Bimetal Ag NP and Au NC modified In2O3 for ultra-sensitive detection of ppb-level HCHO

Detecting trace ppb-level of formaldehyde (HCHO) in indoor ambient and human exhaled breath using metal oxide semiconductor (MOS) gas sensor has attracted increasing attention. Herein, Ag nanoparticles (Ag NP) modified In 2 O 3 and Au nanocage (Au NC) modified In 2 O 3 as well as bimetal Ag NP and Au NC co-modified In 2 O 3 were successfully prepared via one-step microwave-assisted solvothermal method and were used to construct semiconductor gas sensor. It is exciting to observe that the sensor based on Ag 6 Au 1 /In 2 O 3 exhibits the highest response of 277 toward 5 ppm HCHO at low operating temperature (170 °C), which is about 7 times, 38 times and 102 times higher than 6 wt. % Ag/In 2 O 3 , 1 wt. % Au/In 2 O 3 and pristine In 2 O 3 , respectively. Moreover, the selectivity and detection limit (down to 26 ppb) of Ag 6 Au 1 /In 2 O 3 sensor to HCHO have been proven to be greatly improved. This excellent sensing performance indicates that the proposed bimetal Ag and Au co-modification with synergistic catalysis effect offers an effective design for highly sensitive and efficient HCHO detection devices. Moreover, the mechanism of HCHO sensing with Au and Ag co-loaded In 2 O 3 was explored by the calculations obtained from first-principle density functional theory studies .