Engineering Highly Stable, Fluorescent and Non-toxic Cu Nanoclusters via Reaction Parameter Optimization

Metal Nanoclusters (NCs) composed of the least number of atoms (few to tens) became very attractive for their emerging properties owing to their ultrasmall size. Preparing copper nanoclusters (Cu NCs) in an aqueous medium with high emission properties, strong colloidal stability, and low toxicity has been a long-standing challenge. Although they are earth-abundant and inexpensive, they are comparatively less explored due to their limitations such as ease of surface oxidation, poor colloidal stability, and high toxicity. To overcome these constraints, we established a facile synthetic route by optimizing the reaction parameters, especially altering the effective concentration of the reducing agent to influence their optical characteristics. The improvement of photoluminescence intensity and superior colloidal stability was modeled from a theoretical standpoint. Moreover, the as-synthesized Cu NCs showed a significant reduction of toxicity in both in vitro and in vivo models. The possibilities of using such Cu NCs as a diagnostic probe towards C. elegans were explored. Also, the extension of our approach towards improving the photoluminescence intensity of the Cu NCs on other ligand systems was demonstrated.