Rapid enantioselective recognition of lysine using a chiral self-assembled nanomaterial with AIE characteristics

Chirality is crucial for the function of biological molecules and various chemical reactions, yet recognizing and detecting it remains a significant challenge. R-BITOP, a Lysine enantiomeric-selective fluorescence probe with AIE Properties was efficiently synthesized via nucleophilic cyclization. Upon reaching a water content of 90%, scanning electron microscopy revealed that the R-BITOP molecules had undergone aggregation and self-assembly into supramolecular J-aggregates, resulting in the formation of irregularly shaped microspheres. Additionally, a novel orange-red fluorescence emission peak was detected at 603 nm. Single crystal diffraction analysis indicated that the self-assembly of R-BITOP into supramolecular structures was driven by both intramolecular and intermolecular hydrogen bonding, as well as significantly strengthened by weak π-π interactions between the electron-deficient B ring of one R-BITOP molecule and the electron-rich A ring of another. The fluorescence emission of the R-BITOP probe exhibited a rapid enhancement corresponding to the increasing concentration of L-Lys via a ICT mechanism with low detection limit to 12 nM and the binding constant was calculated to be 2.25 × 10⁵ M^-1. The fluorescence lifetime of R-BITOP was only 0.35 ns, which was significantly prolonged to 4.26 ns after interacting with L-Lys. Concurrently, its morphological characteristics transitioned from an irregular spherical configuration to a reticular microporous architecture.