Surface Tailoring on Atomically Precise Gold Nanocluster for Aggregation-Induced Emission and Bioimaging Application

Aggregation-induced emission (AIE) is not only considered a key strategy for effectively enhancing the luminescence of atomically precise metal nanoclusters (MNCs) but can also broaden their applications. However, the synthesis of MNCs with AIE performance still poses significant challenges. Herein, a strategy of specific-site “surgery” was employed to tailor surface motifs of Au₂₄(SR)₂₀ NC by a two-step ligand-exchange method, in which the outmost two Au₄S₅ motifs were tailored into two S─Au─P and two P atoms, resulting in an [Au₁₈(TBBT)₁₂(TFPP)₄]²⁺ NC (where TBBT is 4-tert-butylphenthiophenol, TFPP is tri-(4-fluorophenyl) phosphine) with the Au₈@(Au₄S₅)₂(SAuP)₂P₂ construction. This precise surgery endows this Au₁₈ NC with dual emission (645 and 810 nm) in the aggregated state but no emission in the soluble solution at room temperature. Furthermore, the AIE photophysical behavior was systematically studied through a combination of experimental and theoretical investigations. The results reveal that the high-energy emission band (645 nm) primarily originates from the restricted intramolecular rotation and vibration of surface ligands and motifs. In contrast, the low-energy emission at 810 nm is predominantly attributed to intermolecular interactions in the aggregated state. Benefiting from its distinct AIE characteristics, the Au₁₈ NC shows excellent potential as a high-performance fluorescent probe for lysosome-targeted bioimaging. This work presents a novel approach for constructing AIE-active MNCs, paving the way for their future biological applications.