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 nanoparticles will significantly reduce the process cost of optical limiting materials.