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

Here we report the thermal properties of weakly stabilized0.9,1.6, and 4.1 nm Au nanoparticles (NPs)/nanoclusters (NCs) attachedto 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 shiftin E (p) due to an increase in NP/NC sizefrom thermal ripening. The size transition temperature (T (t)) decreases with decreasing NP/NC size following theorder of 4.1 nm (509 & DEG;C) > 1.6 nm (132 & DEG;C) > 0.9 nm(90 & DEG;C/109 & DEG;C, two transitions) as compared to the bulk meltingpoint (T (m,b)) for Au of 1064 & DEG;C. The T (t) generally agrees with models describing thesize-dependent melting point of Au NPs (T (m,NP)) for 4.1 and 1.6 nm diameter Au NPs but is higher than the modelsfor 0.9 nm Au NCs. Scanning electron microscopy (SEM) and UV-vissize analysis confirm the electrochemical results. The thermal stabilityof electrode-supported metal NPs/NCs is important for their effectiveuse in catalysis, sensing, nanoelectronics, photovoltaics, and otherapplications.