Self-assembly of photoluminescent copper(I)-dithiol multilayer thin films and bulk materials

Self-assembled multilayer thin films have been prepared on Au and mercaptosilanized glass substrates by alternate surface derivatization with Cu2+ ion and alkanedithiols. The films deposited on glass show intrinsic orange-red photoluminescence and were studied by fluorescence spectroscopy. A strongly photoluminescent solid was also obtained by reaction of 1,6-hexanedithiol with cupric perchlorate in ethanolic solution. Multilayer structures on Au were studied by ellipsometry and X-ray photoelectron spectroscopy (XPS). Both in the solid material and in the self-assembled thin films, XPS measurements suggest Cu is present in the +1 oxidation state. This was also confirmed by cyclic voltammetry of Cu ion adsorbed to a self-assembled monolayer of 1,6-hexanedithiol on gold. Metal-metal interactions in the form of clustering might contribute to the unusual photophysical properties observed in both types of materials.