Crystal and Solution Photoluminescence of MAg₂₄(SR)₁₈ (M = Ag/Pd/Pt/Au) Nanoclusters and Some Implications for the Photoluminescence Mechanisms

Abstract

We prepare a series of MAg24(SR)18 (M = Ag/Pd/Pt/Au) nanoclusters (NCs) with similar core–inner shell–outer shell structures and investigate their crystal and solution photoluminescence. The core silver atom replacement by the Pd/Pt/Au atom obviously tunes the geometric and electronic structures of Ag25(SR)18 NC. The crystal photoluminescence intensities sequence hints a core-atom-directing charge transfer from the ligands to the metal kernels. Both the calculated NPA charge and the measured Aginner shell–Sterminal bond length support the proposed mechanism. Further experiments show the solvent influence on the NCs photoluminescence supported by the blue-shift of emissions of MAg24(SR)18 NCs and the solvent-dependent photoluminescence intensity sequences. Especially, for PtAg24(SR)18, the quantum yield is almost 100-fold greater in CH3CN (18.6%) than in CH2Cl2 (0.2%). However, the emission wavelengths of the series of NCs are barely influenced by the solvent type. This work indicates the importance of the core atom and the solvent to the photoluminescence of core–inner shell–outer shell silver NCs, having important implications for the photoluminescence mechanisms and tuning of noble metal nanoparticles.