Methylbenzene sensors using Ti-doped NiO multiroom spheres: Versatile tunability on selectivity, response, sensitivity, and detection limit

Pure and Ti-doped NiO multiroom spheres were prepared via ultrasonic spray pyrolysis, and their gas sensing characteristics were investigated. The sensor using 10 at% Ti-doped NiO multiroom spheres exhibited an unprecedented high response (resistance ratio = 337.8) to 1 ppm p-xylene at 350 ℃, whereas the sensor using pure NiO multiroom spheres exhibited a negligibly low response (1.3). Moreover, the control of the Ti doping and film thickness provided intriguing strategies for tuning the xylene and methylbenzene sensing characteristics, such as the selectivity, response, sensitivity (slope between response and gas concentration), and detection limit. The versatile tunability on gas sensing characteristics was explained by the Ti-doping-induced variation of the oxygen adsorption, mesoporosity, specific surface area, and charge-carrier concentration, as well as the control over the reforming and oxidation of the analyte gases using the multiroom-structured micro-reactors with high catalytic activity.