Luminescent Gold Nanoparticles with Mixed Valence States Generated from Dissociation of Polymeric Au(I) Thiolates

The dissociation process of glutathione−gold(I) polymers in aqueous solution resulted in the formation of a class of ∼2 nm gold nanoparticles. Different from the same sized but NaBH4 reduced gold nanoparticles, these nanoparticles exhibited strong luminescence but no surface plasmon absorption. Luminescence lifetimes of the nanoparticles were found strongly dependent on excitation wavelengths, and singlet and triplet excited states involving the emission were found degenerate in energy. X-ray photoelectron spectroscopic studies showed that nearly 40−50% of the gold atoms in the luminescent nanoparticles were in the gold(I) state, which are responsible for the unique optical properties of the luminescent gold nanoparticles. These luminescent nanoparticles can be considered an intermediate state between luminescent gold(I) complexes and reduced nonluminescent gold nanoparticles.