Hierarchical NiO Superstructures/Foam Ni Electrode Derived from Ni Metal-Organic Framework Flakes on Foam Ni for Glucose Sensing

Two-Dimensional Nanorod-Shaped Co(II) Coordination Polymer on Three-Dimensional Metallic Foam: A Hybrid Platform for Electrochemical Oxidation of Glucose

This study unveils a novel electrochemical biosensor for monitoring glucose in biological fluids by employing nanorods of a cobalt-bispyridyl/dicarboxylate framework grown in a layer-by-layer manner on a highly porous nickel substrate. The hybrid microporous system has a bicatalytic effect on glucose oxidation due to the synergistic catalytic impact of the nickel and cobalt ions with varying oxidation states as electroactive sites. In addition, the controlled growth of inorganic-organic frameworks changes the mechanism of electron transfer from a diffusion-controlled process to an adsorption-controlled process, thus yielding a low onset oxidation potential (∼0.21 V/Ag-AgCl) and a high current intensity (∼1 mA) for the oxidation of glucose in alkaline media. A fast response time (∼2 s) and a reasonably high sensitivity (0.14 μA μM-1) within a broad linear range (40-360 μM) have determined the suitability and superiority of the hybrid electrode for glucose monitoring compared to many metal-organic-based biosensors. The facile fabrication process of the Co(II) coordination polymer/Ni substrate with a large surface area that benefits from the synergetic catalytic activity of nickel-cobalt hybrids may pave the way for the development of novel hybrid electrodes for biosensors and direct glucose fuel cells.

Ag Functionalized In2O3 Derived From MIL-68(In) as an Efficient Electrochemical Glucose Sensor

In this study, Ag@In2O3 modified nickel foam (NF) was reported for its role as a non-enzymatic glucose sensor. Ag@In2O3 was prepared by a simple two-step method; preparation of a metal-organic framework (MOF) MIL-68(In) by solvothermal method, entrapment of Ag + by adding AgNO3 then drying it for 2 h to complete the entrapment process and subsequent calcination at 650°C for 3 h. The Ag@In2O3 modified NF was employed as a non-enzymatic glucose sensor to determine glucose concentrations in an alkaline medium. Two linear ranges were obtained from Ag@In2O3 modified electrode, i.e., 10 μM to 0.8 mM and 0.8–2.16 mM with a sensitivity of 3.31 mA mM−1 cm−2 and 1.51 mA mM−1 cm−2 respectively, with a detection limit of 0.49 µM. Ag@In2O3 modified NF exhibited high selectivity for glucose, among other interfering agents.

The controllable synthesis of urchin-shaped hierarchical superstructure MOFs with high catalytic activity and stability

A novel dissolution-crystallization-attachment strategy was developed to synthesize urchin-shaped superstructure metal-organic frameworks (MOFs) with self-assembled one-dimensional nanorods. The superstructure MOFs not only inherited the high activity of nanosized MOFs but also displayed the high stability of microsized MOFs.

Nanocomposite synthesis strategies based on the transformation of well-tailored metal-organic frameworks

Increasing the complexity of nanomaterials in terms of their structure and chemical composition has attracted significant attention, because it can yield unique scientific outcomes and considerable improvements for practical applications. Various approaches are being developed for the synthesis of nanostructured composites. Coordination polymers (CPs) emerged as new precursors in solid-state reactions for nanomaterials nearly two decades ago; the repetitively arranged inorganic and organic units can facilitate the production of nanoscale particles and porous carbon upon thermal decomposition. Metal-organic frameworks (MOFs), a subgroup of CPs featuring crystalline and porous structures, have subsequently become primary objects of interest in this field, as can be seen by the rapidly increasing number of reports on this topic. However, unique composite materials with increasingly complex nanostructures, which cannot be achieved via conventional methods, have been rarely realised, even though conventional MOF research has enabled the delicate control of structures at the molecular level and extensive applications as templates. In this regard, a comprehensive review of the fabrication strategies of MOF-based precursors and the thermal transformation into functional nanomaterials is provided herein, with a particular emphasis on the recent developments in nanocomposite research. We briefly introduce the roles and capabilities of MOFs in the synthesis of nanomaterials and subsequently discuss diverse synthetic routes for obtaining morphologically or compositionally advanced composite nanomaterials, based on our understanding of the MOF conversion mechanism.

Non-enzymatic glucose sensor based on a g-C3N4/NiO/CuO nanocomposite

In this paper, a non-enzymatic glucose sensor was developed based on a g-C₃N₄/NiO/CuO nanocomposite immobilized on a glassy carbon electrode (GCE). Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) were utilized for the characterization of the synthesized g-C₃N₄/NiO/CuO nanocomposite. The electrocatalytic activity of the nanocomposite was investigated by cyclic voltammetry, and the amperometric technique was applied for monitoring glucose. The g-C₃N₄/NiO/CuO/GCE exhibited better electrocatalytic performance than g-C₃N₄/GCE, g-C₃N₄/CuO/GCE and g-C₃N₄/NiO/GCE. Under optimized conditions, the proposed sensor offered a linearity ranging from 0.4 μM to 8.5 mM with a detection limit of 0.1 μM and a sensitivity of 362.12 μA mM^-1 cm^-2. The constructed sensor displayed favorable reproducibility, outstanding selectivity, and long-term performance. These results reveal that the sensor is a promising candidate for blood glucose sensing.

General synthesis of hierarchical sheet/plate-like M-BDC (M = Cu, Mn, Ni, and Zr) metal-organic frameworks for electrochemical non-enzymatic glucose sensing

Two-dimensional metal-organic frameworks (2D MOFs) are an attractive platform to develop new kinds of catalysts because of their structural tunability and large specific surface area that exposes numerous active sites. In this work, we report a general method to synthesize benzene dicarboxylic acid (BDC)-based MOFs with hierarchical 3D morphologies composed of 2D nanosheets or nanoplates. In our proposed strategy, acetonitrile helps solvate the metal ions in solution and affects the morphology, while polyvinylpyrrolidone (PVP) serves as a shape-control agent to assist in the nucleation and growth of MOF nanosheets. PVP also acts as a depletion agent to drive the assembly of the hierarchical sheet/plate-like M-BDC under solvothermal conditions. Further, we also demonstrate the flexibility of the proposed method using numerous coordinating metal ions (M = Cu, Mn, Ni, and Zr). The potential of these MOFs for electrochemical glucose sensing is examined using the hierarchical sheet-like Ni-BDC MOF as the optimum sample. It drives the electrocatalytic oxidation of glucose over a wide range (0.01 mM to 0.8 mM) with high sensitivity (635.9 μA mM-1 cm-2) in the absence of modification with carbon or the use of conductive substrates. It also demonstrates good selectivity with low limit of detection (LoD = 6.68 μM; signal/noise = 3), and fast response time (<5 s).

A facile and sensitive electrochemical sensor for non-enzymatic glucose detection based on three-dimensional flexible polyurethane sponge decorated with nickel hydroxide

A novel three-dimensional nickel hydroxide/polyurethane (Ni(OH)₂/PU) electrode was prepared by a simple and environmentally friendly method and used for non-enzymatic detection of glucose. The Ni(OH)₂/PU electrode was obtained by one-pot hydrothermal method of loading nickel hydroxide on a cheap, easily available and flexible polyurethane sponge, which is facile and energy-saving. The porous structure of the polyurethane sponge provides a large surface area and a rich electrochemical active site for the electrode, which is beneficial to the oxidation reaction of glucose on the surface of the electrode with Ni(OH)₂. The Ni(OH)₂/PU electrode structure was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry test was used to study the catalytic performance of Ni(OH)₂/PU electrode for oxidation of glucose and the chronoamperometry was used to investigate the detection performance of Ni(OH)₂/PU electrode on glucose. The results indicate that this non-enzymatic glucose sensor had a high sensitivity of 2845 μA mM^-1 cm^-2, a low detection limit of 0.32 μM (S/N = 3), a detection range of 0.01-2.06 mM and response time of less than 5 s. In addition, the Ni(OH)₂/PU electrode had excellent selectivity, reproducibility and stability and also exhibited effective detection of glucose in fetal bovine serum (FBS). In summary, Ni(OH)₂/PU electrode had broad prospects as an excellent candidate for non-enzymatic glucose sensors. The study also opens up a facile and energy-saving approach for preparing three-dimensional (3D) functionalized polymer electrode via hydrothermal method as electrochemical sensors.

A novel dual-tasking hollow cube NiFe2O4-NiCo-LDH@rGO hierarchical material for high preformance supercapacitor and glucose sensor

Binary transition metal oxides as electroactive materials have continuously aroused grumous attention due to their high theoretical specific capacitance, high valtage window, and multiple oxidation states. However, the tiny specific surface area, poor conductivity and unsatisfactory cycle stability limit their practical application. Hence, a synthetic strategy is designed to fabricate a dual-tasking hollow cube nickel ferrite (NiFe₂O₄) - based composite (NiFe₂O₄-NiCo-LDH@rGO) with hierarchical structure. The composite is constructed by firstly preparing hollow NiFe₂O₄ from cube-like Ni - Fe bimetallic organic framework (NiFe-MOF), and then integrating nickel cobalt layered double hydroxide (NiCo-LDH) nanowires, together with reduced graphene oxide (rGO) via pyrolysis in conjuction with hydrothermal method. The NiFe₂O₄ possessing cubic hollow structure contributes to a huge accessible surface area, meanwhile alleviates large volume expansion/contraction effect, which facilitates suffcient permeation of the electrolyte and rapid ion/charge transport, and results in high cycling stability. The introduction of layered NiCo-LDH results in hierarchical structure and thus offers maximum contact areas with electrolyte, which heightens the specific capacitance of obtained composite and enhances the electro-catlytic activity towards oxidation of glucose. Furthermore, rGO layer greatly improves the electrical conductivity and ion diffusion/transport capability of composite. Benefiting from the unique structure and individual components of NiFe₂O₄-NiCo-LDH@rGO composite, the electrode delivers a high specific capacitance (750 C g^-1) and superb durability. Simultaneously, the asymmetrical device based on NiFe₂O₄-NiCo-LDH@rGO as positive electrode delivers remarkable energy density (50 Wh kg^-1). Moreover, NiFe₂O₄-NiCo-LDH@rGO exhibits good sensing performance with a sensitivity of 111.86 µA/µM cm^-2, the wide linear range of 3.500 × 10^-5 - 4.525 × 10^-3 M, and the detection limit of 12.94 × 10^-6 M with a signal to noise ratio of 3. Consequently, the NiFe₂O₄-NiCo-LDH@rGO could provide a prospective notion constructing bifunctional materials with hollow-cube hierarchical structure in the field of supercapacitors and electrochemical sensors.

A non-enzymatic glucose sensor with enhanced anti-interference ability based on a MIL-53(NiFe) metal–organic framework

The MIL-53(NiFe) MOF was used as a molecular sieve to improve the anti-interference ability in glucose detection.

Synthesis of a novel Au nanoparticles decorated Ni-MOF/Ni/NiO nanocomposite and electrocatalytic performance for the detection of glucose in human serum

A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles (AuNPs) decorated Ni metal-organic-framework (MOF)/Ni/NiO nanocomposite. Ni-MOF/Ni/NiO nanocomposite was synthesized by one-step calcination of Ni-MOF. Then AuNPs were loaded onto the Ni-based nanocomposites' surface through electrostatic adsorption. Through characterization by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy disperse spectroscopy (EDS) mapping, it is found that the AuNPs were well distributed on the surface of Ni-based nanocomposite. Cyclic voltammetric (CV) study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto it. Amperometric study demonstrated that the Au-Ni nanocomposites modified glassy carbon electrode (GCE) exhibited a high sensitivity of 2133.5 mA M^-1 cm^-2 and a wide linear range (0.4-900 μM) toward the oxidation of glucose with a detection limit as low as 0.1 μM. Moreover, the reproducibility, selectivity and stability of the sensor all exhibited outstanding performance. We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results. It is believed that AuNPs decorated Ni MOF/Ni/NiO nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications.

Highly sensitive and selective non-enzymatic monosaccharide and disaccharide sugar sensing based on carbon paste electrodes modified with perforated NiO nanosheets

Fabrication and characterization of enzyme-free electrochemical sensor for the sensing of monosaccharide and disaccharide sugars based on perforated NiO nanosheets (NSs).

Porous NiCo2O4 nanoarray-integrated binder-free 3D open electrode offers a highly efficient sensing platform for enzyme-free glucose detection

Porous binary metal oxide NiCo₂O₄ NWA/CC was prepared and utilized as a 3D binder-free open electrode for enzyme-free sensing with high performance.

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.

Ni-Based metal–organic framework derived Ni@C nanosheets on a Ni foam substrate as a supersensitive non-enzymatic glucose sensor

Uniform and compact porous Ni@C nanosheet membranes on Ni foam showing remarkable electrocatalytic activity for non-enzymatic glucose sensing.

Fabrication of Palladium Nanoparticles on Porous Aromatic Frameworks as a Sensing Platform to Detect Vanillin

Here, we report the fabrication of palladium nanoparticles on porous aromatic frameworks (Pd/PAF-6) using a facile chemical approach, which was characterized by various spectro- and electrochemical techniques. The differential pulse voltammetry (DPV) response of Pd/PAF-6 toward the vanillin (VA) sensor shows a linear relationship over concentrations (10-820 pM) and a low detection limit (2 pM). Pd/PAF-6 also exhibited good anti-interference performance toward 2-fold excess of ascorbic acid, nitrophenol, glutathione, glucose, uric acid, dopamine, ascorbic acid, 4-nitrophenol, glutathione, glucose, uric acid, dopamine, and 100-fold excess of Na(+), Mg(2+), and K(+) during the detection of VA. The developed electrochemical sensor based on Pd/PAF-6 had good reproducibility, as well as high selectivity and stability. The established sensor revealed that Pd/PAF-6 could be used to detect VA in biscuit and ice cream samples with satisfactory results.

Non-enzymatic detection of glucose using poly(azure A)-nickel modified glassy carbon electrode

A simple, sensitive and selective non-enzymatic glucose sensor was constructed in this paper. The poly(azure A)-nickel modified glassy carbon electrode was successfully fabricated by the electropolymerization of azure A and the adsorption of Ni(2+). The Ni modified electrode, which was characterized by scanning electron microscope, cyclic voltammetry, electrochemical impedance spectra and X-ray photoelectron spectroscopy measurements, respectively, displayed well-defined current responses of the Ni(III)/Ni(II) couple and showed a good activity for electrocatalytic oxidation of glucose in alkaline medium. Under the optimized conditions, the developed sensor exhibited a broad linear calibration range of 5 μM-12mM for quantification of glucose and a low detection limit of 0.64μM (3σ). The excellent analytical performance including simple structure, fast response time, good anti-interference ability, satisfying stability and reliable reproducibility were also found from the proposed amperometric sensor. The results were satisfactory for the determination of glucose in human serum samples as comparison to those from a local hospital.

Hierarchical Cu/Cu(OH)2 nanorod arrays grown on Cu foam as a high-performance 3D self-supported electrode for enzyme-free glucose sensing

Hierarchical Cu/Cu(OH)₂ nanorod arrays grown on Cu foam (Cu/Cu(OH)₂ NRA/CF) were prepared via a three-step strategy involving the synthesis of Cu(OH)₂ NRA/CF, the preparation of Cu NRA/CF, and the growth of Cu(OH)₂ nanoparticles on Cu NRA/CF.