Silver nanoparticles certainly have the potential to be the building blocks of future photonic and plasmonic devices as the field of nanotechnology matures [1, 2]. The aim of this work is to develop a simple method to modify the synthesis of long-time stable Ag nanoparticles and the study of the nonlinear optical properties of these nanoparticles under low power continuous wave (CW) He-Ne laser irradiation. Nonlinear refractive index, n2, for three input intensities, is easily measured by the z-scan methods. The obtained nanoparticles were also characterized by means of UV-Vis. Absorption spectroscopy and transmission electron microscopy (TEM). The Ag nanoparticles were synthesized by the reduction of Ag+ ions in the aqueous starch dispersion. The approach was quite simple and straightforward. In a typical preparation, a 100 μl aliquot of 0.1 M solution of AgNO3 was added to 50 ml of a 0.2% (wt) aqueous solution of soluble starch. After complete dissolution of these components, an aqueous solution of NaOH 0.05 M was continuously added drop wise in the system and the pH of solution adjust at 6. The nanoparticles were characterized by ultra violet-visible spectroscopy (UVVis) and transmission electron microscopy (TEM). The investigation of the nonlinear optical characteristics of silver nano particles suspension was carried out using the CW He-Ne laser and the transmission z-scan technique. We have reported a simple route for the synthesis of relatively monodisperse silver nanoparticles, reduced and stabilized by soluble starch. The silver nanoparticles stabilized with soluble starch are found to be stable in solution over a period of six months at room temperature and show no signs of aggregation. The average nanoparticles size was obtained from TEM analysis is 26.5 nm that agreed fairly well with UV-Vis absorption spectroscopy results. The z-scan measurements, performed with CW He-Ne laser, revealed that the nonlinear refractive index in this crystal is in the range of 10-7 cm2/W that mostly agrees with result of diffraction pattern.
