Microemulsion-Based Fabrication of Organic Nanocrystals for Persistent Phosphorescence Bioimaging

Abstract

Persistent phosphorescence eliminates the need for light excitation and thus avoids the issue of autofluorescence, holding great promise in various fields. To achieve bright phosphorescence emission, many methods were developed to confine most organic persistent phosphorescent materials in a rigid environment aiming to quench nonradiative relaxation pathways; among them, the nanocrystal method is a good candidate which can rigidify the molecules as well as offer the desirable water dispersity and size for further bioapplications. However, the current efficient preparation of phosphorescent nanocrystals still remains challenging. This study reports an efficient microemulsion-based method for the fabrication of phosphorescent nanocrystals with a desired diameter in the nanosize range (below 200 nm), a high phosphorescence quantum yield of about 6.5%, and ultralong persistent phosphorescence to the timescale after the removal of the external light source, making it easy for the commercial imaging system to detect, which is suitable for practical bioimaging. Furthermore, the synthesized nanocrystals with biocompatibility were utilized directly for in vitro imaging, showing effective cellular uptake and bright phosphorescence emission, which provides a reasonable strategy to develop a phosphorescent nanocrystal for application.