Constructing multi-dimensional hydrogen bond (H-bond) regulated single-molecule systems with multi-emission remains a challenge. Herein, we report an excited-excited intramolecular transfer (ESIPT) featured chromophore (HBT-DPI) that shows flexible emission tunability via the multi-dimensional regulation of intra- and intermolecular H-bonds. The feature of switchable intramolecular H-bonds is induced via incorporating two hydrogen bond acceptors into a single-molecule system, HBT-DPI, allowing the “turn on/off” of ESIPT process by forming isomers with distinct intramolecular H-bonds. In response to different solvent environments, the obtained four types of crystal/cocrystals vary in the contents of isomers and the molecular packing modes, which are mainly guided by the intermolecular H-bonds, exhibiting non-emissive features or emissions ranging from green to orange. Moreover, we demonstrate the practical utility of this fluorescent material for visualizing hydrophobic/hydrophilic areas on large-scale heterogeneous surfaces of modified PVDF membranes and quantitatively estimate the surface hydrophobicity, providing a new approach for hydrophobicity/hydrophilicity monitoring and measurement.

A rapid and convenient strategy to monitor the productivity of biomanufacturing is essential for the research in optimizing relevant bioprocesses. In this work, we have developed a fluorescein-derived probe (FL-DT) that reacts rapidly with thiol groups via 1, 4-Micheal addition reaction of the sulfhydryl to unsaturated ketone and releases fluorescence. FL-DT specifically forms fluorescent adduct with two adjacent thiols in a protein of interest (POI), making the probe a reliable tool for protein quantification. The production of xylanase fused with a short di-Cys tag was then successfully monitored and quantified with FL-DT in E. coli system under different protein expression conditions, providing useful information for optimizing the bioprocess. Our work provides a convenient and efficient strategy for POI labeling and monitoring bioproduction.