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Author: Yekaterina Leonidovna Lyubarskaya
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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"The research presented in this dissertation focuses on the study of self-assembled monolayers (SAMs) in the modification of surface properties of different substrates for various applications. Self-assembled monolayers are organic molecules that can be deposited on a variety of surfaces, such as those of metals, metal-oxides, and semiconductors. Formation of SAMs on any inorganic material provides a ubiquitous way to impart desirable chemical and physical properties of organic and biological molecules to the inorganic substrate. It has been demonstrated that single molecules and their self-assembled monolayers can significantly alter the physical and electronic properties of inorganic conductors; moreover, studies have shown that the performance of many electrical devices can be transformed by modifying inorganic electrodes with organic SAMs. This is especially important for the development of next generation of ultra-compact electronic devices, in which the ability to control the interfacial charge-transport with a single monolayer of organic molecules would be ideal. We have developed different organic electronic architectures as test beds for studying the effect of monolayer properties, such as structural and geometrical parameters, on their electronic properties. By using a typical organic electronic device as a sensitive test platform, slight changes in a monolayer property, such as length, have been detected by studying the current- voltage characteristics (JV) of organic diodes functionalized with self-assembled monolayers (SAMs) of varying alkyl chain-length. Next, we describe the application of SAMs based on n-octylphosphonic acid (C8PA) and 1H,1H,2H,2H-perfluorooctanephosphonic acid (PFOPA) as anode buffer layers in C60-based organic photovoltaic (OPV) devices. We used the OPV platform to compare stabilities of organic monolayers exposed to ambient conditions with SAMs positioned inside working OPV devices. We found that the stabilities are different, suggesting the degradation mechanisms are distinct. The degradation of the OPV efficiency with respect to air exposure was significantly reduced with the perfluorinated PFOPA compared to the aliphatic C8PA. We attributed the OPV degradation to moisture diffusion from the top aluminum electrode and we discuss that the lowering of the anode work function is the result of hydrolysis of the SAM buffer layer. Next, we demonstrated the dependence of molecular electronic properties on the functional group substitution and that the changes in these properties can be measured using the organic light-emitting (OLED) platform. Specifically, we compared bilayered organic monomolecular systems immobilized on an inorganic electrode as the charge-injecting components of the organic light emitting diodes (OLEDs). Our bilayered interfaces comprise ordered inert primary and functional reactive layers, and they differ in only one parameter: the molecular structure of the terminal functional group. We demonstrate that we can visualize the differences in the charge transfer dynamics of two bilayered systems via patterned electroluminescence. In addition, we describe a new protocol for the preparation of shape-controlled multicomponent particles comprising metallic (Au and Ti), magnetic (Ni), and oxide (SiO2, TiO2) layers. First, we discuss the application and attractiveness of the colloidal structures, Janus Particles (JPs), that possess two different surfaces, varying either in polarity, hydrophilicity, etc. Next, we present our method for specifically controlling the composition, shape, and size of the micro-JPs. We demonstrate how this protocol permits fabrication of non-symmetrical particles by orthogonally functionalizing their opposite sides using well-established organosilanes and thiol chemistries (based on SAMs). We propose that these colloids may be used as convenient materials for studying non-symmetrical self-assembly at the meso- and micro-scales, due to their unique geometries and surface chemistries"--Pages viii-x.
Author: Yekaterina Leonidovna Lyubarskaya
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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Book Description
"The research presented in this dissertation focuses on the study of self-assembled monolayers (SAMs) in the modification of surface properties of different substrates for various applications. Self-assembled monolayers are organic molecules that can be deposited on a variety of surfaces, such as those of metals, metal-oxides, and semiconductors. Formation of SAMs on any inorganic material provides a ubiquitous way to impart desirable chemical and physical properties of organic and biological molecules to the inorganic substrate. It has been demonstrated that single molecules and their self-assembled monolayers can significantly alter the physical and electronic properties of inorganic conductors; moreover, studies have shown that the performance of many electrical devices can be transformed by modifying inorganic electrodes with organic SAMs. This is especially important for the development of next generation of ultra-compact electronic devices, in which the ability to control the interfacial charge-transport with a single monolayer of organic molecules would be ideal. We have developed different organic electronic architectures as test beds for studying the effect of monolayer properties, such as structural and geometrical parameters, on their electronic properties. By using a typical organic electronic device as a sensitive test platform, slight changes in a monolayer property, such as length, have been detected by studying the current- voltage characteristics (JV) of organic diodes functionalized with self-assembled monolayers (SAMs) of varying alkyl chain-length. Next, we describe the application of SAMs based on n-octylphosphonic acid (C8PA) and 1H,1H,2H,2H-perfluorooctanephosphonic acid (PFOPA) as anode buffer layers in C60-based organic photovoltaic (OPV) devices. We used the OPV platform to compare stabilities of organic monolayers exposed to ambient conditions with SAMs positioned inside working OPV devices. We found that the stabilities are different, suggesting the degradation mechanisms are distinct. The degradation of the OPV efficiency with respect to air exposure was significantly reduced with the perfluorinated PFOPA compared to the aliphatic C8PA. We attributed the OPV degradation to moisture diffusion from the top aluminum electrode and we discuss that the lowering of the anode work function is the result of hydrolysis of the SAM buffer layer. Next, we demonstrated the dependence of molecular electronic properties on the functional group substitution and that the changes in these properties can be measured using the organic light-emitting (OLED) platform. Specifically, we compared bilayered organic monomolecular systems immobilized on an inorganic electrode as the charge-injecting components of the organic light emitting diodes (OLEDs). Our bilayered interfaces comprise ordered inert primary and functional reactive layers, and they differ in only one parameter: the molecular structure of the terminal functional group. We demonstrate that we can visualize the differences in the charge transfer dynamics of two bilayered systems via patterned electroluminescence. In addition, we describe a new protocol for the preparation of shape-controlled multicomponent particles comprising metallic (Au and Ti), magnetic (Ni), and oxide (SiO2, TiO2) layers. First, we discuss the application and attractiveness of the colloidal structures, Janus Particles (JPs), that possess two different surfaces, varying either in polarity, hydrophilicity, etc. Next, we present our method for specifically controlling the composition, shape, and size of the micro-JPs. We demonstrate how this protocol permits fabrication of non-symmetrical particles by orthogonally functionalizing their opposite sides using well-established organosilanes and thiol chemistries (based on SAMs). We propose that these colloids may be used as convenient materials for studying non-symmetrical self-assembly at the meso- and micro-scales, due to their unique geometries and surface chemistries"--Pages viii-x.
Author: Dominic Pascal Goronzy
Publisher:
ISBN:
Category :
Languages : en
Pages : 242
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Book Description
Self-assembled monolayers (SAMs) are an advantageous platform for probing the fundamental interactions that dictate the spontaneous formation of nanostructures and supramolecular assemblies and directly affect macroscale properties. As such, SAMs provide an avenue for creating surfaces with defined chemical and physical properties. The assembly of these nanoscale constructs is driven by three primary factors: the interface between the substrate and the monolayer, the interactions between the adsorbate molecules, and the interface between the monolayer and the environment. I studied an icosahedral cage boron cluster, the carborane, as a building block for SAMs with properties that we can tune to advantage. Carboranes have several favorable traits, including providing a scaffold for a variety of functional groups. A chalcogenide group, typically a thiol, is used for surface attachment; moreover, bifunctional carboranes also enable control of the valency during assembly and greater reactivity at the environmental interface of the SAM. Additionally, isomers of carboranethiol have distinct dipole moments in terms of orientation and magnitude. The dipoles can lead to the formation of long-range dipole dipole networks within the SAM, which can stabilize the SAM and also modify the surface properties of the material. The rigid, symmetric backbone of the carborane cage results in SAMs that are relatively pristine and defect free. Due to these advantageous traits, carboranes enable the creation of monolayers with tunable interactions at the SAM interfaces. This system not only enables myself and others to study the molecular forces of assembly but also facilitates the simultaneous modification of both chemical and physical properties of surfaces and interfaces. This thesis describes several carborane based surface assemblies and the variable interactions they have within the SAM interfaces. The introduction of a second thiol group to the carborane cage can be used to modulate the interaction of the SAM with the substrate. Carboranedithiol SAMs exhibit two binding modes, a monovalent state and a divalent state. The presence of these two modes enables tuning of valency using acid base chemistry and thus the ratio of singly bound to dual bound surface molecules can be modified during deposition. Another avenue to alter the interactions at the substrate-monolayer interface is to use an alternative functional group for surface attachment. A chalcogenide group similar to thiol is selenol, however carboraneselenolate SAMs have a distinct surface morphology compared to carboranethiolate SAMs. Carboraneselenolate SAMs exhibit a dynamic double lattice where surface molecules appear to switch between high- and low-conductance binding modes. This morphology is consistent with other cage molecule selenolate SAMs and is typically associated with substrate-mediated interactions. In contrast, the carboraneselenolate SAMs are resistant to thermal rearrangement and desorption due to the dipole dipole interactions within the monolayer. Carboranethiols can be modified by adding a carboxylic acid functional group that both alter the interactions within the monolayer and provide a platform for further reactions at the environmental interface. The introduction of a laterally positioned carboxyl functional group increases the steric demands of the molecule, thereby decreasing the packing density, but also enables hydrogen bonding interactions within the monolayer. The pKa of the surface bound carboxylic acid is shifted such that it is approximately two pH units less acidic than in solution. This shift is driven by the dielectric of the environment that the carboxyl group experiences on the surface, which is determined by the intermolecular interactions within the monolayer, partial desolvation, and the proximity to the substrate surface. The carboxyl group also remains available for further chemistry on the surface and can coordinate with a variety of metal ions or be used as an attachment point for performing chemical lift off lithography (CLL). This lithographic technique was performed successfully on several types of carboxyl carboranethiolate SAMs. The use of these SAMs also enabled the characterization of the post CLL substrate surface via scanning tunneling microscopy. This analysis revealed the molecules left behind during the CLL process are either in small molecular islands or sparsely packed, highly mobile molecules. There remain many opportunities for further chemistry to be performed with these carboxyl terminated SAMs or with carboranethiol SAMs with other additional functional groups. Carborane-based SAMs are a versatile system that provides a high degree of tunability at all three interfaces of a SAM. The work presented lays the foundation for further application in lithography, like CLL, as well as the use of these SAMs in organic electronics and devices and as interfacial materials.
Author:
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Languages : en
Pages :
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Nanostructured materials play a vital role in almost all aspects of science and technology in the 21st century. The materials include nanoparticles, nanofilms, biological membranes etc. whose physicochemical properties are size-dependent. Thin films have wide range of applications in various branches of science. One of the efficient methods to form miniaturized structures for device applications is to fabricate nanostructured films on different substrates. Surfactant assembly on metallic and non-metallic surfaces based on self assembly and Langmuir-Blodgett technique offers a unique way to form thin films at molecular levels. The process of formation of unimolecular assemblies gives the flexibility of tuning the properties of underlying substrates for various applications including wetting characteristics, lubrication, passivation, mimicking biological phenomena etc. Towards this direction, self assembled monolayers (SAMs) of alkanethiols on gold and silver surfaces have been studied comprehensively for the past two decades. The reported literature on short chain length thiol-based monolayers is however, limited since the formation using conventional methods yield poor quality monolayers. The short chain length monolayers are useful in various applications like tribology, layer-by-layer assemblies, biosensors etc. Hence, it is essential to reproducibly form SAMs of various chain lengths and understand their properties. The present study is related to the formation of SAMs of alkanethiols and diselenides on gold and silver surfaces to form ordered and well-oriented monolayers. Monolayers of varying chain lengths (CH3(CH2)nSH where n = 3, 5, 7, 9, 11, 15) have been formed on gold and silver surfaces using different methods, (1) adsorption from neat thiols; (2) adsorption under electrochemical control and (3) adsorption from alcoholic solutions of the thiols. The characteristics features of the SAMs have been followed based on three different aspects, (i) structure and.
Author: Zhenan Bao
Publisher: CRC Press
ISBN: 1351837575
Category : Technology & Engineering
Languages : en
Pages : 578
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Book Description
The remarkable development of organic thin film transistors (OTFTs) has led to their emerging use in active matrix flat-panel displays, radio frequency identification cards, and sensors. Exploring one class of OTFTs, Organic Field-Effect Transistors provides a comprehensive, multidisciplinary survey of the present theory, charge transport studies, synthetic methodology, materials characterization, and current applications of organic field-effect transistors (OFETs). Covering various aspects of OFETs, the book begins with a theoretical description of charge transport in organic semiconductors at the molecular level. It then discusses the current understanding of charge transport in single-crystal devices, small molecules and oligomers, conjugated polymer devices, and charge injection issues in organic transistors. After describing the design rationales and synthetic methodologies used for organic semiconductors and dielectric materials, the book provides an overview of a variety of characterization techniques used to probe interfacial ordering, microstructure, molecular packing, and orientation crucial to device performance. It also describes the different processing techniques for molecules deposited by vacuum and solution, followed by current technological examples that employ OTFTs in their operation. Featuring respected contributors from around the world, this thorough, up-to-date volume presents both the theory behind OFETs and the latest applications of this promising technology.
Author: Deyue Yan
Publisher: John Wiley & Sons
ISBN: 047093476X
Category : Technology & Engineering
Languages : en
Pages : 414
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Book Description
A much-needed overview of the state of the art of hyperbranched polymers The last two decades have seen a surge of interest in hyperbranched polymers due to their ease of synthesis on a large scale and their promising applications in diverse fields, from medicine to nanotechnology. Written by leading scientists in academia and industry, this book provides for the first time a comprehensive overview of the topic, bringing together in one complete volume a wealth of information previously available only in articles scattered across the literature. Drawing on their work at the cutting edge of this dynamic area of research, the authors cover everything readers need to know about hyperbranched polymers when designing highly functional materials. Clear, thorough discussions include: How irregular branching affects polymer properties and their potential applications Important theoretical basics, plus a useful summary of characterization techniques How hyperbranched polymers compare with dendrimers as well as linear polymers Future trends in the synthesis and application of hyperbranched polymers Geared to novices and experts alike, Hyperbranched Polymers is a must-have resource for anyone working in polymer architectures, polymer engineering, and functional materials. It is also useful for scientists in related fields who need a primer on the synthesis, theory, and applications of hyperbranched polymers.
Author: Sabu Thomas
Publisher: Elsevier
ISBN: 032346145X
Category : Technology & Engineering
Languages : en
Pages : 294
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Book Description
Thermal and Rheological Measurement Techniques for Nanomaterials Characterization, Second Edition covers thermal and rheological measurement techniques, including their principle working methods, sample preparation and interpretation of results. This important reference is an ideal source for materials scientists and industrial engineers who are working with nanomaterials and need to know how to determine their properties and behaviors. - Outlines key characterization techniques to determine the thermal and rheological behavior of different nanomaterials - Explains how the thermal and rheological behavior of nanomaterials affect their usage - Provides a method-orientated approach that explains how to successfully use each technique
Author: Limin Wang
Publisher:
ISBN:
Category :
Languages : de
Pages :
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Self-assembled monolayers, form a dense assembly of organic molecules on various solid substrates and have caught strong attention due to their large number of potential applications in sensors, biochips, anti-fouling surface, organic electronics, optical devices, etc.. Silane- and thiol-containing molecules represent two classes of the most extensively investigated SAMs. Silane-based monolayers show good stability in their physical and chemical properties which allow them to be further functionalized by different surface chemical reactions or electrochemical oxidation lithography, while the simple and reproducible preparation procedure of thiol-containing SAMs attached to Ag/Au substrates motivates their use, e.g., as analytes in SERS applications. In this thesis, three different potential applications for SAMs were investigated to introduce surface chemical reactions on silane-based SAMs, to utilize surface modification by electrochemical oxidation lithography on OTS monolayers, and finally to investigate the stability of SERS substrates when being immersed into different solvents and buffer solutions utilizing 4-ATP as probe molecules.
Author: Abraham Ulman
Publisher:
ISBN: 9780125330244
Category : Monomolecular films
Languages : en
Pages : 0
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This work looks at thin films and self-assembled monolayers of thiols. It is aimed at researchers in chemistry, materials science, electrical engineering, biology and condensed matter physics.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Englisch: The present study displays new methods for the synthesis of structured inorganic materials with novel architecture in micrometer and nanometer range. The main role of the special design is based on template induced precipitation of inorganic materials on self - assembled monolayers. Suitable substrates are gold - coated glass slides and gold colloids, which show behavior like molecules, and at the same time they still display many properties of extended solids. On these substrates thiols can be adsorbed to form a monomolecular layer, which interferes with the physical properties of the obtained surface. The synthesis of special thiols, tuned for the special need in current applications, represents a main focus in the present study. Gold coated glass as templates were used in the first part of this work. The precipitation of calcium carbonate was examined due to the film thickness of the adsorbed monolayer. Aragonite, one of the three important calcium carbonate phases, is formed on self assembled monolayers under ambient conditions using a polyaromatic amide surface with film thickness in ranges of 5 - 400 nm as nucleation template. The parameters that could be controlled were the polaramide chain length, the?-substituent at the polymer, the connection to the gold surface using different amino thiols and the crystallization temperature. Here, the control of thickness of a polyaramide monolayer during its preparation using a step polymerization technique is presented the first time. By using self - assembled monolayers (SAM) of alkane thiols gold-coated glass slides have been patterned. Through the use of a special thiol terminated with a styrene monomer, microstructures of 5 to 10 æm width and 70 Å height have been formed on the surface by graft polymerization of styrene. These patterned gold slides have then been used to template the precipitation of thin titania films from ethanolic solutions of titanium isopropoxide to create microstructured architectu.
Author: Nicholas D. Spencer
Publisher: World Scientific
ISBN: 9814289426
Category : Technology & Engineering
Languages : en
Pages : 690
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The focus of the book is the modification of surfaces to tailor them for a specific purpose. Using this method of surface modification, materials chosen for their bulk properties (tensile strength, temperature stability, density, price can be optimized for any particular application, which can lead to improved hardness, biological inertness or activity, corrosion resistance, low or high friction or adhesion, water repellency or wettability, or catalytic activity. The works of the author — many of his crucial papers are included — touches upon these surface properties and spans fields including catalysis, analytical surface science, self-assembled monolayers, tribology, biomaterials, superhydrophobicity and polymer coatings.
