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

The threat of terrorism and the need for homeland security calls for advanced technologies to detect the concealed explosives safely and efficiently. We demonstrated highly sensitive and selective detection of traces of nitroaromatic explosive compounds by functionalizing gallium nitride (GaN) nanowires with titanium dioxide (TiO2) 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 TiO2 nanoclusters (NCs) using sputtering technique. The photo-modulated GaN/TiO2 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/TiO2 nanowire-nanocluster hybrids towards the different aromatic and nitroaromatic compounds at room temperature. The GaN/TiO2 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 explosive detectors that could be manufactured cheaply in large numbers.