Enhancement of Crystallization of Ionic Liquids by Scanning Irradiation with Focused Ultrashort Laser Pulses

This study investigates the crystallization behavior of the ionic liquid 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) induced by focused irradiation with ultrashort laser pulses with the pulse duration of 100 fs or 5 ps. The crystallization was significantly enhanced through scanning irradiation compared to single-point irradiation, probably due to an increase in numbers of laser-induced bubbles and less temperature elevation. The scanning irradiation with 5 ps laser pulses resulted in a higher crystallization probability than that with 100 fs laser pulses, which is attributed to the larger bubbles generated by 5 ps pulses (≥1 mm) compared to those with 100 fs pulses (≪1 mm). Our findings that focused scanning irradiation with 5 ps laser pulses can efficiently induce crystal nucleation will offer a guiding principle for the efficient crystal nucleation of various compounds, impacting a broad range of scientific and industrial fields such as crystal engineering and materials science.