Nanostructured porous microshell films for microsensing applications
Abstract
Gas sensors are widely used in industrial, medical, domestic and environmental applications. Thermally and environmentally stable materials like metal oxides films provide low cost detection of poisonous and combustible gases by measuring small changes in conductance. Metal oxide nanoparticles have shown to improve gas detection by increasing the active surface area. Previous work on porous Sb:SnO2 nanostructured microshell sensing films exhibited over one order of magnitude increase in gas sensitivity to trace amount of gases compared to microporous nanoparticle sensing films. This was attributed to their multiscale 3-D porous architecture that promoted gas diffusion and maximized the active surface area. In this study, we expand this work by fabricating porous microshell films composed of multiple materials and of varying shell thicknesses. Combinations of tin oxide, zinc oxide and silica nanoparticle based porous microshells have been fabricated by electrostatically controlled layer-by-layer (LbL) deposition of nanoparticles on latex microspheres, which served as sacrificial templates. Films composed of interconnected nanoparticle decorated microshells were deposited on the microhotplate sensor platform and the latex cores were removed by heating the films to 380° C. Changes in sensor film conductance, caused by the exposure to different test gases (water, NO2, CO and MEK) in a dry air background, were measured at different temperatures. The optimal temperature conditions for different nanoparticle microshell films were determined and microstructural characteristics of the sensing films were assessed to explain their sensing performance. Enhanced sensitivity and selectivity of these multi-material microshell based films to gas concentrations as low as 0.01 parts per million are reported for different operating conditions.
Degree
M.S.M.S.E.
Advisors
Martinez, Purdue University.
Subject Area
Materials science
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