Hyper-Rayleigh scattering and continuum generation of salt induced aggregates of Silver nanoparticles: The effect of cation size (Li+, Na+ and K+)

The effect of cation size (Li+, Na+ and K+, counterion Cl−) on the hyper-Rayleigh scattering (HRS) and continuum generation capability of salt induced aggregates of silver nanoparticles (AgNPs) was studied using femtosecond laser pulses. It was observed that while on addition of NaCl and KCl, HRS intensities of AgNPs were greatly enhanced (∼50×), upon addition of LiCl this enhancement was rather modest (∼4×). Continuum generation was also observed only from NaCl and KCl induced aggregates. These observations suggest that smaller size and hence higher ionic charge density of the Li+ ion is not conducive to the formation of aggregates.