Size dependence of the surface plasmon enhanced second harmonic response of gold colloids: towards a new calibration method

Hyper Rayleigh scattering in solution is used for the determination of the first order hyperpolarizability beta(colloid) Of gold colloids in the size range 5-22 nn; these hyperpolarizabilities are found to range from 0.60 x 1 0(-25) esu for 5 nm diameter colloids to up to 16.6 x 10(-25) esu for 22 nm diameter colloids at the second harmonic wavelength of 532 nm; the strong size dependence of the hyperpolarisabilities reported here suggests that hy per Rayleigh scattering experiments can efficiently be used to calibrate th e particle diameter of colloidal suspensions.