-acceptor system composed of a porphyrin, fullerene (C60) and a BF2-chelated dipyrromethene (BODIPY) with a supramolecular arrangement in the form of porphyrin-BODIPY-C60, one of the few reported in literature. By selectively exciting BODIPY and ZnP moieties, efficient singlet-singlet energy transfer from 1BODIPY * to ZnP in toluene was observed in the case of the dyad ZnP-BODIPY. However, when ZnP is excited, electron transfer occurred with the formation ZnP.+-BODIPY-C60.- charge separated state persisting for microseconds.
Download or read book Fundamentals of Photoinduced Electron Transfer written by George J. Kavarnos and published by Wiley-VCH. This book was released on 1993 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fundamentals of Photoinduced Electron Transfer written by Bertram H. Raven and published by Wiley-VCH. This book was released on 1983-03 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: Devoted exclusively to the basic theories, concepts and applications of light-initiated electron transfer processes, Fundamentals of Photoinduced Electron Transfer is the first book to deliver an introductory-level account of this highly active research area in a concise and easy-to-follow pedagogical manner. No prior knowledge of photochemistry is assumed or required. The author introduces essential background information on photochemistry and electrochemistry and presents a systematic account of the photoinduced electron transfer process. He carefully explains the fundamental thermodynamic equation governing the photoinduced electron, explores the diverse realm of electron photochemistry reactions and provides a survey of today's most important applications. Coverage also features discussion on classical and nonclassical theories to faster insight on a host of underlying molecular and environmental factors. Novel applications such as solar energy conversion, artificial photosynthesis, semiconductor technology, organized assemblies, and molecular electronic devices are described in appropriate detail. Fundamentals of Photoinduced Electron-Transfer is of special value as both a learning tool and working reference in photochemistry, physical chemistry, molecular physics, spectroscopy and electrochemistry.
Download or read book Fundamentals of Photoinduced Electron Transfer written by G. J. Kavarnos and published by Wiley-VCH. This book was released on 1993-08-19 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Devoted exclusively to the basic theories, concepts and applications of light-initiated electron transfer processes, Fundamentals of Photoinduced Electron Transfer is the first book to deliver an introductory-level account of this highly active research area in a concise and easy-to-follow pedagogical manner. No prior knowledge of photochemistry is assumed or required. The author introduces essential background information on photochemistry and electrochemistry and presents a systematic account of the photoinduced electron transfer process. He carefully explains the fundamental thermodynamic equation governing the photoinduced electron, explores the diverse realm of electron photochemistry reactions and provides a survey of today's most important applications. Coverage also features discussion on classical and nonclassical theories to faster insight on a host of underlying molecular and environmental factors. Novel applications such as solar energy conversion, artificial photosynthesis, semiconductor technology, organized assemblies, and molecular electronic devices are described in appropriate detail. Fundamentals of Photoinduced Electron-Transfer is of special value as both a learning tool and working reference in photochemistry, physical chemistry, molecular physics, spectroscopy and electrochemistry.
Download or read book Quatre pi ces com dies en un acte de Georges Feydeau written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanisms of Photoinduced Electron Transfer written by Indian Academy of Sciences and published by . This book was released on 1992 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy and Electron Transfer in Photosynthetic Reaction Centers and Biohybrid Antenna Complexes written by Michelle Alice Harris and published by . This book was released on 2014 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on two areas studied in an effort to increase important fundamental understandings of electron and energy transfer events leading to solar conversion in natural and artificial systems: (1) electron transfer in the bacterial photosynthetic reaction center (RC) and (2) biohybrid photosynthetic light harvesting (LH) complexes containing native-like peptides and synthetic chromophores. The RC in photosynthetic bacteria converts light energy to chemical energy through a series of electron transfer steps to separate charge across a membrane. The native process has a ~100% quantum yield of electron transfer down one cofactor branch (the L-side) whereas the seemingly symmetrical branch (the M-side) with identical pigments is inactive. Understanding M-side inactivity has been the goal of numerous studies, and has been investigated through mutations of the native peptides to favor electron transfer down the M-side or disfavor electron transfer down the L-side. In these mutants, the normal bacteriochlorophyll-bacteriochlorophyll primary electron donor is replaced with a bacteriochlorophyll-bacteriopheophytin dimer (bacteriopheophytin is the Mg-free analog of bacteriochlorophyll). This switch alters the mechanisms, rates, and yields of electron transfer in heterodimer RCs compared to wild-type. We have investigated the effects of three further mutations in which either the L or M macrocycle of the dimer is a bacteriopheophytin, for a total of eight combinations (e.g., addition of a hydrogen bond to the dimer, swap of nearby amino acids). Using ultrafast transient absorption spectroscopy to observe changes in the rate and the yield of L- versus M-side charge separation, the contributions of the electronic and energetic factors to directionality of electron transfer in RCs were assessed. The second area of my studies has been to investigate biohybrid antenna complexes formed by combining native-length bacterial LH peptide analogs with designer chromophores. The native LH systems are highly efficient. When a photon is absorbed, the energy is transferred to the RC with near unity quantum yield. However, the complex doesn't absorb parts of the solar spectrum in the visible and near-infrared regions. To address this deficiency, we performed four major studies on biohybrid antennas: (1) relay energy transfer between, (2) studies on location, density and spectral coverage of conjugated chromophores, (3) studies on bioconjugatable chromophores of hydrophobic, hydrophilic and amphiphilic nature, and (4) incorporation of non-bioconjugatable amphiphilic chromophores. Static emission and transient absorption studies indicate energy transfer efficiencies comparable to those found in native antenna systems.
Download or read book Photoinduced Electron Transfer from a Fundamental Understanding to Potential Applications written by Natalie Renuka Banerji and published by . This book was released on 2009 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the transfer of an electron from a donor to an acceptor after one of them has been electronically excited by the absorption of light appears to be a very simple reaction, there are still many open questions concerning the detailed mechanism of photoinduced electron transfer. It is nevertheless a fascinating and very important reaction, given its key importance in photosynthesis and many modern approaches to solar energy conversion. The objective of this PhD thesis was thus to use ultrafast, femtosecond-resolved spectroscopy in order to gain a better insight to photoinduced electron transfer occuring for closed-shell organic molecules in liquid solution, in particular where the relative geometry of the reaction partners is concerned. The investigations span a large variety of electron donor-acceptor systems, ranging from the intramolecular to the bimolecular case and from simple model systems to complex architectures with potential apllications in solar energy coversion.
Download or read book Towards Artificial Photosynthesis written by Valentine Ivanov Vullev and published by . This book was released on 2001 with total page 1206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photoinitiated Electron Transfer in Multichromophoric Species written by and published by . This book was released on 1988 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research project involves the design, synthesis and study of molecules which mimic many of the important aspects of photosynthetic electron and energy transfer. The knowledge gained from the study of synthetic model systems which abstract features of the natural photosynthetic apparatus can be used to design artificial photosynthetic systems which employ the basic physics and chemistry of photosynthesis to help meet mankind's energy needs. More specifically, the proposed models are designed to mimic the following aspects of natural photosynthetic multistep electron transfer: electron donation from a tetrapyrrole excited singlet state, electron transfer between tetrapyrroles, electron transfer from tetrapyrroles to quinones, and electron transfer between quinones with different redox properties.
