Nitro-Aromatic Explosive Sensing Using GaN Nanowire-Titania Nanocluster Hybrids

Globalization of terrorist attacks in recent years calls for advanced technologies to detect the concealed explosives effectively. We demonstrate a highly sensitive and selective detection of traces of nitro-aromatic explosive compounds by functionalizing gallium nitride (GaN) nanowires with titania (TiO₂) nanoclusters to address this issue. The ultraviolet light photo-modulated GaN/TiO₂ nanowire-nanocluster (NWNC) hybrids show 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 NWNC hybrids towards the different aromatic and nitroaromatic compounds at room temperature. The GaN/TiO₂ hybrids are able to detect trinitrotoluene (TNT) concentrations as low as 500 ppt in air and dinitrobenzene concentrations as low as 10 ppb in air in approximately 30 s. The noted sensitivity range of the devices for TNT is 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 showed very sensitive and selective response to TNT when compared to interfering compounds like toluene with good reproducibility. Integration of different NWNC hybrids on the same substrate could lead to tiny, highly sensitive, selective, low-power and smart explosive detectors that could be manufactured cheaply in large numbers.