Effect of Albumin on Underpotential Lead Deposition and Stripping on Ag‐RDE

Abstract

AbstractThe effects of adsorption of bovine serum albumin (BSA) on the electrodeposition and stripping of Pb‐adatoms at a Ag‐RDE in acetate buffer solutions have been studied. The adsorbed BSA molecules have been found to inhibit the lead adsorption process. A decrease in the apparent charge transfer coefficient α for Pb‐adatom desorption from 0.39 to 0.34 in the presence of adsorbed BSA molecules has been attributed to the electric field screening by multiply charged BSA in the adsorption film, since no major lateral interactions between Pb and BSA have been observed. The kinetics of BSA adsorption on a Ag‐RDE was followed by Pb‐adatom probe technique in the range of low BSA coverage, 0<θBSA<0.4. The adsorption (k1) and desorption (k−1) rate constants were determined as follows: k1=2.42×10−4 cm/s, k−1=1.12×10−14 mol cm−2 s−1. The equilibrium constant for BSA adsorption on Ag electrode from 3×10−8 M BSA solution, also determined from the Pb‐adatom probe method, was: Kads=2.17×107 L/mol and the corresponding Gibbs free energy of adsorption: ΔG°ads=−9.99 kcal/mol (−41.85 kJ/mol). The formation of BSA films on Ag electrodes has been confirmed by EQCN mass transients and AFM imaging. It follows from these experiments that BSA molecules adsorb in horizontal orientation and form a film on Ag with 4 nm thickness.