Non-linear optical properties of silver nanoparticles prepared by hydrogen reduction method

Silver nanoparticles have been prepared using hydrogen gas as the reducing agent for silver nitrate and poly(vinyl pyrrolidone) as the capping agent; the reaction was carried out at 70 °C for 3 h. The size of the nanoparticles was found to be about 20 nm as analyzed using transmission electron micrographs. The X-ray diffraction pattern revealed the face-centered cubic (fcc) structure of silver nanoparticles. The linear absorption of Ag nanoparticles, α, is obtained about 3.71 cm−1. The non-linear refractive indices of silver nanoparticles were defined by the z-scan technique using CW He–Ne laser (λ = 632.8 nm) at different incident intensities. The magnitude of non-linear refractive index (n2) was measured to be in the order of 10−7 (cm2/W) with a negative sign. Therefore self-defocusing phenomena is taking placed for Ag nanoparticles.