Probing non-equilibrium inner structure of polymeric nanoparticle via aggregation-induced emission of luminogen

A molecular segregation inside a nanoparticle was crucial for its properties but usually hard to be determined, especially for organic particles. Herein, non-equilibrium polymeric nanoparticles loading a luminogen via an aggregation-induced emission (AIE) were prepared via an instant formation process, flash nanoprecipitation (FNP). Small organic molecules, polymeric excipients , and oily compounds were used as coprecipitants to reveal effects of conjugate moiety, glass transition temperature ( T g ), and a condensed state of a coprecipitant on the fluorescence (FL) intensity of the suspension. The results indicated that the addition of a small molecule in a solid state without any conjugate moiety or a polymeric excipient with high T g would facilitate enhancing the FL intensity, while a coprecipitant with a conjugate moiety or low T g or in liquid would decrease the intensity. Moreover, this study revealed that the nanoparticle formed via FNP had a randomly packed inner structure where different compositions tended to evenly distribute inside rather than a micellar structure with a phase-separated core-shell one. These findings provided a guide to selecting a suitable coprecipitant for AIE-luminogen nanoparticles in applications. The developed probing method would also benefit for better understanding the particle formation kinetics in FNP.