Effect of Different Process Parameters on the formation of Silver Nanoparticles using Crude and Modified Neem (Azadirachta indica) Leaf Extracts

Abstract

In recent times, the biosynthesis of nanoparticles, which has led to significant growth in the field of nanotechnology. The use of plant extracts has become an impetus in this field as it is a simple and eco-friendly method. This study was an attempt to study different parameters in biosynthesis of silver nanoparticles using Azadirachta indica (Neem) leaf extracts. Four different process parameters such as concentrations of neem leaf extract, types of neem leaf extract, mixing ratios and the reaction time period were investigated on the formation of silver nanoparticles. Initially, the formation of silver nanoparticles was detected by the visual observation. Then, the synthesized silver nanoparticles were characterized using UV-Visible spectroscopy and scanning electron microscopy (SEM).  The change of color from yellow to reddish brown color confirmed the formation of silver nanoparticles.  The silver surface plasmon resonance (SPR) band obtained in the expected visible range of UV-Visible spectroscopy confirmed the synthesis of the nanoparticles. SEM images showed that silver nanoparticles are roughly spherical and of uniform particle size, and the average particle size is 100 nm. Further, the maximum absorbance of SPR band was considerably varied with different process parameters used in the present study.  The UV-Visible spectra of 2.5 g/100 mL of crude neem leaf extract without any dilution showed maximum absorbance in the expected range with the mixing ratio of (Neem and AgNO₃) 1:8.  However, the maximum absorbance of modified neem leaf extracts (pH 10) resulted lower in value than the crude extracts in the 20 times diluted sample with the mixing ratio of 1:9. Moreover, modified extract with UV radiation exposure increased the absorbance in the expected visible range.  It concludes that fine tuning of the bioprocess parameters would enhance nanoparticle synthesis.