Red-Emitting Copper Nanoclusters: From Bulk-Scale Synthesis to Catalytic Reduction

A large-scale, easy synthesis of red fluorescent copper nanoclusters (CuNCs) from a cheap source copper acetate, monohydrate has been reported. A proteinaceous amino acid cysteine has been used to stabilize these clusters at room temperature. These nanoclusters have been thoroughly characterized by UV–vis absorption, fluorescence spectroscopy, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) spectrometry, transmission electron microscopy (TEM), X-ray powder diffraction analysis, cyclic voltametry (CV), and X-ray photoelectron spectroscopy. MALDI-TOF analysis indicates that the nanocluster is a Cu5(Cys)3 species. Computational studies revealed the energy optimized structure of Cu5(Cys)3 with most possible arrangements of Cu atoms and their interactions with stabilizing ligands. It is evident from the structure that vacant Cu sites are available; hence, these sites can be used for binding with substrate molecules for catalytic reactions. Interestingly, these as-synthesized red-emitting nanocluster catalyze the degradation of 4-nitrophenol (toxic chemical used in industries) to almost nontoxic 4-aminophenol at room temperature. These nanoclusters (powdered) can also be recycled as catalyst for another time. This type of new nanocatalyst for the organic transformation of a toxic to nontoxic material holds future promise for the development of novel large-scale nanocatalytic materials.