Single step synthesis and optical limiting properties of Ni-Ag and Fe-Ag bimetallic nanoparticles

Magnetic nanoparticles have several applications in biology and medicine, and recently, their use for optical applications is gaining substantial attention. In this paper we report a single step solution based synthesis of Ni-Ag and Fe-Ag bimetallic nanoparticles using hydrazine hydrate as the reducing agent. Structural, plasmonic, and nonlinear optical properties of the prepared nanoparticles are investigated using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-Vis absorption spectroscopy and Z-scan. UV-Vis absorption studies reveal surface plasmon resonance (SPR) absorption at 400 nm which exhibits a small red shift with particle size due to scattering. XRD, EDS, HRTEM and SPR absorption confirm the presence of Ni-Ag and Fe-Ag nanoparticles. Nonlinear optical studies are carried out using the open aperture Z-scan technique employing 5 ns as well as 100 fs laser pulses. The nonlinearity is found to have contributions from absorption saturation, two-photon absorption, excited state absorption and induced thermal scattering of light. The effective nonlinear absorption in Ni-Ag and Fe-Ag nanoparticles is found to be higher than that of pristine Ag nanoparticles. The potential of these materials for optical limiting and photonic applications is discussed. (c) 2012 Elsevier B.V. All rights reserved.