Green Synthesis of Silver Nanoparticles Using Justicia adhatoda Leaf Extract: Characterization and Nonlinear Optical Applications

This study reports the synthesis of silver nanoparticles (AgNPs) using leaf extract of Justicia adhatoda. This green and eco-friendly method produces highly stable AgNPs, which are characterized using various techniques, including UV–visible absorbance, FT-IR, XRD, FESEM, and TEM. A strong surface plasmon resonance (SPR) is observed at a wavelength of 411 nm. The functional groups present in the AgNPs are identified using FT-IR, revealing a peak at 456 cm⁻¹ corresponding to Ag⁺ bond vibration. The crystalline properties of AgNPs are examined via XRD, with an average crystal size measured at 23.33 nm. Moreover, FESEM and TEM studies revealed that the nanoparticles possess a spherical shape. The Z-scan technique is employed at a wavelength of 405 nm to investigate the third-order nonlinear optical (NLO) responses of AgNPs. The nonlinear refractive index (n₂) and nonlinear absorption coefficient (β) are attributed to self-defocusing and reverse saturable absorption (RSA) processes. A significant third-order NLO susceptibility is measured, estimated to be in the order of 10⁻⁷ esu. Overall, the experimental results clearly indicate that the green synthesis of AgNPs using the leaf extract of Justicia adhatoda represents a promising material for NLO applications.