Gates, Byron D.

It is important that all workers understand the health and safety risks of their work environment. It has been demonstrated that exposure to nanoparticles can lead to potential health concerns. A 1 mL nanoparticle solution spill can contain >10^9 nanoparticles, with the particles invisible to the human eye. This nanoparticle spill can cause further contamination in the work environment as workers transfer the particles from one area to another if the nanoparticles are not properly remediated. Therefore, it is essential that effective methods be developed for early identification and clean-up of such spills to avoid potential hazards to those working with these particles. One goal of this research is to develop a methodology that is simple to implement on a global scale to rapidly detect the presence of nanoparticles in different workplace environments to accompany methods for the remediation of spills containing nanoparticles. X-ray fluorescence spectroscopy was identified as a portable solution to potentially identify the presence of and the extent of a spill containing nanoparticles. Many other techniques could also be utilized, but the ease of use at the point of contamination without the requirement of sample preparation makes this an attractive solution in nanoparticle remediation. Another goal of this research is to develop an efficient, effective and inexpensive means to remediate spills containing nanoparticle contaminants. The implementation of these remediation procedures would change how nanoparticles are treated in the workplace and promote a healthy work environment when using materials that would otherwise go unnoticed due to their small size. Remediation of nanoparticles spilled in the workplace requires a method of acknowledging that these unseen particles are appropriately being removed and to avoid spreading these particles to a wider extent throughout the workplace. Analytical techniques were used to monitor the presence of nanoparticle contaminants and, in combination with techniques to encapsulate nanomaterials within a spill, were used to assess the appropriateness of these remediation techniques for cleaning up simulated spills. These studies demonstrate a series of methods to progressively remove nanoparticle contamination from countertops in the workplace.

This paper describes an innovative and simple technique for analyzing defects in silane-based self-assembled monolayers. The assembly of monolayers is a simple method for chemically modifying surfaces, which can be important for resisting chemical attack or adhesion of biomolecules. Measuring the molecular scale properties of monolayers and the reproducibility of their ability to uniformly modify a surface requires tools that provide limits of detection at the level of at least a few atoms per million with specificity to the top couple nanometers of the surface. To achieve this level of sensitivity a new technique is developed that combines spectroscopy and microscopy techniques (particularly atomic force microscopy) with chemical amplification of exposed silicon in self-assembled monolayers of silane molecules. This development is an important achievement for monitoring the quality of monolayers as a function of modifications to the method(s) used to deposit the silane molecules. Techniques presented here could be easily extended to assessing the molecular scale quality of other surface modifications.

Silane-based self-assembled monolayers (SAMs) are commonly used as protective coatings against chemical etchants and adhesion of biomolecules. The conventional methods of producing SAMs are very time consuming and energy intensive processes. This thesis presents an efficient technique to produce silane-based SAMs approximately 300 times faster while consuming over 750 times less energy than the conventional method. Silane-based SAMs produce monolayers containing various types of defects. New techniques are developed to identify defects in SAMs and to correct for them. Chemical amplification of defects is developed for easily detecting defects in SAMs by traditional microscopy and spectroscopy techniques. Extraction and refilling methods are used to increase the packing density of the molecules in these monolayers and reduce the number of defects present in SAMs. By increasing the efficiency of silane deposition and improving the packing density of molecules, high quality SAMs can be produced within a short period of time.