We have designed and synthesized a novel ratiometric fluorescent chemodosimeter MHF-based ESIPT process for specific detection of cysteine among the biological thiols. The probe MHF shows very weak blue fluorescence under UV excitation. Upon addition of cysteine (Cys), the reaction of Cys with MHF induces acrylate hydrolysis, thereby enabling the ESIPT process to shift the weak blue emission to a strong green emission with about 20-fold enhancement. We utilized ¹H NMR spectra to elucidate the fluorescence sensing mechanism. Moreover, the cellular imaging experiment indicated the MHF possessed excellent selectivity, low cytotoxicity, and desirable cell permeability for biological applications.

The first “off–on” and ratiometric fluorescent method based on ICT mechanism for picric acid (PA) recognition in the near infrared region was constructed. Key advantages of the unique molecular architecture can fulfil the ratiometric response to electron-deficient featured PA which inclines to quench fluorescence of all reported sensors for PA.

In this review, we will summarize our recent progress in the design and application of novel organic sensors with emission in the near-infrared region (600–900 nm). By coupling different functional groups with excited-state intramolecular proton transfer (ESIPT) segments, new probes are developed to achieve a large Stokes shift, high sensitivity, and selectivity and to tune the emission toward the near-infrared region. The developed probes exhibit attractive optical properties for bioimaging and environmental science applications. In addition, we further discuss the photophysical properties of ESIPT dyes and how their fluorescence could be affected by structural/environmental factors, which should be considered during the development of robust ESIPT-based fluorescence probes. Their potential applications as imaging reagents are illustrated for intracellular membranes, mitochondria, lysosomes, and some biomolecules.

Furan-based copolyesters were synthesized via polytransesterification of 2,5-furandicarboxylic acid (FDCA) with ethylene glycol (EG) and 1,4-butylene glycol (BG). The composition and thermal properties of the obtained copolyesters were characterized in detail by ¹H NMR and elemental analysis, differential scanning calorimeters (DSC) and thermogravimetric analysis (TGA). The ¹H NMR results showed that the ethylene segment content was consistently lower than that of butylene in the obtained copolyesters in comparison with the comonomer feeds. The reactivities of EG and BG with FDCA were intensively investigated. On the basis of kinetic studies, EG was found to be less reactive than BG. The thermal properties of the obtained copolyesters could be adjusted by variation of the EG/BG molar ratios in the copolyesters.

An NIR-emitting probe (λ_em ∼ 700 nm) with a large Stokes shift (Δλ ≈ 234 nm) is synthesized by using excited-state intramolecular proton transfer (ESIPT). The phenolic proton, which controls ESIPT, acts as a switch to give strong fluorescence at pH ≈ 5. The probe can selectively show lysosome organelles, therefore leading to a lysosome probe without exhibiting “an alkalinizing effect”.