Fabrication of a Au@SnO2 core–shell structure for gaseous formaldehyde sensing at room temperature

This paper describes the fabrication of a Au@SnO2 core–shell structure using the sol gel method to manufacture the sensing materials. The properties of the sensing material were analyzed with UV–vis spectra, Fourier transform infrared spectroscopy, and transmission electron microscopy. The SnO2 material showed no response, whereas 1 wt% Au/SnO2 exhibited a 2.4 sensor response. The response t90 (for a result equaling 90% of the equilibrium signal) and recovery tr90 (to adjust the signal to 90% background signal) times of the 1 wt% Au/SnO2 material measured 240 s and 210 s, respectively. Au@SnO2 further enhanced the sensor response to 2.9 while reducing the response and recovery times to 80 s and 62 s. This study also demonstrates a formaldehyde gas-sensing mechanism involving HCHO adsorption and surface reaction and product desorption.