Highly efficient solution grown CuXO/Cu nanostructures for catalytic reduction of nitroarenes and visual colorimetric detection of Zn2+ using clock reaction of methylene blue

Abstract

Catalytic conversion of water pollutants into environmentally benign products has emerged as a highly promising technique in the realm of environmental remediation. Among metal and metal oxide nanoparticles, copper/copper oxide nanoparticles serve as an ideal catalyst to reduce hazardous aquatic pollutants in order to protect the environment. In the present study, a simple chemical oxidation method was used for the synthesis of Cu(OH)₂ nanowire, which was then annealed in argon atmosphere at different temperatures. On annealing, Cu(OH)₂ gets transformed into oxide forms, CuO and/or Cu₂O. The significance of the synthesized nanomaterial for the catalytic conversion of organic pollutants like para-nitrophenol (p-NP) and para-nitroaniline (p-NA), to para-aminophenol (p-AP) and para-phenylenediamine (p-PDA), respectively, in the presence of NaBH₄ was studied and their catalytic activities were compared, and the rate constants were found to be 0.016 s⁻¹ and 0.021 s⁻¹ for p-NP and p-NA respectively. Due to the increased surface area, which improves charge carrier separation and adsorption, the CuO/Cu₂O hybrid nanowires established excellent catalytic behavior for the conversion of these harmful pollutants into useful products within a few minutes. In addition to this, the heterojunction of CuO/Cu₂O hybrid nanowires formed are effectively catalyze the “clock reaction,” which is a periodic reversible switching of reactions between colorless leucomethylene blue and blue colored methylene blue. This property of the developed nanocomposite has been used in the visual colorimetric detection of Zn²⁺ions, with high limit of detection of 53 nM and high sensitivity. Morphology and surface analysis were obtained by X ray diffraction, Raman, and Scanning Electron Microscopic analysis and the reaction kinetics were studied by UV–visible spectroscopy. The recyclability of the synthesized catalyst was investigated over five cycles, and it maintained consistent performance, achieving 95% conversion efficiency for p-NP and 93% for p-NA after the five cycles.

Graphical abstract