Fine-tuning the fluorescence emission wavelength of gold nanoclusters in the protein-directed synthesis: the effect of silver ions.

Highly fluorescent gold nanoclusters have attracted much attention recently. Here, we reported a "green", facile method for fine-tuning the fluorescence emission wavelength of gold nanoclusters synthesized with bovine serum albumin (BSA). The principle of the experimental work involved the utilization of BSA as the reductant for the synthesis of gold nanoclusters and the addition of small amounts of silver ions in the synthesis process for tuning the fluorescence properties of the synthesized gold nanoclusters. Our results showed that fluorescence emission wavelength of the synthesized gold nanoclusters could be fine-tuned in a fairly wide range (- 90 nm) by addition of different quantities of silver nitrate in the synthesis process. In addition, with increasing silver ions quantity the emission wavelength of the gold nanoclusters varied in a non-monotonic manner. In this way, gold nanoclusters emitting yellow, orange or red fluorescence with decent quantum yields were readily obtained in a single batch.