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Fluorescent nanomaterials such as metal nanoclusters (NCs) have become one of the most essential nanomaterial and attracted abundant attention in research due to their excellent photophysical properties and wide range of applications. Furthermore, metal nanoclusters have been predominantly investigated owing to its excellent optical properties, simple synthetic routes,low toxicity and excellent photostability. However, limited advancements and progress have been executed in fabricating hydrophilic and highly luminescent metal NCs. Copper is an eco-friendly, low-cost metal which is progressively advancing into focus for metal NCs research. In comparison to the extensively studied gold nanoclusters (Au NCs) and silver nanoclusters (Ag NCs), systematic and analytical applications of the copper nanoclusters (Cu NCs) are relatively limited and still at an early stage. In this review, we fixate on contemporary advances in the analytical applications of Cu NCs based on their behavior and properties of light. This work specifically addresses optical properties and some emerging applications of Cu NCs. The study seeks to unravel some unique photophysical properties of Cu NCs in its solid state, namely concentration/aggregation induced emission enhancement, thermally activated delayed fluorescence (TADF), by which both singlet and triplet excitons can be harvested. Furthermore, the as-synthesized Cu NCs used in this study was remarkably excellent, garnering ~20% quantum yield in colloidal and solid-state form, respectively. CuNC/PVA nano-composites can exhibit unique solidstate- induced dual-mode emissions of thermally activated delayed fluorescence (TADF) and phosphorescence at ambient environment. The outstanding performance of Cu NCs in solid-state makes it an excellent biocompatible nanoemitters light-emitting devices.
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