Preparation of Ag@ZnO core–shell nanostructures by liquid-phase laser ablation and investigation of their femtosecond nonlinear optical properties

Abstract

Ag@ZnO core–shell nanostructures, ZnO nanoparticles (NPs), and Ag NPs were synthesized by laser ablation in water using 8 ns, 1064 nm, and 50 mJ/pulse. The structural, morphological, componential, and optical properties of as-synthesized NPs were examined by X-ray diffraction, transmission electron microscopy, electron diffraction spectrum, and ultraviolet–visible absorption, respectively. The third-order nonlinear optical properties of aqueous dispersions of three NPs were characterized by performing Z-scan experiments with femtosecond laser pulses at 800 nm. It is shown that three NPs exhibit the positive refractive nonlinearity in the absence of nonlinear absorption and the third-order nonlinear refraction index increases in the order of NPs ZnO < Ag < Ag@ZnO. The results indicate that the Ag@ZnO core–shell nanostructure is a promising candidate for applications in ultrafast all-optical switching.