Tuning Surface Chemo-Resistivity of Au Ultra-Thin Films Using Metal Deposition via Surface Limited Redox Replacement of Pb UPD Monolayer.

Presented work investigates the chemo-resistivity of Au ultra-thin films whose surface is modified by deposition of few monolayers of Au, Pd or AuPd alloy. The model adsorbate in this study was HS- ion from 0.1 M NaCl solution having concentrations range from 0 to 40 ppm. The Au surface modification was done using deposition via surface limited redox replacement of underpotentially deposited Pb monolayer. Modified Au films have shown higher chemo-resistivity 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 chemo-resistive sensor design and performance.