The role of gold catalyst on the sensing behavior of ZnO nanorods for CO and NO2 gases

A facile one-pot strategy was developed for the assembly of gold nanoparticles (Au NPs) onto single crystalline ZnO nanorods using cetyltrimethylammonium bromide (CTAB) as a capping agent. Zinc oxide nanorods were synthesized by hydrothermal method whereas the Au NPs (below 5 nm) were deposited on the surface of ZnO nanorods by the solution growth method. Gas sensing properties of Au/ZnO nanorods were studied at various temperatures for various concentrations of reducing (CO) and oxidizing (NO2) gases in synthetic air and compared with pristine ZnO nanorods. Sensor fabricated by Au/ZnO nanorods showed significantly enhanced sensing performances for CO gas while opposite was the case with NO2 gas as compared to pristine ZnO nanorods. The highest response of Au/ZnO nanorods for CO gas was 12 at 150 °C while for ZnO nanorods, it was 6.12 at 400 °C. Whereas the highest response of Au/ZnO nanorods for NO2 gas was 4.14 while for ZnO nanorods, it was 10 at 300 °C. It was found that Au NPs acted as promoter for CO gas while inhibiter for NO2 gas sensing due to their different sensing mechanisms. This study suggested that noble metals decoration of ZnO nanorods can be used for selectivity issue between CO and NO2 gases.