Ligand Shell Isomerization Induces Different Fluorescence Origins of Two Au28 Nanoclusters.

Abstract

Understanding the origin of the photoluminescence (PL) phenomenon in ligand-protected metal nanoclusters is of paramount importance in both fundamental science and practical applications. In this study, we have studied the origin of fluorescence emission of two thiolate-ligand-protected Au28 clusters (Au28(CHT)20 and Au28(TBBT)20) by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. Theoretical calculation results show that the ligand shell isomerization induces different ligand motif-to-metal core charge transfers (LMCT) of Au28(TBBT)20 and Au28(CHT)20. Moreover, in Au28(CHT)20, the emission process of S2 → S0 can compete favorably with the internal conversion of S2 → S1. Furthermore, the high quantum yield of Au28(CHT)20 is attributed to its high symmetric structure, which leads to less energy dissipation during the structural relaxation process.