Fluorescent Au nanoclusters stabilized by silane: facile synthesis, color-tunability and photocatalytic properties.

Synthesis of tunable, luminescent metal nanoclusters remains challenging due to their tendency to aggregate. Herein, we report a simple photoreduction method to synthesize fluorescent silane-stabilized Au nanoclusters. By altering the molar ratio of stabilizer and Au precursor, emissions of the as-prepared Au nanoclusters can be tuned in the wavelength range of 538-580 nm. High resolution transmission electron microscopy results showed that the variation in the size of the as-formed nanoclusters (1.2-2.0 nm) might be responsible for this emission shift. The as-synthesized gold nanoclusters have a relatively long fluorescence lifetime, from 34.04 to 46.83 ns, and luminescence quantum yields of 0.26-3.16%, depending on the fluorescence at the specific emission wavelength. Compared with bulk gold, these silane-stabilized Au nanoclusters possess special electronic structures and exhibit semiconductor-like features such as an absorption edge in the visible region, which gives rise to their visible excitation at 400-450 nm. As demonstrated by the degradation of methylene blue under visible irradiation, the synthesized Au nanoclusters can also function as a promising cluster photocatalyst, just like many other semiconductor counterparts.