Bisulfite (HSO₃–)/Sulfite (SO₃²–) is widely used as a food additive, but excessive use often leads to serious consequences, so the detection of HSO₃–/SO₃²– is of great importance. In this paper, a novel 1,4-diethylpiperazine-modified coumarin-benzopyran derivative (probe QLP) has been synthesized and characterized. In PBS (10 mM, pH = 7.4), QLP displays good selectivity and is sensitive for HSO₃–/SO₃²– over various analytes with fluorescent “OFF–ON” rapid responding (2 min), long-wavelength emission (600 nm), and a detection limit of 177 nM. With the treatment of HSO₃–/SO₃²–, the color of the QLP solution obviously changes from blue-green to yellow, and the fluorescent color of QLP changes from colorless to amaranth. The fluorescence-enhanced mechanism is qualitatively evaluated by density functional theory calculations using the CAM-B3LYP/6-31G (d) method, which reveals that the photoinduced electron transfer leads to the fluorescence emission of the QLP-SO₃H adduct. Importantly, nontoxic QLP can be used to detect HSO₃–/SO₃²– in sugar, natural water samples, and living cells and localized to the mitochondria and monitor the mitochondrial HSO₃–/SO₃²– level.

Luminescent Tb³⁺ functionalized metal–organic frameworks (MOFs) are prepared and act as food preservatives sensor and water scavenger for NO₂–. Classical metal–organic frameworks with uncoordinated N atoms in pores are elected as carrier to encapsulate Tb³⁺ ions. This Tb³⁺ incorporated material reveals excellent characteristic green luminescence of Tb³⁺ and good fluorescence stability in water. Subsequently, we choose this probe for sensing NO₂– among several food preservative compounds, showing a highly sensitive capability for detection of NO₂–; it is then proved that the Dexter energy transfer (DET) causes the luminescent quenching between Tb³⁺ and NO₂–, achieving the detection of NO₂–. This probe is also employed to detect the NO₂– in real water samples and act as water scavenger to remove the NO₂– in drinking water, showing a good removal capacity 3.45 mg (75.0 μmol) of NO₂– per gram of particles.

Despite their status of being widely used as food additives, bisulfite (HSO₃–)/sulfite (SO₃²–) can pose serious health risks when they are excessively added. Therefore, it is vital to develop a new method for detecting HSO₃–/SO₃²– in foodstuff. In this paper, a benzopyran-benzothiazole derivative (probe DCA–Btl) with near-infrared emission was designed and synthesized by constructing a “push-pull” electronic system. DCA–Btl can selectively recognize HSO₃–/SO₃²– via a colorimetric and fluorescence dual channel in DMF/PBS (1:1, v/v, pH = 8.4), and the emission wavelength of DCA–Btl can reach 710 nm. The fluorescence quenching of DCA–Btl after recognition of HSO₃– is attributed to the photoinduced electron transfer (PET) process of the adduct DCA–Btl-HSO₃– as evaluated by the DFT/TD-DFT method. In addition, DCA–Btl has many advantages, including a large Stokes shift (95 nm), good anti-interference ability, and little cytotoxicity. What’s more, DCA–Btl has been successfully applied for the detection of HSO₃–/SO₃²– in actual water samples and food samples such as sugar, red wine, and biscuits with satisfying results, as well as for fluorescent imaging of HSO₃– in living MCF-7 cells.

Most previous studies have focused on the effects of salt on anaerobic digestion (AD) for hydrogen or methane production. However, the effects of salt on two-stage AD and the related approaches to mitigate the adverse effects of high salinity on hydrogen and/or methane production were seldom addressed. In this study, addition of Air-nanobubble water (Air-NBW) was adopted to mitigate the inhibition of high salinity on co-production of hydrogen and methane from two-stage AD of food waste (FW). In the Air-NBW added reactors with 0–30 g NaCl/L, hydrogen yield was increased by 21–65% with the subsequent methane yield elevated by 14–43% when compared to the corresponding deionized water (DW) group. This study for the first time confirmed that when two-stage AD of FW was exposed to the same salinity level, addition of Air-NBW could enhance enzymatic activities at the individual stage. Results of electron transport system (ETS) activity further demonstrate that addition of Air-NBW may promote the electron transfer associated with the synthesis of hydrogen and methane. Therefore, an efficient approach for hydrogen and methane recovery from the two-stage AD of FW under high salinity was proposed through improving microbial electron transfer and corresponding enzymatic activities at each stage via Air-NBW addition.