Cr-doped Co3O4 nanorods as chemiresistor for ultraselective monitoring of methyl benzene

Ultrasensitive and selective detection of methyl benzenes was achieved for Co3O4 nanorods through Cr-doping. Pure and 1.17-1.89 at% Cr-doped Co3O4 nanorods were synthesized by a solvothermal reaction, followed by calcination at 400 °C for 2 h. The gas-sensing properties of the nanorods were tested to methyl benzene (toluene and xylene) and compared with interfering gases (benzene, ethanol, ammonia, CO and NO2) at various concentrations (0.25-5 ppm) and temperatures (250-350 °C). The results demonstrated that Cr-doping significantly enhanced the response to methyl benzenes while suppressing cross-responses to interfering gases, resulting in selectivity for methyl benzene. The ultraselectivity to methyl benzene in the Cr-doped Co3O4 nanorods was attributed to catalytic activity and the abundant adsorbed oxygen of the Cr oxides and Co3O4 for the partial oxidation of methyl benzenes to more active chemical species.