Highly lipophilic and solid emissive N-annulated perylene bisimide synthesis for facile preparation of bright and far-red excimer fluorescent nano-emulsions with large Stokes shift

Abstract

In this study, we synthesized a novel perylene bisimide (PBI) derivative, whose bay area (1, 6, 7, and 12-positions) was annulated by nitrogen atoms (PBI-NC8), and incorporated it into a nano-emulsion for the rapid preparation of bright nanoprobes for bio-imaging. PBI-NC8 was easily obtained and exhibited outstanding solubility in the liquid core of the nano-emulsions (up to 20 wt%), while the parent PBI exhibited limited dissolution (only 0.3 wt%). The resulting nano-emulsions exhibited several ideal features such as greater brightness at a large Stokes shift (140 nm) than that of a quantum dot (QDot 655), sufficient photostability, and long storage stability. These properties were derived from not only the solubility of PBI-NC8, but also its more efficient static excimer fluorescence in the red to far-red region in the aggregated state (Φfl, solid = 0.22) than that of PBI (Φfl, solid = 0.053).