Dual-quenching electrochemiluminescence resonance energy transfer system from CoPd nanoparticles enhanced porous g-C3N4 to FeMOFs-sCuO for neuron-specific enolase immunosensing

For the diagnosis and therapy of small cell lung cancer (SCLC), the accurate and sensitive determination of neuron-specific enolase (NSE) content is crucial. This work outlines a dual-quenching electrochemiluminescence resonance energy transfer (ECL-RET) immunosensor based on the double quenching effects of iron base metal organic frameworks (FeMOFs) loaded with small sized CuO nanoparticles (FeMOFs-sCuO) towards CoPd nanoparticles (CoPdNPs) enhanced porous g-C₃N₄ (P-C₃N₄-CoPdNPs). To be specific, we prepared a porous g-C₃N₄ (P-C₃N₄) which has a rich porous structure, and significantly increased the specific surface area and the number of reaction sites of P-C₃N₄. Meanwhile, the CoPdNPs were loaded onto P-C₃N₄ to improve the ECL luminescence property of P-C₃N₄/K₂S₂O₈ system through acting as a coreaction accelerator. In addition, the ultraviolet-visible (UV-vis) absorption spectra of FeMOFs and small sized CuO nanoparticles (sCuO) showed considerable overlap with the ECL emission spectra of P-C₃N₄ appropriately. Therefore, FeMOFs with high specific surface area were prepared and well combined with sCuO to effectively dual-quenching the ECL emission of P-C₃N₄ based on resonance energy transfer. Hence, a new type ECL-RET couple made up of P-C₃N₄-CoPdNPs (donor) and FeMOFs-sCuO (acceptor) were developed for the first time. A certain amount of P-C₃N₄-CoPdNPs, Ab₁, BSA, NSE were modified layer by layer onto the electrode surface. Then FeMOFs-sCuO-Ab₂ bioconjugates was incubated through the immune recognition binding. As a result, a sandwich-type ECL biosensor was manufactured successfully for NSE immunoassay. Under optimal experimental conditions, the limit of detection (LOD) and the limit of quantitation (LOQ) of the prepared ECL sensor for NSE analysis was 20.4 fg mL^-1 and 7.99 fg mL^-1, respectively, with the relative standard deviation (RSD) of 1.68%. The linear detection range was 0.0000500-100 ng mL^-1. The studied immunosensor had satisfactory sensitivity, specificity and reproducibility, manifesting the suggested sensing strategy might offer a good technical means and theoretical basis for the sensitivity analysis of NSE and has a potential application in clinical diagnosis analysis.

Highly efficient iodine capture and ultrafast fluorescent detection of heavy metals using PANI/LDH@CNT nanocomposite

Here, the hybrid material of polyaniline/layered double hydroxide@carbonnanotubes (PANI/LDH@CNT) is considered a multifunctional material. Instrumental methods, including FTIR, XRD, TEM, SEM, and TGA/DTA were utilized to characterize PANI/LDH@CNT. The polymerization method created PANI/LDH@CNT as an adsorbent to remove toxic iodine in hexane solution with a capture capacity of 303.20 mg g^-1 during 9 h. It is 900 mg g^-1 in the vapor phase within 24 h. After three cycles, the PANI/LDH@CNT could be regenerated while maintaining 91.90 % iodine adsorption efficiency. Due to the presence of free amine (-N) groups, OH^-, CO₂H, and π-π conjugated structures in the PANI/LDH@CNT, it is also explored for efficient iodine uptake. It was demonstrated that the pseudo-first-order (PFO) and Langmuir model had the optimum correlation with the kinetic and isotherm data, respectively. Moreover, the use of PANI/LDH@CNT is not only limited to iodine capture; it can also be utilized as a sensitive sensor that displays a fluorescence "turn-off" response for Mn⁷⁺ and Cr⁶⁺ ions and a fluorescence "turn-on" response in the case of Al³⁺ ions. The fluorescence intensity of the PANI/LDH@CNT was turned off in the presence of Mn⁷⁺ and Cr⁶⁺ because of the fluorescence inner filter effect (IFE) mechanism. In contrast, the fluorescence intensity was turned on in the case of Al³⁺, relying on the chelation-enhanced fluorescence (CHEF) effect mechanism. Under optimal conditions, the limit of detection (LOD) of 51, 59, and 81 nM for Mn⁷⁺, Cr^6+, and Al³⁺, respectively. According to the literature, this is probably the first example based on PANI/LDH@CNT as a multifunctional hybrid material employed as an adsorbent for capturing radioactive iodine and as a chemosensor for detecting heavy metal ions in aqueous solutions.

Cationic Metal–Organic Framework-Based Mixed-Matrix Membranes for Fast Sensing and Removal of Cr2O72− Within Water

Considering that metal–organic framework (MOF)-polymer mixed-matrix membranes (MMMs) can overcome the drawbacks of intrinsic fragility and poor processability of pure-MOF membranes, we designed MOF-based MMMs for efficient removal and fast fluorescence sensing of heavily toxic ions within water systems simultaneously. In this work, a series of MOF-based MMMs are prepared by mixing a hydrolytically stable cationic [Eu₇ (mtb)₅(H₂O)₁₆]·NO₃ 8DMA·18H₂O (denoted as Eu-mtb) MOF material into poly (vinylidene fluoride) with high loadings up to 70%. The free volume at the interface between the polymer and Eu-mtb particles, combined with the permanent porosity and uniform distribution of Eu-mtb particles, enables these MMMs to show fast enrichment of Cr₂O₇^2- from solutions and consequently have a full contact between the analyte and MOFs. The developed Eu-mtb MMM (70wt% loading) thus shows both efficient removal and exceptional fluorescence sensing of Cr₂O₇^2- in aqueous media. The overall adsorption capacity of the Eu-mtb MMM (70 wt% loading) for Cr₂O₇^2- reaches up to 33.34 mg/g, which is 3.4 times that of powder-form Eu-mtb. The detection limit of the Eu-mtb MMM (70 wt% loading) for Cr₂O₇^2- is around 5.73 nM, which is lower than that of the reported powder-form Eu-mtb. This work demonstrates that it is feasible to develop flexible luminescent MOF-based MMMs as a significant platform for efficient removal and sensitive sensing of pollutants from water systems simultaneously.

Wheel-like Gd42 Polynuclear Complex with Significant Magnetocaloric Effect

Two novel wheel-like lanthanide nanoclusters with 42 nuclearity [Ln42L14(OH)28(OAc)84] (abbreviated as Ln42, 1-Gd; 2-Dy, HL=3-methoxysalicylaldehyde O-vanillin) were structurally and magnetically characterized. The Ln42 species were constructed by O-vanillin and lanthanide...

A multi-responsive luminescent sensor based on a stable Eu(iii) metal–organic framework for sensing Fe3+, MnO4−, and Cr2O72− in aqueous solutions

A stable benzothiadiazole-based Eu(iii) metal–organic framework with cco topology has been successfully constructed, and represents the multifunctional fluorescence sensor toward Fe3+, MnO4− and Cr2O72− in aqueous solutions.

Coordination networks for the recognition of oxo-anions

Crystalline coordination networks with an infinite extended framework, also known as coordination polymers (CPs) or metal-organic frameworks (MOFs), have attracted significant attention owing to their tremendous performance in an extensive range of applications. The unique structural features and high stability of coordination networks are responsible for their utilization and potential in diverse fields especially in the area of sensing using luminescent CPs/MOFs. The recognition of toxic oxo-anions present in water is a crucial and first step towards environmental remediation, mainly in the case of water pollution. Accordingly, the utilization of luminescent coordination networks has received significant interest, particularly for the recognition of various toxic oxo-anions, which are considered a threat to aquatic life and the environment. In this frontier article, we summarize recent reports on luminescent CPs/MOFs, their utilization for the sensing of oxo-anions and the chemistry of the interaction of oxo-anions with CPs/MOFs, which is responsible for tuning their optical signals.

Visible-light excitable Eu3+-induced hyaluronic acid-chitosan aggregates with heterocyclic ligands for sensitive and fast recognition of hazardous ions

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu³⁺-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu³⁺ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N-donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2': 6',2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (K_sv) values, enabling selective, rapid and sensitive recognition of Cr₂O₇^2- and Fe³⁺ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples.

A fluorescence red-shift and turn-on sensor for acetylacetone derived from ZnII-based metal–organic framework with new topology

JXUST-4 with a rare (3,3,7)-c topology net has been prepared, acting as a fluorescent sensor for acac through obvious fluorescence red-shift and enhancement with excellent properties.

Single molecule magnet behavior and magnetic refrigeration of carbonyl oxygen-bridged tetranuclear lanthanide complexes

Three lanthanide complexes were fabricated and characterized. 1 exhibited cryogenic magnetic refrigeration property and 3 displayed slow relaxation of the magnetization.

Polyoxometalate-based metal–organic frameworks for heterogeneous catalysis

POM-based MOFs simultaneously possessing the virtues of POMs and MOFs exhibit excellent heterogeneous catalytic properties.

The construction of a multifunctional luminescent Eu-MOF for the sensing of Fe3+, Cr2O72− and amines in aqueous solution

A 3D Eu(iii)-based metal–organic framework has been synthesized as a multiresponsive chemosensor for highly sensitive and selective detection of Fe3+, Cr2O72− and amines in water.

A porous anionic zinc(ii) metal–organic framework for gas adsorption, selective uptake of dyes and sensing of Fe3+ by Tb3+ ion encapsulation

A 3D anionic, porous MOF exhibits selective adsorption of cationic dyes and can be used as a fast-response fluorescence sensor for the detection of Fe3+ ions by Tb3+ ion encapsulation.

Pore-Functionalized and Hydrolytically Robust Cd(II)-Metal-Organic Framework for Highly Selective, Multicyclic CO2 Adsorption and Fast-Responsive Luminescent Monitoring of Fe(III) and Cr(VI) Ions with Notable Sensitivity and Reusability

Metal-organic frameworks (MOFs) show a distinctive pre-eminence over other heterogeneous systems for adsorption of carbon dioxide (CO₂) gas and fluorescence detection of water contaminating ions, where integration of both these attributes along with enhancement of pore functionality and water stability is crucial for potential applications related to environmental remediation. Pore functionalization has been achieved in a 2-fold interpenetrated, mixed-ligand Cd(II)-framework [Cd_1.5(L)₂(bpy)(NO₃)]·2DMF·2H₂O (CSMCRI-5) (HL = 4-(4-carboxyphenyl)-1,2,4-triazole, bpy = 4,4'-bipyridine, DMF = dimethylformamide, CSMCRI = Central Salt & Marine Chemicals Research Institute) by utilizing a bifunctional ligand HL. The bpy-pillared framework, containing diverse Cd(II) nodes, optimum sized voids, and free N-atom affixed one-dimensional porous channels, shows notable structural robustness in diverse organic solvents and water. In spite of a negligible surface area, the activated MOF (5a) exhibits good CO₂ uptake and highly selective CO₂ adsorption over N₂ (259.94) and CH₄ (14.34) alongside minor loss during multiple CO₂ adsorption-desorption cycles. Luminescence studies demonstrate extremely selective and ultrafast sensing of Fe³⁺ ions in the aqueous phase with notable quenching (1.13 × 10⁴ M^-1) as well as an impressive 98 ppb limit of detection (LOD). Importantly, Fe³⁺ detection is exclusively retained under simulated physiological conditions. The framework further serves as a quick-responsive scaffold for toxic CrO₄^2- and Cr₂O₇^2- anions, where individual quenching constants (CrO₄^2-: 1.73 × 10⁴ M^-1; Cr₂O₇^2-: 5.42 × 10⁴ M^-1) and LOD values (CrO₄^2-: 280 ppb; Cr₂O₇^2-: 320 ppb) rank among the best sensory MOFs for aqueous phase detection of Cr(VI) species. It is imperative to stress vivid monitoring of all these aqueous pollutants by a handy paper-strip method, besides outstanding applicability of 5a toward their recyclable detection. Mechanism of selective quenching is comprehensively investigated in light of the absorption of the excitation/emission energy of the host framework by an individual studied analyte.

Novel Ce(III)-Metal Organic Framework with a Luminescent Property To Fabricate an Electrochemiluminescence Immunosensor

We designed a novel luminescent metal-organic framework (MOF) named Ce-TCPP-LMOF (CTM) through a simple one-pot solvothermal method. CTM was synthesized by using the emerging electrochemiluminescent (ECL) material (4,4',4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) as the organic ligand and Ce(III) as the metal node. We found that CTM not only has the remarkable ability to emit light but also has a uniform "sandwich biscuit" shape and suitable nanoscale size, which are promising for further applications. We also applied CTM to construct a novel ECL immunosensor and achieve sensitive detection of the proprotein convertase subtilisin/kexin type 9 (PCSK9), a biomarker related to cardiovascular diseases. To further amplify the ECL signal of CTM, a novel dual-amplified signal strategy was established by inducing a polyamidoamine dendrimer (PAMAM) and gold nanoparticles (AuNPs). Importantly, we first proved that the ECL signal of the CTM/S₂O₈^2- system could be enhanced by the PAMAM electric field. As the electron transfer rate was accelerated by the AuNP layer, this ECL signal was further enhanced in AuNP-modified electrodes. The ECL immunosensor showed desirable performance for PCSK9 analysis within a detection range of 50 fg mL^-1 to 10 ng mL^-1 and a low limit of detection of 19.12 ± 2.69 fg mL^-1. Real sample detection suggested that the immunosensor holds great potential for analyzing clinical serum samples.

A robust 3D In–MOF with an imidazole acid ligand as a fluorescent sensor for sensitive and selective detection of Fe3+ ions

A stable In(iii)-MOF with a versatile 5-(1H-imidazol-1-yl)isophthalic acid ligand can be used as a fluorescent sensor for Fe³⁺ detection.

Modulation of magnetic relaxation behaviors via replacing coordinated solvents in a series of linear tetranuclear Dy4 complexes

Four linear tetranuclear Dy₄ complexes with different coordinated solvents exhibit distinct magnetic relaxation behaviors.

Temperature-induced structural transformations accompanied by changes in magnetic properties of two copper coordination polymers

Two ferromagnetic copper compounds have been synthesized under different temperature, which represented the rare example of structural transformations resulting from the coordination modes of organic ligands supported by magnetic results.

A luminescent Eu coordination polymer with near-visible excitation for sensing and its homologues constructed from 1,4-benzenedicarboxylate and 1H-imidazo[4,5-f][1,10]-phenanthroline

Ln-CPs were constructed to achieve luminescent Eu-CP excited at a wide excitation band including the visible region for sensing.