Flexible Electrospun PVdF-HFP/Ni/Co Membranes for Efficient and Highly Selective Enzyme Free Glucose Detection

Effect of Guest Solvents on the Ionic Conductivity and Electrochemical Performance of Metal-Organic Framework-Based Magnesium Semi-Solid Electrolytes

Developing suitable electrolytes is crucial for the advancement of rechargeable magnesium batteries. Recently, metal-organic frameworks (MOFs) have shown a great interest in the field of solid electrolytes for metal ion batteries. However, the ionic conductivity as well as the electrolyte stability in the presence of Mg electrodes are shown to be strongly dependent on the guest solvent used to solvate Mg salts in MOFsSEs. Our measurements showed that full evacuation of the MOF structure before semi-solid electrolytes (sSEs) preparation is crucial for achieving relatively low Mg overpotentials regardless of the ionic conductivity values. Moreover, the behavior of the anode/MOFsSEs interfaces (MOF: α-Mg3 [HCOO]6 ; Mg salt : MgCl2 -Mg[TFSI]2 (1 : 1 wt %); guest solvent: acetone, DMF, DEG, DME and tetraglyme) was investigated by EIS, CV and galvanostatic measurements. The current comparative study of the electrochemical deposition processes of magnesium from MOFsSEs revealed that magnesium deposition/dissolution reactions vary depending on the MOF structure, the guest anion species as well as the nature of the guest solvents.

Current advancements and prospects of enzymatic and non-enzymatic electrochemical glucose sensors

This review discusses the most current developments and future perspectives in enzymatic and non-enzymatic glucose sensors, which have notably evolved over the preceding quadrennial period. Furthermore, a thorough exploration encompassed the sensor's intricate fabrication processes, the diverse range of materials employed, the underlying principles of detection, and an in-depth assessment of the sensors' efficacy in detecting glucose levels within essential bodily fluids such as human blood serums, urine, saliva, and interstitial fluids. It is worth noting that the accurate quantification of glucose concentrations within human blood has been effectively achieved by utilizing classical enzymatic sensors harmoniously integrated with optical and electrochemical transduction mechanisms. Monitoring glucose levels in various mediums has attracted exceptional attention from industrial to academic researchers for diabetes management, food quality control, clinical medicine, and bioprocess inspection. There has been an enormous demand for the creation of novel glucose sensors over the past ten years. Research has primarily concentrated on succeeding biocompatible and enhanced sensing abilities related to the present technologies, offering innovative avenues for more effective glucose sensors. Recent developments in wearable optical and electrochemical sensors with low cost, high stability, point-of-care testing, and online tracking of glucose concentration levels in biological fluids can aid in managing and controlling diabetes globally. New nanomaterials and biomolecules that can be used in electrochemical sensor systems to identify glucose concentration levels are developed thanks to advances in nanoscience and nanotechnology. Both enzymatic and non-enzymatic glucose electrochemical sensors have garnered much interest recently and have made significant strides in detecting glucose levels. In this review, we summarise several categories of non-enzymatic glucose sensor materials, including composites, non-precious transition metals and their metal oxides, hydroxides, precious metals and their alloys, carbon-based materials, conducting polymers, metal-organic framework (MOF)-based electrocatalysts, and wearable device-based glucose sensors deeply.

Highly sensitive surface plasmon resonance sensor with surface modified MoSe2/ZnO composite film for non-enzymatic glucose detection

The rapid and accurate assessment of glucose concentration has been demonstrated to play a significant role in human health, such as the diagnosis and treatment of diabetes, pharmaceutical research and quality monitoring in the food industry, necessitating further development of the performance for glucose sensor especially at low concentrations. However, glucose oxidase-based sensors suffer from crucial restriction in bioactivity because of their poor environmental tolerance. Recently, catalytic nanomaterials with enzyme-mimicking activity, known as nanozymes, have gained considerable interest to overcome the drawback. In this scenario, we report an inspiring surface plasmon resonance (SPR) sensor for non-enzymatic glucose detection employing ZnO nanoparticles and MoSe2 nanosheets composite (MoSe2/ZnO) as sensing film, featuring desirable advantages of high sensitivity and selectivity, lab-free and low cost. The ZnO was used to specifically recognize and bind glucose, and further signal amplification was realized by incorporating of MoSe2 owing to its larger specific surface area and favorable bio-compatibility, as well as high electron mobility. These unique features of MoSe2/ZnO composite film result in an obvious improvement of sensitivity for glucose detection. Experimental results show that the measurement sensitivity of the proposed sensor could reach 72.17 nm/(mg/mL) and a detection limit of 4.16 μg/mL by appropriately optimizing the componential constitutions of MoSe2/ZnO composite. In addition, the favorable selectivity, repeatability and stability are demonstrated as well. This facile and cost-effective work provides a novel strategy for constructing high-performance SPR sensor for glucose detection and a prospective application in biomedicine and human health monitoring.

Enhanced adsorption of resorcinol onto phosphate functionalized graphene oxide synthesized via Arbuzov Reaction: A proposed mechanism of hydrogen bonding and π-π interactions

Phosphate functionalized graphene oxide (PGO) was successfully prepared by Arbuzov reaction and employed for adsorption of resorcinol from an aqueous phase. The phosphate functional groups were successfully incorporated onto the PGO surface by the formation of P-C bonds as identified by the analysis of FTIR and XPS spectra. The evaluation of adsorption capacity of resorcinol onto PGO exhibited significant improvement of resorcinol removal, achieving an adsorption capacity of 50.25 mg/g in the pH range of 4-7 which was 15 times higher than pristine graphene oxide. The addition of 2.4 M and 5 M NaCl in the adsorption system significantly increased the adsorption capacity towards resorcinol from 50.25 mg/g to 82.10 mg/g and 128.10 mg/g, respectively. Based on kinetics and adsorption isotherm studies, Pseudo-First-Order and Langmuir model are the best model to describe the adsorption process indicating that the adsorption is dominantly controlled by physisorption. The thermodynamic analysis suggested that the adsorption process was the favorable, spontaneous, and endothermic process. Besides, the interplay of hydrogen bonding and π-π interactions is proposed to be the governing physisorption mechanism. The outstanding reusability and better adsorption performance make PGO a promising adsorbent for environmental remediation of resorcinol.

Toward High Power Generating Piezoelectric Nanofibers: Influence of Particle Size and Surface Electrostatic Interaction of Ce-Fe2O3 and Ce-Co3O4 on PVDF

Development of flexible piezoelectric nanogenerator (PENG) is a real challenge for the next-generation energy-harvesting applications. In this paper, we report highly flexible PENGs based on poly(vinylidene fluoride) (PVDF)/2 wt % Ce-Fe₂O₃ and PVDF/2 wt % Ce-Co₃O₄ nanocomposite fibers. The incorporation of magnetic Ce-Fe₂O₃ and Ce-Co₃O₄ greatly affects the structural properties of PVDF nanofibers, especially the polymeric β and γ phases. In addition, the new composites enhanced the interfacial compatibility through electrostatic filler-polymer interactions. Both PVDF/Ce-Fe₂O₃ and PVDF/Ce-Co₃O₄ nanofibers-based PENGs, respectively, produce peak-to-peak output voltages of 20 and 15 V, respectively, with the corresponding output currents of 0.010 and 0.005 μA/cm² under the force of 2.5 N. Enhanced output performance of the flexible nanogenerator is correlated with the electroactive polar phases generated within the PVDF, in the presence of the nanomaterials. The designed nanogenerators respond to human wrist movements with the highest output voltage of 0.15 V, for the PVDF/Ce-Fe₂O₃ when subjected to hand movements. The overall piezoelectric power generation is correlated with the nanoparticle size and the existing filler-polymer and ion-dipole interactions.

Three-Dimensional Graphene-Carbon Nanotube-Ni Hierarchical Architecture as a Polysulfide Trap for Lithium-Sulfur Batteries

Despite their high energy density and affordable cost compared to lithium-ion (Li-ion) batteries, lithium-sulfur (Li-S) batteries still endure from slow reaction kinetics and capacity loss induced by the insulating sulfur and severe polysulfide diffusion. To address these issues, we report here nickel nanoparticles filled in vertically grown carbon nanotubes (CNTs) on graphene sheets (graphene-CNT-nickel composite (Gr-CNT-Ni)) that are coated onto a polypropylene separator as a polysulfide trap for the construction of high-loading sulfur cathodes. The hierarchical porous framework of Gr-CNT physically entraps and immobilizes the active material sulfur, while the strong chemical interaction with Ni nanoparticles in Gr-CNT-Ni inhibits polysulfide diffusion. The covalently interconnected electron conduction channels and carbon shell-confined metal active sites provide feasible paths for the continual regeneration of active material during the charge-discharge process. Benefitting from these novel morphological and structural features, the Li-S cell with the Gr-CNT-Ni as a polysulfide trap demonstrates high specific capacity and good cycle life. This work provides new avenues for synergistically combining the advantages of hierarchical porous carbon architectures and metal active sites for the development of high-performance cathodes for Li-S batteries.

A novel nonenzymatic hydrogen peroxide amperometric sensor based on Pd@CeO2-NH2 nanocomposites modified glassy carbon electrode

Herein, (3-aminopropyl)triethoxysilane functionalized cerium (IV) oxide (CeO₂-NH₂) supported Pd nanoparticles were synthesized. The nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and High-resolution transmission electron microscopy (HRTEM). The Pd@CeO₂-NH₂ showed better electrocatalytic response to the reduction of H₂O₂ than CeO₂-NH₂. The fabricated sensor exhibited two linear responses to the reduction of H₂O₂. The first one was from 0.001 to 3.276 mM with 0.47 μM of a limit of detection (LOD) (S/N = 3) and excellent sensitivity of 440.72 μA mM^-1 cm^-2 and the second one was from 3.276 to 17.500 mM with the sensitivity of 852.65 μA mM^-1 cm^-2 in the optimum conductions. Also, the sensor exhibited 91% of electrocatalytic activity toward H₂O₂ after having been used for 30 days and the reproducibility was also satisfactory. The sensor response to H₂O₂ was not affected by ascorbic acid, fructose, glycine, dopamine, arginine, mannose, glucose, uric acid, Mg⁺², Ca⁺², and phenylalanine at the studied potential. Also, the fabricated sensor was used to determine H₂O₂ in milk samples. The results show that the constructed sensor can be a promising devise for the determination of H₂O₂ in real samples.

Three-dimensional porous self-assembled chestnut-like nickel-cobalt oxide structure as an electrochemical sensor for sensitive detection of hydrazine in water samples

Three-dimensional NiCo₂O₄ is a kind of superior sensing material owing to its high electron transfer capability, large available surface area and numbers of active sites. In this work, NiCo₂O₄ of the three-dimensional chestnut-like structure were easily achieved through a one step hydrothermal process. Afterwards, the morphology and structure were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Based on the three-dimensional porous chestnut-like NiCo₂O₄, an electrochemical sensor for hydrazine (N₂H₄) detection is fabricated. This electrochemical platform can realize good selectivity, excellent stability, high sensitivity (∼2154.4 μA mM^-1 cm^-2), and low detection limit (0.3 μM), as well as a wide linear range from 1 μM to 1096 μM. The synergistic effect of nickel-cobalt in such mixed transition metal oxides which Co in Co₃O₄ is partially replaced by Ni are beneficial for enhancing sensing properties. This study proves that three-dimensional porous chestnut-like NiCo₂O₄ is electrochemically active for catalytic performance which is particular and promising material for good application in the practical detection of N₂H₄.

Fe2Ni2N nanosheet array: an efficient non-noble-metal electrocatalyst for non-enzymatic glucose sensing

It is very important to develop enhanced electrochemical sensing platforms for molecular detection and non-noble-metal nanoarray architecture, as electrochemical catalyst electrodes have attracted great attention due to their large specific surface area and easy accessibility to target molecules. In this paper, we demonstrate that an Fe₂Ni₂N nanosheet array grown on Ti mesh (Fe₂Ni₂N NS/TM) shows high electrocatalytic activity toward glucose electrooxidation in alkaline medium. As an electrochemical glucose sensor, such an Fe₂Ni₂N NS/TM catalyst electrode demonstrates superior sensing performance with a short response time of less than 5 s, a wide linear range of 0.05 μM-1.5 mM, a low detection limit of 0.038 μM (S/N = 3), a high sensitivity of 6250 μA mM^-1 cm^-2, as well as high selectivity and long-term stability.

A highly sensitive electrochemical immunosensor for hepatitis B virus surface antigen detection based on Hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme-signal amplification

Here we prepared an electrochemical immunosensor employing Au sheet as working electrode, Fe₃O₄ magnetic nanoparticles (MNPs) as supporting matrix and hemin/G-quadruplex DNAzyme as signal amplifier for determination of hepatitis B virus surface antigen (HBsAg). First, the primary antibody of HBs (Ab₁) was immobilized on the surface of the carboxyl-modified MNPs. Then, the assembly of antibody and alkylthiol/G-quadruplex DNA/hemin on gold nanoparticles was used as bio-bar-coded nanoparticle probe. Protein target was sandwiched between the primary antibody of HBs (Ab₁) immobilized on the MNPs and hemin bio-bar-coded AuNPs probe labeled antibody (Ab₂). Hemin/G-quadruplex structure as HRP mimicking-DNAzyme significantly improved the catalytic reduction of H₂O₂ by oxidation of methylene blue (MB). Square wave voltammetry signals of MB provided quantitative measurements of HBsAg with a linear concentration range of 0.3-1000 pgmL^-1 and detection limit of 0.19 pgmL^-1. Due to efficient catalytic activity of HRP mimicking-DNAzyme, the proposed immunosensor exhibited high sensitivity and it holds great promise for clinical application and provides a new platform for immunosensor development and fast disease diagnosis.

Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode

Ultra-fast (∼1 s) and highly sensitive (1889.8 μA mM⁻¹ cm⁻²) enzyme-free glucose biosensing on a unique NiNiO core–shell electrode.

A controllable honeycomb-like amorphous cobalt sulfide architecture directly grown on the reduced graphene oxide–poly(3,4-ethylenedioxythiophene) composite through electrodeposition for non-enzyme glucose sensing

A facile, controllable two-step electrodeposition route was developed, whereby a honeycomb-like amorphous Co_xS_y architecture was obtained via direct growth on rGO–PEDOT/GCE as an electrode for glucose detection.

Ni-Co bimetal nanowires filled multiwalled carbon nanotubes for the highly sensitive and selective non-enzymatic glucose sensor applications

The facile, time and cost efficient and environmental benign approach has been developed for the preparation of Nickel (Ni)-Cobalt (Co) alloy nanowires filled multiwalled carbon nanotubes (MWCNTs) with the aid of mesoporous silica nanoparticles (MSN)/Ni-Co catalyst. The controlled incorporation of Ni-Co nanostructures in the three dimensional (3D) pore structures of MSN yielded the catalytically active system for the MWCNT growth. The inner surface of MWCNTs was quasi-continuously filled with face-centered cubic (fcc) structured Ni-Co nanowires. The as-prepared nanostructures were exploited as non-enzymatic electrochemical sensor probes for the reliable detection of glucose. The electrochemical measurements illustrated that the fabricated sensor exhibited an excellent electrochemical performance toward glucose oxidation with a high sensitivity of 0.695 mA mM^-1 cm^-2, low detection limit of 1.2 μM, a wide linear range from 5 μM-10 mM and good selectivity. The unprecedented electrochemical performances obtained for the prepared nanocomposite are purely attributed to the synergistic effects of Ni-Co nanowires and MWCNTs. The constructed facile, selective and sensitive glucose sensor has also endowed its reliability in analyzing the human serum samples, which wide opened the new findings for exploring the novel nanostructures based glucose sensor devices with affordable cost and good stability.

Unusually Huge Charge Storage Capacity of Mn3O4-Graphene Nanocomposite Achieved by Incorporation of Inorganic Nanosheets

Remarkable improvement in electrode performance of Mn3O4-graphene nanocomposites for lithium ion batteries can be obtained by incorporation of a small amount of exfoliated layered MnO2 or RuO2 nanosheets. The metal oxide nanosheet-incorporated Mn3O4-reduced graphene oxide (rGO) nanocomposites are synthesized via growth of Mn3O4 nanocrystals in the mesoporous networks of rGO and MnO2/RuO2 2D nanosheets. Incorporation of metal oxide nanosheets is highly effective in optimizing porous composite structure and charge transport properties, resulting in a remarkable increase of discharge capacity of Mn3O4-rGO nanocomposite with significant improvement of cyclability and rate performance. The observed enormous discharge capacity of synthesized Mn3O4-rGO-MnO2 nanocomposite (∼1600 mA·h·g(-1) for the 100th cycle) is the highest value among reported data for Mn3O4-rGO nanocomposite. Despite much lower electrical conductivity of MnO2 than RuO2, the MnO2-incorporated nanocomposite at optimal composition (2.5 wt %) shows even larger discharge capacities with comparable rate characteristics compared with the RuO2-incorporated homologue. This finding underscores that the electrode performance of the resulting nanosheet-incorporated nanocomposite is strongly dependent on its pore and composite structures rather than on the intrinsic electrical conductivity of the additive nanosheet. The present study clearly demonstrates that, regardless of electrical conductivity, incorporation of metal oxide 2D nanosheet is an effective way to efficiently optimize the electrode functionality of graphene-based nanocomposites.

Fe3O4@PEG-SO3H rod-like morphology along with the spherical nanoparticles: novel green nanocomposite design, preparation, characterization and catalytic application

A new heterogeneous nanocatalyst was successfully synthesized, completely characterized and efficiently applied in the synthesis of dihydropyrimidines.

Study on the adsorption of Hg(ii) by one-pot synthesis of amino-functionalized graphene oxide decorated with a Fe3O4 microsphere nanocomposite

An easy one-pot solvothermal strategy approach has been reported on the preparation of ethylenediamine (EDA) decorated with magnetite/graphene oxide (EDA–Fe₃O₄/GO) nanocomposites and employed as a recyclable adsorbent for Hg(ii) in aqueous solution.

Vapor grown carbon fiber combined with polyaniline and gold nanoparticles in composite bioelectrodes and their application in glucose fuel cells

In this study, novel VGCF-based composite bioelectrodes PANI/VGCF/GOx and AuNPsNGCF/GOx are fabricated and compared to CNT-based bioelectrodes.

NiO/Ag heterostructure: enhanced UV emission intensity, exchange interaction and photocatalytic activity

The effect of direct Ag coating on the optical and catalytic properties of NiO flake-like structures has been investigated in detail in this work.

Nickel-Cobalt Oxide Decorated Three-Dimensional Graphene as an Enzyme Mimic for Glucose and Calcium Detection

Glucose and calcium ion play key roles in human bodies. The needlelike NiCo2O4 nanostructures are in situ deposited on three-dimensional graphene foam (3DGF) by a facile hydrothermal procedure. The structure and morphology of the hierarchical NiCo2O4/3DGF are characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. With the self-standing NiCo2O4/3DGF as electrochemical electrode, it can realize the high-sensitivity detections for glucose and calcium ion. The limit of detection can reach 0.38 and 4.45 μM, respectively. In addition, the electrochemical electrode presents excellent selectivity for glucose and calcium ion. This study demonstrates that NiCo2O4/3DGF is a unique and promising material for practical application in both glucose and calcium ion sensing.

Design and development of Co3O4/NiO composite nanofibers for the application of highly sensitive and selective non-enzymatic glucose sensors

Cobaltosic oxide/nickel oxide (Co₃O₄/NiO) composite nanofibers were synthesizedviaan electrospinning technique and their electrocatalytic activities toward non-enzymatic glucose sensors were evaluated in detail.