Sustainable synthesis of silver nanoparticles using Alstonia scholaris for enhanced catalytic degradation of methylene blue

Abstract The present work described a simple, green, and fast approach for the synthesis of silver nanoparticles using an aqueous fruit extract of Alstonia scholaris(AS-AgNPs). The role of plant extract was identified as both reducing as well as capping agent in the synthesis of AS-AgNPs. The formation of AS-AgNPs was confirmed through the visible color change from pale yellow to brown and the respective surface plasmon resonance (SPR) peak observed at 426 nm in the UV-Visible (UV-Vis) spectrum. Further, the synthesized AS-AgNPs were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy with Energy dispersive spectrum (SEM with EDS), High resolution transmission electron microscopy (HR-TEM), and Dynamic light scattering (DLS) with Zeta potential. The DLS derived average particle size and poly dispersion index (PDI) of AS-AgNPs are about 50 nm and 0.664 with Zeta potential of -22.4 mV, suggested the presence of mono and polydispersive AS-AgNPs with good stability. The synthesized AS-AgNPs were mainly distributed (56 %) as a quasi-spherical shape with size ranges from 5 to 50 nm revealed by SEM and TEM images. Moreover, the catalytic reduction of methylene blue (MB) by AS-AgNPs has been accessed via time-dependent UV-Vis spectroscopy. The UV-Vis results suggested that AS-AgNPs show enhanced catalytic activity on the reduction of MB by aqueous sodium borohydride with pseudo first-order kinetics and the calculated rate constant was about 0.7 × 10−3 s−1. Overall, the green synthesized AS-AgNPs have a great catalytic potential in the degradation of MB in water.