(722i) Controlled Synthesis of Organic Nano/Micro-Wires on Gold Nanoparticle Seeds for Sensors Applications

This research focuses on new method of nano/micro-wire sensor fabrication. Though nanotechnology has been studied for over decades, only very few nano/micro-wire sensors has successfully reached market. The major difficulties are complicated manufacture processes and high cost. Our previous and ongoing research shows that gold nano-particles (GNPs) can direct and confine the growth of organic nanorods, like tetrathiafulvalene bromide charge transfer salt (TTFBr) and copper tetracyanoquinodimethane (CuTCNQ). GNPs of different size and shape were first deposited on highly oriented pyrolytic graphite (HOPG) by applying pules of certain overpotential. When depositing the organic TTFBr or CuTCNQ wires onto the GNP decorated HOPG, the size of the organic crystals is confined by the GNP size and the organic wires grow preferentially on GNPs. Nanorods as small as 7 nm in height were nucleated on GNP of 20 nm in height. Applying this patented substrate-mediated crystallization process, organic rods were successfully deposited onto photolithographic electrode. By exposing the nano/micro-wires to ammonia gas and monitoring the impedance change, the CuTCNQ nano/micro-wire sensor achieved a sub ppm detection limit and a fast response. By further tuning chemical structures and conductivity of the nano/micro-wires, and applying different types of organic nano/micor-wires in an array, the selectivity towards ammonia, especially against humidity variation, can also be improved. Currently, this pattern is being commercialized together with some other companies. This work is supported by the National Science Foundation, US Army Research Office, and MTRAC.