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Semiconducting TiO2-B nanowires were synthesized and their chemical sensor performance was studied. It was found that the TiO2-B nanowires exhibited a large and reversible change in electrical resistivity when exposed to trace vapor of nitroaromatic and nitroamine explosives. The sensor showed high sensitivity and fast response at room temperature. The chemiresistive effect was attributed to the adsorption of high electronegativity explosives on the TiO2-B nanowires and a consequent depletion of charge carriers in the nanowires by surface states created by the explosive molecules. The role of the TiO2-B nanowires is proposed to impart both an extremely large surface area for the adsorption of gas molecules and a surface enriched in hydroxyl groups which connect to nitro groups of the explosive molecules. Chemiresistive sensors made of TiO2-B semiconducting nanowires promised to achieve micro-sized devices with several orders of magnitude reduction in dimensions, weight, and power consumption over current explosive detectors.