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

Abstract

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 × 10−3 and 6.22 × 10−3 S−1.