Bottom‐Up Selective Growth of Ultralong Organic Phosphorescence Nanocrystals with Optimized Crystal Forms for In Vivo Optical Imaging

Ultralong organic phosphorescence (UOP) materials are valuable for biological imaging to avoid interference from fluorescence background signals because of their delayed emission property. Obtaining nanocrystals with high phosphorescence quantum yield is a critical factor to achieve high-quality UOP imaging. Herein, a pair of host-guest UOP doped system with variable crystal forms for the host is constructed. By exploring the relationship between the crystal form of the host and the UOP of the doped system, the importance of host crystal form is revealed to achieve high quantum yield UOP in doped systems. Furthermore, to overcome the low crystallinity and numerous defects faced by traditional bottom-up strategies for nanocrystal preparation, a strategy is proposed for the selective preparation of nanocrystals with the target crystal form. Through controlling the evaporation rate of the solvent, the ordered growth of crystals can be effectively regulated to obtain nanocrystals with different crystal forms for bioimaging applications.