Lipophilic Red-Emitting Oligomeric Organic Dots for Moisture Detection and Cell Imaging

The development of self-assembled organic dots (ODs) with lipophilic fluorescent properties has significant potential in various applications, especially in sensing and bioimaging. Herein, we report a one-pot gram-scale synthesis of lipophilic red-emitting oligomeric L-ODs with high quantum yield (39.3%), which is prepared by a solvothermal condensation of o-phenylenediamine and L-tartaric acid. Interestingly, as-prepared ODs show no solid and aqueous emission but intense red fluorescence in the majority of organic solvents. The titration of water indicates that ODs can be applied to the moisture detection of organic solvent. And since ODs exhibit excellent biocompatibility, they are successfully used as a lipophilic red-emitting imaging reagent. Furthermore, contrast experiment and theoretical simulation are adopted to reveal the photoluminescence mechanism of L-ODs. Thus, the hydrogen-bond-induced red-shift of the benzimidazole intermediate is thought to be the main reason for the intense red-emitting fluorescence of the prepared L-ODs. The gram-scale and simple reaction without any purification suggests that these lipophilic oligomeric ODs have a promising prospect in the application of fluorescent probe and lipophilic environment imaging.