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 Cu ₅ (Cys) ₃ species. Computational studies revealed the energy optimized structure of Cu ₅ (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.