Solvent-Dependent Size and Phase of Vanadyl Phthalocyanine Nanoparticles Formed by Laser Ablation of VOPc Crystal-Dispersed Solution

Intense excimer laser irradiation of vanadyl phthalocyanine (VOPc) microcrystals dispersed in poor solvents yields VOPc nanoparticles, which was confirmed to be common among some representative solvents. The mean diameters of the nanoparticles formed in water, methanol, ethanol, 1-propanol, and ethyl acetate were determined to be 50 nm, 46 nm, 37 nm, 32 nm, and 38 nm, respectively. Absorption spectral analysis of the nanoparticles indicates that the VOPc nanoparticles from ethanol, 1-propanol, and ethyl acetate exhibit stable phase II, while those from water exhibit phase I and those from methanol cannot be identified. To understand the solvent effect, we attempted to correlate the mean diameter and the absorption spectrum with various solvent parameters such as density, viscosity, thermal diffusivity, dipole moment, dielectric constant, and solubility. Experimentally, the thermal diffusivity of a solvent can be correlated with nanoparticle formation, which is considered in relation to the ablation mechanism.