Nonlinear optical absorption in silver nanoparticles synthesized using Brownea grandiceps leaf extract

Abstract

This work focuses on the nonlinear optical (NLO) characteristics of biosynthesized silver nanoparticles (Ag NPs) prepared using an aqueous extract of Brownea grandiceps leaves. The formation of Ag NPs is confirmed by UV–Visible spectroscopy through the appearance of a characteristic surface plasmon resonance peak at 425 nm. A crystallite size of 12.6 nm is estimated from XRD analysis, which also revealed a prominent (111) peak corresponding to face-centered cubic (fcc) silver. The presence of bioactive compounds in the leaf extract, responsible for nanoparticle formation and stabilization, is confirmed by FTIR spectroscopy. TEM images reveal nanoparticles with an average size of 28.6 nm and a uniformly distributed spherical morphology. Open-aperture Z-scan measurements using 5 ns laser pulses at 532 nm is used to investigate the NLO response of the biosynthesized Ag NPs. The sample exhibits saturable absorption at low excitation intensities, which transitions to strong reverse saturable absorption with increasing intensity. Therefore, these biogenic Ag NPs offer great promise for NLO applications such as optical limiting and optical switching.