Silver ions-regulated two-stage photoluminescence transformations of glutathione-capped gold nanoclusters from near-infrared (NIR) to visible region: Anti-galvanic reaction and Ag deposition

Abstract

In the present study, glutathione-capped gold nanoclusters (AuNCs@GSH) were prepared by an improved hydrothermal method, which showed near-infrared (NIR) emission centered at 805 nm. Besides, Ag+ can induce the NIR emission transformations in a two-stage mode under different concentration ranges of Ag+. At the first stage (0.50–15 μM), a new emission at 615 nm was generated while the original NIR emission was quenched upon Ag+ addition; at the second stage (15–120 μM), it shifted to 720 nm gradually along with more Ag+ addition, which realized precise regulation of the emission range of metal nanoclusters from red to NIR region. The in-depth mechanism investigation revealed the transformations in both stages originated from the anti-galvanic reaction (AGR) of AuNCs toward Ag+ and Ag deposition. In detail, the first stage was attributed to the formation of bimetallic gold and silver nanoclusters (Au-AgNCs); while the second stage ascribed to the Ag deposition-induced size growth and composition changes of Au-AgNCs. Therefore, the present study supplies a simple and rapid method for preparing NIR-emitted AuNCs and provides a facile approach to regulate the photoluminescence ranges based on the AGR and Ag deposition.