Download or read book Photoinduced Intramolecular Charge Transfer in Donor Acceptor Biaryls and Resulting Applicational Aspects Regarding Fluorescent Probes and Solar Energy Conversion written by Michael Maus and published by Universal-Publishers. This book was released on 1998 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study is focused on the effects of photoinduced intramolecular charge transfer (CT) in three differently twisted donor-acceptor (D-A) biphenyls. Taking into account a further pair of differently twisted D-A biaryls new universal insights into the photoinduced electronic and conformation dynamics of D-A biaryls are obtained. Furthermore, possible applications in fields of solar energy conversion and fluorescence sensing of microenvironments are demonstrated. Experimental means of stationary and time-resolved (ps to s) luminescence, transient absorption (sub-ps), polarization spectroscopy, high pressure and low temperature techniques are employed in conjunction with quantum chemical calculations. Twist angle and solvent dependent electron transfer (ET) interactions between the D and A aryl moieties are responsible for the low lying and solvatochromic intramolecular CT electron band which gains unusually high intensity through strong electronic coupling of the pure 1ET with the ground (S0) and 1La state. As regards the class of biaryl compounds, for the first time, an excited state electron transfer from the D to the A could be monitored by dual spectrally separated stimulated fluorescence bands with precursor-successor relationship on a sub-ps timescale for the D-A biphenyls. It is concluded that, in additon to the electronic interaction of 1ET with S0 and 1La, the electronic interaction with a close lying 1Lb state plays a fundamental role in the ET dynamics and the 1CT-S0 transition probability in D-A biaryls. The initial photoinduced conformational relaxation occurs towards planarity in all biaryls investigated. However, various results evidence that the highly twisted D-A biphenyl additionally performs a slow "excited state intramolecular back twist rotation" leading to a solvent polarity dependent conformational equilibrium between a more planar (CT) and a more twisted (CTR) conformer in S1(1CT). Using global analysis of the biexponential fluorescence decays as a function of temperature and pressure in medium polar solvents, the kinetics, thermodynamics, viscosity control and decomposed emission spectra associated with this adiabatic photoreaction are determined. The twist angle dependent ability of the D-A biphenyls to serve as fluorescent probes of micropolarity, changes of microviscosity or matrix order, protic solvents and pH is investigated. In particular, fluorescence sensing of pH seems to be promising.
Download or read book Photoinduced Intramolecular Charge Transfer in Donor receptor Biaryls and Resulting Applicational Aspects Regarding Fluorescent Probes and Solar Energy Conversion written by Michael Maus and published by . This book was released on 1998 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polymers in Organic Electronics written by Sulaiman Khalifeh and published by Elsevier. This book was released on 2020-04-01 with total page 617 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymers in Organic Electronics: Polymer Selection for Electronic, Mechatronic, and Optoelectronic Systems provides readers with vital data, guidelines, and techniques for optimally designing organic electronic systems using novel polymers. The book classifies polymer families, types, complexes, composites, nanocomposites, compounds, and small molecules while also providing an introduction to the fundamental principles of polymers and electronics. Features information on concepts and optimized types of electronics and a classification system of electronic polymers, including piezoelectric and pyroelectric, optoelectronic, mechatronic, organic electronic complexes, and more. The book is designed to help readers select the optimized material for structuring their organic electronic system.Chapters discuss the most common properties of electronic polymers, methods of optimization, and polymeric-structured printed circuit boards. The polymeric structures of optoelectronics and photonics are covered and the book concludes with a chapter emphasizing the importance of polymeric structures for packaging of electronic devices. - Provides key identifying details on a range of polymers, micro-polymers, nano-polymers, resins, hydrocarbons, and oligomers - Covers the most common electrical, electronic, and optical properties of electronic polymers - Describes the underlying theories on the mechanics of polymer conductivity - Discusses polymeric structured printed circuit boards, including their rapid prototyping and optimizing their polymeric structures - Shows optimization methods for both polymeric structures of organic active electronic components and organic passive electronic components
Download or read book Photoinduced Charge and Energy Transfer Processes in Molecular Aggregates written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project involved the experimental probing of the electronic excited states generated by photoinduced (center-to-center) electron and energy transfer processes in several classes of transition metal donor/acceptor (D/A) complexes. Some of the general properties inferred from these studies should be useful in the design of new systems for energy conversion applications. Pursuit of the project goals has involved the determination of electron transfer efficiencies and the detailed study of variations in the electronic spectra of D/A complexes. This has resulted in the study of some very fundamental issues of photoinduced charge transfer and the identification of some of the constraints on its efficiency. The experimental studies of the competition between the degradative non-radiative unimolecular relaxation of transition metal excited states and their transfer of charge from these excited states to external acceptors have involved a range of techniques such as transient decay kinetics, photoacoustic calorimetry and transient or stationary state spectroscopy. The substrates synthesized for these studies were selected to provide model systems, or series of model systems to probe the validity of models of electronic excited states and their reactivity. The work during the last few years has focused largely, but not exclusively, on the use of emission spectral band shapes to probe the properties of charge transfer (CT) excited states. Bandshape variations are one of the very few approaches for systematically probing electronic excited states and good band shape resolution is necessary in order to gain information about the structural variations that correlate with excited state reactivity. Differences in molecular structure correlate with differences in chemical reactivity, and the variations in emission bandshapes are well known to relate to variations in the molecular structural differences between the excited and ground electronic states. However, it is has been rarely noticed that configurational mixing of the lowest energy excited state with other electronic states leads to unique distortions of the lowest energy excited state which result in modifications in the vibronic structure and bandshape of the emission. We have used the emission sideband shapes to evaluate patterns of ground state-excited state and excited state-excited state configurational mixing in some simple series of complexes.
Download or read book Charge transfer and Other Excitonic State in Conjugated Polymer written by Dhanashree Moghe and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last few decades there has been tremendous progress in organic photovoltaics (OPVs), with efficiencies reaching over 10%. Still, many factors including the origin and the dynamics of charge carrier involved are debatable. New and sensitive techniques are constantly being devised to identify the origin of free charges. At the same time, a lot of research has also been devoted to synthesize low bandgap material such that its absorption spectra overlap with that of the solar spectrum. The most important hindrance in organic semiconductors is the formation of bound electron-hole (exciton) charge pair upon photoexcitation. Additional energy is required to dissociate the bound pair to generate free charges for photovoltaic application. The most popular and efficient way to dissociate excitons is to fabricate a bulk heterojunction solar cell, which comprises of a blend of at least two polymers: one donor and the other acceptor. It is very well established that the presence of fullerene (acceptor) helps in transfer of the negative charges from the donor polymer to fullerene, making the exciton slightly less bound. The nanometer scale islands further help in migration of charges. A crucial aspect of our studies has been evaluating the role of various excitonic states such as charge-transfer and triplet excitonic states in device efficiencies. The focus of this work was on diketopyrrolopyrrole (DPP)- based donor-acceptor (D-A) type conjugated copolymers which have low bandgap energies and have been known to show high efficiency in organic photovoltaics. These copolymers have D-A unit present in the same chain, which lowers the optical bandgap of the material. Variation of either the donor or the acceptor fraction offers an option to tune the optical bandgap by using the same D-A chromophores. The D-A configuration also results in the separation of positive and negative charges within the same polymeric chain, which is the intramolecular charge-transfer excitonic state. We analyze the intramolecular charge-transfer state using bias dependent absorption studies, which allowed us to estimate the binding energy of intramolecular exciton. Later, we performed density functional theory (DFT) and time dependent DFT calculations to identify the origin of the intramolecular exciton absorption. Taking the copolymers as donor (and fullerene as acceptor) in an organic photovoltaic device, we probe the (intermolecular) charge-transfer states formed at the copolymer/fullerene interface . We utilize monochromatic photocurrent method and a highly sensitive (and fast) Fourier transform photocurrent spectroscopy technique to probe the intermolecular charge-transfer states in the device. Our analyses show that the optical bandgap difference between the copolymers and fullerene plays a pivotal role in stabilization /destabilization of charge - transfer states in copolymer-fullerene systems. The triplet excitons are also known to play an important role in OPV efficiency. We probe the diffusion length of triplet exciton in ladder-type polymers by devising a simple, yet efficient method using optical modulation spectroscopy (photoinduced absorption spectroscopy). The diffusion length of triplet excitons is estimated to be almost three orders of magnitude more than the singlet excitons . Further, by implementing a 1D random-walk model to the photoinduced absorption data, we estimate diffusivities of the triplet exciton in our sample.
Download or read book Photoinduced Intramolecular Electron Transfer in Donor acceptor Molecules written by Jerzy Herbich and published by . This book was released on 1998 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Photoinduced Charge Separation in Linked Donor acceptor chromophore Systems Final Report written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A major experimental challenge in any study of intramolecular donor/acceptor (D/A) interactions is separating the variables which affect coupling. This is especially difficult when trying to evaluate the extent of through-bond superexchange. The systems of dinuclear complexes described below are unique in that the D/A connectivity can be varied without concomitant changes in D/A separation and relative orientation. Consequently, it has been possible to experimentally evaluate the effect of D/A linkage on coupling without introducing ambiguities from other structural changes. Furthermore, some of these systems are amenable to detailed theoretical treatment which allows quantitative comparisons between experiment and theory. A much more detailed picture of the D/A interaction is, thus, provided. Sections of this report include: unique structural aspects of[M(BBA)[sub 3]M[prime]] complexes; energy transfer in photoexcited[Ru(II)(BBA)[sub 3]Fe(II)][sup 4+] complexes; electrochemical investigation of[Fe(BBA)[sub 3]Fe][sup 4+]; optically-induced electron transfer in[Fe(II)(BBA)[sub 3]Fe(III)][sup 5+] mixed-valent complexes, where BBA=[alpha], [omega]-bisbipyridylalkane.
Download or read book Topics in Fluorescence Spectroscopy written by Joseph R. Lakowicz and published by Springer Science & Business Media. This book was released on 1994-11-30 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: Time-resolved fluorescence spectroscopy is widely used as a research tool in bioch- istry and biophysics. These uses of fluorescence have resulted in extensive knowledge of the structure and dynamics of biological macromolecules. This information has been gained by studies of phenomena that affect the excited state, such as the local environment, quenching processes, and energy transfer. Topics in Fluorescence Spectroscopy, Volume 4: Probe Design and Chemical Sensing reflects a new trend, which is the use of time-resolved fluorescence in analytical and clinical chemistry. These emerging applications of time-resolved fluorescence are the result of continued advances in laser detector and computer technology. For instance, pho- multiplier tubes (PMT) were previously bulky devices. Miniature PMTs are now available, and the performance of simpler detectors is continually improving. There is also considerable effort to develop fluorophores that can be excited with the red/ne- infrared (NIR) output of laser diodes. Using such probes, one can readily imagine small time-resolved fluorometers, even hand-held devices, being used fordoctor’s office or home health care.
Download or read book Semiconducting and Metallic Polymers written by Alan J. Heeger and published by OUP Oxford. This book was released on 2010-07-29 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique properties of conducting and semiconducting (conjugated) polymers make them one of the most attractive areas of interdisciplinary materials science and technology. Written by a pioneer in the field, this book is the first aimed at teaching graduate students, postdoctoral scientists, and specialists in industry about this exciting field.
Download or read book Glucose Sensing written by Chris D. Geddes and published by Springer Science & Business Media. This book was released on 2007-12-29 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: An essential reference for any laboratory working in the analytical fluorescence glucose sensing field. The increasing importance of these techniques is typified in one emerging area by developing non-invasive and continuous approaches for physiological glucose monitoring. This volume incorporates analytical fluorescence-based glucose sensing reviews, specialized enough to be attractive to professional researchers, yet appealing to a wider audience of scientists in related disciplines of fluorescence.
Download or read book Fluorescence and Phosphorescence Spectroscopy written by Stephen G Schulman and published by Elsevier. This book was released on 2017-05-17 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluorescence and Phosphorescence Spectroscopy: Physicochemical Principles and Practice deals with the physicochemical principles and applications of fluorescence and phosphorescence spectroscopy in experimental biology and chemistry. Topics covered include the absorption of light by molecules; instrumentation for the measurement of fluorescence and phosphorescence; solvent and acidity effects on electronic spectra; and polarization of fluorescence and phosphorescence. Comprised of four chapters, this book begins with a discussion on photophysical processes in isolated molecules and molecules in solution, paying particular attention to thermal equilibration of electronically excited molecules, phototautomerism, and coordination by metal ions. The next chapter describes the instrumentation for measuring fluorescence and phosphorescence, which consists essentially of a light source to electronically excite the sample; a monochromator to separate the light of desired energy from the source; a sample compartment; a second monochromator to isolate the sample's fluorescence energy from the excitation energy; a photodetector to translate the fluorescent light into an electrical signal; and a readout system such as a galvanometer or a recorder, coupled with an amplifier to determine the intensity of fluorescent light that is emitted. The final chapter is devoted to various applications of fluorescence and phosphorescence spectroscopy, including the analysis of organic and inorganic compounds. This monograph is written primarily for analytical chemists and biological scientists.
Download or read book Zinc Catalysis written by Stephan Enthaler and published by John Wiley & Sons. This book was released on 2015-04-27 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Filling the gap in the market for comprehensive coverage of this hot topic, this timely book covers a wide range of organic transformations, e. g. reductions of unsaturated compounds, oxidation reactions, Friedel-Crafts reactions, hydroamination reactions, depolymerizations, transformations of carbon dioxide, oxidative coupling reactions, as well as C-C, C-N, and C-O bond formation reactions. A chapter on the application of zinc catalysts in total synthesis is also included. With its aim of stimulating further research and discussion in the field, this is a valuable reference for professionals in academia and industry wishing to learn about the latest developments.
Download or read book Handbook of Synthetic Photochemistry written by Angelo Albini and published by John Wiley & Sons. This book was released on 2010-02-01 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unique in its focus on preparative impact rather than mechanistic details, this handbook provides an overview of photochemical reactions classed according to the structural feature that is built in the photochemical step, so as to facilitate use by synthetic chemists unfamiliar with this topic. An introductory section covers practical questions on how to run a photochemical reaction, while all classes of the most important photocatalytic reactions are also included. Perfect for organic synthetic chemists in academia and industry.
Download or read book Iptycenes Chemistry written by Chuan-Feng Chen and published by Springer Science & Business Media. This book was released on 2012-12-02 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Iptycenes Chemistry: From Synthesis to Applications provides a comprehensive overview of the development of iptycene chemistry in the past seventy years. This book covers: (1) the basic nomenclature and general properties of iptycenes and their derivatives; (2) the synthesis and functionalization reactions of triptycenes, pentiptycenes, higher iptycenes, heterotriptycenes, and homotriptycenes; (3) the methods for the preparation of iptycene-based polymers with different types; and (4) the applications of iptycenes and their derivatives in molecular machines, materials science, host-guest chemistry, self-assembly, coordination chemistry, physical organic chemistry, medicinal chemistry, and so on. Consequently, such a book is not only helpful to researchers working in iptycene chemistry, but can also facilitate future research in wide areas.
Download or read book Heterogeneous Photocatalysis written by Juan Carlos Colmenares and published by Springer. This book was released on 2015-12-24 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book explains the principles and fundamentals of photocatalysis and highlights the current developments and future potential of the green-chemistry-oriented applications of various inorganic, organic, and hybrid photocatalysts. The book consists of eleven chapters, including the principles and fundamentals of heterogeneous photocatalysis; the mechanisms and dynamics of surface photocatalysis; research on TiO2-based composites with unique nanostructures; the latest developments and advances in exploiting photocatalyst alternatives to TiO2; and photocatalytic materials for applications other than the traditional degradation of pollutants, such as carbon dioxide reduction, water oxidation, a complete spectrum of selective organic transformations and water splitting by photocatalytic reduction. In addition, heterogeneized polyoxometalate materials for photocatalytic purposes and the proper design of photocatalytic reactors and modeling of light are also discussed. This book appeals to a wide readership of the academic and industrial researchers and it can also be used in the classroom for undergraduate and graduate students focusing on heterogeneous photocatalysis, sustainable chemistry, energy conversion and storage, nanotechnology, chemical engineering, environmental protection, optoelectronics, sensors, and surface and interface science. Juan Carlos Colmenares is a Professor at the Institute of Physical Chemistry, Polish Academy of Sciences, Poland. Yi-Jun Xu is a Professor at the State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry, Fuzhou University, China.
