A calixarene–BODIPY fluorescent sensor for selective Fe3+ detection in environmental water samples: insights into static and dynamic quenching mechanisms

Field-deployable supramolecular fluorescent sensing platform for selective dual-mode detection of thiamethoxam in complex environmental matrices

A Schiff base-functionalized europium metal-organic framework for turn-off fluorescence sensing of Cu2.

Developing a low-cost, highly sensitive, and accurate fluorescence-based approach for Cu2+ detection is crucial for reducing heavy metal pollution in industrial effluent. Here, we report a newly synthesized Schiff base europium metal-organic framework (Eu-MOF) and demonstrate its use for turn-off fluorescent detection of Cu2+. A Schiff base ligand derived from 2-aminoterephthalic acid and 2-hydroxynicotinaldehyde was coordinated with Eu3+ to construct the framework, enabling a simple and rapid sample pretreatment procedure. The material exhibited pH-dependent fluorescence behavior. With the concentration range of 2.5 to 500 mg L-1, a linear response to Cu2+ was observed. The limit of quantification (LOQ) was 2.5 mg L-1, while the limit of detection (LOD) was 0.83 mg L-1. The method was effectively performed on vinegar, tea, fruit juice, and water samples, yielding spike recoveries of 84.5%-100.9% and relative standard deviations (RSDs) of 1.7%-4.8%. This method can be used to determine Cu2+ in various matrices.

Triadic Mn–ZnS/MOF/MIP Fluorescent Sensor for Highly Sensitive and Selective Sulfathiazole Detection

Sulfathiazole (STH) pollution has been increasing, with a strong need for a sensitive and selective analysis method. In this paper, a three-component fluorescent sensing platform with Mn2+-doped ZnS quantum dots in a metal–organic framework coated with a surface molecularly imprinted polymer (Mn-ZnS-MOF-MIP) for selective sensing of sulfathiazole is proposed. This synergistic sensor platform combines Mn-ZnS-insensitive emission, MOF-assisted analyte enrichment, and imprinting-based molecular recognition. The sensing platform displays a characteristic turn-off fluorescence with a dominant static quenching mechanism. Under optimal conditions, a broad sensing range with a low detection limit of 13.75 nM can be obtained. Outstanding selectivity among similar sulfonamides, biomolecules, and metal ions were achieved with high reproducibility, stability, and reusability. This sensing platform was shown to analyze sulfathiazole accurately in aqueous samples and blood serum with high recoveries, within the range of 90.00–104.24%, compared to high-performance liquid chromatography methods.

A ratiometric fluorescence sensor based on Eu3+@tetrafluorosuccinic acid functionalized UiO-67: Enhancing the detection performance of ofloxacin through pre-concentration effect.

The excessive use of ofloxacin (OFL) has led to its persistent residues in water sources and animal-derived foods, posing a threat to human health. Therefore, it is urgent to develop fluorescent sensing materials capable of detecting ofloxacin in water environments and food matrices. Herein, a novel Eu3+@tetrafluorosuccinic acid-functionalized ratiometric fluorescent material Eu3+@UiO-67-TFSA was prepared by a two-step post-synthetic modification of UiO-67. In the concentration range of 1-15 μM, the Eu3+@UiO-67-TFSA had a limit of detection (LOD) of 0.42 μM for OFL, which was approximately 3.90 times lower than that of the non-fluorinated Eu3+@UiO-67-SA (LOD = 1.64 μM). The improved sensing performance could be attributed to the pre-concentration effect provided by the Eu3+@UiO-67-TFSA. The possible detection mechanism was systematically elucidated through relevant experiments and density functional theory (DFT) calculation. Moreover, the constructed smartphone-assisted visual sensing platform was successfully applied to detect OFL in actual food samples and real water environment samples.

Signal-enhanced photoelectrochemical aptasensor for the detection of sulfadiazine based on Fe3O4/3D g-C3N4 heterojunction.

The contamination of the environment with the sulfadiazine (SDZ) antibiotic poses a significant risk to human and animal health and contributes to the emergence of drug-resistant bacteria. Conventional detection methods are often time-consuming and require sophisticated instrumentation. Herein, we developed a sensitive SDZ detection method based on a high-performance photoelectrochemical (PEC) aptasensor. Using an iron oxide (Fe3O4) functionalized three-dimensional graphitic carbon nitride (3DCN) nanocomposite. The 3DCN substrate was initially prepared through supramolecular self-assembly employing an ionic liquid as a template, followed by thermal polycondensation. Then, Fe3O4 nanoparticles bearing abundant hydroxyl groups were covalently anchored onto the 3DCN matrix via a solvothermal method. The incorporation of Fe3O4 broadened the visible-light absorption, facilitating charge separation and transport, and acting as an effective electron donor. Operating in a "signal-on" mode, the proposed aptasensor exhibited excellent analytical performance with a broad linear range (0.1 nM-1000 nM), a low detection limit (215 pM), and outstanding selectivity, stability, and reproducibility. The practical applicability was successfully validated by detecting SDZ in river water and milk with recoveries of 98.1-99.8%. Overall, the Fe3O4/3DCN-based PEC aptasensor is a robust, sensitive, cost-effective with good potential for food safety, environmental monitoring, and public health protection.

From colorimetric sensing to molecular logic: A Schiff Base probe for dual Cu2+ and Fe3+ recognition.

The development of efficient optical probes for the detection of biologically and environmentally important metal ions remains a significant research challenge. Herein, we report a Schiff base-derived colorimetric probe, (E)-2-((2-hydroxy-3-methoxybenzylidene)amino)benzamide (P), for the selective detection of Cu2+ and Fe3+ ions in a DMSO-H2O (1:9, v/v) medium. Probe P exhibits distinct colorimetric responses toward the target ions, accompanied by the appearance of new absorption bands at 409 nm for Cu2+ and 690 nm for Fe3+, enabling naked-eye discrimination. The sensing response arises from coordination-induced electronic redistribution within the probe framework. The probe displays high sensitivity, with detection limits of 0.83 μM for Cu2+ and 0.62 μM for Fe3+. A 1:1 binding stoichiometry was supported by Job's plot and ESI-MS analyses, while FTIR studies provided additional evidence for the proposed binding mode. Furthermore, density functional theory (DFT) calculations provided insight into the electronic features of the resulting complexes. The practical utility of the probe was demonstrated through the determination of Cu2+ and Fe3+ ions in water samples with satisfactory recoveries. In addition, the probe was employed to construct molecular logic operations, including INHIBIT and YES gates. These results highlight probe P as a simple, sensitive, and effective platform for dual-ion sensing and molecular logic applications.