Starch-supported gold nanoparticles and their use in 4-nitrophenol reduction

Gold nanoparticles (AuNPs) have been synthesized through a green synthesis method using mung bean starch (MBS) as both reducing and stabilizing agents. The chemical state was analyzed by X-ray photoelectron spectroscopy (XPS). The crystalline structures were characterized by X-ray diffraction (XRD). The thermal properties were measured by thermogravimetric analysis and differential thermal analysis (TGA/DTA). The surface morphology was investigated by scanning electron microscopy (SEM). In order to investigate the catalytic activity, the mung bean starch-supported AuNPs (MBS-AuNPs) was utilized as a heterogeneous catalyst in the reduction of 4-nitrophenol (4-NP) in the presence of sodium borohydride (NaBH4). The kinetic studies under the different experimental conditions were performed in order to determine the activation parameters from the Arrhenius and Eyring equations. It was found that the activation energy (Ea), activation enthalpy (ΔH#) and activation entropy (ΔS#) were calculated to be 47.42 kJ mol−1, 44.78 kJ mol−1 and −261.49 kJ mol−1, respectively. In addition, the catalytic activity was 73% reduction after recycling at the end of the fifth use. This work offers a non-toxic procedure for the synthesis of nanoparticles using starch-rich polymers with a great promise toward other potential applications.