Tungsten oxide clusters decorated ultrathin In2O3 nanosheets for selective detecting formaldehyde

- Although WOx does not show sensing ability towards formaldehyde, the response of In2O3 nanosheets was greatly enhanced by the addition of WOx.
- WOx/In2O3 nanosheets could detect trace amount of gaseous formaldehyde in air at a low working temperature (170 °C).
- The WIO-4 sensor exhibits low detection limit, excellent selectivity, good stability, short response time and recovery time.

To guarantee the human health, it is important to monitor the amount of formaldehyde in air. However, it is difficult to detect formaldehyde at low concentration level. Here, WOx clusters decorated In2O3 nanosheets were synthesized for the first time via a simple and convenient impregnating method. The sensors based on the above WOx/In2O3 composites show excellent sensing performance to trace formaldehyde gas at a relative low operating temperature (170 °C). The gas sensor based on 4 wt% WOx/In2O3 exhibits the lowest detection limit (i.e. 0.1 ppm), short response time (1 s) and acceptable recovery time (67 s). Furthermore, the response value of 4 wt% WOx/In2O3 composite sensor is about twice as high as that of the sensor based on pure In2O3. It is believed that the enhanced sensing performance can be predominantly attributed to the additional active sites induced by the formation of WOx-In2O3 heterojunction between WOx nano-clusters and In2O3 nanosheets.