Novel Photoluminescent Gold Complexes Prepared at Octanethiol–Water Interfaces: Control of Optical Properties by Addition of Silver Ions

Octanethiol (C8-SH) was shaken with an aqueous solution containing Au(III) and/or Ag(I) ions. The C8-SH molecules reacted with the Au(III) ions to form red-luminescent Au thiolates. The addition of silver ions generated blue-luminescent species, and red-luminescent species also formed in the reaction solution. The blue-luminescent species contained gold–silver (AuAg) bimetallic thiolate complexes. Increasing the silver fraction resulted in higher yields of the blue-luminescent species, but the spectral properties of the two kinds of complexes were almost independent of the silver fraction. X-ray photoelectron spectroscopy (XPS) indicated that the complexes contained metal gold (Au(0)) and silver ions (Ag(I)). The addition of thiol-terminated poly(ethylene oxide) (mPEG-SH) assisted the dialysis of the blue-luminescent complexes. Transmission electron microscope (TEM) investigations revealed the presence of metallic complexes (5 nm) and complex aggregates (50–200 nm). Luminescent sites, which were bimetallic sites containing gold and silver atoms, were formed in the complexes.