Charge State Tuning and Photochemical Stability of Au25(SR)18 Nanoclusters

Abstract

The photolysis of the gold nanoclusters Au₂₅(SR)₁₈^z (R=C₂H₄Ph and C₁₂H₂₅, z=1−, 0 and 1+) NCs in halogenated solvents such as dichloromethane leads to changes in the charged states of the Au₂₅(SR)₁₈^z observed using UV-Visible and ¹H NMR spectroscopic techniques. Matrix-assisted laser desorption/ionization mass spectrometry results proved that during charge transformation from anion to neutral and eventually cation forms, the size of nanoclusters remains intact. Electrochemistry of Au₂₅(SR)₁₈ has enabled the monitoring of these changes by cyclic voltammetry, indicating decay in the redox peak current upon irradiation. In the absence of light and/or in a non-halogenated solvent, e. g., tetrahydrofuran, no substantial change in the photophysical signatures of Au₂₅ nanoclusters was observed. These observations highlight the importance of selecting appropriate solvent(s) in the synthesis and photochemical studies of atomically precise metal nanoclusters and the possibility of using photochemistry in halogenated solvents to synthesize different charge states of atomically precise metal nanoclusters. Thus, other monodispersed molecule-like nanoclusters, with various sizes and charges, can be achieved via this photosynthetic protocol under controlled conditions, e. g., solvent, light, and photolysis duration.