Chiang Mai Journal of Science

 In this study, silver nanoparticles (AgNPs) were synthesized through a green synthesis method using mung bean starch as both reducing and stabilizing agents. The optimum synthesis time was investigated. The absorption spectra of the colloidal solution were recorded by UV-vis. The XPS spectra were used to analyze the chemical state of nanomaterials. The crystalline structure of synthesized AgNPs was determined by XRD. The thermal properties of samples were measured by TGA. The surface morphology of the as-prepared sample was analyzed by SEM, while the EDX spectra were used to confirm the presence of elements. In order to investigate the catalytic activity, the supported nanoparticles was utilized as heterogeneous catalyst in the reduction of 4-nitrophenol (4-NP). It was found that the supported AgNPs exhibited a good catalytic activity toward the 4-NP reduction in the presence of sodium borohydride (NaBH₄). The kinetic studies under the different conditions were performed in order to determine the activation parameters from the Arrhenius and Erying equations. The activation energy (E_a), activation enthalpy (DH^#) and activation entropy (DS^#) were calculated to be 24.33 kJ mol^-1, 21.69 kJ mol^-1 and -252.85 kJ mol^-1, respectively. The catalytic activity of mung bean starch-stabilized AgNPs was 75% reduction after recycling at the end of the fifth use.