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

Abstract

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 (R_g/R_a = 65, R_g is the sensor resistance measured in a mixture of target gases and R_a is the resistance measured in air) compared with the pristine Co₃O₄ NW sensor (R_g/R_a = 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.