Two-Step Electrochemical Au Nanoparticle Formation in Polyaniline

Abstract

Abstract Insertion of Au nanoparticles (NPs) in polyaniline (PANI) is investigated using a two-step electrochemical process. In the first step, tetrachloroaurate anions (AuCl4−) are attached on the protonated imine sites of PANI while holding the potential at + 0.8 V vs. Ag/AgCl. The applied electrochemical potential prevents any reduction of the PANI/AuCl4− complex. After rinsing of excess AuCl4−, a controlled reduction is carried out via cyclic voltammetry (CV). We demonstrate that the reduction leads to a nucleation and growth of Au NPs whose density and size dispersion depend on the Au loading in PANI. Adding more deposition cycles increases the Au NP density and size. We further use Rutherford backscattering spectrometry (RBS) to quantify the Au uptake in PANI. We also find that the Au distribution is initially homogeneous across the PANI layer whereas the increasing number of deposition cycles leads to a surface segregation of Au. We propose a two-step growth model based on our experimental results. Finally, we discuss the results with respect to the formation of atomic Au clusters reported previously using the same deposition method.