Synthesis of Silver Nanoparticles Using Low Molecular Weight Lignin: Insights Into the Effect of Reaction Parameters on Synthesis

ABSTRACT

Herein, lignin extracted from Parthenium hysterophorus was utilized as a reducing agent in the synthesis of silver nanoparticles (AgNPs). The reaction conditions were optimized by observing the effect of varying the reaction time, temperature, the concentration of silver nitrate (AgNO ₃ ) and the amount LMwLg on the surface plasmon resonance peak of AgNPs. The nanoparticles were analyzed using a UV–Vis spectrophotometer, Fourier transform infrared spectrophotometer, transmission electron microscope, energy dispersive X‐ray measurements, and X‐ray powder diffraction. From the results obtained, the optimum parameters which gave the highest SPR peak at 436 nm during synthesis were 60°C, 140 min, 0.1 M AgNO ₃ , and 0.4% w/v LMwLg respectively. The particles were monodispersed, spherical in nature with a mean diameter of 20.81 nm, crystalline structure with an average crystallite size of 20.1 nm while the EDX spectra confirmed that the nanoparticles were majorly composed of silver. Moreover, the AgNPs were stable under storage as the SPR peak remained unchanged after 6 months, were polydisperse with diameter of 100–1000 nm as observed from light scattering and they were active against selected microorganism. In conclusion, LMwLg was used as reducing agent to synthesize antimicrobial AgNPs as an alternative to conventional chemical methods.