Abstract
Microcrystalline powder of several dye compounds suspended in a poor solvent was converted into their nanoparticle dispersion by irradiating with the third harmonics of nanosecond Nd3+: YAG laser (355 nm, 7 ns, 10 Hz). The colored colloidal solutions were stable during more than 1 week without any surfactants. Dye nanoparticles with the mean size of about 50 nm were confirmed by SEM observation, and the mean size was almost the same for all compounds. The nanoparticle formation was analyzed by visible absorption measurement. The laser fluence dependence demonstrates that laser ablation of microcrystals is considered to be responsible to nanoaparticle formation. The mechanism is discussed in terms of the urtrafast photo-thermal conversion process and the subsequent fragmentation of microcrystal.
