Nanocrystallization: A Unique Approach to Yield Bright Organic Nanocrystals for Biological Applications

Abstract

A new bottom-up method is developed for the fabrication of uniform organic nanocrystals with high brightness and good water dispersity. The effectiveness of the approach is demonstrated through the developing of an AIEgen with significant color and brightness difference in crystalline and amorphous states, which allows us to clearly visualize the amorphous-crystalline transition in solution. Fine-tuning the solvent to antisolvent ratio controls the morphology of the nanoaggregates formed in the aqueous media, but to a much lesser extent, the size. A stress-induced seed assisted crystallization method was subsequently developed to produce uniform nanocrystals with around 100 nm size. The nanocrystals have been successfully applied for cancer cell imaging and in vivo vascular imaging, which clearly reveal the importance of nanocrystallization in improving the fluorescent signals of organic nanoparticles. The nanocrystallization strategy thus opens new opportunities to bring crystallization-associated optical properties into aqueous media for biomedical applications.