Study On The Three Order Nonlinear Optical Properties Of Ag-Rh Alloy Nanoparticles Prepared By Chemical Reduction Method

The poly?Polyvinylpyrrolidone,PVP?protected colloidal bimetallic Ag-Rh nanoparticles?NPs?with different concentration and metal mole ratio were prepared by chemical reduction method which is based on dropwise addition of KBH₄.The microstructure and the nonlinear optical effect of the colloidal nanoparticles had been characterized.The Transmission electron microscopy?TEM?and High-resolution transmission electron microscopy?HR-TEM?were used to characterize their structures and particle sizes.The UV-VIS optical absorption spectra of bimetallic nanoparticles prepared with different concentration and molar ratios revealed that the colloidal dispersions prepared are not a simple mixture of monometallic Ag and Rh nanoparticles.Besides,with the increase of the concentration,the position of the absorption peak remained unchanged and the intensity of the absorption peak enhanced.Femtosecond laser pulse-based single-beam Z-scan analysis was employed to investigate the third-order nonlinear optical response of colloidal bimetallic Ag-Rh nanoparticles aqueous dispersions with different concentration,molar ratios and laser power,expounding the related mechanism.The Z-scan methods showed that the sign of nonlinear refractive index of colloidal Ag-Rh nanoparticles is negative and it is a kind of self-defocusing materials.