Sensing trace amounts of nitro-aromatic explosives using nanowire-nanocluster hybrids

Abstract

ABSTRACT The threat of terrorism and the need fo r homeland security calls for advanced technologies to detect the concealed explosives safely and efficiently. We demonstrated highly sensitive and selective detection of traces of nitro-aromatic explosive compounds by functionalizing gallium nitride (GaN) nanowires with titanium dioxide (TiO 2 ) nanoclusters to address this issue. The hybrid sensor devices were developed by fabricating two-terminal devices using individual GaN nanowires (NWs) followed by the deposition of TiO 2 nanoclusters (NCs) using sputtering technique. The photo-modulated GaN/TiO 2 NWNC hybrids showed remarkable selectivity to benzene and related aromatic compounds, with no measureable response for other analytes at room temperature. This paper presents the sensing characteristics of GaN/TiO 2 nanowire-nanocluster hybrids towards the different aromatic and nitroaromatic compounds at room temperature. The GaN/TiO 2 hybrids were able to detect trinitrotoluene (TNT) concentrations as low as 500 pmol/mol (ppt) in air and dinitrobenzene concentrations as low as 10 nmol/mol (ppb) in air in approximately 30 s. The noted sensitivity range of the devices for TNT was from 8 ppm down to as low as 500 ppt. The detection limit of Dinitrotoluene , nitrobenzene , nitrotoluene, toluene and benzene in air is 100 ppb with a response time of ~ 75 s. The devices show very sensitive and selective response to TNT when compared to interfering compounds like toluene. Integration of this nano-scale technology could lead to tiny, highly sensitive, selective, low-power and smart explos ive detectors that could be manufact ured cheaply in large numbers. Keywords : explosives, sensors, nitro-aromatics, nanowire-nanocluster