Shape dependence of nonlinear optical behaviors of gold nanoparticles

Tetrahedral, icosahedral, and cubic gold nanoparticles have been synthesized in experiment by reducing chloroauric acid with ethylene glycol (EG) in the presence of poly(vinylpyrrolidone) (PVP). The nonlinear properties of the gold nanoparticles have been investigated by using the Open-aperture Z-scan technique with the nanosecond pulse at a wavelength of 532 nm. It shows out that all the gold nanoparticles possess strong optical nonlinearities when being excited at their surface plasmon resonances. It is identified that the nonlinear properties of the gold nanoparticles are dependent on their shapes, and the icosahedra gold nanoparticles show much better nonlinear optical properties than the tetrahedral and cubic ones. Moreover, the mechanism for the process of the nonlinear properties is also analyzed.