Development of high performance ammonia sensor based on Al doped SnO2 operable at room temperature

Abstract

This study aims to synthesize Al-doped SnO2 nanostructures using a sol–gel process and investigate their gas-sensing properties, notably ammonia (NH3) detection at ambient temperature. X-ray diffraction (XRD) examination validated the tetragonal crystal structure of the produced Al: SnO2 materials. Field emission scanning electron microscopy (FE-SEM) images showed aggregation of the prepared samples. Transmission electron microscopy (TEM) was used to evaluate the structural and morphological properties of AlS-2 and AlS-8, and selected area electron diffraction (SAED) confirms the crystal structure. As the concentration of Al doping in SnO2 nanostructures increased, the optical band gap (Eg) values decreased. The chemical composition was analyzed using X-ray photoelectron spectroscopy (XPS). Gas sensing studies were conducted on NH3 gas concentrations ranging from 5 to 300 ppm, and AlS-8 emerged as the most promising sensor, with substantial responsiveness, rapid response, recovery durations (21 s/18 s), and linear behavior at ambient temperature. This improved performance shows that AlS-8 has the potential to be an excellent NH3 detector, due to the higher adsorption of oxygen species made possible by Al doping. Surprisingly, continuous measurements over 30 days at five-day intervals revealed significant reactivity of the AlS-8 sensor even at concentrations as low as 100 ppm of NH3 gas.