Solvatofluorochromism of polyethyleneimine-encapsulated Ag nanoclusters and their concentration-dependent fluorescence

Abstract

The solvatochromism of metal nanoclusters is still a highly debatable topic. In this work, based on hyperbranched polyethyleneimine (PEI)-encapsulated Ag nanoclusters, we present some interesting results on the chemical environment-responsive fluorescence of Ag nanoclusters in 11 different solvents, which may shed some light on this issue. In water and alcohols, the nanoclusters emit intense blue fluorescence; when they are dispersed in water–tetrahydrofuran (THF) mixtures, the fluorescent color changes from intense blue (in pure water) to intense yellow (in pure THF); when they are dispersed in ethylene glycol monomethyl ether, the fluorescence changes from blue to green over time. However, while the fluorescence emission changes, no obvious band shift is exhibited in the absorption features of Ag nanoclusters. Therefore, the PEI-capped Ag nanoclusters show obvious solvatofluorochromic but not solvatochromic properties. Furthermore, the emission from these clusters can also be tuned from blue to yellow by changing the concentration of the Ag nanoclusters.