Search Results (22)

Carbon quantum dots (CQDs), with their excellent photoluminescence, tunable surface chemistry, and low toxicity, have emerged as versatile nanomaterials in sensing technologies. Meanwhile, metal–organic frameworks (MOFs) possess exceptionally porous architectures and extensive surface areas, and tunable functionalities ideal for molecular recognition and analyte enrichment. The synergistic integration of CQDs and MOFs has significantly expanded the potential of hybrid materials with enhanced selectivity, sensitivity, and multifunctionality. While several reviews have addressed QD/MOF systems broadly, this review offers a focused and updated perspective on CQDs@MOFs composites specifically tailored for food safety and environmental sensing applications. This review provides a comprehensive analysis of recent advances in the design, synthesis, and surface functionalization of these hybrids, emphasizing the mechanisms of interaction, photophysical behavior, and performance advantages over conventional sensors. Special attention is given to their use in detecting food contaminants such as heavy metals, pesticides, antibiotics, mycotoxins, pathogens, and aromatic compounds. Key strategies to enhance stability, selectivity, and detection limits are highlighted, and current challenges and future directions for practical deployment are critically discussed. Full article

Metal–organic frameworks (MOFs) or coordination polymers have gained enormous interest in recent years due to their extraordinary properties, including their high surface area, tunable pore size, and ability to form nanocomposites with various functional materials. MOF materials possess redox-active properties that are beneficial for electrochemical sensing applications. Furthermore, the tunable pore size and high surface area improve the adsorption or immobilization of enzymes, which can enhance the sensitivity and selectivity for specific analytes. Additionally, MOF-derived metal sulfides, phosphides, and nitrides demonstrate superior electrical conductivity and structural stability, ideal for electrochemical sensing. Moreover, the functionalization of MOFs further increases sensitivity by enhancing electrode–analyte interactions. The inclusion of carbon materials within MOFs enhances their electrical conductivity and reduces background current through optimized loading, preventing agglomeration and ensuring uniform distribution. Noble metals immobilized on MOFs offer improved stability and catalytic performance, providing larger surface areas and uniform nanoparticle dispersion. This review focuses on recent developments in MOF-based biosensors specifically for glucose, dopamine, H₂O₂, ascorbic acid, and uric acid sensing. Full article

Metal phenolic networks (MPNs) have attracted significant attention due to their environmentally benign nature, broad compatibility, and universal adhesive properties, making them highly effective for modifying adsorbent surfaces. These supramolecular complexes are formed through the coordination of metal ions with natural phenolic ligands, resulting in stable structures while retaining the active adsorption sites of the ligands, thereby enhancing the adsorption performance of unmodified substrates. Among various MPNs, metal ion gallic acid (GA) networks are particularly well-known for their exceptional stability, biological activity, and superior adsorption ability. This review offers a comprehensive examination of GA-based MPN adsorbents, focusing on their formation chemistry, characterization techniques, and applications. The coordination chemistry underlying the stability of GA–metal complexes is analyzed through equilibrium studies, which are critical for understanding the robustness of MPNs. The main analytical methods for assessing metal ligand interactions are discussed, along with additional characterization techniques for evaluating adsorbent properties. This review also explores various synthesis and performance enhancement strategies for GA-based MPN adsorbents, including stand-alone MPNs, MPN-mediated mesoporous materials, MPN-MOF composites, and MPN-coated substrates. By consolidating current advancements in MPN-based adsorbents and offering fundamental insights into their chemistry and characterization, this review serves as a valuable resource for researchers seeking to develop stable, functional metal-organic materials. It aims to drive innovation in sustainable and efficient adsorbent technologies for diverse environmental and industrial applications. Full article

Asthma and allergic rhinitis (AR) stand as prevalent chronic ailments impacting children within the United States. It is approximated that as many as 40% of American children exhibit symptoms indicative of AR, a condition which, if inadequately managed, could potentially lead to the onset of additional illnesses such as asthma, rhinosinusitis, allergic conjunctivitis, and otitis media. We have devised a universal synthetic pathway to encapsulate small molecules of montelukast sodium within Metal–Organic Frameworks (MOFs) for the treatment of asthma and AR. Two distinct Cu-MOFs, namely single linker and mixed linker MOFs, were synthesized through the solvothermal method utilizing 1,4-benzenedioic acid (BDC) and 4,4′-dipyridile as linkers. The synthesized Cu-MOFs underwent thorough examination employing various analytical techniques including BET, SEM, FTIR, and PXRD. These MOFs hold promise as potential vehicles for drug delivery applications. Various proportions of Cu-MOF-1 and Cu-MOF-2 were dispersed alongside montelukast sodium. Notably, the 1:1 ratio of both MOFs exhibited enhanced drug absorption compared to other ratios. Furthermore, Cu-MOF-2 demonstrated superior drug absorption overall when contrasted with Cu-MOF-1. This investigation also delves into the drug release dynamics from different ratios of MOFs and the drug. The drug release analysis was conducted in a phosphate-buffered saline (PBS) solution with a pH of 7.4, and the absorbance values were measured using a UV-visible spectrometer at distinct time intervals. Drug molecules are effectively encapsulated within MOFs and demonstrate controlled release through the establishment of hydrogen bonding or π–π interactions between the drug molecules and MOFs. Despite notable advancements in the utilization of MOFs for biomedical purposes, additional enhancements are necessary before they can be considered viable therapeutic modalities. Full article

In this study, we designed three promising platforms based on metal–organic frameworks (MOFs) to develop paper-based analytical devices (PADs) for biosensing applications. PADs have become increasingly popular in field sensing in recent years due to their portability, low cost, simplicity, efficiency, fast detection capability, excellent sensitivity, and selectivity. In addition, MOFs are excellent choices for developing highly sensitive and selective sensors due their versatility for functionalizing, structural stability, and capability to adsorb and desorb specific molecules by reversible interactions. These materials also offer the possibility to modify their structure and properties, making them highly versatile and adaptable to different environments and sensing needs. In this research, we synthesized and characterized three different amino-functionalized MOFs: UiO-66-NH₂ (Zr), MIL-125-NH₂ (Ti), and MIL-101-NH₂ (Fe). These MOFs were used to fabricate PADs capable of sensitive and portable monitoring of alkaline phosphatase (ALP) enzyme activity by laser-induced fluorescence (LIF). Overall, amino-derivated MOF platforms demonstrate significant potential for integration into biosensor PADs, offering key properties that enhance their performance and applicability in analytical chemistry and diagnostics. Full article

Solid-phase microextraction (SPME) has been widely proposed for the extraction, clean-up, and preconcentration of analytes of environmental concern. Enrichment capabilities, preconcentration efficiency, sample throughput, and selectivity in extracting target compounds greatly depend on the materials used as SPME coatings. Supramolecular materials have emerged as promising porous coatings to be used for the extraction of target compounds due to their unique selectivity, three-dimensional framework, flexible design, and possibility to promote the interaction between the analytes and the coating by means of multiple oriented functional groups. The present review will cover the state of the art of the last 5 years related to SPME coatings based on metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular macrocycles used for environmental applications. Full article

Layer-by-layer (LbL) immobilization of DNA aptamers in the realm of electrochemical detection of heavy metal ions (HMIs) offers an enhancement in specificity, sensitivity, and low detection limits by leveraging the cross-reactivity obtained from multiple interactions between immobilized aptamers and developed material surfaces. In this research, we present a LbL approach for the immobilization of thiol- and amino-modified DNA aptamers on a Ag-incorporated cobalt-succinate metal–organic framework (MOF) (Ag@Co-Succinate) to achieve a cross-reactive effect on the electrochemical behavior of the sensor. The solvothermal method was utilized to synthesize Ag@Co-Succinate, which was also characterized through various techniques to elucidate its structure, morphology, and presence of functional groups, confirming its suitability as a host matrix for immobilizing both aptamers. The Ag@Co-Succinate aptasensor exhibited extraordinary sensitivity and selectivity towards Hg(II) ions in electrochemical detection, attributed to the unique binding properties of the immobilized aptamers. The exceptional limit of detection of 0.3 nM ensures the sensor’s suitability for trace-level Hg(II) detection in various environmental and analytical applications. Furthermore, the developed sensor demonstrated outstanding repeatability, highlighting its potential for long-term and reliable monitoring of Hg(II). Full article

This study investigates electrospun fibers of metal-organic frameworks (MOFs), particularly CuBTC and ZIF-8, in polyacrylonitrile (PAN) for the solid-phase extraction (SPE) of Tamoxifen (TAM) and its metabolites (NDTAM, ENDO, and 4OHT) from human blood plasma. The focus is on the isolation, pre-concentration, and extraction of the analytes, aiming to provide a more accessible and affordable breast cancer patient-monitoring technology. The unique physicochemical properties of MOFs, such as high porosity and surface area, combined with PAN’s stability and low density, are leveraged to improve SPE efficiency. The study meticulously examines the interactions of these MOFs with the analytes under various conditions, including elution solvents and protein precipitators. Results reveal that ZIF-8/PAN composites outperform CuBTC/PAN and PAN alone, especially when methanol is used as the protein precipitator. This superior performance is attributed to the physicochemical compatibility between the analytes’ properties, like solubility and polarity, and the MOFs’ structural features, including pore flexibility, active site availability, surface polarity, and surface area. The findings underscore MOFs’ potential in SPE applications and provide valuable insights into the selectivity and sensitivity of different MOFs towards specific analytes, advancing more efficient targeted extraction methods in biomedical analysis. Full article

A novel ZIF-8 assisted polyacrylamide functionalized silica polar stationary phase was prepared by a facile method of adding ZIF-8 nanoparticles and silica into polyacrylamide (PAM) aqueous solution, and then stirring the mixture until the solution was evaporated absolutely with the help of mechanical agitator. Interestingly, the prepared stationary phase (PAM-Sil@ZIF-8/PAM) showed favorable hydrophilicity, as demonstrated by good separation performance and strong retention ability toward several types of polar compounds, such as amino acids, saccharides, and alkaloids. In addition, PAM-Sil@ZIF-8(50 mg)/PAM showed better separation performance compared with amino-modified silica and Sil/PAM stationary phase due to the addition of ZIF-8. Furthermore, it was demonstrated that the addition of ZIF-8 improved the specific surface area and provided extra interaction sites for the stationary phase and analytes, which is beneficial for the separation of samples. In addition, the column efficiency can reach 7861.9 plates/m for colchicine. Moreover, it exhibited good stability and reproducibility under our operation conditions. In short, a novel stationary phase, which can be used for hydrophilic interaction liquid chromatography, was obtained and proved that the separation performance of polymer modifying silica stationary phase can be greatly improved by the addition of MOF nanoparticles. Full article

Water pollution from dyes is harmful to the environment, plants, animals, and humans and is one of the most widespread problems afflicting people throughout the world. Adsorption is a widely used method to remove contaminants derived from the textile industry, food colorants, printing, and cosmetic manufacturing from water. Here, aiming to develop new low-cost and up-scalable adsorbent materials for anionic dye remediation and water decontamination by electrostatic interactions, two cationic resins (R1 and R2) were prepared. In particular, they were obtained by copolymerizing 4-ammonium methyl and ethyl styrene monomers (M1 and M2) with dimethylacrylamide (DMAA), using N-(2-acryloylamino-ethyl)-acrylamide (AAEA) as cross-linker. Once characterized by several analytical techniques, upon their dispersion in an excess of water, R1 and R2 provided the R1- and R2-based hydrogels (namely R1HG and R2HG) with equilibrium degrees of swelling (EDS) of 900% and 1000% and equilibrium water contents (EWC) of 90 and 91%, respectively. By applying Cross’ rheology equation to the data of R1HG and R2HG’s viscosity vs. shear rate, it was established that both hydrogels are shear thinning fluids with pseudoplastic/Bingham plastic behavior depending on share rate. The equivalents of -NH₃⁺ groups, essential for the electrostatic-based absorbent activity, were estimated by the method of Gaur and Gupta on R1 and R2 and by potentiometric titrations on R1HG and R2HG. In absorption experiments in bulk, R1HG and R2HG showed high removal efficiency (97–100%) towards methyl orange (MO) azo dye, fluorescein (F), and their mixture (MOF). Using F or MO solutions (pH = 7.5, room temperature), the maximum absorption was 47.8 mg/g in 90′ (F) and 47.7 mg/g in 120′ (MO) for R1, while that of R2 was 49.0 mg/g in 20′ (F) and 48.5 mg/g in 30′ (MO). Additionally, R1HG and R2HG-based columns, mimicking decontamination systems by filtration, were capable of removing MO, F, and MOF from water with a 100% removal efficiency, in different conditions of use. R1HG and R2HG represent low-cost and up-scalable column packing materials that are promising for application in industrial wastewater treatment. Full article

The accumulation of toxic heavy metal ions continues to be a global concern due to their adverse effects on the health of human beings and animals. Adsorption technology has always been a preferred method for the removal of these pollutants from wastewater due to its cost-effectiveness and simplicity. Hence, the development of highly efficient adsorbents as a result of the advent of novel materials with interesting structural properties remains to be the ultimate objective to improve the adsorption efficiencies of this method. As such, advanced materials such as metal–organic frameworks (MOFs) that are highly porous crystalline materials have been explored as potential adsorbents for capturing metal ions. However, due to their diverse structures and tuneable surface functionalities, there is a need to find efficient characterization techniques to study their atomic arrangements for a better understanding of their adsorption capabilities on heavy metal ions. Moreover, the existence of various species of heavy metal ions and their ability to form complexes have triggered the need to qualitatively and quantitatively determine their concentrations in the environment. Hence, it is crucial to employ techniques that can provide insight into the structural arrangements in MOF composites as well as their possible interactions with heavy metal ions, to achieve high removal efficiency and adsorption capacities. Thus, this work provides an extensive review and discussion of various techniques such as X-ray diffraction, Brunauer–Emmett–Teller theory, scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectroscopy, and X-ray photoelectron spectroscopy employed for the characterization of MOF composites before and after their interaction with toxic metal ions. The review further looks into the analytical methods (i.e., inductively coupled plasma mass spectroscopy, ultraviolet-visible spectroscopy, and atomic absorption spectroscopy) used for the quantification of heavy metal ions present in wastewater treatment. Full article

Population growth and industrial development have exacerbated environmental pollution of both land and aquatic environments with toxic and harmful materials. Luminescence-based chemical sensors crafted for specific hazardous substances operate on host-guest interactions, leading to the detection of target molecules down to the nanomolar range. Particularly, the luminescence-based sensors constructed on the basis of metal-organic frameworks (MOFs) are of increasing interest, as they can not only compensate for the shortcomings of traditional detection techniques, but also can provide more sensitive detection for analytes. Recent years have seen MOFs-based fluorescent sensors show outstanding advantages in the field of hazardous substance identification and detection. Here, we critically discuss the application of MOFs for the detection of a broad scope of hazardous substances, including hazardous gases, heavy metal ions, radioactive ions, antibiotics, pesticides, nitro-explosives, and some harmful solvents as well as luminous and sensing mechanisms of MOF-based fluorescent sensors. The outlook and several crucial issues of this area are also discussed, with the expectation that it may help arouse widespread attention on exploring fluorescent MOFs (LMOFs) in potential sensing applications. Full article

In this contribution, we report on the solid-state-photodynamical properties and further applications of a low dimensional composite material composed by the luminescent trans-4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) dye interacting with a two-dimensional-metal organic framework (2D-MOF), Al-ITQ-HB. Three different samples with increasing concentration of DCM are synthesized and characterized. The broad UV-visible absorption spectra of the DCM/Al-ITQ-HB composites reflect the presence of different species of DCM molecules (monomers and aggregates). In contrast, the emission spectra are narrower and exhibit a bathochromic shift upon increasing the DCM concentration, in agreeance with the formation of adsorbed aggregates. Time-resolved picosecond (ps)-experiments reveal multi-exponential behaviors of the excited composites, further confirming the heterogeneous nature of the samples. Remarkably, DCM/Al-ITQ-HB fluorescence is sensitive to vapors of electron donor aromatic amine compounds like aniline, methylaniline, and benzylamine due to a H-bonding-induced electron transfer (ET) process from the analyte to the surface-adsorbed DCM. These findings bring new insights on the photobehavior of a well-known dye when interacting with a 2D-MOF and its possible application in sensing aniline derivatives. Full article

Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications. Full article

Long-range surface plasmon resonance (LRSPR), generated from a coupled plasmon polariton in a thin metal slab sandwiched by two dielectrics, has attracted more and more attention due to its merits, such as longer propagation and deeper penetration than conventional single-interface surface plasmon resonance. Many useful applications related to light–medium interaction have been demonstrated based on the LRSPR effect, especially in the sensing area. Here, we propose and demonstrate an LRSPR-based refractive index sensor by using a SiO${}_2$-Au-TiO${}_2$ heterostructure, in which a D-shaped honeycomb-microstructure optical fiber (MOF) is designed as the silica substrate and then deposited with a gold film and thin-layer titanium dioxide (TiO${}_2$). By using the full-vector finite-element method (FEM), this heterostructure is numerically investigated and demonstrated to excite LRSPR without a buffer layer, which is usually necessary in previous LRSPR devices. Through comprehensive discussion about the influence of structural parameters on the resonant wavelength, the excitation of the LRSPR in the proposed heterostructure is revealed to be highly related to the effective refractive index of MOF’s fundamental core mode, which is mainly determined by the MOF’s pitch, the thicknesses of the silica web and the planar-layer silica. Moreover, the thin-layer TiO${}_2$ plays an important role in significantly enhancing the resonance and the sensitivity to analyte’s refractive index as well, when it is coated on the top of the Au film rather than between the metal and waveguide. Finally, the proposed LRSPR sensor based on SiO${}_2$-Au-TiO${}_2$ heterostructure shows an ultra-high wavelength sensitivity of 20,100 nm/RIU and the corresponding minimum resolution is as low as $4.98\times {10}^{-7}$ RIU. Thus, the proposed LRSPR device offers considerable potential for sensing applications in biomedical and biochemical areas. Full article