Nonlinear optical properties of AgRh colloidal bimetallic nanoparticles fabricated via chemical reduction method

The poly (N-vinyl-2-pyrrolidone)-protected AgRh nanoparticles (NPs) with various solution concentration (0.66, 1.32, 1.98 mM/L) were prepared by a simple route based on dropwise addition of KBH4 (Reducing agent). Their morphology analysis and structures were characterized by Ultraviolet-visible spectra (UV-vis), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HR-TEM). Femtosecond laser pulse-based single-beam Z-scan technology was employed to investigate the third-order nonlinear optical response of AgRh BNPs aqueous dispersions for the first time. As-prepared alloy-structured AgRh BNPs showed a higher third-order nonlinear optical response than Ag nanoparticles. The results indicate that the sign of nonlinear refractive index of AgRh nanoparticles is negative. The third-order nonlinear optical response of different solution concentration samples can be ascribed to the electromagnetic coupling in the near field. The fabrication of such bimetallic nanopa...