Rapid detection of tertiary butylated hydroquinone in food samples using Mn-MOF@f-CNF composite-modified screen-printed electrode

Hydroquinone-based organic molecules are often used as unavoidable preservatives in the food industry. Among these additives, tertiary butylated hydroquinone (TBHQ) is widely employed as a preservative in various processed foods. However, the potential health risks associated with the excessive presence of TBHQ in food products have raised significant concerns. To address this pressing issuea novel binder-free composite composed of a manganese metal-organic framework and functionalized carbon nanofibers (Mn-MOF/f-CNF) has been developed as an electrode modifier for the ultrasensitive detection of TBHQ in food samples. The Mn-MOF/f-CNF composite was achieved using the ultrasonication method, revealing a lamellar sheet-like structure of the Mn-MOF and the curly thread-like fibrous structure of f-CNF. The developed Mn-MOF/f-CNF/SPE sensor system resulted in well-defined redox signals for TBHQ detection in a neutral pH solution. Compared to the unmodified SPE system, the modified system showed approximately a 300 mV reduction in overpotential and a twofold increase in peak current signal for TBHQ detection. The Mn-MOF/f-CNF/SPE sensor system showed a linear concentration window of 0.01 to 800 μM with a sensitivity of 6.28 µA µM-1 cm-2 and the obtained detection limit was 1.36 nM. Additionally, the proposed sensor displayed excellent reproducibility and repeatable results with an RSD of less than 5%. The real-time applicability of the Mn-MOF/f-CNF/SPE sensor system was demonstrated using real samples such as potato chips and instant noodles, showing excellent results with a recovery range of 95.1-98.5%.

CuO-ZIF-8 modified electrode surface as a new electrochemical sensing platform for detection of free chlorine in aqueous solution

This work has applied metal-organic frameworks (MOFs) with high adsorbability and catalytic activity to develop electrochemical sensors to determine free chlorine (free-Cl) concentrations in aqueous media. A zeolitic imidazolate frameworks, Zn(Hmim)2 (ZIF-8) has been synthesized and incorporated with CuO nanosheets to decorate a glassy carbon electrode (GCE) and provide a new sensor for free-Cl determination. The as-prepared ZIF-8 and CuO-ZIF-8 composites have been characterized by FESEM, EDX, XRD, and FT-IR analyses. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) utilized to characterize the CuO-ZIF-8/GC modified electrode electrochemically, demonstrated the ability of the sensor to measure free-Cl concentration. Using differential pulse voltammetry (DPV) and under the optimal conditions, the prepared CuO-ZIF-8/GC modified electrode showed a linear response in the 0.25-60 ppm range with a 12 ppb detection limit (LOD) for free-Cl concentration. Finally, the fabricated sensor was applied to analyze free-Cl from actual swimming pool water samples with promising 97.5 to 103.0% recoveries.

Design and Synthesis of a Novel Binuclear Palladium Complex as a Turn on Fluorescent Receptor for Neurotransmitter Dopamine

A novel binuclear palladium complex has been synthesized by the reaction of tetramethylethylenediamine palladium nitrate and sodium salt of pyromellitic acid. UV vis, NMR as well as fluorescent titration techniques show that this binuclear palladium complex interacts with neurotransmitter dopamine. The fluorescence of the palladium complex in aqueous solution gets enhanced with the gradual addition of the neurotransmitter dopamine which makes this complex to act as a turn on fluorescent sensor for neurotransmitter dopamine.

Preparation of CoFe@C composite modified electrode for neohesperidin dihydrochalcone sensing and its application in Chinese medicine

CoFe@C was first prepared by calcining the precursor of CoFe-metal-organic framework-74 (CoFe-MOF-74), then an electrochemical sensor for the determination of neohesperidin dihydrochalcone (NHDC) was constructed, which was stemmed from the novel CoFe@C/Nafion composite film modified glassy carbon electrode (GCE). The CoFe@C/Nafion composite was verified by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) was used to evaluate its electrical properties as a modified material for an electrochemical sensor. Compared with CoFe-MOF-74 precursor modified electrode, CoFe@C/Nafion electrode exhibited a great synergic catalytic effect and extremely increased the oxidation peak signal of NHDC. The effects of various experimental conditions on the oxidation of NHDC were investigated and the calibration plot was tested. The results bespoken that CoFe@C/Nafion GCE has good reproducibility and anti-interference under the optimal experimental conditions. In addition, the differential pulse current response of NHDC was linear with its concentration within the range 0.08 ~ 20 µmol/L, and the linear regression coefficient was 0.9957. The detection limit was as low as 14.2 nmol/L (S/N = 3). In order to further verify the feasibility of the method, it was successfully used to determine the content of NHDC in Chinese medicine, with a satisfactory result, good in accordance with that of high performance liquid chromatography (HPLC).

A non-enzymatic glucose sensor based on a mesoporous carbon sphere immobilized Co-MOF-74 nanocomposite

Exploration of credible non-enzymatic glucose sensors with high selectivity and sensitivity is of great significance for early clinical monitoring of glucose concentration and preventing the threat of diabetes to human health. Here, mesoporous carbon (MC) sphere immobilized Co-MOF-74 nanorods (NRs), denoted as Co-MOF-74 NRs/MC, were successfully prepared, in which the nanostructural porous carbon sphere was obtained using cobalt glycolate as the built-in template followed by a subsequent carbonization and acid treatment, and the MC spheres were then in situ deposited on the surface of Co-MOF-74 NRs via a solvothermal method. Benefiting from the good conductivity of the grafted porous carbon spheres and the abundant active sites, as well as the permeability of microporous MOF-74 nanocrystals, the Co-MOF-74 NRs/MC modified glassy carbon electrode (GCE) exhibited effective non-enzymatic glucose sensing performance with a fast response time (less than 3 s) and a glucose sensitivity of 98.0 μA cm-2 mM-1. Furthermore, the Co-MOF-74 NRs/MC/GCE showed a favourable anti-interference capability in the presence of various interferents and good long-term reusability. The applicability of Co-MOF-74 NRs/MC/GCE for glucose sensing in real serum samples was also investigated, verifying the applicability of the electrode for targeted glucose monitoring in practical applications.

Design and Application of Electrochemical Sensors with Metal-Organic Frameworks as the Electrode Materials or Signal Tags

Metal-organic frameworks (MOFs) with fascinating chemical and physical properties have attracted immense interest from researchers regarding the construction of electrochemical sensors. In this work, we review the most recent advancements of MOF-based electrochemical sensors for the detection of electroactive small molecules and biological macromolecules (e.g., DNA, proteins, and enzymes). The types and functions of MOF-based nanomaterials in terms of the design of electrochemical sensors are also discussed. Furthermore, the limitations and challenges of MOF-based electrochemical sensing devices are explored. This work should be invaluable for the development of MOF-based advanced sensing platforms.

A Comprehensive Review of Metal-Organic Framework: Synthesis, Characterization, and Investigation of Their Application in Electrochemical Biosensors for Biomedical Analysis

Many studies have addressed electrochemical biosensors because of their simple synthesis process, adjustability, simplification, manipulation of materials' compositions and features, and wide ranges of detection of different kinds of biomedical analytes. Performant electrochemical biosensors can be achieved by selecting materials that enable faster electron transfer, larger surface areas, very good electrocatalytic activities, and numerous sites for bioconjugation. Several studies have been conducted on the metal-organic frameworks (MOFs) as electrode modifiers for electrochemical biosensing applications because of their respective acceptable properties and effectiveness. Nonetheless, researchers face challenges in designing and preparing MOFs that exhibit higher stability, sensitivity, and selectivity to detect biomedical analytes. The present review explains the synthesis and description of MOFs, and their relative uses as biosensors in the healthcare sector by dealing with the biosensors for drugs, biomolecules, as well as biomarkers with smaller molecular weight, proteins, and infectious disease.

Carbon Nanotube Based Metal-Organic Framework Hybrids From Fundamentals Toward Applications

Metal-organic frameworks (MOFs) materials constructed by the coordination chemistry of metal ions and organic ligands are important members of the crystalline materials family. Owing to their exceptional properties, for example, high porosity, tunable pore size, and large surface area, MOFs have been applied in several fields such as gas or liquid adsorbents, sensors, batteries, and supercapacitors. However, poor conductivity and low stability hamper their potential applications in several attractive fields such as energy and gas storage. The integration of MOFs with carbon nanotubes (CNTs), a well-established carbon allotrope that exhibits high conductivity and stability, has been proposed as an efficient strategy to overcome such limitations. By combining the advantages of MOFs and CNTs, a wide variety of composites can be prepared with properties superior to their parent materials. This review provides a comprehensive summary of the preparation of CNT@MOF composites and focuses on their recent applications in several important fields, such as water purification, gas storage and separation, sensing, electrocatalysis, and energy storage (supercapacitors and batteries). Future challenges and prospects for CNT@MOF composites are also discussed.

Electrochemical determination of tetrabromobisphenol A in water samples based on a carbon nanotubes@zeolitic imidazole framework-67 modified electrode

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework. It possesses an excellent adsorption capacity (92.12 mg g⁻¹) for the flame retardant tetrabromobisphenol A (TBBPA). The composite was characterized by transmission and scanning electron microscopy, FTIR and X-ray diffractometry. It was then used to modify an acetylene black electrode. Electrochemical studies showed the current response of the modified electrode to be larger than that of electrodes modified with CNTs-COOH or ZIF-67 only. Electrochemical impedance spectroscopy showed this material combination to improve the conductivity of ZIF-67. The addition of perfluorodecanoic acid further improves the response. The sensor is stable, reproducible, and has a linear range of 0.01–1.5 μM TBBPA concentration, with a 4.2 nM detection limit (at S/N = 3). The sensor was successfully applied to the detection of TBBPA in spiked rain and pool water samples.

Carbon nanotubes@zeolitic imidazole framework-67 (CNTs@ZIF-67), a conductive composite was prepared from carboxylic carbon nanotubes and a cobalt–imidazole framework.

Prospective of nanoscale metal organic frameworks [NMOFs] for cancer therapy

Nano metal organic frameworks (NMOFs) belong to the group of nanoporous materials. Over the decades, the conducted researches explored the area for the potential applications of NMOFs in areas like biomedical, chemical engineering and materials science. Recently, NMOFs have been explored for their potential use in cancer diagnosis and therapeutics. The excellent physico-chemical features of NMOFs also make them a potential candiadate to facilitate drug design, delivery and storage against cancer cells. In this review, we have explored the characterstic features, synthesis methods, NMOFs based drug delivery, diagnosis and imaging in various cancer types. In addition to this, we have also pondered on the stability and toxicological concerns of NMOFs. Despite, a significant research has been done for the potential use of NMOFs in cancer diagonostic and therapeutics, more information regarding the stability, in-vivo clearance, toxicology, and pharmacokinetics is still needed to ehnace the use of NMOFs in cancer diagonostic and therapeutics.

Electroosmotic Flow Behavior of Viscoelastic LPTT Fluid in a Microchannel

In many research works, the fluid medium in electroosmosis is considered to be a Newtonian fluid, while the polymer solutions and biological fluids used in biomedical fields mostly belong to the non-Newtonian category. Based on the finite volume method (FVM), the electroosmotic flow (EOF) of viscoelastic fluids in near-neutral (pH = 7.5) solution considering four ions (K+, Cl-, H+, OH-) is numerically studied, as well as the viscoelastic fluids' flow characteristics in a microchannel described by the Linear Phan-Thien-Tanner (LPTT) constitutive model under different conditions, including the electrical double layer (EDL) thickness, the Weissenberg number (Wi), the viscosity ratio and the polymer extensibility parameters. When the EDL does not overlap, the velocity profiles for both Newtonian and viscoelastic fluids are plug-like and increase sharply near the charged wall. Compared with Newtonian fluid at Wi = 3, the viscoelastic fluid velocity increases by 5 times and 9 times, respectively, under the EDL conditions of kH = 15 and kH = 250, indicating the shear thinning behavior of LPTT fluid. Shear stress obviously depends on the viscosity ratio and different Wi number conditions. The EOF is also enhanced by the increase (decrease) in polymer extensibility parameters (viscosity ratio). When the extensibility parameters are large, the contribution to velocity is gradually weakened.

Fabrication of hierarchical MIL-68(In)-NH2/MWCNT/CdS composites for constructing label-free photoelectrochemical tetracycline aptasensor platform

It is essential to develop a highly efficient detection platform for tetracycline (Tc). Herein, based on well-designed hierarchical MIL-68(In)-NH₂/MWCNT/CdS composites as a highly efficient transducer, a label-free visible light driven photoelectrochemical (PEC) aptasensor was systematically fabricated. Characterization results indicate that the forming of MIL-68(In)-NH₂/CdS heterojunction remarkable facilitated the transfer and inhibited the recombination of charge carriers. Moreover, the transfer properties of multiwalled carbon nanotubes (MWCNTs) further improved the photoelectric conversion efficiency by adjusting electron transport routes. The aptamer as a biorecognition unit was grafted on the modified electrode by chemical bonding effect, and Tc molecules could be captured through the specific interaction of aptamer and Tc in solution. The concentration of Tc was detected by observing the fluctuation of photocurrent signals. Under optimized conditions, the proposed aptasensor showed the broad linear range from 0.1 nmol L^-1 to 1 μmol L^-1 with a low detection limit (LOD) of 0.015 nmol L^-1. Furthermore, the high sensitivity, excellent reproducibility and favorable stability of the PEC sensing platform indicated the potential applications for antibiotic residues detecting in environmental media.

Nanoscaled Metal-Organic Frameworks for Biosensing, Imaging, and Cancer Therapy

Owing to the progressive development of metal-organic frameworks (MOFs) synthetic processes and their unique characters associated with the excellent performance-selectable composition, tunable pore scale, large surface area, and good thermal stability, MOFs have captured the interest and the imagination of an increasing number of scientists working in different fields. In the area of biomedical applications, MOFs are especially involved in sensing, molecular imaging, and drug delivery, with strong contributions to the whole nanomedicine area. Recently, these materials have been scaled down to nanometer sizes with the advancement of chemical synthesis gradually reaching an adjustable level. This review mainly discusses and summarizes the general synthesis, properties, and biomedical applications of nanoscaled MOFs and their composites in biosensing, imaging, and cancer therapy within the latest three years. The remaining challenges and future opportunities in this field, in terms of processing techniques, maximizing composite properties, and prospects for clinical applications, are also indicated.

An efficient and sustainable catalytic reduction of carbon–carbon multiple bonds, aldehydes, and ketones using a Cu nanoparticle decorated metal organic framework

Economical, reusable, eco-friendly sustainable process is reported that involve low amount of hydrazine hydrate.

Synthesis, functionalization, and applications of metal–organic frameworks in biomedicine

Metal–organic frameworks (MOFs), also known as coordination polymers, have attracted extensive research interest in the past few decades due to their unique physical structures and potentially vast applications.

Passivation of the surface imperfection of TiO2 by using ZIF-8 for efficient carrier separation/transfer

Photoelectrochemical (PEC) water splitting offers a promising chance for energy generation on a global scale.

Construction of an ultrasensitive non-enzymatic sensor to investigate the dynamic process of superoxide anion release from living cells

In this work, a novel non-enzymatic superoxide anion (O₂•^-) sensor was constructed based on Ag nanoparticles (NPs) / poly (amidoamine) (PAMAM) dendrimers and used to investigate the dynamic process of O₂•^- release from living cells. The AgNPs/PAMAM nanohybrids were characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated electrode exhibited excellent catalytic activity toward the reaction of O₂•^- with a super low detection limit (LOD) of 2.530 × 10^-13M (S/N = 3) and wide linear range of 8 orders of magnitude. It could fulfill the requirement of real-time measurement O₂•^- released from living cells. Furthermore, zymosan was chosen as the stimulant to induce O₂•^- generation from cancer cells (rat adrenal medulla pheochromocytoma cell (PC12)). The electrochemical experiment results indicated that the levels of intracellular O₂•^- depended on the amount of Zymosan. A large amount of O₂•^- generated in the living cells by added heavy stimulant could damage cells seriously. More importantly, a vitro simulation experiment confirmed the role of superoxide dismutase (SOD) for the first time because it could maintain the O₂•^- concentration at a normal physiological range. These findings are of great significance for evaluating the metabolic processes of O₂•^- in the biological system, and this work has the tremendous potential application in clinical diagnostics to assess oxidative stress.

Engineering phase transformation of cobalt selenide in carbon cages and the phases' bifunctional electrocatalytic activity for water splitting

Using Co-based metal-organic frameworks as the precursor, we synthesized cobalt selenide (CoSe₂) nanoparticles imbedded in carbon cages. By simply controlling the annealing conditions, phase transformation of CoSe₂ from the orthorhombic phase to the cubic phase has been realized. Benefitting from the metallic character, the cubic phase CoSe₂ shows greatly enhanced electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The as-prepared cubic phase CoSe₂ electrode possesses onset overpotentials of 43 and 200 mV, and Tafel slopes of 51 and 83 mV dec^-1 for HER and OER, respectively, which are remarkably superior to that of the orthorhombic phase CoSe₂ catalyst and comparable to those of commercial noble-metal catalysts. In addition, the cubic phase CoSe₂ electrode also demonstrates excellent stability after long-term operations. Our work not only provides a high performance catalyst for water splitting, but also introduces a new route to the design of a highly efficient catalyst by phase transformation.

Nano Metal-Organic Framework-Derived Inorganic Hybrid Nanomaterials: Synthetic Strategies and Applications

Nano- (or micro-scale) metal-organic frameworks (NMOFs), also known as coordination polymer particles (CPPs), have received much attention because of their structural diversities and tunable properties. Besides the direct use, NMOFs can be alternatively used as sacrificial templates/precursors for the preparation of a wide range of hybrid inorganic nanomaterials in straightforward and controllable manners. Distinct advantages of using NMOF templates are correlated to their structural and functional tailorability at molecular levels that is rarely acquired in any other conventional template/precursor. In addition, NMOF-derived inorganic nanomaterials with distinct chemical and physical properties are inferred to dramatically expand the scope of their utilization in many fields. In this review, we aim to provide readers with a comprehensive summary of recent progress in terms of synthetic approaches for the production of diverse inorganic hybrid nanostructures from as-synthesized NMOFs and their promising applications.

An updated roadmap for the integration of metal–organic frameworks with electronic devices and chemical sensors

This review highlights the steps needed to bring the properties of MOFs from the chemical lab to the microelectronics fab.

A facile water-stable MOF-based “off–on” fluorescent switch for label-free detection of dopamine in biological fluid

An Abtz–CdI₂–MOF was developed as an “off–on” fluorescent switch for label-free detection of dopamine without any surface modification or functionalization.

Bimetal–organic-frameworks-derived yolk–shell-structured porous Co2P/ZnO@PC/CNTs hybrids for highly sensitive non-enzymatic detection of superoxide anion released from living cells

Bimetal-organic framework derived yolk–shell–structured porous Co₂P/ZnO@PC/CNTs were used as highly active electrocatalysts for electrochemical sensing of superoxide anions.