Ambient temperature selective ammonia gas sensor based on SnO2-APTES modifications

In order to deal with the well-known lack of selectivity of SnO2 based gas sensors, the functionalization of SnO2 was performed. Liquid silanization by 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules bearing acyl chloride with alkyl or ester end functional groups. Modified sensors with APTES, alkyl and ester end functional groups were successfully characterized by Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR). No response was observed for APTES and alkyl modified SnO2 sensors to ammonia gas at room temperature while the SnO2 sensor modified with ester end group was found to be sensitive and selective to ammonia gas at room temperature. This implies that the response is generated by ester functional groups. Working at low temperature is also one of the advantages of these sensors as well as the selectivity with respect to other gases like acetone and ethanol.