Investigation of composites of carbon black and metallocycles, and functionalized transition-metal nanoparticles as chemiresistive vapor sensors

Abstract

An electronic nose is a man-made implementation of an olfactory system that is comprised of an array of broadly cross-reactive sensors. Electronic noses are used in the food industry, environmental monitoring, explosive detection and medical diagnosis. Our laboratory has focused in the development and implementation of arrays of low power, inexpensive chemiresistive thin films, that are able to identify and quantify a diverse collection of vapors and mixtures of vapors. Novel bioinspired sensors, and array chamber architectures are constantly been developed and improved to fulfill the desired performance of such arrays in different applications. This work details the development and the sensing performance of novel sensor materials based on composites of carbon black and metalloporphyrins, and organically-functionalized gold (Au) and titanium (IV) dioxide (TiO2) nanoparticles. Composites of carbon black and metalloporphyrin complexes were developed and optimized to sensitively detect and classify a series of organic vapors. Such sensors films also exhibited a high sensitivity towards trace levels of ammonia (NH3(g)) and 2,4,6-trinitrotoluene (TNT) in air. Such composites broaden the types of materials that can be used for this type of low-power chemiresistive vapor sensing, and broaden the types of analytes that can be sensitively detected to include inorganic gases and explosives, as well as organic vapors. Au and TiO2 nanoparticles were synthesized and functionalized with a variety of ligands. These materials allowed for molecular control of the interparticle physicochemical properties such as electron transfer. Details about the performance of each unique functionalized Au or TiO2 nanoparticle film upon exposure to a variety of organic vapors was described as a function of ligand length, structure and other physicochemical properties. The discrimination performance for arrays of such sensors was also evaluated.