Electrochemical insights into layered assemblies of silver nanoparticles, poly-L-lysine, and bovine serum albumin

This study presents a comprehensive exploration of the electrochemical behavior of layer-by-layer assemblies comprising silver nanoparticles (AgNPs), poly-l-lysine (PLL), and bovine serum albumin (BSA) on gold surfaces. AgNPs were synthesized using the reduction of silver ions with the synergy of ascorbic acid and citrate in the presence of sodium chloride. The obtained silver nanoparticles were characterized using transmission electron microscopy, dynamic light scattering and UV-Vis spectroscopy. A typical preparation produced AgNPs with a plasmon peak at 402 nm, a diameter of 27.5 nm and zeta potential of −37 mV. Employing a drop-coating approach, we successfully achieved stable multilayers of AgNPs, PLL, and BSA. Cyclic voltammetry revealed well-defined, bell-shaped oxidation and reduction peaks of AgNPs within the multilayers, demonstrating complete conversion to AgCl and back to Ag. Notably, the stripping of AgNPs on a monolayer of PLL prepared at pH 4.00 resulted in the highest current intensity, contrasting with lower intensities observed for PLL monolayers prepared at pH 7.01 and pH 9.01. Despite the absence of a splitting reduction peak in the presence of biopolymer materials, a noteworthy observation emerged: the peak splitting exclusively occurred when PLL/AgNP layers, terminated with PLL, were exposed to BSA in the solution.