Defense Date

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Collinson

Abstract

This work utilized the sol-gel process in two ways. First, macroporous silica thin films were developed using a combination of casting techniques and templating. Macroporsity was introduced to the silica thin films by either doping the silica sol before casting or by ordering the template on a substrate and then casting a sol over it. These techniques were first used to create silica thin films with long microchannel pores (200 nm x 60 µm) from a doped sol with the bacteria, B. Megaterium, as the template for nanomaterial formation. To enable the formation long microchannels, the flexible bacteria chains were aligned by using light scratches on the substrate surface as anchors for the bacteria’s adhesive cell capsule. Polystyrene (PS) sphere templates were then used in several studies to obtain silica thin films with well-ordered “nanowells,” single-layer hemispherical pores that allowed direct access to the substrate beneath the film. Copper and gold nanoparticles were integrated into moderately packed films by electrodepostion and monolayer self-assembly, respectfully. The size of the nanoparticles was controlled by the time of the electrodeposition or the time of exposure to an electroless growth solution. The final study with polystyrene latex sphere templates produced high quality, well-packed films containing well-defined nanowells over almost the entire conductive substrate. This was accomplished by separating the ordering of the templates on the substrate from film formation. Electroless growth was used to control the size and shape of the gold nanoparticles and the electrochemical properties of the resultant films were studied, showing an enhanced response to negatively charged redox probes. Sol-gel techniques were then used to create high aspect ratio silica nanotubes and pillars. The electroassisted deposition of silica was carried out in the pores of track-etched membranes, allowing supported nanotubes with dimensions of 100 – 400 nm x 10 µm to be obtained. The mechanism of silica formation in the tubular template was studied and it was found that growth occurred first by nanotube formation, followed by further growth through tube from the electrode to the other side of the pore. This allowed for partially filled tubes and solid pillars to be obtained. The method was found to be flexible and characteristics such as tube length, chemical functionality and porosity to be controlled.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

August 2012

Included in

Chemistry Commons

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