Tunable Photoluminescence of Closed-Shell Heterobimetallic Au−Ag Dicyanide Layered Systems

The excited-state properties of the layered La[Ag(CN)2]3 and La[Au(CN)2]3 systems have been examined and compared with mixed-metal systems of varying metal ratios such as La[Ag0.78Au0.22(CN)2]3, La[Ag0.55Au0.45(CN)2]3, La[Ag0.33Au0.67(CN)2]3, and La[Ag0.19Au0.81(CN)2]3. We have found that these mixed-metal systems luminesce quite strongly at room temperature at an energy that is tunable and depends on the Au:Ag stoichiometric ratio. The emission energy of the mixed-metal samples lies between those of the pure Au and Ag systems. This provides evidence that the excited states responsible for this emission are delocalized over the Ag and Au centers. The strong luminescence of the mixed-metal systems at ambient temperatures is in stark contrast to the weak luminescence behavior of pure La[Au(CN)2]3 and La[Ag(CN)2]3 samples, which makes the mixed-metal systems more viable than the pure systems for practical applications.