NaBH4 reduction of ortho and para-nitroaniline catalyzed by silver nanoparticles synthesized using Tamarindus indica seed coat extract

摘要

This study deals with reduction of ortho and para-nitroaniline by NaBH4 with silver nanoparticles (AgNPs), synthesized by use of a green method, as catalyst. In the synthesis of the AgNPs an aqueous extract of Tamarindus indica (T. indica) seed coat was used as a reducing and capping agent. The effects of extract concentration and reaction time on formation of the AgNPs were studied by use of UV-visible (UV-Vis) spectroscopy. The stable AgNPs were characterized by dynamic light scattering (DLS), measurement of zeta potential, Fourier-transform infrared (FTIR) spectroscopy, and high-resolution transmission electron microscopy (HRTEM) with energy-dispersive spectrum analysis. Appearance of a yellow color and generation of a surface plasmon resonance peak in UV-Vis spectroscopy confirmed formation of the AgNPs. The FTIR results suggested that the phytoconstituents of T. indica seed coat extract are responsible for reduction of the Ag+ and protection of the AgNPs. HRTEM studies showed the size of the AgNPs was approximately 30-50 nm; their shape was distorted spherical. The TEM results were consistent with DLS study. The catalytic efficacy of stable AgNPs in the reduction of o and p-nitroaniline was studied by UV-Vis spectroscopy. The calculated rate constants (k) for catalytic reduction of o and p-nitroaniline by AgNPs were 2.43 x 10(-3) and 6.22 x 10(-3) S-1.