Photoinduced Formation and Intercluster Conversion of a Thiol-Templated Copper Nanocluster

The preparation of metal nanoclusters through light–matter interaction is an unexplored realm of nanomaterials research. A comprehensive understanding of the stages involved in the growth process of nanoclusters is scant in the literature. Herein, we report the photoinduced formation of yellow-emissive copper nanoclusters (Y-CuNCs) from a binuclear copper complex [Cu2(SPhCl)2(PPh3)4], which was subsequently observed to undergo photoinduced conversion to green-emissive copper nanoclusters (G-CuNCs). We were able to characterize the intermediate complexes, fragments, and nanoclusters formed in the process, which were attributed to the precursors for the formation of CuNCs. To the initially formed binuclear copper complex Cu2(SPhCl)2(PPh3)4, irradiation with ultraviolet (UV) light (λ ∼ 365 nm) resulted in the Y-CuNCs. Further, upon irradiation of the solution of Y-CuNCs with UV light, the Y-CuNCs convert to G-CuNCs via photoinduced intercluster conversion. The formation of both CuNCs has been extensively studied through UV–vis absorption features, photoluminescence studies, and lifetime measurements. The formation of CuNCs and photoinduced intercluster conversion has been confirmed with the help of transmission electron microscopy images, electrospray ionization mass spectroscopy (ESI-MS) analysis, and 31P NMR data analysis. Moreover, a plausible mechanism of intercluster conversion has also been substantiated with the help of ESI-MS data analysis.