Regulation of Silver Nanoclusters with 4 Orders of Magnitude Variation of Fluorescence Lifetimes with Solvent-Induced Noncovalent Interaction

Regulation on the structure endows ligand-protected metal nanoclusters (NCs) with various optical properties and expands their applications in sensing, bioimaging and catalysis. The noncovalent interactions inside NCs, both ligand-ligand and ligand-metal interactions, also play an important role in the structure modulation but have been rarely studied so far. Herein, we report silver-based NCs with orange emission (cluster 1) and blue emission (cluster 2), both prepared from silver-glutathione (Ag(I)-GSH) supramolecular assemblies (cluster 0), and reversible conversion among them was achieved by manipulating noncovalent interaction. Clusters 1 and 2 exhibit a 4 orders of magnitude variation in fluorescence lifetime and dramatically different excited state dynamics. The investigations of Fourier transformed infrared (FT-IR) spectra, circular dichroism (CD) spectra, and femtosecond-resolved transient absorption (TA) spectra reveal that the intramolecular noncovalent interaction regulates the structure of NCs. In cluster 1, carboxyl coordinates with silver forced surface ligation, while hydrogen bonds link GSH ligands in cluster 2. The results demonstrate that intramolecular noncovalent interaction could be used to alter the structures and optical properties of NCs, which provide new perceptions on the regulation of NCs.