Abstract
Abstract The SnO2 powders were synthesized by sol-gel method in this work. By BET analysis, we chose the proper powders with high specific surface area and porosity for the following application. Next, the selected powders were mixed with PVB and solvent to make a paste. The paste was coated onto the Al2O3 substrate by spin coating to make a thin film, and subsequently treated with calcination at high temperature to remove the solvent and polymer. It was confirmed by SEM that the calcined SnO2 thin film was a well porous structure. In addition, we doped the thin film with Au by sputtering and with Ag by dip-coating, in which the thin film was dipped in the Ag colloidal suspension. Then, the Au/Ag-doped SnO2 thin film was fixed in the bottom of the reactor, inputted with CO gas and meanwhile recorded the corresponding change of sensitivity and reaction time at various concentrations. We found that sensitivity was affected by CO concentration, while reaction time was affected by operating temperature, and both of them were affected by Au and Ag. In our experiment, the SnO2 thin film doped without any dopants of Au and Ag showed unacceptable result of sensitivity as well as reaction time at low temperature. Although its sensitivity could be raised by doping with Au, however, that increased the recovery time due to the well adsorbing ability of CO for Au, could be improved by doping additional Ag which is helpful to adsorb O2-. Therefore, SnO2 thin film doped with both Au and Ag could show excellent sensitivity, short reaction and recovery time at low temperature and CO concentration.