Tuning Surface Chemoresistivity of Au Ultrathin Films Using Metal Deposition via Surface-Limited Redox Replacement of the Underpotentially Deposited Pb Monolayer

The presented work investigates the chemoresistivity of Au ultrathin films, whose surface is modified by deposition of few monolayers of Au, Pd, or AuPd alloy. The model adsorbate in this study was the HS- ion from 0.1 M NaCl solution having concentrations ranging from 0 to 40 ppm. The Au surface modification was carried out using deposition via surface-limited redox replacement of the underpotentially deposited Pb monolayer. Modified Au films have shown higher chemoresistivity than the pristine ones. Our results and analysis suggest that these improvements are due to increased concentration of surface defects and enhanced scattering cross-section per adsorbate induced by chemical modification of the surface by Pd. The significance of our findings is discussed for practical applications shining more light on the importance of surface preparation for chemoresistive sensor design and performance.