A combined XPS, XANES and STM/STS study of gold and silver deposition on metal sulphides

Synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS), scanning tunneling microscopy and spectroscopy (STM/STS) have been used to characterize gold and silver species spontaneously deposited from aqueous HAuCl4 or AgNO3 solutions onto metal sulphides. An increase in Au 4f binding energies was found for unusually large, 5 nm and larger, Au0 particles; concurrently, STS revealed a positive correlation between the current magnitude and the particle size. Possible mechanisms behind the effects were considered.