Luminescent Metal-organic Framework Research Articles

A fluorescent MOF and its synthesized MOF@cotton composite: Ratiometric sensing of vitamin B2 and antibiotic drug molecule

Here, we demonstrated the synthesis of a zinc based luminescent MOF, 1 (NDC = 2,6- naphthalenedicarboxylate) for the ratiometric detection of biomarker riboflavin (RBF; vitamin B2) in water dispersed medium. Further, this MOF detected two other antibiotic drug molecules, nitrofurantoin (NFT) and nitrofurazone (NZF). The detection of these analytes is very quick (∼seconds), and the limit of detection (LOD) for RBF, NZF and NFT are calculated as 16.58 ppm, 47.63 ppb and 56.96 ppb, respectively. The detection of these analytes was also comprehended by solid, solution, cost-effective paper strip method i.e., triphasic identification capabilities. The sensor is reusable without losing its detection efficacy. The sensor further showed the recognition abilities of these antibiotics in real field samples (river water, urine and tablet) and RBF in vitamin B2 pills and food samples (milk and cold drinks). The sensing merit of 1 urged us to fabricate of 1@cotton fabric composite, which exhibited the colorimetric detection of these analytes. In-depth experimental analysis suggested that the occurrence of photo-induced electron transfer (PET), fluorescence resonance energy transfer (FRET), and the inner filter effect (IFE) are the possible sensing mechanisms for the recognition of the antibiotics drug. The FRET mechanism is responsible for the recognition of RBF. The sensing mechanism is further supported by the theoretical analysis and the excited lifetime measurement.

A metal-organic framework-based sensor for specific detection of tetracycline in milk

Molecularly imprinted fluorescent sensors are of interest to researchers due to their specificity, high sensitivity, and stability. In this study, the fluorescence-imprinted sensor (NH2-MIL-53/MIP) for the detection of tetracycline (TC) in animal-derived foods was developed based on the characteristics of luminescent metal-organic frameworks (MOFs) and molecularly imprinted polymers (MIPs). The MOFs provide fluorescence sensing signals and large specific surface areas, while the MIPs provide the specific recognition sites for TC. As a result, the sensor exhibits a wide detection range (0.05–50 μg/mL), high sensitivity (LOD of 0.006 μg/mL), fast detection speed and good selectivity. The sensing principle can be attributed to photoinduced electron transfer. Furthermore, the sensor can determine TC in milk with good recovery rates (95.05–104.71 %). This work addresses the limitation of current molecularly imprinted sensors such as slow corresponding speed and limited detection capability, providing valuable insights for target determination in complex systems.

Dual-Emission Single Sensing Element-Assembled Fluorescent Sensor Arrays for the Rapid Discrimination of Multiple Surfactants in Environments.

Surfactants are considered as typical emerging pollutants, their extensive use of in disinfectants has hugely threatened the ecosystem and human health, particularly during the pandemic of coronavirus disease-19 (COVID-19), whereas the rapid discrimination of multiple surfactants in environments is still a great challenge. Herein, we designed a fluorescent sensor array based on luminescent metal-organic frameworks (UiO-66-NH2@Au NCs) for the specific discrimination of six surfactants (AOS, SDS, SDSO, MES, SDBS, and Tween-20). Wherein, UiO-66-NH2@Au NCs were fabricated by integrating UiO-66-NH2 (2-aminoterephthalic acid-anchored-MOFs based on zirconium ions) with gold nanoclusters (Au NCs), which exhibited a dual-emission features, showing good luminescence. Interestingly, due to the interactions of surfactants and UiO-66-NH2@Au NCs, the surfactants can differentially regulate the fluorescence property of UiO-66-NH2@Au NCs, producing diverse fluorescent "fingerprints", which were further identified by pattern recognition methods. The proposed fluorescence sensor array achieved 100% accuracy in identifying various surfactants and multicomponent mixtures, with the detection limit in the range of 0.0032 to 0.0315 mM for six pollutants, which was successfully employed in the discrimination of surfactants in real environmental waters. More importantly, our findings provided a new avenue in rapid detection of surfactants, rendering a promising technique for environmental monitoring against trace multicontaminants.

A dual-mode biosensor based on silica inverse opal photonic crystals modulated electrochemiluminescence and dye displacement colorimetry for the sensitive detection of synthetic cathinone in water environment

To address the challenges posed by signal capacity limitations and the reliance of sensing methods on single analytical information, this study developed an electrochemiluminescence (ECL) and colorimetric dual-mode sensing platform for the precise detection of 4-chloroethcathinone (4-CEC) in water environments. Firstly, the accurate alignment of the reflection wavelength of appropriately sized silica inverse opal photonic crystals (SIOPCs) with the ECL emission wavelength of luminescent metal-organic frameworks (PCN-224) has been achieved via diameter modulation. This innovative design, which cleverly utilized the band-edge effect, improved the luminous intensity of the ECL sensor, leading to a significant boost in analytical performance. Secondly, the establishment of a colorimetric detection method for confirming the presence of 4-CEC in samples through visual observation of color changes was achieved by employing an aptamer-based dye displacement reaction, utilizing differential binding affinities between the aptamer and both the sulforhodamine B (SRB) and 4-CEC. Under the optimal experimental conditions, the dual-mode sensor demonstrated ECL detection of limits (LOD) of 2.6 × 10−13 g/L and colorimetric LOD of 6.5 ng/L for 4-CEC. These findings highlighted the tremendous potential of developing streamlined and efficient dual-signal readout platforms using ECL aptamer sensors for the precise determination of other Synthetic cathinones (SCs) in water environments.

A highly sensitive and selective Zn-based luminescent MOF for specific detection of trinitrotoluene in aqueous phase

The existence of nitroaromatic compounds, specifically 2,4,6-trinitrotoluene (TNT), in water reservoirs poses significant health risks, necessitating robust detection and monitoring strategies. In this study, we leverage the exceptional properties of the previously synthesized metal-organic framework (MOF), PUC2 as a highly luminescent probe for selective and sensitive detection of TNT in aqueous media. PUC2 exhibits remarkable luminescence, emitting a vivid blue light, making it an ideal candidate for TNT detection. Our investigations reveal that PUC2 demonstrates outstanding sensitivity, achieving an impressive detection limit of 0.145 μM towards TNT which can be attributed to the robust probe-analyte interactions evident from the quenching constant (Ksv) value of 0.18 × 104M−1. An intriguing aspect of PUC2 is its adaptability to a wide pH range, maintaining its sensing capabilities effectively in aqueous phase with pH levels ranging from 4 to 11. The predominant quenching mechanism in this context appears to be photoinduced electron transfer (PET), with an additional enhancement through Forster resonance energy transfer (FRET). The unique combination of structural features and exceptional sensing capabilities of PUC2 opens up new avenues for environmental monitoring and security applications, highlighting its potential as a highly effective luminescent sensor for detecting hazardous substances like TNT.

A strategy for the enhanced development of latent fingermarks with minimally destructive to DNA based on fluorescence Eu-Tb metal–organic framework

Fingermarks identification have always been the most effective and reliable way for individuals determination among the forensic science. The fingermarks at the scene of the case as the valuable physical evidence to analyze the trajectory of criminal behavior and portray the characteristics of the suspect play an irreplaceable role in the process of investigation. To reach its pivotal biometric individualization, the luminescent metal–organic framework (Eu@Tb-LL) was prepared via a simple optimized solvothermal method for visualizing the latent fingermarks with minimally destructive to DNA in this work. Eu@Tb-LL exhibited ideal optical stability and fluorescence intensity at the wavelength of 530 and 620 nm during revealing latent fingermarks. Meanwhile, Eu@Tb-LL is more effective than indandione (commonly used in the site investigation) in revealing aged fingermarks. More significantly, the Eu@Tb-LL superimposed on commercial manifestation reagents (Hfb) enhanced the effect of Hfb for revealing blood latent fingermarks on the non-porous objects. In addition, the STR testing results performed after the visualization process proved the Eu@Tb-LL was minimally destructive to DNA with a confidence interval of 95 %, exhibiting promising prospects for practical criminal investigation applications.

Functional Group-Assisted Fluorescence Sensing Platform for Nanomolar-Level Detection of an Antineoplastic Drug and a Neurotransmitter from Environmental Water and Human Biofluids.

A fast, sensitive, selective, and biocompatible dual sensor of an antineoplastic medication (methotrexate) and a neurotransmitter (adrenaline) is still being searched by present-day scientists. To overcome this issue, we have designed a functionalized, robust, bio-friendly luminescent MOF for the sensitive, selective, and rapid monitoring of methotrexate and adrenaline. This probe is the first ever reported MOF-based fluorescence sensor of methotrexate and second only for adrenaline. This fluorescence probe has a very low limit of detection (LOD) of 0.34 and 11.2 nM for adrenaline and methotrexate, respectively. The sensor can detect both the targeted analytes rapidly within 5 s. It can also detect adrenaline and methotrexate from human blood serum and urine accurately and precisely. This reusable sensor is equally efficient in detecting methotrexate from environmental water specimens. Biocompatible, user-friendly, and inexpensive chitosan@MOF@cotton composites were fabricated for the detection of adrenaline and methotrexate from the nanomolar to the micromolar range by the naked eye under a fluorescence lamp. This probe displayed high reproducibility, precision, and accuracy in sensing methotrexate and adrenaline. Fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE) are the possible mechanisms for adrenaline and methotrexate sensing, respectively. The possible mechanism was supported by using required instrumental techniques and theoretical simulations.

Multiresponsive luminescent metal–organic framework for cooking oil adulteration detection and gallium(III) sensing

A new 3D metal–organic framework {[Cd16(tr2btd)10(dcdps)16(H2O)3(EtOH)]∙15DMF}n (MOF 1, tr2btd = 4,7-di(1,2,4-triazol-1-yl)benzo-2,1,3-thiadiazole, H2dcdps = 4,4′-sulfonyldibenzoic acid) was obtained and its luminescent properties were studied. MOF 1 exhibited bright blue-green luminescence with a high quantum yield of 74 % and luminescence quenching response to a toxic natural polyphenol gossypol and luminescence enhancement response to some trivalent metal cations (Fe3+, Cr3+, Al3+ and Ga3+). The limit of gossypol detection was 0.20 µM and the determination was not interfered by the components of the cottonseed oil. The limit of detection of gallium(III) was 1.1 µM. It was demonstrated that MOF 1 may be used for distinguishing between the genuine sunflower oil and oil adulterated by crude cottonseed oil through qualitative luminescent and quantitative visual gossypol determination.

Construction of Multifunctional Luminescent Lanthanide MOFs for Luminescent Sensing of Temperature, Trifluoroacetic Acid Vapor and Explosives.

Metal-organic frameworks (MOFs) with multifunctional and tunable optical properties have unique advantages in the field of sensing, and the structure and properties of MOFs are significantly influenced by the ligands. In this study, a Y-type tricarboxylic acid ligand containing amide bonds was synthesized through functional guidance, and three isomorphic and heterogeneous three-dimensional MOFs (Eu-MOF, Tb-MOF, and Gd-MOF) were obtained by solvothermal reaction. Further studies revealed that both the Tb-MOF and Eu-MOF could selectively detect picric acid (PA). The luminescence quenching of the two MOFs by PA was attributed to competing absorption and photoelectron energy transfer mechanisms. In addition, due to the energy transfer between Tb and Rhodamine B, Rhodamine B was encapsulated into Tb-MOF. The obtained material exhibited a linear relationship between the temperature parameters I544/I584 and temperature within the range of 280-400 K, the correlation coefficient (R2) reached an impressive value of 0.999, and the absolute sensitivity of the sample used for temperature sensing was 1.534% K-1. What is more, the material exhibited a good response to trifluoroacetic acid vapor, which suggests the potential of the material for temperature sensing and detection of trifluoroacetic acid vapor. The designed and investigated strategy can also serve as a reference for further research on excellent multifunctional sensors.

Metal-organic Frameworks: Emerging Luminescent Sensors

Abstract: Metal-organic frameworks (MOFs), a crystalline material, are a new type of inorganicorganic hybrid material. MOFs are of great interest to researchers in chemistry and material science due to their various chemical and physical properties, and features include their remarkable surface area, high porosity, flexibility, structural variety, flexibility, extreme porosity, a large surface area, augmented adsorption/desorption kinetics, biocompatibility and functional tunability. MOFs are multi-dimensional crystals and have extended net-like frameworks from molecular building units such as inorganic metal nodes and organic linkers. The structurally diverse MOFs have found applications in chemical sensing and several other fields, such as energy applications, biomedicine, and catalysis. Numerous researchers from other fields have been drawn to this topic by the intrinsic potential to absorb gas molecules, which has led to the applications of gas storage and heterogeneous catalysis. Because of their low framework density, open metal sites for interaction, adjustable pore size, fast response with high sensitivity and selectivity, and real-time monitoring, luminescent metalorganic frameworks, or LMOFs, have piqued the interest of a large scientific community as a promising candidate for sensor applications. A number of characteristics, including non-toxicity, biodegradability, and reasonably priced, varied functionality, are important factors in the use of MOFs in chemo- and biosensing. MOFs can be very promising candidates as selective and sensitive chemosensors for the detection of cations, anions, small molecules, gases and explosives. In this manuscript, we address recent research advances in the use of metal-organic-framework-based luminescent sensors for detecting some small molecules and various metal ions in aqueous biological and environmental samples. A wide range of materials may be reached in the emerging field of synthetic and material chemistry, thanks to the capacity to change the pore size and chemically functionalize its nature without changing its architecture.

Luminescent metal organic frameworks and their fluorescence sensing application

Metal-organic framework materials (MOFs) provide remarkable advantages in the field of identification and detection due to their structural flexibility, aperture adaptation, and distinctive fluorescence features. Fluorescent MOF-based chemical sensors have been developed more regularly in recent years to detect a wide range of chemicals. By introducing the research status of MOFs, the research advancement of fluorescence sensors, the overview of MOF materials, construction methods, and luminescence mechanism, as well as the suggestion of further research on the application of MOFs in the low-temperature environment, the use of fluorescent metal-organic skeleton materials as fluorescence sensors is briefly analyzed.

Carbon-dots encapsulated luminescent metal–organic frameworks@surface molecularly imprinted polymer: A facile fluorescent probe for the determination of chloramphenicol

In this study, carbon dots (CDs)-encapsulated luminescent metal–organic frameworks@surface molecularly imprinted polymer (CDs@MOF@SMIP) was facilely prepared and applied as fluorescent probe for specific identification and sensitive detection of chloramphenicol (CAP) in food. Fluorescent CDs, serving as signal tags, were encapsulated within metal–organic backbones (ZIF-8), yielding luminescent MOF materials (CDs@ZIF-8). The synthesized CDs, CDs@ZIF-8 and CDs@ZIF-8@SMIP were investigated by morphological and structural characterizations (UV–Vis, XRD, FT-IR, BET, TEM). The CDs@ZIF-8@SMIP probe was demonstrated to have remarkable selectivity and sensitivity towards CAP. Its fluorescence decreased linearly with CAP concentration from 0.323 μg L-1 (0.001 μM) to 8075.0 μg L-1 (25.0 μM), featuring a low detection limit of 0.08 μg L-1. The CDs@ZIF-8@SMIP-based fluorescence strategy achieved satisfactory recoveries (95.5 % − 101.0 %) in CAP-spiked commercial foods with RSD < 4.4 % (n = 3). These results indicate that this method can effectively detect trace CAP in food matrices and has broad application prospects.

Metal-organic framework modified molecularly imprinted polymers-based sensor for fluorescent sensing of tetracycline in milk

Tetracycline (TC) residues have a serious impact on human health, sustainable development of animal husbandry and aquaculture. Herein, a novel sensor (Cr-MOF@MIP) for TC detection was developed by modifying molecularly imprinted polymers (MIPs) on the surface of a luminescent metal-organic framework (MOFs). The sensor not only possesses excellent fluorescence stability and specific recognition sites, but also enables selective aggregation of the target. Subsequently, the physicochemical properties of Cr-MOF@MIP, such as morphological structure, crystal shape, surface area, pore size and functional groups, were characterized. Under the optimized conditions, the relative fluorescence intensity of the Cr-MOF@MIP fluorescent sensor decreased gradually and linearly as the TC concentration increased from 0.2 μg/mL to 50 μg/mL. The limit of detection (LOD) of TC was 0.032 μg/mL. In addition, the sensor has higher selectivity for TC compared to non-imprinted polymers (NIPs), with a bursting mechanism of Cr-MOF@MIP mainly attributed to the fluorescence resonance energy transfer. Remarkably, in the complex systems of milk, its specific detection of TC was demonstrated with satisfactory recoveries (90.06–104.34 %). It is expected that the development of Cr-MOF@MIP sensor will provide a new way of thinking for easy, rapid, highly selective and cost-effective analysis in complex samples.

Post-synthetic modification of MIL-53(Fe) with Tb3+ and guanosine monophosphate: Construction of a fluorescent dual-target sensor

The development of fluorescence-based multi-target sensing sensors has great potential for applications in food safety monitoring and biomedical analysis. Nevertheless, the intricate design remains a hurdle in the construction of these sensors. Luminescent metal-organic frameworks (LMOFs) are suitable materials for the construction of multi-target fluorescent sensors due to their ability to introduce multiple luminescent centers and specific reaction sites through post-synthetic modification (PSM). In this study, a dual-target fluorescent sensor was fabricated via PSM of MIL-53(Fe) with Tb3+ and guanosine monophosphate (GMP). The Tb-GMP@MIL-53(Fe) sensor, with multiple luminescent centers and specific recognition sites, successfully achieved the detection of hydrogen peroxide (H2O2) and acid phosphatase (ACP) with a limit of detection (LOD) of 0.18 μM and 0.73 U/L, respectively. More significantly, this study demonstrates the potential of post-synthetic modified LMOFs in developing dual/multiple-target fluorescent sensors, expanding the scope of sensor designs for various analytes.

Fluorescence sensing and device fabrication with luminescent metal-organic frameworks.

Metal-organic frameworks (MOFs) are a novel class of hybrid porous multi-functional materials consisting of metal ions/clusters and organic ligands. MOFs have exclusive benefits due to their tunable structure and diverse properties. Luminescent MOFs (LMOFs) exhibit both porosity and light emission. They display abundant host and guest responses, making them conducive to sensing. Currently, LMOF sensing research is gaining more depth, with attention given to their device and practical applications. This work reviews recent advancements and device applications of LMOFs as chemical sensors toward ions, volatile organic compounds, biomolecules, and environmental toxins. Furthermore, the detection mechanism and the correlation between material properties and structure are elaborated. This analysis serves as a valuable reference for the preparation and efficient application of targeted LMOFs.

Luminescent MOFs Based on Thiazolo[5,4-d]thiazole as a Chemosensor for the Detection of Environmental Contaminants

Luminescent metal-organic frameworks (LMOFs) are considered special candidates for the sensation and detection of particular analytes. Thiazolo[5,4-d]thiazoles (TTZs) are an ideal type of heterocycles for fluorophores with π-bridge moieties demonstrating structure-function characteristics. LMOFs with excellent sensing properties can be constructed by incorporating heterocyclic aromatic thiazolo[5,4-d]thiazole into the framework. This study has elaborated on LMOFs containing thiazolo[5,4-d]thiazole unit for the detection of environmental contaminants, such as toxic anions, aromatic compounds, and heavy metal ions.

Luminescent metal–organic frameworks as optical sensors for selective sensing towards Fe3+ and Cu2+

Luminescent metal–organic frameworks (LMOFs) have emerged as promising luminescent sensors for remarkable and selective sensing towards Fe3+ and Cu2+via a “turn-off/turn-on” strategy.

Simple fluorochromic detection of chromium with ascorbic acid functionalized luminescent Bio-MOF-1.

The bioaccumulation of various heavy metals in the environment and agriculture is posing serious hazards to human health. Hexavalent chromium is one of the most encountered heavy metal pollutants. The routine monitoring of Cr(VI) via simple methods assumes great analytical significance in sectors like environmental safety, food quality, etc. This study reports a novel biocompatible and luminescent metal-organic framework (ascorbic acid functionalized Bio-MOF-1) based "Turn-on" nanoprobe for rapid and sensitive optical detection of Cr(VI). Bio-MOF-1 has been synthesized, functionalized with ascorbic acid (AA), and then comprehensively characterized for its key material properties. The presence of Cr(VI) results in the photoluminescence recovery of Bio-MOF-1/AA. Using the above approach, Cr(VI) is detected over a wide concentration range of 0.02 to 20 ng mL-1, with the limit of detection being 0.01 ng mL-1. The nanoprobe is capable of detecting Cr(VI) in real water as well as in some spiked food samples. Hence, the ascorbic acid functionalized Bio-MOF-1 nanoprobe is established as a potential on-field detection tool for Cr(VI).

Two new Cd-based metal–organic frameworks for afterglow detection of Fe3+ and NH3

The present study showcases two Cd-based MOFs that exhibit potential as afterglow probes for the “turn off” and “turn on” detection of Fe3+ ions and NH3, respectively.

Rational fabrication of an anionic zinc carboxylate framework as a fluorescent probe for 2,6-pyridinedicarboxylic acid.

Sensitive, rapid and convenient sensing of 2,6-pyridinedicarboxylic acid (DPA, a biomarker for Bacillus anthracis) is crucial for the screening and diagnosis of anthrax. Metal organic framework (MOF)-based sensors are very promising for sensing DPA; however, the design and construction of high-performance sensors with high specificity and sensitivity is still challenging. In this work, a novel luminescent carboxylate MOF (TTCA-Zn) was assembled and employed specifically for the recognition of DPA. We found that it has a three-dimensional anionic framework structure with sqc topology and uses [NH2(CH3)2]+ as the counter ions. The fluorescence intensity of TTCA-Zn displays a "turn-on" response to the addition of DPA and can function as a high-performance fluorescent sensor of DPA over a wide detection range of 0 to 70 μM, with a low detection limit of 14 nM. The sensing mechanism is also systematically investigated. This work not only reports a new fluorescence sensing material for DPA, but also provides a strategy for the structural design, assembly, and application of such sensors.