Size and Phase Control in Quinacridone Nanoparticle Formation by Laser Ablation in Water

Abstract

Quinacridone (QA) nanoparticles were formed by nanosecond laser ablation of QA microcrystalline powder dispersed in water. The particle size and phase were examined at two different excitation wavelengths of 355 and 580 nm. At a fluence of 95 mJ/cm2, the mean sizes of the formed nanoparticles were approximately 22 and 50 nm at 355 and 580 nm excitations, respectively. The absorption spectra of the nanoparticles prepared by 355 nm laser pulses showed the caracteristic bands of the initial β-form QA in the fluence range from 30 to 120 mJ/cm2. On the other hand, 580 nm laser pulses with fluences of 50 to 118 mJ/cm2 caused the spectra to become similar to that of γ-form QA. We demonstrate that the crystalline phase and mean size of QA nanoparticles can be controlled by tuning the intensity and wavelength of laser pulses.