Selective Determination of HOCl in Environmental Water Samples and Real-Time Detection of HOCl Levels in Live Cells via Ratio Fluorescence Imaging Based on Eu³⁺-Modified and Carbon Dot-Encapsulated Metal Organic Frameworks

Hypochlorous acid (HOCl) is one kind of significant ROS and a typical environmental pollution, which is closely linked to our food chain and threatens human health. Hence, a dual-emission ratiometric fluorescent nanoprobe (N-CDs@Eu-UiO-66-(COOH)2) for sensitive and specific determination of HOCl was fabricated based on Eu3+-modified and carbon dot-encapsulated MOFs. The N-CDs were encapsulated into MOFs, which can greatly improve their photostability and resistance to photobleaching in aqueous solution. The N-CDs@UiO-66-(COOH)2 was modified by Eu3+ ions, which can emit the red characteristic fluorescence of Eu3+ ions via the antenna effect. HOCl can quench the fluorescence of N-CDs through oxidizing hydroxyl groups on its surface, while the characteristic fluorescence of Eu3+ remains unchanged. The ratiometric fluorescence nanoprobe of N-CDs@Eu-UiO-66-(COOH)2 was thus fabricated for detecting HOCl. The nanoprobe has high sensitivity and selectivity, and its LOD (3σ/K) can attain 15.0 nM. Moreover, the N-CDs@Eu-UiO-66-(COOH)2 nanoprobe can also be applied for real-time detection of HOCl levels in the live cells via ratio fluorescence imaging, which can serve as a noninvasive tool for sensitively detecting fluctuations of HOCl levels in the living cells. This work can provide a promising application in environmental monitoring and real-time monitoring HOCl levels in vivo

A Specific Turn-On Fluorescent Sensing for Ultrasensitive and Selective Detection of Phosphate in Environmental Samples Based on Antenna Effect-Improved FRET by Surfactant

Phosphate is not only an important indicator for aquatic ecosystems, but also plays vital roles in biosystems. A new strategy for ultrasensitive and selective detection of phosphate is fabricated based on a new insight found in this paper, in which a lower concentration of surfactant sodium dodecylbenzenesulfonate (SDBS) can greatly induce fluorescence resonance energy transfer (FRET) from ciprofloxacin (CIP) to Eu³⁺ in the CIP-Eu³⁺ complex. Surfactant SDBS does not act as a sensitizer for enhancing the fluorescence intensity of the system, but acts as a sensitizer of FRET and makes the native fluorescence of CIP quenched completely (switch off). Eu³⁺ ions can coordinate with the oxygen-donor atoms of phosphate, which weakens FRET from CIP to Eu³⁺ and results in the fluorescence recovery of CIP (turn on). The multicomplex of the CIP-Eu³⁺-phosphate has more sensitive fluorescent response than that of the reported coordination nanoparticle-based fluorescent probes. The LOD (S/N = 3) of this sensing system can attain 4.3 nM. The possible interferential substances existing in environmental samples, such as 17 common metal ions, 11 anions, and fulvic acid investigated, do not interfere with the phosphate detection. This sensing system has been successfully applied for phosphate detection in environmental samples such as wastewater, surface water, and atmospheric particulates. This work not only develops a fluorescent probe for the phosphate detection, but also provides a new strategy for designing fluorescent probes based on FRET or coordination nanoparticles

A study on the fluorescence behaviour and structure of thulium's ion association compound Tm(BPMPHD)₂. CTMAB

313-316The fluorescence behaviour of the Tm-BPMPHD-CTMAB system and the affecting factors have been studied. The solid complex of Tm-BPMPHD has been synthesized. Tests indicate that the composition ratios are 1:2:1 for Tm:BPMPHD:CTMAB. From the IR and NMR spectra, it is found that in the Tm(BPMPHD)2 complex, Tm3+ coordinates with four oxygen atoms of BPMPHD in Its enol form. The structure of the Tm(BPMPHD)2.CTMAB has been proposed. The luminescence mechanism is also discussed

Probing the Molecular Interaction of Triazole Fungicides with Human Serum Albumin by Multispectroscopic Techniques and Molecular Modeling

Triazole fungicides, one category of broad-spectrum fungicides, are widely applied in agriculture and medicine. The extensive use leads to many residues and casts potential detrimental effects on aquatic ecosystems and human health. After exposure of the human body, triazole fungicides may penetrate into the bloodstream and interact with plasma proteins. Whether they could have an impact on the structure and function of proteins is still poorly understood. By using multispectroscopic techniques and molecular modeling, the interaction of several typical triazole fungicides with human serum albumin (HSA), the major plasma protein, was investigated. The steady-state and time-resolved fluorescence spectra manifested that static type, due to complex formation, was the dominant mechanism for fluorescence quenching. Structurally related binding modes speculated by thermodynamic parameters agreed with the prediction of molecular modeling. For triadimefon, hydrogen bonding with Arg-218 and Arg-222 played an important role, whereas for imazalil, myclobutanil, and penconazole, the binding process was mainly contributed by hydrophobic and electrostatic interactions. Via alterations in three-dimensional fluorescence and circular dichroism spectral properties, it was concluded that triazoles could induce slight conformational and some microenvironmental changes of HSA. It is anticipated that these data can provide some information for possible toxicity risk of triazole fungicides to human health and be helpful in reinforcing the supervision of food safety