Doctoral Dissertations

Date of Award

5-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

John Z. Larese

Committee Members

Robert J. Hinde, Frank Vogt, Philip Rack

Abstract

Metal oxides (MO) and their surfaces play a vital role in numerous phenomena, including metal surface passivation, catalysis, integrated optoelectronic technology, and pollution monitoring via solid-state gas sensing. This experimental study seeks to aid in the development of accurate and predictive theoretical models of the potential energy surfaces described in the interaction of these small molecules with the magnesium oxide (MgO) substrate. MgO, with its structural simplicity and capacity to be fabricated with a predominantly (100) exposed face, is an ideal representative of the MO family popular for both experimental and theoretical studies. Using high-resolution volumetric adsorption isotherms, a thermodynamic investigation of n-butane and 1-butene on MgO systems resulted in the accurate determination of the two dimensional compressibility, differential enthalpy and entropy, heat of adsorption and isosteric heat of adsorption in the temperature range between 158 K and 198 K for n-butane and between 160 K and 195 K for 1-butene.

The synthesis of mesoporous silica spheres with hollow interiors has attracted much attention due to their potential application in drug delivery, encapsulation, catalysis, separation, gas adsorption, sensors, and nanodevices. Various methods have been attempted in order to develop procedures for making reproducible and dependable methods of hollow mesoporous silica particles; these include sol-gel, emulsion, and organic polymer. However, despite reports of mesoporous silica being synthesized using different templates and under various reaction conditions, there is no single mechanism, which can be used to universally explain the microscopic details of formation and growth of the uniform pore and ordered pore structure. This work seeks to investigate the role played by concentrations and ratios of the reactants and experimental conditions (such as pH temperature, and stirring speed) on the formation of mesoporous silica spheres. By using several different characterization techniques such as small angle x-ray scattering, volumetric adsorption/desorption isotherms, scanning electron microscopy, and Fourier transform infrared spectroscopy insight into the formation mechanism and the ability to produce specific and tailored mesoporous silica particles is gained.

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