Electrochemical Analysis of the Thermal Stability of 0.9-4.1 nm Diameter Gold Nanoclusters.

Here we report the thermal properties of weakly stabilized 0.9, 1.6, and 4.1 nm Au nanoparticles (NPs)/nanoclusters (NCs) attached to indium-tin-oxide- or fluorine-doped-tin-oxide-coated glass electrodes (glass/ITO or glass/FTO). The peak oxidation potential ( E p ) for Au measured by anodic stripping voltammetry (ASV) is indicative of the NP/NC size. Heating leads to a positive shift in E p due to an increase in NP/NC size from thermal ripening. The size transition temperature ( T t ) decreases with decreasing NP/NC size following the order of 4.1 nm (509 °C) > 1.6 nm (132 °C) > 0.9 nm (90 °C/109 °C, two transitions) as compared to the bulk melting point ( T m,b ) for Au of 1064 °C. The T t generally agrees with models describing the size-dependent melting point of Au NPs ( T m,NP ) for 4.1 and 1.6 nm diameter Au NPs but is higher than the models for 0.9 nm Au NCs. Scanning electron microscopy (SEM) and UV-vis size analysis confirm the electrochemical results. The thermal stability of electrode-supported metal NPs/NCs is important for their effective use in catalysis, sensing, nanoelectronics, photovoltaics, and other applications.