Environmentally Benign Production of Ionic Liquids in CO2-Expanded Systems

The need to reduce air pollution in chemical manufacturing processes continues to drive the search for alternative solvents. Ionic Liquids (ILs) have emerged in recent years as a promising solution. In contrast to traditional organic solvents, ILs have negligible volatility, which eliminates air emissions and harmful worker exposure concerns. Various combinations of cations and anions afford distinct properties to an IL, such as melting point, solvation properties, and phase behavior; thus making it possible to molecularly design or engineer ILs for specific tasks across many chemical sectors. Unfortunately, many ILs are synthesized and processed using the very organic solvents which they are purportedly replacing. Despite the exponential growth in this field, very little work focuses on developing alternative synthesis and production methods for ILs. The objective of this dissertation is to investigate novel economically viable and environmentally benign methodologies for ionic liquid production. Three solvent platforms: 1) conventional organic solvents; 2) compressed and supercritical CO2; 3) CO2-Expanded DMSO are considered for the synthesis of IL synthesis. A full understanding of the kinetics and effects of solvent in the synthesis of ILs is of great importance for optimally selecting a benign and economically viable solvent for IL production. Empirical LSER expression, correlating kinetic rate constant with solvent polarity was obtained, which will facilitate rapid data generation needed for engineering production processes of different ILs in varied solvent systems. While some general trends for these Mentshukin-type reactions are widely known, quantitative second (2nd) order rate constants are reported here. The use of CO2 in the synthesis of ILs has many advantages over conventional solvents. CO2 induces IL-solvent mixtures to split into IL-rich and organic solvent-rich phases that can be decanted or extracted for easy separations, simply by controlling pressure, temperature and CO2 loading. This work demonstrates that CO2 is a flexible and tunable solvent for the synthesis of the model IL 1-hexyl-3-methylimidazolium bromide ([HMIm][Br]). Previously, our group has found that among ten organic solvents, DMSO has the highest kinetic rate for the synthesis of [HMIm][Br]). Although DMSO is a relatively environmentally benign solvent, it is beset with a high boiling point (189oC), rendering it both economically and environmentally non-feasible as a solvent option. The synthesis and processing of ILs in gas-expanded DMSO alleviates these issues. Furthermore, gas expanded liquids reduce the amount of organic solvent needed for the reaction. This work, for the first time, leverages the kinetic benefits of DMSO and the thermodynamic advantages of benign CO2 for the production of ILs. Specifically, this study explored another promising solvent media; CO2 expanded liquid DMSO (CXLs).Non-complex separation schemes are proposed from mixture phase behavior. Kamlet-Taft polarity parameters for CO2 expanded DMSO are also reported. Experimental high-pressure phase equilibria data were measured and modeled for CO2 binary, ternary and pseudo-binary systems encountered in the synthesis of [HMIm][Br]. Unique chemical and thermodynamic behaviors are observed in the IL-synthesis mixtures. Using estimated critical properties to correlate the vapor-liquid equilibrium, the Peng-Robinson equations of state, with van der waals 2-parameter mixing rules, were found to sufficiently correlate data. The phase equilibrium data allow better understanding and kinetic characterization of the synthesis of ILs with CO2. Results have important ramifications on the kinetics and process constraints of an actual IL synthesis in high pressure systems. Design considerations for optimizing solvents ratio, kinetic properties and separations are discussed. Here, the systematic risk assessment methodology was extended to ILs systems. Environmental assessments of different IL synthesis routes studied here are performed and presented. Potential issues (unit operations that have the most impact on the environment and profitability) in the life cycle of the processes are identified. Green sustainable methodology was extended to applications of ILs viz cellulose valorization and processing, separations and the fabrication of cellulosic materials

Development and characterization of novel indigoid chromophores, photoswitches and molecular machinery

The photochemistry and photophysical properties of hemiindigo based photoswitches and indigo based molecular machines were examined. It could be shown that hemiindigos are a class of virtually unexplored, potent photoswitches supporting high photoisomerization ratios with blue over green to yellow and red light, high thermal bistabilities, good quantum yields and high tolerance of the photoreactions towards solvent polarity changes. The introduction of a chiral acyl or aryl axis on the hemiindigo chromophore at the indoxyl nitrogen was tested with various substitution patterns to explore the influence of electronics and sterics on the photophysical properties, electronic circular dichroism spectra and the motion of the passive chiral axes. Introduction of two chiral axes to the well-known indigo chromophore was carried out. The potential of these molecules as prospective molecular motors and -machines was demonstrated, giving insights into novel photoinduced- and thermal motions, which is crucial for the design of nanomachines and molecular robots. Also, addressability within the biooptical window was achieved, as all photosteps can be driven with low energy, 625 nm LED light, making the application of likewise systems available on biological tissues in vitro and in vivo. Three permanently charged, thermally bistable hemiindigos were synthesized and their photochemical properties in the gas phase and in solution were investigated. Several permanently charged hemiindigo photoswitches were tested in water and their photophysical properties as well as their ability to bind to DNA/RNA was scrutinized. Furthermore, the measurement procedures and automatization of photophysical measurements were improved

PEDOT:PSS charge storage devices integrated into textiles for smart textile application

Smart textile systems enable interaction of the user with his/her environment through sensing and actuation. They find application in sports garment, future fashion with visual light interaction, health and tele monitoring, sound responsive garments for managing autism, and in personal protective clothing etc. Smart textile systems consist of sensors, actuators, power supply unit, data processors and interconnects for transmission of signals and/or data. The energy supply unit can either be energy generated on the spot, or as a form of stored energy in batteries. Currently, the batteries used with smart textile systems, are non-flexible, bulky and weighty, and cannot be compared with the comfort of the textiles themselves. Therefore, this research addresses the fabrication of a suitable charge storage device well integrated into textile and that could provide power to the smart textile system. The developed devices are light weight, flexible and reliable

Characterization, modeling, and simulation of multiscale directed-assembly systems

Nanoscience is a rapidly developing field at the nexus of all physical sciences which holds the potential for mankind to gain a new level of control of matter over matter and energy altogether. Directed-assembly is an emerging field within nanoscience in which non-equilibrium system dynamics are controlled to produce scalable, arbitrarily complex and interconnected multi-layered structures with custom chemical, biologically or environmentally-responsive, electronic, or optical properties. We construct mathematical models and interpret data from direct-assembly experiments via application and augmentation of classical and contemporary physics, biology, and chemistry methods. Crystal growth, protein pathway mapping, LASER tweezers optical trapping, and colloid processing are areas of directed-assembly with established experimental techniques. We apply a custom set of characterization, modeling, and simulation techniques to experiments to each of these four areas. Many of these techniques can be applied across several experimental areas within directed-assembly and to systems featuring multiscale system dynamics in general. We pay special attention to mathematical methods for bridging models of system dynamics across scale regimes, as they are particularly applicable and relevant to directed-assembly. We employ massively parallel simulations, enabled by custom software, to establish underlying system dynamics and develop new device production methods

Chemical approaches to ubiquitous computing

Dissertação apresentada para obtenção do Grau de Doutor em Química, perfil de Química Física, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologi

Molecular dynamics simulations of liquid crystals and photoresponsive systems

Neisseria gonorrhoeae (Ngo) expressing the outer membrane protein OpaHSPG can adhere to and invade epithelial cells via binding to heparan sulphate proteoglycan (HSPG) receptors. In this study, we have investigated the role of syndecan-1 and syndecan-4, two members of the HSPG family, in the uptake of Ngo by epithelial cells. When overexpressed in HeLa cells, both syndecans co-localize with adherent Ngo on the host cell surface. This overexpression of syndecan-1 and syndecan-4 leads to a three- and sevenfold increase in Ngo invasion respectively. In contrast, transfection with the syndecan-1 and syndecan-4 mutant constructs lacking the intracellular domain results in an abrogation of the invasion process, characteristic of a dominant-negative mode of action. A concomitant loss of the capacity to mediate Ngo uptake was also observed with syndecan-4 mutant constructs carrying lesions in the dimerization motif necessary for the binding of protein kinase C (PKC) and phosphatidylinositol 4,5-bisphosphate (PIP2), and mutants that are deficient in a C-terminal EFYA amino acid motif responsible for binding to syntenin or CASK. We conclude that syndecan-1 and syndecan-4 can both mediate Ngo uptake into epithelial cells, and that their intracellular domains play a crucial role in this process, perhaps by mediating signal transduction or anchorage to the cytoskeleton

National Educators' Workshop: Update 1989 Standard Experiments in Engineering Materials Science and Technology

Presented here is a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 89, held October 17 to 19, 1989 at the National Aeronautics and Space Administration, Hampton, Virginia. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

Doctor of Philosophy

dissertationIn this dissertation, we explored the synthesis of water-soluble and photoluminescence behavior near infrared emitting (610 nm) gold nanoparticles terminated by mercaptoalkanoic acid and possessing UV range (200~350 nm) excitation. Different effects were monitored as a function of reaction condition including different gold and ligand concentrations, types of ligands, solvents and pH. It is understood that Gold-thiol complexes were formed and developed into nanoparticle-supported complexes. Analyses of the excitation spectra suggests the origin of the photoluminescence to be transitions from the triplet energy state of LMMCT with the electrons transferred from excited orbitals of Au/Au(I) sites of the gold surface. It is also the reason for the enhanced photostability compared with those produced as free molecules via other synthesis methods. The pH dependency of the emission intensity and excitation spectra alteration of the gold nanoparticles was also explored. The emission intensity of the gold nanoparticle showed linear dependency on the pH change in the weak acidic to basic region above the pH 6 with a small peak appearance at pH 4. This trend was accompanied by a distinctive excitation peak wavelength change from 280-290 nm to 250-260 nm at pH 6.. A brush configuration change of the surface ligands was proposed to explain the pH dependency. In the charged and extended form of the carboxylic acid ligands, the accessibility of water to the gold nanoparticles surface is greater than in the uncharged collapsed form. Thus, in the collapsed form, the local hydrophobicity at the gold surface is higher and theCT excitation spectrum shifts to the blue. Its biocompatibility, as suggested by the cytotoxicity test and reactive oxygen species (ROS) generation test, provides broader opportunities for this product to be utilized in biological systems

The Renaissance of Isothermal Titration Calorimetry

This dissertation is a composite of some of the research that I have conducted during the course of my PhD study. The larger goal of this dissertation is to renew the interests among the scientific community for an otherwise under-appreciated technique called Isothermal Titration Calorimetry. The resurgence of calorimetry in the biophysical community and the shift to investigations of more complex biological systems signal a real need for more sophisticated analysis techniques. This dissertation expounds on new ITC analysis methods that we have developed as well as results from the study of thermodynamic properties of higher order DNA structures. In 1978, Peter Privalov described the first use of microcalorimetry to obtain the thermodynamic properties for removing calcium from parvalbumin III protein. Fast forward 36 years: modern day electronics, highly efficient thermally conductive and chemically inert materials, in conjunction with sensitive thermal detectors, has transformed the original calorimeter into a device capable of measuring heat changes as small as 0.05 nanowatts, which is equivalent to capturing heat from an incandescent light bulb a kilometer away. However, analytical methods have not kept pace with this technology. Commercial ITC instruments are typically supplied with software that only includes a number of simple interaction models. As a result, the lack of analysis tools for more complex models has become a limiting factor for many researchers. We have recently developed new ITC fitting algorithms that we have incorporated into a userriendly program (CHASM©) for the analysis of complex ITC equilibria. In a little over a year, CHASM© has been downloaded by over 370 unique users. Several chapters in this dissertation demonstrate this software’s power and versatility in the thermodynamic investigations of two model systems in both aqueous and non-aqueous media. In chapter VI, we assembled a model NHE-III1 : a novel structure of Gquadruplex in a double stranded form and studied its structural complexity and binding interactions with a classical G-quaduplex interactive ligand known as TMPyP4. In chapter VII, we reported the thermodynamic properties of a novel PAH system in which weak dispersion forces are solely responsible for formation of the supramolecular complexes