Advanced oxidation technology (AOPs) is an effective technology to treat water pollution, which has attracted recent attention. The non-selective and strong oxidation properties of hydroxyl radicals (·OH) in the AOPs reaction process are efficient enough to degrade pollutants. CuFeS₂/g-C₃N₄ (CFS/CN) photofenton catalyst was synthesized by a simple hydrothermal/calcination method for degradation of Rhodamine B (RhB). The results show that CFS/CN 1:2.5 has the optimum catalytic performance for RhB degradation at 0.10 g/L catalyst, 10 mg/L RhB concentration, 50 μL H₂O₂ addition and pH value 1. In addition, the degradation efficiency of CFS/CN for RhB is 90% at 15 min and nearly 96% at 20 min. According to the results of cyclic experiments, CFS/CN has a good cyclic stability. It is indicated that CFS/CN catalysts could provide a potential application for RhB degradation.

Supercapacitors have a wide range of potential applications in new energy storage and electric cars due to their high capacity, high power density, and extended cycle life, and the electrode materials are a key to enhancing the supercapacitor performance. NiCoMnSe electrode materials were prepared by a simple low-temperature hydrothermal reaction method and a heat-treatment selenization method using ZIF-67 as a template. The optimum electrochemical performance was obtained via adding carbon nanotube (CNT) or graphene oxide (GO) to the ZIF-67 template. The results show that the optimum NiCoMnSe/CNT electrode has a specific capacitance of 624.0 F/g at 1 A/g and a multiplicative performance of 90.1% at 10 A/g. The capacity retention rate is 88% at 15 A/g for 1000 cycles. This superior capacitive performance is attributed to the presence of CNT introducing additional mesopores around NiCoMnSe, thus enhancing the contact between the electrolyte and the active material. The NiCoMnSe/CNT/activated carbon device exhibits a high energy density (43.3 W·h/kg) at a power density of 800 W/kg and a good capacity retention (i.e., 91.4% after 1000 cycles) due to the asymmetric nature of the supercapacitor.

Transition metal sulfide is an active material with high specific capacitance. MnS/Ni₃S₂ electrode material was hydrothermal prepared on nickel foam by a simple and time-saving method. The effects of hydrothermal reaction time and temperature on the morphology and electrochemical performances of the sample were investigated. The results show that MnS/Ni₃S₂ electrode material has high specific capacitance and excellent magnification performance, and the retention rate of specific capacitance is 90% after 2500 cycles. A hybrid supercapacitor device is assembled with MnS/Ni₃S₂ as the positive electrode and activated carbon (AC) as the negative electrode. MnS/Ni₃S₂//AC can provide 30.2 Wh·kg^–1 energy density when the power density is 700 W·kg^–1. The specific capacitance retention is 116.0% after 3000 cycles. It shows that MnS/Ni₃S₂ is expected to provide potential application value in supercapacitor.

Using blue-emitting UiO–66–NH₂ with red-emitting Eu–MOF as fluorescence groups, a ratio fluorescence probe (UiO–66–NH₂@Eu–MOF) was constructed and successfully applied to the determination of trace PO₄^3– ions in environmental water samples. A ratiometric fluorescent probe for the determination of trace PO₄^3– ions in environmental water samples was constructed via combining blue-emitting UiO–66–NH₂ with red-emitting Eu–MOF. As PO₄^3– ions concentration increases, the coupling of PO₄^3– ions with Zr⁴⁺ ions in UiO–66–NH₂ leads to a weakened ligand–metal charge transfer effect, effectively restoring the luminescence of UiO–66–NH₂. Also, an intense coordination of Eu³⁺ ions with PO₄^3– ions can hinder the ligand–metal energy transfer, destroy the "antenna" effect, and lead to the quenching of Eu–MOF fluorescence. Under optimal conditions, a ratio of the fluorescence intensity at 445 nm to the fluorescence intensity at 633 nm is linearly related to PO₄^3– ions concentration in the range of 1–12 μmol/L. The sensor constructed has a good selectivity and accuracy, thus providing an effective way for the rapid detection of PO₄^3– ions.

As an energy storage device, supercapacitors are practically used in many fields due to their high power density and long service life. Among the components of supercapacitors, electrode materials play a key role in the performance of the device, it is thus of great significance to prepare electrode materials with superior electrochemical performance. NiCo₂S₄ was prepared by a hydrothermal method using nickel acetate and cobalt acetate as raw materials, glutathione as a morphology control agent and a sulfur source. The effect of hydrothermal reaction time on the microstructure, morphology and electrochemical performance of NiCo₂S₄ was investigated. The results show that the NiCo₂S₄ material prepared under the action of glutathione has a yolk shell structure. The specific capacitance is 1552.7 F/g when the current density is 0.5 A/g, and the specific capacitance can be maintained at 61.3% at 10A/g. After 2000 cycles, the specific capacitance retention of the material can be maintained at 79.3%. A supercapacitor can be assembled with NiCo₂S₄ and activated carbon as positive and negative electrodes, respectively. This hybrid supercapacitor can provide 33.9 W·h/kg energy density when the power density is 800 W/kg. After 2000 charge and discharge cycles, the specific capacitance retention rate is 89%.

A ratiometric fluorescent probe (CQDs/Eu³⁺) was constructed with carbon quantum dots (CQDs) and europium ions (Eu³⁺) as fluorophores for the detection of ciprofloxacin (CIP). At excitation at 395 nm wavelength, CQDs/Eu³⁺ has an intense blue fluorescent peak at 459 nm, and a weak red fluorescent peak at 616 nm in the presence of CIP. The fluorescence (FL) intensity of CQDS at 459 nm is enhanced based on the antenna effect. The major factors like ratio of CQDs and Eu³⁺, response time and stability were optimized, The results show that the ratio fluorescent probe has a specific recognition ability for CIP. And there is a linear relationship between the fluorescence intensity ratio (F₄₅₉/F₆₁₆) and concentration of CIP (0–7×10^–6 mol/L), and the lowest detection limit for CIP is 0.3×10^–6 mol/L. This probe can be used for the detection of CIP in milk under the addition of CIP.

A ratiometric fluorescent probe was constructed with carbon quantum dots (CQDs) and europium ions (Eu³⁺) as a fluorophore for the visual detection of teracycline (TC). In this ratiometric probe, CQDs/Eu³⁺ has an intense blue fluorescence peak at 439 nm and a weak red fluorescence peak at 616 nm under the excitation of 380 nm wavelength. The fluorescence peak intensity of CQDs at 439 nm gradually decreases based on the inner filter effect. The fluorescence intensity of Eu³⁺ at 616 nm increases due to an antenna effect with the addition of TC. The experimental factors, such as CQDs and Eu³⁺ ratio, response time, stability, etc., were optimized. The results show that the ratio fluorescent probe has a specific recognition ability for TC. A linear relationship between the fluorescence intensity ratio(F₆₁₆/F₄₃₉) and different concentrations of TC (0–50 μM) was established with a detection limit of 0.68 µM. With the addition of TC, the color of the ratio fluorescent probe solution under ultraviolet light gradually changes from blue to red and is used for the detection of TC in milk with the recoveries ranging from 92.5% to 1 14.8%. In addition, a TC test paper was also prepared, which can be quickly used for a visual test paper detection of TC.