Template‐ and Additive‐free Electrosynthesis and Characterization of Spherical Gold Nanoparticles on Hydrophobic Conducting Polydimethylsiloxane

Carbon ‐ doped poly(dimethylsiloxane) (C ‐ PDMS) modified with gold nanoparticles (AuNPs) is a highly promising material for the development of flexible lab ‐ on ‐ chip biosensors. Here, we present an electrochemical method to prepare stabilizer ‐ free AuNPs directly on hydrophobic conducting substrates like C ‐ PDMS without physical or chemical pre ‐ treatment of the C ‐ PDMS substrate. Using a potentiostatic triple pulse strategy, spherical, non ‐ stabilized AuNPs of diameter 76±5 nm could be deposited within 5 s with narrow size ‐ dispersion on the hydrophobic C ‐ PDMS substrate in the absence of any structure directing or stabilizing agent. The detailed investigation of the mechanism of electrochemical formation of gold seeds and their three ‐ dimensional growth on the hydrophobic surface along with nanomechanical atomic force — scanning electrochemical microscopy (QNM ‐ AFM ‐ SECM) characterization as well as conductive AFM allowed developing this fast electrochemical strategy with control in the desired size and size ‐ dispersion of AuNPs. A detailed electrochemical investigation using cyclic voltammetry, anodic differential pulse voltammetry, and electrochemical impedance spectroscopy was conducted to characterize the electrochemical behavior of uncapped AuNPs deposited on C ‐ PDMS. The Fc + (MeOH) 2 /Fc(MeOH) 2 redox reaction at AuNPs ‐ C ‐ PDMS showed an improved charge transfer coefficient and heterogeneous charge transfer rate constant compared to the bare C ‐ PDMS substrate.