Size-controlled electrochemical synthesis of hemispherical gold nanoparticles on ITO substrates

A simple two-step approach, which combines the seeded growth strategy and the cyclic voltammetric (CV) growth technique, has been developed to prepare hemispherical gold nanoparticles (Au NPs) on indium tin oxides (ITO) substrates. Au nanoseeds that were pre-deposited on ITO surface by pulse chronoamperometry have successfully served as nuclei for the following CV growth of Au NPs. The rapid alternation of the anodic and cathodic potential sweep during CV growth has greatly promoted the isotropic growth of Au NPs. The factors that have great effects on the size and growth rate of the Au NPs during CV growth were systematically investigated. The particle size increases monotonically with increasing the number of CV cycles, and the particles undergo a clear cycle-by-cycle growth mechanism, which provides a powerful tool to control the particle size by simply varying the number of CV cycles. The average one-cycle-growth rate of Au NPs was determined by the scan rate of CV measurements, and the higher the scan rate, the lower the growth rate. The scan-rate-dependent growth rate provides another powerful tool to modulate the growth rate by varying the potential scan rate. A average one-cycle-growth rate of ca. 0.94 nm was obtained at scan rate of 400 mV • s^{- 1}, and monodisperse Au NPs with diameters from 45 to around 300 nm and a narrow size distribution have been successfully prepared on ITO substrates. The obtained Au NP modified electrodes exhibited high activity toward CO electrooxidation.