A colorimetric and NIR fluorescent probe for ultrafast detecting bisulfite and organic amines and its applications in food, imaging, and monitoring fish freshness

Herein, for the first time, we have successfully constructed a novel near-infrared (NIR) emission fluorescent probe Dpyt for ultrafast detecting (within 5 s) bisulfate and organic amines based on a 1,2-dihydrocyclopenta[b]chromene-barbiturate conjugation system. Upon addition of bisulfate or organic amines, Dpyt displayed a distinct color change from blue to colorless or from purple to blue, respectively, suggesting that the Dpyt can be used to detect two analytes by the naked eye. Based on quantum chemistry calculations, the fluorescence quenching of Dpyt after the addition of HSO3- is caused by the photoinduced electron transfer (PET) process of the adduct Dpyt-HSO3-. The fluorescence enhancement of Dpyt caused by most organic amines is due to the enhanced intramolecular charge transfer (ICT) process of deprotonated Dpyt. Notably, Dpyt can be applied for detecting HSO3- in actual food samples such as red wine and sugar, as well as for imaging of HSO3- and representative propylamine in living cells. And more importantly, indicator labels constructed by filter paper loaded with Dpyt can visually monitor the freshness of salmon in real-time by daylight and fluorescence dual-mode. The comparison with national standard method of China manifests that indicator labels are a valid tool to assess the freshness of seafood.

Molecular simulations of understanding the Na+ ion structure, dynamic and thermodynamic behavior in ionic liquids: Butyl ammonium hydrogen bisulfate and tri-butyl ammonium hydrogen bisulfate

This manuscript presents the all-atom molecular dynamics simulations to investigate intermolecular structure and solvation thermodynamics of Na+ ion in two different ammonium-based protic ionic liquids (1) Butyl Ammonium hydrogen bisulfate [BA+][HSO4-], (2) Tri-butyl ammonium hydrogen bisulfate [TBA+][HSO4-]. The ionic liquid [BA+][HSO4-] show a more coordinated behavior when compared to [TBA+][HSO4-], which is observed over the temperature range from 278 K to 348 K. Hydrogens of the cations show a hydrogen bonding interaction with oxygens of anions. The cationic [TBA+] molecules show more solvation behavior with anions when compared to the [BA+]. The Na+ ion show a strong coordination structure with [HSO4-] in [TBA+][HSO4-] when compared to the [BA+][HSO4-]. We further calculate the detailed solvation free energy (ΔG) calculations using thermodynamic integration. We found that the ΔG of Na+ is more favorable in [TBA+][HSO4-] when compared to [BA+][HSO4-] in the temperature range varying from 278 K to 348 K. With the temperature rise, we observe the more favorable solvation of Na+ in both ionic liquids. On the other hand, the solvation of Cl- becomes less favorable. Overall, this manuscript provides detailed molecular level structural and thermodynamic origins of Na+ in protic ionic liquids useful for designing and developing sustainable electrolytes for Na+ battery applications.

A dual electron-withdrawing enhanced selective/sensitive chemodosimeter for detection on bisulfate and its living cell imaging

Fluorescence detection of sulfur dioxide has attracted great interest from researchers in recent years. Usually double bonds and aldehyde group were employed as reaction sites for sulfur dioxide. In this work, the double bond was linked with cyano and carboxyl group as dual electron-withdrawing to enhance the reaction reactivity between the probe and sulfite. Meanwhile, coumarin with good biocompatibility was introduced as fluorophore. Thus D-π-A form constructs intramolecular charge transfer (ICT), the probe has weak yellow fluorescence emission (565 nm), after addition reaction taking place between the probe and bisulfate, conjugated double bond is broken, the system showed a short-wavelength fluorescence emission (483 nm). All these realized a ratiometric fluorescence detection for bisulfate. The study found that dual electron-withdrawing groups enhanced the specificity and sensibility (with a low detection limit 82 nM) of the probe recognizing bisulfate. These excellent properties led directly to the use of probes to image sulfur dioxide in living cells. Further applications are still being on the way.