Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Physical Chemistry

PDF

University of Massachusetts Amherst

2015

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

Contact Angles And Contact Lines Around Particles At Isotropic And Anisotropic Liquid Interfaces, Nesrin Senbil Nov 2015

Contact Angles And Contact Lines Around Particles At Isotropic And Anisotropic Liquid Interfaces, Nesrin Senbil

Doctoral Dissertations

Liquid interfaces, capillarity and self-assembly of particles at interfaces are important in nature and technology. When a particle is adsorbed to a liquid interface, the contact line of the particle with the liquid interface and the associated contact angle are the crucial parameters that drive assembly of the particles. We looked at how the shape of the liquid interface and the shape of the particle affect the contact angle and the shape of the contact line. We used millimeter-sized PDMS-coated glass spheres and measured the contact angles at isotropic (planar) and anisotropic interfaces (saddle and cylindrical in shape). Anisotropy of …

Go to article

Impact Of Fabrication Parameters On The Internal Structure Of Poly(3-Hexylthiophene) Nanoparticles, Dana Desiree Algaier Nov 2015

Impact Of Fabrication Parameters On The Internal Structure Of Poly(3-Hexylthiophene) Nanoparticles, Dana Desiree Algaier

Doctoral Dissertations

Morphological control of organic functional materials is central to understanding and improving upon current technologies. The ability to create hierarchical assemblies with purposeful design from nano to meso scale has remained largely unattainable. This body of work aims to provide a foundation for creating nanoscale domains of poly (3-hexylthiophene) (P3HT) that can be used as building blocks to larger scale assemblies. We present a method for the fabrication of P3HT nanoparticles on the ability to vary the particle size and more importantly, the internal structure. We have identified the oil phase and surfactant as parameters able to influence the nature …

Go to article

Quantum Calculations Of Aldol Condensation In Acidic Zeolites, Angela N. Migues Nov 2015

Quantum Calculations Of Aldol Condensation In Acidic Zeolites, Angela N. Migues

Doctoral Dissertations

We have used Density Functional Theory to model the mixed aldol condensation reaction catalyzed by acidic zeolites. We have studied the convergence of barriers for the keto-enol tautomerization of acetone in cluster models of HZSM-5 and HY ranging in size from 3-37T. A key finding was that activation barriers for keto-enol tautomerization of acetone in both zeolites (~20 kcal/mol) are significantly higher than those for the condensation reaction between the acetone enol and formaldehyde in 11T cluster models of HZSM-5 and HY. Moreover we found that three zeolite clusters of HZSM-5, similarly sized but including different structural features of the …

Go to article

Protein Charge Anisotropy Mediated Self-Association And Phase Separation, Daniel P. Seeman Nov 2015

Protein Charge Anisotropy Mediated Self-Association And Phase Separation, Daniel P. Seeman

Doctoral Dissertations

Protein charge anisotropy results from the asymmetric distribution of charged residues on the exterior of a particular protein. Interactions between proteins and other macromolecules can be described in terms of attractive electrostatics; since electrostatic free energies, at optimal I, are on the order of kT, it is unlikely that such associations would result in desolvation, thus it is reasonable to consider such intermolecular attractions as being mediated by hydrated protein surfaces. Such interactions can be broken down in terms of a single protein interacting with a range of “binding partners”, including (1) protein-protein interactions, (2) protein-polymer interactions, and …

Go to article

Design And Application Of Organic Electronic Materials: Pendant Tuning In Polymeric And Molecular Systems, Jonathan S. Tinkham Aug 2015

Design And Application Of Organic Electronic Materials: Pendant Tuning In Polymeric And Molecular Systems, Jonathan S. Tinkham

Doctoral Dissertations

Designing and synthesizing materials for use in organic electronic materials requires fine control over their optical and electronic properties. Variations through substitution can be used to tune solubility and electronic properties, but this can result in degradation of other properties. Substitution with orthogonal pendant groups in both molecular and polymeric systems has the potential for allowing tunability while decreasing the perturbation of other desirable properties of the parent system. This idea was explored through experimental and computational work. Computational modelling was used to understand and predict the properties of molecular and polymeric systems to narrow the wide number of choices …

Go to article

Time-And Polarization-Resolved Photoluminescence Studies Of Directional Coupling In Isolated Semiconductor Nanostructures, Joelle A. Labastide Aug 2015

Time-And Polarization-Resolved Photoluminescence Studies Of Directional Coupling In Isolated Semiconductor Nanostructures, Joelle A. Labastide

Doctoral Dissertations

TIME-AND POLARIZATION-RESOLVED STUDIES OF DIRECTIONAL COUPLING IN ISOLATED SEMICONDUTOR NANOSTRUCTURES MAY 2015 JOELLE A. LABASTIDE, B.S. UNIVERSITY OF MASSACHUSESSTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMERST Directed by Professor Michael D. Barnes Development of new materials and assembly strategies for organic semiconductor-based optoelectronic materials is a problem of great interest worldwide, as researchers seek to resolve the questions pertinent to the creation of inexpensive, reliable, efficient, and stable active layer components. Organic semiconductors as the basis for photovoltaic active layers show significant promise for these applications. However, there is still much that needs to be understood about the molecular scale structural …

Go to article

Catalytic Methane Dissociative Chemisorption Over Pt(111): Surface Coverage Effects And Reaction Path Description, Inara Colon-Diaz Mar 2015

Catalytic Methane Dissociative Chemisorption Over Pt(111): Surface Coverage Effects And Reaction Path Description, Inara Colon-Diaz

Masters Theses

Density functional theory calculations were performed to study the dissociative chemisorption of methane over Pt(111) with the idea of finding the minimum energy path for the reaction and its dependence on surface coverage. Two approaches were used to evaluate this problem; first, we used different sizes of supercells (2x2, 3x3, 4x4) in order to decrease surface coverage in the absence of pre-adsorbed H and CH3 fragments to calculate the energy barriers of dissociation. The second approach uses a 4x4 unit cell and surface coverage is simulated by adding pre-absorbed H and CH3 fragments. Results for both approaches show …

Go to article

Design, Syntheses And Study Of Bodipy-Based Materials For Use As Electron Transporters In Organic Electronics, Ambata Poe Mar 2015

Design, Syntheses And Study Of Bodipy-Based Materials For Use As Electron Transporters In Organic Electronics, Ambata Poe

Doctoral Dissertations

Organic photovoltaics (OPVs) are desirable for the harvesting of solar energy. They provide distinct advantages over their inorganic counterparts, especially the high absorption coefficients of organic materials and their ability to be processed using inexpensive solution methods. This allows for potential development of lightweight and flexible devices for portable electronics. One of the drawbacks of organic photovoltaics is the low power conversion efficiency of the devices. Efforts to improve the efficiency often take place through molecular design of the electron rich donor material to improve light absorption of the active layer. However, significantly less effort has been put into modifying …

Go to article

Aggregation And Interfacial Behavior Of Charged Surfactants In Ionic Liquids, Lang Chen Mar 2015

Aggregation And Interfacial Behavior Of Charged Surfactants In Ionic Liquids, Lang Chen

Doctoral Dissertations

Room-temperature ionic liquids (ILs) exhibit a unique set of properties, leading to opportunities for numerous applications such as green solvents, batteries and lubricants. Their properties can be greatly tuned and controlled by addition of surfactants. It is therefore critical to obtain a better understanding of the aggregation and interfacial behavior of surfactants within ILs. Firstly, the phase diagram and aggregation isotherms of surfactants in several distinct ILs were investigated by solubility and tensiometry. A connection between solubility of the surfactant and the physical properties of the underlying ionic liquid was established. We found that the interfacial energy was crucial in …

Go to article