Localization of Au Nanoclusters on Layered Double Hydroxides Nanosheets: Confinement-Induced Emission Enhancement and Temperature-Responsive Luminescence

Gold nanoclusters (Au NCs) stand for a new type of fluorescent nanomaterials with outstanding optical properties due to their discrete electronic energy and direct electron transition. However, relative low quantum yield (QY) of Au NCs in aqueous or solid state has limited their photofunctional applications. To improve the fluorescent performances of Au NCs and find an effective approach for the fabrication of Au NCs-based films, in this work, Au NCs are localized onto 2D layered double hydroxides (LDHs) nanosheets via a layer-by-layer assembly process; the as-fabricated (Au NCs/LDH) n ultrathin films (UTFs) show an ordered and dense immobilization of Au NCs. The localization and confinement effects imposed by LDH nanosheets induce significantly increased emissive Au(I) units as confirmed by X-ray photoelectron spectroscopy and periodic density functional theoretical simulation, which further results in promoted QY (from 2.69% to 14.11%) and prolonged fluorescence lifetime (from 1.84 µs to 14.67 µs). Moreover, the ordered (Au NCs/LDH) n UTFs exhibit well-defined temperature-dependent photoluminescence (PL) and electrochemiluminescence (ECL) responses. Therefore, this work supplies a facile strategy to achieve the immobilization of Au NCs and obtain Au NCs-based thin films with high luminescent properties, which have potential applications in PL and ECL temperature sensors.