Spontaneous electron transfer from C60 to Au ions: oxidation of C60 and hole doping

Abstract

Spontaneous oxidation of C₆₀ by Au ions was observed. When C₆₀ was guided to make contacts with Au³⁺ ions in aqueous HAuCl₄ solution, electrons were spontaneously transferred from C₆₀ to Au³⁺ ions, resulting in hole (h⁺) doped C₆₀ cations and Au nanoparticles on a C₆₀ layer. This spontaneous electron transfer occurs due to the galvanic displacement from C₆₀ to Au³⁺ ions owing to the energy difference between Fermi energy level of C₆₀ (−4.7 eV) and standard reduction potential of Au³⁺ ion (+1.002 V). The oxidation of C₆₀ as well as the consequent formation of reduced Au nanoparticles were confirmed by atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemistry. The switch of majority charge carrier type from electron to hole and its stability in air were also confirmed by monitoring I–V_g characteristic curves of a C₆₀ field effect transistor (FET) device before and after the reaction with Au³⁺ ions.