Development of a portable zeolite-based gas sensor

The selection and discrimination of gases is based on differences in pore size, pore shape, and polarity of selected zeolites. This research involves developing a nanoporous zeolite dye combination as the gas-sensing portion of a hybrid optical and optoelectronic integrated system. Zeolite combined with florescent dye will provide the electro-optical sensing that can be readily integrated into microelectro-niechanical systems (MEMS) in a portable detector. The research project involves the testing and analyzing of host-guest fluorescence properties using a tunable laser diode and a confocal spectrometer microscope. The gas mixtures (adsorbates) are being modeled and measured for heat of adsorption, diffusivity. and transport properties (including flow rate, mass transfer coefficient, response time, and regeneration time) for each combination of zeolite dye adsorbent. The overall project goal is to use the results generated in the labs to develop, fabricate and test a MEMS/HEMS chemical sensor array. One unique aspect of the research is a procedure to change the hydrophobic hydrophilic properties of the nanocrystalline zeolites by functionalizing the zeolites using chlorosilane reagents. The reagents will react with the silanol groups (Si-OH) on the zeolite surface resulting in a change in the adsorption properties of the substrate, the magnimde of winch will depend on the type of zeolite. The changes in adsorption properties, in combination with differences in pore sizes and shapes, will result in considerable discrimination between different adsorbed species. Because of the high surface area (- 1000 m2 g) and regular pore size (0.4 - 1.4 mn). the nanoporous zeolite-based chemical sensor array will be sensitive, selective, stable, operate at room temperature, have fast response, and be easy to regenerate.