Microwave-assisted synthesis of L-cysteine-capped nickel nanoparticles for catalytic reduction of 4-nitrophenol

A simple and efficient microwave-assisted procedure for synthesis of L-cysteine-capped nickel nanoparticles (cyst-Ni NPs) in ethylene glycol solvent was demonstrated. The as-synthesised NPs were characterised by ultraviolet–visible (UV–Vis) spectrophotometer, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The cyst-Ni NPs are proved to be excellent heterogeneous catalysts for the 100 % reduction of 4-nitrophenol (4-NPh) in the presence of reductant (NaBH4) within reaction time of 40 s. In contrast, Raney nickel in similar sample environments shows only 25.5 % reduction. The kinetic and energetic behaviours of cyst-Ni NPs were also studied, and the reduction reaction is determined to follow pseudo-first-order kinetics with a rate constant value of 0.115 s-1 and activation energy of 36.1 kJmol-1. In addition to its high catalytic competence, cyst-Ni NPs catalyst exhibits excellent recyclability with negligible catalytic poisoning.