Applications of sol-gel materials in analytical chemistry

This thesis describes the development of sol-gel materials for use in analytical chemistry. An overview of the sol-gel process, as well as an introduction to chemical sensors, are presented in Chapter 1. A novel approach to the use of crown ethers for the removal of Sr² is discussed in Chapter 2. Disulfonated, dibenzo-18-crown-6 encapsulated within a sol-gel matrix is used for the removal of strontium (11) ions from aqueous systems. Sol-gel materials "doped" with crown ethers are shown to exhibit higher uptake of the target metal (Sr²) compared to blank, non-ligand containing gels. In Chapter 3, a chemical sensor based on the deflection of a surface modified silicon microcantilever is presented. A thin film of sol-gel was applied to one side of the micro-cantilever surface using a spin coating procedure. The sensor has been shown to give different responses to vapor phase analytes of varying chemical composition, as well as to varying concentrations of a given analyte. Ethanol, a highly polar molecule, exhibits a strong affinity for the polar sol-gel coating resulting in a large response, pentane, a nonpolar hydrocarbon, shows very little response. The sol-gel coating has also been shown to function as a backbone for the immobilization of chemically selective phases on the cantilever surface. Reaction of the sol-gel film with chlorotrimethylsilane and subsequent capping of the remaining reactive surface silanols with hexamethyldisilazane increase the non-polar nature of the film. This results in an increase in the response of the sensor to non-polar analytes. The effects of film thickness and cantilever structure thickness on response were also investigated.