Preparation of Organic Nanoparticle Colloids by Laser Ablation and Their Nonlinear Optical Properties

Suspension of micrometer-sized 1,4-bis(4-methylstyryl)benzene(p-MSB) was converted into colloidal nanocrystal solution by irradiation with an femtosecond laser(800 nm, 1 kHz). The prepared nanocrystals were rectangular with ca. 100 nm in size. The same crystal structure as that of bulk crystals was confirmed by X-ray diffraction measurement. UV-Vis spectra and emission spectra of the nanoparticle dispersions in dichloromethane(poor solvent) were examined. The nanocrystal exhibits large quantum yield(89%). The nonlinear optical properties of the nanocrystals were further studied by Z-scan technique with femtosecond laser duration of 120 fs at a wavelength of 800 nm. The results show that the nanocrystals exhibit strong nonlinear absorption.