Fabrication of FRET based nano sensor from biomass-derived fluorescent carbon quantum dots and naphthalimide for ratiometric detection of nitric oxide: To examine nitrite levels in meat samples

Real-time and specific monitoring of nitric oxide and evaluating of the oxidative stress in living cells and zebrafish under the pollutant exposure using a carbon dot-based composite fluorescent probe

Nitric oxide (NO) functions as an essential signalling molecule in various physiological and pathological pathways. In vitro and vivo redox processes mediated by reactive oxygen species (ROS) and nitric oxide (NO) directly influence the intracellular state. In this study, a red-emitting fluorescent nanoprobe, N,S-CDs@Zn-ICA, was synthesized to monitor NO fluctuations in living cells and zebrafish under the exposure to various pollutants. Red-emissive carbon dots (N,S-CDs) were synthesized by a hydrothermal method using o-phenylenediamine and urea as carbon / nitrogen sources, and H2SO4 as sulfur source. Glutathione (GSH) was introduced to link N,S-CDs with metal organic complexes (Zn-ICA) through an amidation reaction to fabricate a carbon dot-based composite fluorescent probe, which greatly improved the selectivity, stability, and response time of the N,S-CDs. The composite probe has high selectivity and sensitivity with limit of detection (LOD) of 96.0 nM. Furthermore, the proposed probe was successfully used to monitor the dynamic changes in NO levels and evaluate oxidative stress in MCF-7 cells and zebrafish under the exposure to various pollutants, including seven heavy metal ions (such as Pb2+, Cd2+, and Hg2+) and nine organic pollutants at different concentrations and exposure times. This work provides a novel strategy for constructing highly selective and red-emitting fluorescent probe for real-time and dynamic monitoring of NO and further evaluating oxidative stress induced by pollutants in vitro and in vivo via fluorescence imaging.

Four polyoxomolybdated-based 3D compounds as supercapacitors and amperometric sensors

Four polyoxomolybdated compounds based on Tetp (Tetp = 4-[4-(2-Thiophen-2-yl-ethyl)-4H-[1, 2, 4]triazole-3-yl]-pyridine), namely [Zn(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Zn-Mo8), [Co(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Co-Mo8), [Cu4(Tetp)6(H2O)2]{H3[K(H2O)3](θ-Mo8O26)(Mo12O40)}·8H2O (Cu-Mo20) and [Cu3(Tetp)3][PMo12O40]·H2O (Cu-PMo12) are synthesized by hydrothermal methods and are used as electrode materials for supercapacitors(SCs) and electrochemical sensors. Inserting polyoxometalates (POMs) with redox active sites into transition metal compounds (TMCs) can improve the internal ion/electron transfer rate, thus effectively enhancing the electrochemical performance. Compared with the parent POMs, four compounds exhibit excellent electrochemical properties. In particular, Cu-PMo12 shows an excellent specific capacitance (812.3 F g-1 at 1 A g-1) and stability (94.42%), as well as a wide detection range (0.05 to 1250 µM) and a low detection limit (0.057 µM) for NO2- sensing.

A dual-emitting fluoroprobe fabricated by aloe leaf-based N-doped carbon quantum dots and copper nanoclusters for nitenpyram detection in waters by virtue of inner filter effect and static quenching principles

Fluorescence sensing technique has been used in environmental analysis due to its simplicity, low cost, and visualization. Although the fruit pulp-based biomass carbon quantum dots (CQDs) have excellent luminescent properties, aloe leaves possess the superiority of being easily accessible in all seasons compared to fruit pulp. Thus, we fabricated Aloe carazo leaf-based nitrogen doping-CQDs (N-CQDs) using a facile hydrothermal approach, which emitted bright blue fluorescence with a quantum yield of 21.4 %. By comparison, the glutathione-encapsulated copper nanoclusters (GSH-CuNCs) displayed strong red fluorescence. A blue/red dual emission based on the N-CQDs/CuNCs mixture was established for nitenpyram detection. At the 350-nm excitation, the N-CQD/CuNCs system produced dual-wavelength emitting peaks at 440 and 660 nm, respectively. Moreover, when nitenpyram was introduced into the system, the fluorescence intensities (FIs) of N-CQDs significantly decreased, whereas the FIs of GSH-CuNCs varied slightly; simultaneously, the solution color changed from bright blue to dark red. Both the spectral overlapping between nitenpyram's UV-Vis absorption and N-CQDs' excitation and almost unchanged fluorescence lifetimes indicated the occurrence of inner-filtering effect (IFE) in the dual-emitting fluoroprobe. In addition, the Stern-Volmer constant (Ksv = 6.92 × 103 M-1), temperature effect, as well as UV-Vis absorption of N-CQD/CuNCs before and after the addition of nitenpyram corroborated the static-quenching behavior. Consequently, the fluorescence-quenching of N-CQDs by nitenpyram was attributable to the joint IFE and static-quenching principles. A good linearity existed between the F660/F440 values and nitenpyram concentrations (0.5-200 μM) with a method detection limit of 0.15 μM. The dual-emitting fluoroprobe provided the satisfactory recoveries (95.0%-107.0 %) for nitenpyram detection in real-world waters, which were comparable with the results of traditional liquid chromatography coupled to tandem mass spectrometry method. Owing to its simple operations, low-cost, and adaptability for on-site outdoor monitoring, the newly developed dual-emitting fluoroprobe possesses great potential applications in routine monitoring of nitenpyram under field conditions.