Novel Luminescent Heterobimetallic Nanoclusters of Copper(I), Silver(I), and Gold(I) Doped in Different Alkali Halide Crystals

Abstract

Heterometallic d10–d10 nano systems of dicyanocuprate(I) with dicyanoaurate(I) or dicyanoargentate(I) doped in different alkali halide hosts (NaCl, NaBr, and KBr) have been studied. In addition to the characteristic emission peaks for each d10 anion cluster, these doped crystals show a new luminescent peak due to the heterometallic interaction between Cu and Au or Cu and Ag. This new long lifetime emission peak occurs at much lower energy than that of single metal doped cases. The relative intensity of these emission peaks depends on the stoichiometric ratios of the corresponding metals doped in alkali halide hosts. Unlike the emission peaks originating from single Cu(I), Ag(I), and Au(I) doped systems, this emission peak from heterometallic interaction is independent of the alkali halide hosts. A spin-forbidden metal–metal-to-ligand charge-transfer transition is proposed, and the Cu–Au emission peak occurs at lower energy than that of Cu–Ag, which is due to the relativistic effect of Au. Density funcational theory and atomistic calculations have been carried out to correlate the theoretical and experimental results.