Tracing Gold Nanoparticle Charge by Electrolyte―Insulator― Semiconductor Devices

A capacitive field-effect electrolyte−insulator−semiconductor (EIS) device was applied for the first time to trace the charge of supported gold nanoparticles (Au-NPs) induced by oxygen plasma treatment or due to storing in aqueous oxidation and reduction solutions. In addition, X-ray photoelectron spectroscopy (XPS) has been used as a reference method to establish the various charge states of the Au-NPs resulting from the different treatment steps. After the oxygen-plasma treatment, a shift of the capacitance−voltage (C−V) curve (and flatband potential) of the Au-NP-covered p-Si−SiO2 EIS structure by about −300 mV was found. The exposure of the EIS sensor surface to an oxidative and a reductive solution resulted in a shift of the C−V curve for −85 and +81 mV, respectively. These observations correlate well with corresponding binding energy shifts in Au 4f core spectra in XPS experiments. The obtained results may open new opportunities for biosensing and biochips based on nanoparticle-charge-gated field-ef...