Synthesis and Characterization of GO/ZIF-67 Nanocomposite: Investigation of Catalytic Activity for the Determination of Epinine in the Presence of Dobutamine

In situ selective selenization of ZIF-derived CoSe2 nanoparticles on NiMn-layered double hydroxide@CuBr2 heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg-1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.

Cobalt-Nickel Layered Double Hydroxides on Electrospun MXene for Superior Asymmetric Supercapacitor Electrodes

Flexible electrodes for energy storage and conversion require a micro-nanomorphology and stable structure. Herein, MXene fibers (MX-CNF) are fabricated by electrospinning, and Co-MOF nanoarrays are prepared on the fibers to form Co-MOF@MX-CNF. Hydrolysis and etching of Co-MOF@MX-CNF in the Ni2+ solution produce cobalt-nickel layered double hydroxide (CoNi-LDH). The CoNi-LDH nanoarrays on the MX-CNF substrate have a large specific surface area and abundant electrochemical active sites, thus ensuring effective exposure of the CoNi-LDH active materials to the electrolyte and efficient pseudocapacitive energy storage and fast reversible redox kinetics for enhanced charging-discharging characteristics. The CoNi-LDH@MX-CNF electrode exhibits a discharge capacity of 996 F g-1 at a current density of 1 A g-1 as well as 78.62% capacitance retention after 3,000 cycles at 10 A g-1. The asymmetric supercapacitor (ASC) comprising the CoNi-LDH@MX-CNF positive electrode and negative activated carbon electrode shows an energy density of 48.4 Wh kg-1 at a power density of 499 W kg-1 and a capacity retention of 78.9% after 3,000 cycles at a current density of 10 A g-1. Density-functional theory calculations reveal the charge density difference and partial density of states of CoNi-LDH@MX-CNF confirming the large potential of the CoNi-LDH@MX-CNF electrode in energy storage applications.

MOF-Derived Co Nanoparticles Catalyst Assisted by F- and N-Doped Carbon Quantum Dots for Oxygen Reduction

The oxygen reduction reaction is crucial in the cathode of fuel cells and metal-air batteries. Consequently, designing robust and durable ORR catalysts is vital to developing metal-air batteries and fuel cells. Metal-organic frameworks feature an adjustable structure, a periodic porosity, and a large specific surface area, endowing their derivative materials with a unique structure. In this study, F and N co-doped on the carbon support surface (Co/FN-C) via the pyrolysis of ZIF-67 as a sacrificial template while using Co/FN-C as the non-noble metal catalysts. The Co/FN-C displays excellent long-term durability and electrochemical catalytic performance in acidic solutions. These performance improvements are achieved because the CQDs alleviate the structural collapse during the pyrolysis of ZIF-67, which increases the active sites in the Co nanoparticles. Moreover, F- and N-doping improves the catalytic activity of the carbon support by providing additional electrons and active sites. Furthermore, F anions are redox-stable ligands that exhibit long-term operational stability. Therefore, the well-dispersed Co NPs on the surface of the Co/FN-C are promising as the non-noble metal catalysts for ORR.

Metal-organic framework-based nanomaterials as opto-electrochemical sensors for the detection of antibiotics and hormones: A review

Increasing trace levels of antibiotics and hormones in the environment and food samples are concerning and pose a threat. Opto-electrochemical sensors have received attention due to their low cost, portability, sensitivity, analytical performance, and ease of deployment in the field as compared to conventional expensive technologies that are time-consuming and require experienced professionals. Metal-organic frameworks (MOFs) with variable porosity, active functional sites, and fluorescence capacity are attractive materials for developing opto-electrochemical sensors. Herein, the insights into the capabilities of electrochemical and luminescent MOF sensors for detection and monitoring of antibiotics and hormones from various samples are critically reviewed. The detailed sensing mechanisms and detection limits of MOF sensors are addressed. The challenges, recent advances, and future directions for the development of stable, high-performance MOFs as commercially viable next-generation opto-electrochemical sensor materials for the detection and monitoring of diverse analytes are discussed.

Interrogating Encapsulated Protein Structure within Metal-Organic Frameworks at Elevated Temperature

Encapsulating biomacromolecules within metal-organic frameworks (MOFs) can confer thermostability to entrapped guests. It has been hypothesized that the confinement of guest molecules within a rigid MOF scaffold results in heightened stability of the guests, but no direct evidence of this mechanism has been shown. Here, we present a novel analytical method using small-angle X-ray scattering (SAXS) to solve the structure of bovine serum albumin (BSA) while encapsulated within two zeolitic imidazolate frameworks (ZIF-67 and ZIF-8). Our approach comprises subtracting the scaled SAXS spectrum of the ZIF from that of the biocomposite BSA@ZIF to determine the radius of gyration of encapsulated BSA through Guinier, Kratky, and pair distance distribution function analyses. While native BSA exposed to 70 °C became denatured, in situ SAXS analysis showed that encapsulated BSA retained its size and folded state at 70 °C when encapsulated within a ZIF scaffold, suggesting that entrapment within MOF cavities inhibited protein unfolding and thus denaturation. This method of SAXS analysis not only provides insight into biomolecular stabilization in MOFs but may also offer a new approach to study the structure of other conformationally labile molecules in rigid matrices.

XRD and Spectroscopic Investigations of ZIF-Microchannel Glass Plates Composites

In this study, new composite materials comprising zeolitic imidazolate framework (ZIF) structures and microchannel glass (MCG) plates were fabricated using the hydrothermal method and their morphological and spectral properties were investigated using XRD, SEM, FTIR, and Raman spectroscopy. XRD studies of powder samples revealed the presence of an additional phase for a ZIF-8 sample, whereas ZIF-67 samples, which were prepared through two different chemical routes, showed no additional phases. A detailed analysis of the FTIR and micro-Raman spectra of the composite samples revealed the formation of stable ZIF structures inside the macropores of the MCG substrate. The hydrophilic nature of the MCG substrate and its interaction with the ZIF structure resulted in the formation of stable ZIF-MCG composites. We believe that these composite materials may find a wide range of important applications in the field of sensors, molecular sieving.

In-situ synthesized ZIF-67 graphene oxide (ZIF-67/GO) nanocomposite for efficient individual and simultaneous detection of heavy metal ions

Heavy metals are ubiquitous in water bodies as a result of anthropogenic activities and over time they accumulate in body thus posing serious health problems. Therefore, it is essential to improve sensing performance, for determination of heavy metal ions (HMIs), of electrochemical sensors. In this work, cobalt-derived MOF (ZIF-67) was in-situ synthesized and incorporated onto the surface of graphene oxide (GO) by simple sonication method. The prepared material (ZIF-67/GO) was characterized by FTIR, XRD, SEM, and Raman spectroscopy. Afterwards, a sensing platform was made by drop-casting synthesized composite onto glassy carbon electrode for individual and simultaneous detection of heavy metal ions pollutants (Hg²⁺, Zn²⁺, Pb²⁺, and Cr³⁺) with estimated detection limits of 2 nM, 1 nM, 5 nM, and 0.6 nM, respectively, when determined simultaneously, that are below the permissible limit by World Health Organization. To the best of our knowledge, this is first report of HMIs detection by ZIF-67 incorporated GO sensor which can successfully determine the Hg⁺², Zn⁺², Pb⁺², and Cr⁺³ ions simultaneously with lower detection limits.

A modified carbon paste electrode with N-rGO/CuO nanocomposite and ionic liquid for the efficient and cheap voltammetric sensing of hydroquinone in water specimens

This paper reports a voltammetric sensor based on copper oxide nanoparticles on nitrogen-doped reduced graphene oxide nanocomposite (N-rGO/CuO)-ionic liquid modified carbon paste electrode (N-rGO/CuO-ILCPE) for determining the hydroquinone (HQ). The N-rGO/CuO was prepared by a facile protocol, followed by characterization via fourier transform-infrared (FT-IR) patterns, field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) analysis. The electrochemical behaviour was linearly symmetrical to various hydroquinone levels (1.0-600.0 μM) with a narrow limit of detection (LOD = 0.25 μM). The diffusion coefficient was also estimated to be 4.1 × 10^-6 cm²/s. The N-rGO/CuO-ILCPE was impressively applicable in determination of hydroquinone in the real specimens.

Electrochemical sensors based on carbon nanostructures for the analysis of bisphenol A-A review

Overuse of Bisphenol A (BPA), a proven endocrine disruptor, has become a serious public health problem across the world. It has the potential to harm both the environment and human health, notably reproductive disorders, heart disease, and diabetes. Accordingly, much attention has been paid to the detection of BPA to promote food safety and environmental health. Carbon based nanostructures have proven themselves well in a variety of applications, such as energy storage, catalysis and sensors, due to their remarkable properties. Therefore, researchers have recently focused on fabricating electrochemical BPA sensors based on carbon nanostructures due to their unique advantages, such as real-time monitoring, simplicity, high selectivity, high sensitivity and easy operation. The purpose of the current review was to summarize the recent findings on carbon nanostructures for electrochemically sensing the BPA, as well as relevant future prospects and ongoing challenges.

Voltammetric Determination of Isoniazid in the Presence of Acetaminophen Utilizing MoS2-Nanosheet-Modified Screen-Printed Electrode

We used MoS₂ nanosheets (MoS₂ NSs) for surface modification of screen-printed electrode (MoS₂NSs-SPE) aimed at detecting isoniazid (INZ) in the presence of acetaminophen (AC). According to analysis, an impressive catalytic performance was found for INZ and AC electro-oxidation, resulting in an appreciable peak resolution (~320 mV) for both analytes. Chronoamperometry, differential pulse voltammetry (DPV), linear sweep voltammogram (LSV), and cyclic voltammetry (CV) were employed to characterize the electrochemical behaviors of the modified electrode for the INZ detection. Under the optimal circumstances, there was a linear relationship between the peak current of oxidation and the various levels of INZ (0.035–390.0 µM), with a narrow limit of detection (10.0 nM). The applicability of the as-developed sensor was confirmed by determining the INZ and AC in tablets and urine specimens, with acceptable recoveries.