Raman spectroscopic study of concentration dynamics in glycine crystallization achieved by optical trapping

This study investigates concentration dynamics during optical trapping-induced crystallization (OTIC) of glycine using Raman spectroscopy. In-situ Raman spectroscopy demonstrated that tightly focused laser beams induced faster concentration increase and crystal nucleation at higher supersaturation compared to loosely focused beams. Also, by varying numerical aperture (NA) values of the objective lens used, it was revealed that higher NA led to achieving a shorter induction time and higher crystallization probability. Remarkably, optical trapping using objective lenses with higher NA generated stable liquid droplets, inhibiting crystallization until considerably higher supersaturation was realized. These findings elucidate the complex interplay between optical forces, supersaturation, and crystallization dynamics on the mechanism of OTIC and offer a new method for precise control of laser-induced crystallization. We believe that the insights gained by this study pave the way for innovative developments in crystal chemistry and promising advancements in photochemistry.