Download or read book Mechanical Control of Charge Transport and Chemical Reactivity in Molecular Junctions written by Leopoldo Meja̕ Restrepo and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Charge transport plays a critical role in a wide range of molecular processes including photosynthesis, redox catalysis, energy storage, biological signaling, and the operation of molecular electronic devices. Understanding and controlling these key events requires establishing how molecular structure influences charge transport and designing physically realizable strategies to manipulate them. This thesis advances the theory, simulation, and interpretation of charge transport experiments in molecular junctions and identifies novel avenues to use external mechanical stimuli to control chemistry and physics in this nanoscale setting. The reason why we focus on molecular junction experiments is because they enable the manipulation of individual molecules and the characterization of their response to external stimuli such as mechanical forces, bias voltages, and electro-magnetic fields. Such a controllable setting is ideal to establish structure-charge transport relations at the single-molecule limit that can inform and resolve the individual molecular contributions to bulk phenomena. We first demonstrate that conductance can act as a sensitive probe of conformational dynamics during the mechanical pulling of molecular junctions. These advances offer an efficient solution to experimentally monitor conformational dynamics at the single-molecule limit. Next, we bridge molecular conductance with mechanochemistry and investigate how to mechanically onset and electrically monitor chemical reactivity in single molecules. In particular, we demonstrate mechanically controlled association and rupture reactions in molecular junctions and show that simultaneous measurements of force and conductance are able to signal reactive events that cannot be distinguished by force or conductance alone. The computations are based on atomistic molecular dynamics and nonequilibrium Green's functions computations of electron transport. At the methodological level, we clarify the utility of the Landauer equation for computing charge transport across molecular junctions immersed in a thermal environment such as solvent. The Landauer equation is central to the modeling of molecular electronics experiments. However, it supposes that the current is coherent (solely due to quantum tunneling) and does not capture the possible influence of the environment in the net current. We isolate physical conditions that require an analysis beyond Landauer and use them to identify chemical motifs capable of stabilizing coherent, incoherent, and intermediate transport mechanisms. Molecular junction experiments typically record the conductance of thousands of freshly formed junctions and report histograms of conductance events. Here, we construct a microscopic theory of such conductance histograms by merging the theory of force spectroscopy developed in biophysics with molecular conductance. The theory enhances the information that can be extracted from molecular electronics experiments, and can be employed to develop schemes to narrow the width of the histograms as desirable for spectroscopic applications and molecular device design. Further, the theory opens key opportunities to atomistically model the conductance histograms, as needed to bridge the gap between theory and experiments."--Pages viii-ix.
Download or read book Charge Transport in Molecular Junctions written by Michele Kotiuga and published by . This book was released on 2015 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, we use and develop first-principles methods based on density functional theory (DFT) and beyond to understand and predict charge transport phenomena in the novel class of nanostructured devices: molecular junctions. Molecular junctions, individual molecules contacted to two metallic leads, which can be systematically altered by modifying the chemistry of each component, serve as test beds for the study of transport at the nanoscale. To date, various experimental methods have been designed to reliably assemble and mea- sure transport properties of molecular junctions. Furthermore, theoretical methods built on DFT designed to yield quantitative agreement with these experiments for certain classes of molecular junctions have been developed. In order to gain insight into a broader range of molecular junctions and environmental effects associated with the surrounding solution, this dissertation will employ, explore and extend first-principles DFT calculations coupled with approximate self-energy corrections known to yield quantitative agreement with experiments for certain classes of molecular junctions. To start we examine molecular junctions in which the molecule is strongly hybridized with the leads: a challenging limit for the existing methodology. Using a physically motivated tight-binding model, we find that the experimental trends observed for such molecules can be explained by the presence of a so-called "gateway" state associated with the chemical bond that bridges the molecule and the lead. We discuss the ingredients of a self-energy corrected DFT based approach to quantitatively predict conductance in the presence of these hybridization effects. We also develop and apply an approach to account for the surrounding environment on the conductance, which has been predominantly ignored in past transport calculations due to computational complexity. Many experiments are performed in a solution of non-conducting molecules; far from benign, this solution is known to impact the measured conductance by as much as a factor of two. Here, we show that the dominant effect of the solution stems from nearby molecules binding to the lead surface surrounding the junction and altering the local electrostatics. This effect operates in much the same way adsorbates alter the work function of a surface. We develop a framework which implicitly includes the surrounding molecules through an electrostatic-based lattice model with parameters from DFT calculations, reducing the computational complexity of this problem while retaining predictive power. Our approach for computing environmental effects on charge transport in such junctions will pave the way for a better understanding of the physics of nanoscale devices, which are known to be highly sensitive to their surroundings.
Download or read book Handbook of Materials Modeling written by Sidney Yip and published by Springer Science & Business Media. This book was released on 2007-11-17 with total page 2903 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first reference of its kind in the rapidly emerging field of computational approachs to materials research, this is a compendium of perspective-providing and topical articles written to inform students and non-specialists of the current status and capabilities of modelling and simulation. From the standpoint of methodology, the development follows a multiscale approach with emphasis on electronic-structure, atomistic, and mesoscale methods, as well as mathematical analysis and rate processes. Basic models are treated across traditional disciplines, not only in the discussion of methods but also in chapters on crystal defects, microstructure, fluids, polymers and soft matter. Written by authors who are actively participating in the current development, this collection of 150 articles has the breadth and depth to be a major contributor toward defining the field of computational materials. In addition, there are 40 commentaries by highly respected researchers, presenting various views that should interest the future generations of the community. Subject Editors: Martin Bazant, MIT; Bruce Boghosian, Tufts University; Richard Catlow, Royal Institution; Long-Qing Chen, Pennsylvania State University; William Curtin, Brown University; Tomas Diaz de la Rubia, Lawrence Livermore National Laboratory; Nicolas Hadjiconstantinou, MIT; Mark F. Horstemeyer, Mississippi State University; Efthimios Kaxiras, Harvard University; L. Mahadevan, Harvard University; Dimitrios Maroudas, University of Massachusetts; Nicola Marzari, MIT; Horia Metiu, University of California Santa Barbara; Gregory C. Rutledge, MIT; David J. Srolovitz, Princeton University; Bernhardt L. Trout, MIT; Dieter Wolf, Argonne National Laboratory.
Download or read book Charge and Exciton Transport through Molecular Wires written by Laurens D. A. Siebbeles and published by John Wiley & Sons. This book was released on 2011-07-18 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: As functional elements in opto-electronic devices approach the singlemolecule limit, conducting organic molecular wires are the appropriate interconnects that enable transport of charges and charge-like particles such as excitons within the device. Reproducible syntheses and a thorough understanding of the underlying principles are therefore indispensable for applications like even smaller transistors, molecular machines and light-harvesting materials. Bringing together experiment and theory to enable applications in real-life devices, this handbook and ready reference provides essential information on how to control and direct charge transport. Readers can therefore obtain a balanced view of charge and exciton transport, covering characterization techniques such as spectroscopy and current measurements together with quantitative models. Researchers are thus able to improve the performance of newly developed devices, while an additional overview of synthesis methods highlights ways of producing different organic wires. Written with the following market in mind: chemists, molecular physicists, materials scientists and electrical engineers.
Download or read book Charge Transport in Single Molecules written by Yueqi Li and published by . This book was released on 2017 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studying charge transport through single molecules is of great importance for unravelling charge transport mechanisms, investigating fundamentals of chemistry, and developing functional building blocks in molecular electronics. First, a study of the thermoelectric effect in single DNA molecules is reported. By varying the molecular length and sequence, the charge transport in DNA was tuned to either a hopping- or tunneling-dominated regimes. In the hopping regime, the thermoelectric effect is small and insensitive to the molecular length. Meanwhile, in the tunneling regime, the thermoelectric effect is large and sensitive to the length. These findings indicate that by varying its sequence and length, the thermoelectric effect in DNA can be controlled. The experimental results are then described in terms of hopping and tunneling charge transport models. Then, I showed that the electron transfer reaction of a single ferrocene molecule can be controlled with a mechanical force. I monitor the redox state of the molecule from its characteristic conductance, detect the switching events of the molecule from reduced to oxidized states with the force, and determine a negative shift of ~34 mV in the redox potential under force. The theoretical modeling is in good agreement with the observations, and reveals the role of the coupling between the electronic states and structure of the molecule. Finally, conclusions and perspectives were discussed to point out the implications of the above works and future studies that can be performed based on the findings.
Download or read book Tunnelling in Molecules written by Johannes Kästner and published by Royal Society of Chemistry. This book was released on 2020-09-22 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum tunnelling is one of the strangest phenomena in chemistry, where we see the wave nature of atoms acting in “impossible” ways. By letting molecules pass through the kinetic barrier instead of over it, this effect can lead to chemical reactions even close to the absolute zero, to atypical spectroscopic observations, to bizarre selectivity, or to colossal isotopic effects. Quantum mechanical tunnelling observations might be infrequent in chemistry, but it permeates through all its disciplines producing remarkable chemical outcomes. For that reason, the 21st century has seen a great increase in theoretical and experimental findings involving molecular tunnelling effects, as well as in novel techniques that permit their accurate predictions and analysis. Including experimental, computational and theoretical chapters, from the physical and organic to the biochemistry fields, from the applied to the academic arenas, this new book provides a broad and conceptual perspective on tunnelling reactions and how to study them. Quantum Tunnelling in Molecules is the obligatory stop for both the specialist and those new to this world.
Download or read book Functional Supramolecular Materials written by Rahul Banerjee and published by Royal Society of Chemistry. This book was released on 2017-05-05 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supramolecular materials have a great number of applications due to the reversibility of their non-covalent molecular interactions, such as reversible hydrogen bonding, host–guest interactions and electrostatic interactions. This book provides a comprehensive source of information on the structure and function of organic and metal–organic supramolecular materials. The chapters of this book provide an overview of supramolecular material assembly at various scales, including the formation of 2D polymers and molecular cages. The role of intermolecular interactions in solid and solution state self-assembly is discussed, as is the role of mechanochemistry on molecular and supramolecular architectures. Finally, novel applications of these materials in molecular recognition, catalysis, light harvesting and environmental remediation are covered. Functional Supramolecular Materials will be of interest to graduate students and researchers in academia and industry in the fields of supramolecular chemistry and functional materials science.
Download or read book Electrochemistry of Carbon Electrodes written by Richard C. Alkire and published by John Wiley & Sons. This book was released on 2016-03-31 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book sets the standard on carbon materials for electrode design. For the first time, the leading experts in this field summarize the preparation techniques and specific characteristics together with established and potential applications of the different types of carbon-based electrodes. An introductory chapter on the properties of carbon together with chapters on the electrochemical characteristics and properties of the different modifications of carbon such as carbon nanotubes, graphene, carbon fiber, diamond or highly ordered pyrolytic graphite provide the reader with the basics on this fascinating and ubiquitous electrode material. Cutting-edge technologies such as carbon electrodes in efficient supercapacitors, Li-ion batteries and fuel cells, or electrodes prepared by screen-printing are discussed, giving a complete but concise overview about the topic. The clearly structured book helps newcomers to grasp easily the principles of carbon-based electrodes, while researchers in fundamental and applied electrochemistry will find new ideas for further research on related key technologies.
Download or read book Molecular Movements and chemical reactivity as conditioned by membranes enzymes and other macromolecules written by and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Materials Chemistry written by L.A. Curtiss and published by Springer Science & Business Media. This book was released on 2004-05-26 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume illustrates the contributions that modern techniques in simulation and modeling can make to materials chemistry research and the level of accuracy achievable. While new developments in simulation and modeling are discussed to some extent, the major emphasis is on applications to materials chemistry including in areas of surface chemistry, solid state chemistry, polymer chemistry and nanoscience. The phenomenal improvement in both theoretical methods and computer technology have made it possible for computational chemistry to achieve a new level of chemical accuracy that is providing significant insight into the effect of chemical reactivity on the behavior of materials and helping to design new materials. Audience: Researchers, teachers, and students in chemistry and physics.
Download or read book Nanoscience And Technology A Collection Of Reviews From Nature Journals written by Peter Rodgers and published by World Scientific. This book was released on 2009-08-21 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains 35 review articles on nanoscience and nanotechnology that were first published in Nature Nanotechnology, Nature Materials and a number of other Nature journals. The articles are all written by leading authorities in their field and cover a wide range of areas in nanoscience and technology, from basic research (such as single-molecule devices and new materials) through to applications (in, for example, nanomedicine and data storage).
Download or read book Handbook of Electrochemistry written by Cynthia G. Zoski and published by Elsevier. This book was released on 2007-02-07 with total page 935 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrochemistry plays a key role in a broad range of research and applied areas including the exploration of new inorganic and organic compounds, biochemical and biological systems, corrosion, energy applications involving fuel cells and solar cells, and nanoscale investigations. The Handbook of Electrochemistry serves as a source of electrochemical information, providing details of experimental considerations, representative calculations, and illustrations of the possibilities available in electrochemical experimentation. The book is divided into five parts: Fundamentals, Laboratory Practical, Techniques, Applications, and Data. The first section covers the fundamentals of electrochemistry which are essential for everyone working in the field, presenting an overview of electrochemical conventions, terminology, fundamental equations, and electrochemical cells, experiments, literature, textbooks, and specialized books. Part 2 focuses on the different laboratory aspects of electrochemistry which is followed by a review of the various electrochemical techniques ranging from classical experiments to scanning electrochemical microscopy, electrogenerated chemiluminesence and spectroelectrochemistry. Applications of electrochemistry include electrode kinetic determinations, unique aspects of metal deposition, and electrochemistry in small places and at novel interfaces and these are detailed in Part 4. The remaining three chapters provide useful electrochemical data and information involving electrode potentials, diffusion coefficients, and methods used in measuring liquid junction potentials. * serves as a source of electrochemical information * includes useful electrochemical data and information involving electrode potentials, diffusion coefficients, and methods used in measuring liquid junction potentials * reviews electrochemical techniques (incl. scanning electrochemical microscopy, electrogenerated chemiluminesence and spectroelectrochemistry)
Download or read book Molecular Electronics An Introduction To Theory And Experiment written by Elke Scheer and published by World Scientific. This book was released on 2010-06-23 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the rapidly developing field of molecular electronics. It focuses on our present understanding of the electrical conduction in single-molecule circuits and provides a thorough introduction to the experimental techniques and theoretical concepts. It will also constitute as the first textbook-like introduction to both the experiment and theory of electronic transport through single atoms and molecules. In this sense, this publication will prove invaluable to both researchers and students interested in the field of nanoelectronics and nanoscience in general.Molecular Electronics is self-contained and unified in its presentation. It may be used as a textbook on nanoelectronics by graduate students and advanced undergraduates studying physics and chemistry. In addition, included are previously unpublished material that will help researchers gain a deeper understanding into the basic concepts involved in the field of molecular electronics.
Download or read book Molecular Switches written by Ben L. Feringa and published by John Wiley & Sons. This book was released on 2011-08-04 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt: Täglich benutzen wir Schalter, um strombetriebene Geräte an- und abzuschalten und kein Compuer würde ohne sie funktionieren. Nach den gleichen Prinzipien funktionieren auch molekulare Schalter, die unter dem Einfluß ihrer Umwelt zwischen zwei definierten Zuständen wechseln können. Im Gegensatz zu den gewöhnlichen Schaltern sind molekulare Schalter aber außerordentlich klein und ihre Anwendung in der Nanotechnologie, Biomedizin und im Computerchipdesign öffnet neue Horizonte. Im vorliegenden Zweibänder berichten Herausgeber und Autoren über molekulare Schalter aus Katenanen und Rotaxanen, Fulgiden, Flüssigkristallen und Polypeptiden. Die Bandbreite der behandelten Themen reicht von chiroptischen Schaltern über multifunktionale Systeme bis hin zu molekularen logischen Schaltungen. Chemiker und Materialwissenschaftler in Industrie und Hochschule, die sich für einen der innovativsten Bereiche ihrer Wissenschaft interessieren, werden dieses Buch mit Gewinn lesen!
Download or read book Quantities Units and Symbols in Physical Chemistry written by International Union of Pure and Applied Chemistry. Physical and Biophysical Chemistry Division and published by Royal Society of Chemistry. This book was released on 2007 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prepared by the IUPAC Physical Chemistry Division this definitive manual, now in its third edition, is designed to improve the exchange of scientific information among the readers in different disciplines and across different nations. This book has been systematically brought up to date and new sections added to reflect the increasing volume of scientific literature and terminology and expressions being used. The Third Edition reflects the experience of the contributors with the previous editions and the comments and feedback have been integrated into this essential resource. This edition has been compiled in machine-readable form and will be available online.
Download or read book Effects of Electric Fields on Structure and Reactivity written by Sason S. Shaik and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Starting with an overview of the theory behind - and demonstrations of the effect of - electric fields on structure and reactivity, this accessible reference work aims to encourage those new to the field to consider harnessing these effects in their own work.
Download or read book The Theory of Open Quantum Systems written by Heinz-Peter Breuer and published by Oxford University Press, USA. This book was released on 2002 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book treats the central physical concepts and mathematical techniques used to investigate the dynamics of open quantum systems. To provide a self-contained presentation the text begins with a survey of classical probability theory and with an introduction into the foundations of quantum mechanics with particular emphasis on its statistical interpretation. The fundamentals of density matrix theory, quantum Markov processes and dynamical semigroups are developed. The most important master equations used in quantum optics and in the theory of quantum Brownian motion are applied to the study of many examples. Special attention is paid to the theory of environment induced decoherence, its role in the dynamical description of the measurement process and to the experimental observation of decohering Schrodinger cat states. The book includes the modern formulation of open quantum systems in terms of stochastic processes in Hilbert space. Stochastic wave function methods and Monte Carlo algorithms are designed and applied to important examples from quantum optics and atomic physics, such as Levy statistics in the laser cooling of atoms, and the damped Jaynes-Cummings model. The basic features of the non-Markovian quantum behaviour of open systems are examined on the basis of projection operator techniques. In addition, the book expounds the relativistic theory of quantum measurements and discusses several examples from a unified perspective, e.g. non-local measurements and quantum teleportation. Influence functional and super-operator techniques are employed to study the density matrix theory in quantum electrodynamics and applications to the destruction of quantum coherence are presented. The text addresses graduate students and lecturers in physics and applied mathematics, as well as researchers with interests in fundamental questions in quantum mechanics and its applications. Many analytical methods and computer simulation techniques are developed and illustrated with the help of numerous specific examples. Only a basic understanding of quantum mechanics and of elementary concepts of probability theory is assumed.
