Assembly-Driven Aggregation-Induced Emission of Gold Nanoclusters with Excitation Wavelength-Dependent Emission and Mechanochromic Property

Metal nanoclusters with aggregation-induced emission (AIE) characteristics are potential nanomaterial candidates for a wide array of advanced optical applications. In this study, a novel self-assembly enhanced AIE strategy utilizing 6-thioguanine (TG)-protected gold nanoclusters (AuNCs) is fabricated with dual-stimuli responsive modes of excitation wavelength-dependent (Ex-De) emission and mechanochromic properties. The sheetlike structures of AuNCs self-assembly (AuNC sheets) with typical AIE characteristics are generated in bad solvent owing to the intermolecular hydrogen-bonds interaction among guanine-rich moieties of TG ligand. Interestingly, the maximum emission peaks of AuNC sheets are red-shifted with the increased excitation wavelengths, indicating Ex-De emission behavior. This phenomenon enables the achievement of wide-range tunable photoluminescence (PL). In addition, the emission peak of AuNC sheets powders before and after grinding displays the bathochromic shift of 110 nm. The "off-on" switch of Ex-De emission behavior in AuNC sheets can be manipulated by changing mechanical pressure. It is speculated that the tunable PL behavior of AuNC sheets originates from multiple excited states due to the existence of different Au(I)<middle dot><middle dot><middle dot>Au(I) distances. The self-assembly-driven AIE strategy of AuNCs with stimuli-responsive allochroic modes will facilitate the recording of rewritable information, opening up a new avenue for high-throughput and multi-dimensional optical security.