AIE Ligand-Based Luminescent Ln-MOFs for Rapid and Selective Sensing of Tetracycline

Eu-MOF-based highly sensitive and selective luminescence probe for trace, in situ and visual detection of flunitrazepam

Flunitrazepam, as an emerging new psychoactive substance classified as a third-generation drug that is more harmful and camouflaged, is gradually proliferating globally. Maliciously used as a criminal tool in homicide and rape cases, it has already caused serious harm to public safety and social stability. Owing to its special molecular structure, low concentration level and rapid metabolic process in the human body, accurate detection of flunitrazepam remains a major challenge, especially for real sample and on-site detection. In this paper, a lanthanide MOF (Eu-MOF) based on bi-ligand was constructed as a luminescence probe and used for the first time to detect trace amounts of flunitrazepam. The 'antenna effect' promotes strong luminescence of Eu-MOF, while the lower LUMO orbital energy level of flunitrazepam allows it to accept electrons from the electron donor leading to quenching of Eu-MOF luminescence. The probe has a high sensitivity and can detect flunitrazepam in the range of 0-800 μM with a detection limit as low as 73 nM. Moreover, flunitrazepam was detected in urine from real samples as well as in a variety of beverages to further validate its accuracy and practicality. The reported Eu-MOF represents one of the pioneering luminescence probes for the detection of flunitrazepam, which offers great promise for the on-site or on-line analysis of flunitrazepam.

A smartphone-integrated bimetallic ratiometric fluorescent probe for specific visual detection of tetracycline antibiotics in food samples and latent fingerprinting

Designing and preparing highly sensitive and accurate fluorescent chemosensors for monitoring tetracycline antibiotics remains a challenge. Herein, a fluorescent chemosensor based on lanthanide metal-organic frameworks (Ln-MOFs) is proposed to realize high-precision monitoring by adjusting the ratio of lanthanide ions. Ln-MOFs with good aqueous stability were prepared by a solvothermal method using Eu3+, Tb3+ and the ligand 4,4',4″-s-triazine-2,4,6-triyltribenzoic acid (H3TATB) in DMF/NMP/H2O. The Ln-MOFs could recognize oxytetracycline (OTC) and doxycycline (DOX), and the detection limits of OTC and DOX were as low as 8.6 and 4.8 nM, respectively. In particular, Eu(1.4 μM)-Tb-MOF sensors were used for visual detection of OTC and DOX in combination with smartphones with detection lines as low as 9.8 nM and 14.2 nM, respectively. Meanwhile, Eu-MOF, Tb-MOF and Eu(1.4 μM)-Tb-MOF can be used for latent fingerprint (LFP) visualization, demonstrating their potential applications in the field of criminal case investigation. The developed probes were successfully applied to determining OTC and DOX in milk, beef and pork with recoveries ranging from 92.0 % to 109.63 % and relative standard deviations (RSDs) ranging from 1.83 % to 4.56 %. Eu(1.4 μM)-Tb-MOF is believed to utilize its lanthanide metal ion coordination and photoinduced electron transfer (PET) mechanism to achieve highly selective and accurate OTC and DOX detection, which is supported by experimental and density functional theory (DFT) calculations.

Lanthanide MOF-based luminescent sensor array for detection and identification of contaminants in water and biomarkers

In today's society, heavy metal ions and antibiotic contaminants have caused great harm to water systems and human health. In this study, six isostructural lanthanide metal-organic frameworks [Ln(H3imda)2(TPA)(H2O)2](Tb for CUST-881, Eu for CUST-882, Dy for CUST-883, Er for CUST-884, Nd for CUST-885, Sm for CUST-886) were constructed by selecting terephthalic acid (TPA) and 4,5-Imidazoledicarboxylic acid (H3imda) and lanthanide metal ions via solvethermal method. Among them, CUST-881 and CUST-882 can selectively detect Fe3+, Cr2O72-, CrO42, and ceftriaxone sodium (CRO) in water systems and uric acid in urine. CUST-881 shows very low detection limits for these five substances. Furthermore, Principal Component Analysis (PCA) was used to distinguish Fe3+, Cr2O72-, CrO42-, and CRO in water. To our knowledge, this is the first time that they have been able to be simultaneously distinguished. In addition, the possible sensing mechanism was studied through UV-visible spectroscopy, Infrared spectroscopy, and PXRD analysis. Furthermore, the probe also showed satisfactory repeatability and recovery when applied to UA samples that simulated urine. Based on the above results, lanthanide metal-organic frameworks have great potential for practical monitoring of contaminants in water environments.

Bifunctional Nanocellulose@MOF composite aerogel for selective fluorescent detection and efficient removal of tetracycline

The antibiotic tetracycline (TC) significantly pollutes water bodies, adversely impacting ecosystems and human health. In this work, a bifunctional platform for simultaneous detection and removal of TC was successfully constructed by in-situ growth of Zr-MOF in BC microspheres. The in-situ growth ensured the stability, while the design of the aerogel microspheres improved the processability, convenience, and recyclability. The macropores and mesopores in the aerogel microspheres significantly improved the molecular mass transfer efficiency, and the sensitivity and selectivity of TC detection and adsorption were improved due to the size-sieving effect of the abundant micropores of Zr-MOF and the supramolecular interaction of the ligand. Owing to the hierarchical pore structure, the adsorption capacity reaches as high as 317.6 mg/g. The enrichment during the adsorption process enhances the interaction between TC and Zr-MOF, thereby significantly improving the detection sensitivity of TC. As expected, BMAT3H5 has a LOD as low as 28 ± 0.012 nM and a KSV as high as 1.89 ± 0.001 × 106 M-1, providing excellent detection performance compared to other work in recent years. The good selectivity to TC was theoretically validated through simulations with Materials Studio software (MS). It provides a novel and practical bifunctional platform for efficient fluorescence detection and adsorption of TC, which has a broad application prospect in the fields of environmental monitoring, water treatment, and food safety testing.

Highly stable Tb(III) metal-organic framework derived from a new benzothiadiazole functionalized ligand for fluorescence recognition of ascorbic acid

Because ascorbic acid (AA) is one of the basic elements to maintain the normal physiological functions of human body, it is urgent to develop a material that can achieve efficient, rapid and in-situ detection for AA. A new fluorescence organic compound 4',4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1'-biphenyl]-4-carboxylic acid) (H2BTBC) based on benzothiadiazole group has been synthesized, which can detect Fe3+ ions by fluorescence turn-off effect with a detection limit of 0.015 μM, as well as recognize linear amines by fluorescence turn-on effect. Moreover, a highly stable Tb(III) metal-organic framework has been solvothermally prepared with H2BTBC, namely {[(CH3)2NH2]2[Tb2(BTBC)4]∙solvents}n (JXUST-39), which can selectively detect AA among biological fluids by fluorescence enhancement effect with a detection limit of 0.077 μM. In addition, the mechanism for JXUST-39 detecting AA is possibly the cooperative effect of absorbance-caused enhancement and charge transfer between JXUST-39 and AA. Moreover, LED lamp beads, fluorescent films and fluorescent detection test paper based on JXUST-39 were prepared to achieve portable detection via fluorescence enhancement effect.

Epitaxial Growth of Multicolor Lanthanide MOFs by Ultrasound for Photonic Barcodes

Epitaxially grown lanthanide metal-organic frameworks (Ln MOFs) exhibit multicolor and characteristic Ln emission with sharp emission bands, which are of great value in the field of information security and anti-counterfeiting. Epitaxial growth of Ln MOFs is generally achieved by solvothermal or hydrothermal methods, which suffer from challenges such as high reaction temperature and long growth time. Here, we report the fast epitaxial growth of multicolor lanthanide MOFs by an ultrasonic method at room temperature. The TbSmSQ shows a core-shell type structure with the Tb ion in the core and Sm in the shell within one crystal and exhibits the characteristic emission lines of Tb and Sm, respectively. The nonporous structure and large distance between lanthanide ions effectively avoid the influence of solvent vapor on the intensity and color of luminescence emission. Its application as photonic barcodes has been studied. This work demonstrates the feasibility of epitaxial growth of multicolor Ln MOFs by the ultrasonic method and its value for anti-counterfeiting and information security applications.

Synthesis and Characterizations of Novel bi-ligand TbEu(cpioa)phen Phosphors with High Quantum Efficiency for WLED Applications

The hydrothermal method was employed to synthesize a novel bi-ligands LnMOF: Ln(cpioa)phen. The secondary ligand 1, 10-phen serves as a bridging agent to further facilitate energy transfer between Ln ions and the primary ligand H3cpioa. A comparison between Ln(cpioa) MOFs (Ln: Tb3+, Eu3+) and Ln(cpioa)phen MOFs (Ln: Tb3+, Eu3+) reveals that addition of the secondary ligand significantly improves the emission intensity by as high as almost 34 times. After detailed structural study, it is found that different Ln ions have the similar coordination in the Ln(cpioa)phen MOF. In addition, the chromaticity of Ln(cpioa)phen MOFs can be easily tuned by the amounts of doping Ln ions. La0.974Tb0.0255Eu0.0005(cpioa)phen MOF has a white emission with a CIE coordinate of (0.323, 0.343). Characterizations of corresponding LED devices show that device based on Ln(cpioa)phen MOF has better photoluminescence performances, which indicates that Ln(cpioa)phen MOF has great potential of for WLED applications.

A Ratiometric Fluorescent Probe Dye-Functionalized MOFs Integrated with Logic Gate Operation for Efficient Detection of Acetaldehyde

Volatile organic compounds (VOCs) are a class of hazardous gases that are widely present in the atmosphere and cause great harm to human health. In this paper, a ratiometric fluorescent probe (Dye@Eu-MOFs) based on a dye-functionalized metal-organic framework was designed to detect VOCs, which showed high sensitivity and specificity for acetaldehyde solution and vapor. A linear correlation between the integrated fluorescence intensity (I510/I616) and the concentration of acetaldehyde was investigated, enabling a quantitative analysis of acetaldehyde in the ranges of 1 × 10-4~10-5 μL/mL, with a low detection limit of 8.12 × 10-4 mg/L. The selective recognition of acetaldehyde could be clearly distinguished by the naked eye under the excitation of UV light. The potential sensing mechanism was also discussed. Significantly, a molecular logic gate was constructed based on the whole system, and finally, a molecular logic network system for acetaldehyde detection connecting basic and integrated logic operations was realized. This strategy provided an effective guiding method for constructing a molecular-level logic gate for acetaldehyde detection on a simple platform.

Cationic Europium-Organic Framework for Chromatographic Column Separation of Ionic Dyes and Stimuli-Responsive Chromic Properties

A novel 3D europium-based cationic framework (Eu-CMOF) has been constructed solvothermally by employing a viologen derivative as an organic functional building unit. Notably, Eu-CMOF demonstrates its capability as a proficient aqueous-phase ion-exchange host, facilitating the remarkable rapid chromatographic column separation of new coccine and malachite green (NC3-/MG+), as well as new coccine and methylene blue (NC3-/MLB+), in mere 2 to 4 min. Adsorption thermodynamics and kinetics of anionic dyes demonstrate that Eu-CMOF exhibits a higher adsorption capacity for NC3-, as evaluated by the Langmuir model, reaching a value of 173 mg·g-1. The pseudo-second-order rate constant is determined to be 3.84 × 10-3 mg-1·g·min-1. Additionally, Eu-CMOF displays reversible photochromic and amine- and ammonia-induced vapochromic behaviors. Further mechanistic studies reveal that these chromic behaviors are primarily attributed to the generation of free viologen radical stimulated by Xe-light or electron-rich amine/ammonia. This research contributes to the development of advanced materials with applications in rapid chromatographic separation and stimuli-responsive chromic properties, showcasing the potential of Eu-CMOF as a versatile platform for practical applications.

Ratiometric fluoroprobe based on Eu-MOF@Tb3+ for detecting tetracycline hydrochloride in freshwater fish and its application in rapid visual detection

Tetracycline hydrochloride (TCH), a prevalent antibiotic in aquaculture for treating bacterial infections, poses challenges for on-site detection. This study employed the reversed-phase microemulsion method to synthesize a uniform nano metal-organic framework (MOF) material, europium-benzene-p-dicarboxylic acid (Eu-BDC), doped with Tb3+ to form a dual-emission fluorescence probe. By leveraging the combined a-photoinduced electron-transfer (a-PET) and inner filter effect (IFE) mechanisms, high-sensitivity TCH detection in Carassius auratus and Ruditapes philippinarum was achieved. The detection range for TCH is 0.380-75 μM, with a low limit of detection (LOD) at 0.115 μM. Upon TCH binding, Eu-BDC fluorescence rapidly decreased, while Tb3+ fluorescence remained constant, establishing a ratiometric fluorescence change. Investigation into the TCH quenching mechanism on Eu-BDC was conducted using time-dependent density functional theory (TD-DFT) calculations and fluorescence quenching kinetic equations, suggesting a mixed quenching mechanism. Furthermore, a novel photoelectric conversion fluorescence detection device (FL-2) was developed and evaluated in conjunction with high-performance liquid chromatography-diode-array detection (HPLC-DAD). This is the first dedicated fluorescence device for TCH detection, showcasing superior photoelectric conversion performance and stability that reduces experimental errors associated with smartphone photography methods, presenting a promising avenue for on-site rapid TCH detection.