Self-assembled gold nanoparticles modified ITO electrodes: The monolayer binder molecule effect

The fabrication of gold attached organosilane-coated indium tin oxide AuNPs-MPTMS/ITO and AuNPs-APTES/ITO electrodes [MPTMS = 3-(mercaptopropyl)-trimethoxysilane, APTES = 3-(aminopropyl)-triethoxysilane, ITO = indium tin oxide] was carried out making use of a well-known two-step procedure and the role played by the –SH and –NH2 functional groups in the two electrodes has been examined and compared using different techniques. Information about particle coverage and inter-particle spacing has been obtained using trasmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) whereas, bulk surface properties have been probed with UV–vis spectroscopy, CV and electrochemical impedance spectroscopy (EIS). The catalytic activity of the two electrodes has been evaluated studying the electrooxidation of methanol in alkaline conditions. The results obtained show that the NH2 functionality in the APTES binder molecule favours the formation of isle-like Au nanoparticle aggregates that lead to both a higher electron transfer and electrocatalytic activity.