Synthesis of TiO2 decorated Co3O4 acicular nanowire arrays and their application as an ethanol sensor

A novel heterostructure of TiO2 modified Co3O4 (TiO2/Co3O4) acicular nanowire (NW) arrays has been fabricated in this study, which demonstrates a good performance for ethanol detection at working temperatures as low as 160 °C. Co3O4 NW arrays were first grown on an Al2O3 substrate patterned with an Ag/Pd electrode by a hydrothermal method, and then TiO2 nanoparticles were decorated on the surface of Co3O4 NW arrays by using pulsed laser deposition (PLD). It is found that after decoration of TiO2, the TiO2/Co3O4 NW array sensor exhibits a much higher response to ethanol (Rg/Ra = 65, Rg is the sensor resistance measured in a mixture of target gases and Ra is the resistance measured in air) compared with the pristine Co3O4 NW sensor (Rg/Ra = 25). Importantly, the TiO2/Co3O4 sensor has shown a detection limit as low as 10 ppm, and a good reproducibility. The reason for the enhanced sensing properties of TiO2/Co3O4 is considered to be due to the formation of a p–n junction between the p-type Co3O4 and n-type TiO2.