Investigation of Ag nanoparticles decorated Ni-Al layered double hydroxide as a gas sensor

Chemiresistive gas sensors based on LDH structure were investigated for the detection of widely used volatile organic compounds (VOCs) including methanol, ethanol, and acetone at room temperature. In order to increase the surface active sites and subsequently improve the detection sensitivity of gas molecules, the use of Ag decoration method along with the creation of porosity on the surface of LDH structures were investigated. In this method, methanol solvent was used as a hole scavenger and UV radiation as a catalyst for binding Ag to the surface of LDH sheets. The microstructure and morphology of the composites were investigated by FESEM, HRTEM, EDS, EDS mapping, XRD, and MS analysis. The investigated parameters included relative humidity, calibration curve, repeatability, selectivity, and response/recovery times. According to the obtained results, the creations of surface corrosion by methanol and decorating the structure with Ag have both affected the sensitivity of the sensors. The pure Ni-Al LDH sensor has a response value of 6.8-250 ppm of ethanol. By increasing the specific surface area and creating LDH nanosheets, the response value can be increased up to 8.52. Also, the addition of Ag NP (Ni-Al LDH decorated with Ag NP) has increased the response up to 10.89. It was also observed that the response times in different modes have the least difference. At the end, the response mechanism was investigated based on the heterojunction theory.