Controlled synthesized of ternary Cu-Co-Ni-S sulfides nanoporous network structure on carbon fiber paper: a superior catalytic electrode for highly-sensitive glucose sensing.

BACKGROUND: Efficient monitoring of glucose concentration in the human body necessitates the utilization of electrochemically active sensing materials in nonenzymatic glucose sensors. However, prevailing limitations such as intricate fabrication processes, lower sensitivity, and instability impede their practical application. Herein, ternary Cu-Co-Ni-S sulfides nanoporous network structure was synthesized on carbon fiber paper (CP) by an ultrafast, facile, and controllable technique through on-step cyclic voltammetry, serving as a superior self-supporting catalytic electrode for the high-performance glucose sensor. RESULTS: The direct growth of free-standing Cu-Co-Ni-S on the interconnected three-dimensional (3D) network of CP boosted the active site of the composites, improved ion diffusion kinetics, and significantly promoted the electron transfer rate. The multiple oxidation states and synergistic effects among Co, Ni, Cu, and S further promoted glucose electrooxidation. The well-architected Cu-Co-Ni-S/CP presented exceptional electrocatalytic properties for glucose with satisfied linearity of a broad range from 0.3 to 16,000 µM and high sensitivity of 6829 µA mM- 1 cm- 2. Furthermore, the novel sensor demonstrated excellent selectivity and storage stability, which could successfully evaluate the glucose levels in human serum. Notably, the novel Cu-Co-Ni-S/CP showed favorable biocompatibility, proving its potential for in vivo glucose monitoring. CONCLUSION: The proposed 3D hierarchical morphology self-supported electrode sensor, which demonstrates appealing analysis behavior for glucose electrooxidation, holds great promise for the next generation of high-performance glucose sensors.

Integration of Triphenylene-Based Conductive Metal-Organic Frameworks into Carbon Nanotube Electrodes for Boosting Nonenzymatic Glucose Sensing.

The rational design and preparation of conductive metal-organic frameworks (MOFs) are alluring and challenging pathways to develop active catalysts toward electrocatalytic glucose oxidation. The hybridization of conductive MOFs with carbon nanotubes (CNTs) in the form of a composite can greatly improve the electrocatalytic performance. Herein, a facile one-step synthetic strategy is utilized to fabricate a Ni3(HHTP)2/CNT (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composite for nonenzymatic detection of glucose in an alkaline solution. The Ni3(HHTP)2/CNT composite, as an electrochemical glucose sensor material, exhibits superior electrocatalytic activity toward glucose oxidation with a wide detection range of up to 3.9 mM, a low detection limit of 4.1 µM (signal/noise = 3), a fast amperometric response time of <2 s, and a high sensitivity of 4774 µA mM-1 cm-2, surpassing the performance of some recently reported nonenzymatic transition-metal-based glucose sensors. In addition, the composite sensor also shows outstanding selectivity, robust long-term electrochemical stability, favorable anti-interference properties, and good reproducibility. This work displays the effectiveness of enhancing the electrocatalytic performance toward glucose detection by combing conductive MOFs with CNTs, thereby opening up an applicable and encouraging approach for the design of advanced nonenzymatic glucose sensors.

Three-dimensional NiO/Co3O4@C composite for high-performance non-enzymatic glucose sensor.

In this study, a new enzyme-free glucose sensor was constructed using the transition metal-based composite material. The synthesis of ZIF-67 entailed the addition of NiO with high catalytic performance. Two-dimensional NiO/Co3O4@C heterojunctions were obtained via pyrolysis of NiO@ZIF-67 in the air at a temperature of 500 â„ƒ. The enzyme-free glucose sensor Nafion/NiO/Co3O4@C/GCE was constructed by modifying NiO/Co3O4@C on a glassy carbon electrode (GCE). The performance of the modified electrode was tested via cyclic voltammetry (CV) and a time-current curve (i-t curve). The linear ranges of the modified electrode were 5 -1000 µM and 1.0- 4.0 mM with sensitivities of 690 and 215.4 µA mM-1 cm-2, respectively. The detection limit was 2.28 µΜ (S/N = 3). The recoveries were in the range of 98.9-99.7% during the detection of real samples. The prepared sensor Nafion/NiO/Co3O4@C/GCE showed excellent electrocatalytic properties with superb reproducibility, stability and anti-interference capability. The sensor has been successfully utilized to determine glucose in real serum samples.

The Facile Preparation of PBA-GO-CuO-Modified Electrochemical Biosensor Used for the Measurement of α-Amylase Inhibitors' Activity.

Element doping and nanoparticle decoration of graphene is an effective strategy to fabricate biosensor electrodes for specific biomedical signal detections. In this study, a novel nonenzymatic glucose sensor electrode was developed with copper oxide (CuO) and boron-doped graphene oxide (B-GO), which was firstly used to reveal rhubarb extraction's inhibitive activity toward α-amylase. The 1-pyreneboronic acid (PBA)-GO-CuO nanocomposite was prepared by a hydrothermal method, and its successful boron doping was confirmed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in which the boron doping rate is unprecedentedly up to 9.6%. The CuO load reaches ~12.5 wt.%. Further electrochemical results showed that in the enlarged cyclic voltammograms diagram, the electron-deficient boron doping sites made it easier for the electron transfer in graphene, promoting the valence transition from CuO to the electrode surface. Moreover, the sensor platform was ultrasensitive to glucose with a detection limit of 0.7 µM and high sensitivity of 906 µA mM-1 cm-2, ensuring the sensitive monitoring of enzyme activity. The inhibition rate of acarbose, a model inhibitor, is proportional to the logarithm of concentration in the range of 10-9-10-3 M with the correlation coefficient of R2 = 0.996, and an ultralow limit of detection of ~1 × 10-9 M by the developed method using the PBA-GO-CuO electrode. The inhibiting ability of Rhein-8-b-D-glucopyranoside, which is isolated from natural medicines, was also evaluated. The constructed sensor platform was proven to be sensitive and selective as well as cost-effective, facile, and reliable, making it promising as a candidate for α-amylase inhibitor screening.

Nonenzymatic Glucose Sensing Using Ni60Nb40 Nanoglass.

Despite being researched for nearly five decades, chemical application of metallic glass is scarcely explored. Here we show electrochemical nonenzymatic glucose-sensing ability of nickel-niobium (Ni60Nb40) amorphous alloys in alkaline medium. Three different Ni60Nb40 systems with the same elemental composition, but varying microstructures are created following different synthetic routes and tested for their glucose-sensing performance. Among melt-spun ribbon, nanoglass, and amorphous-crystalline nanocomposite materials, nanoglass showed the best performance in terms of high anodic current density, sensitivity (20 mA cm-2 mM-1), limit of detection (100 nM glucose), stability, reproducibility (above 5000 cycles), and sensing accuracy among nonenzymatic glucose sensors involving amorphous alloys. When annealed under vacuum, only the heat-treated nanoglass retained a similar electrochemical-sensing property, while the other materials failed to yield desired results. In nanoglass, a network of glassy interfaces, compared to melt-spun ribbon, is plausibly responsible for the enhanced sensitivity.

In-situ facile preparation of highly efficient copper/nickel bimetallic nanocatalyst on chemically grafted carbon nanotubes for nonenzymatic sensing of glucose.

Measuring glucose in a convenient and economical manner is crucial for diabetes diagnostics and surveillance. Ongoing efforts are devoted to nonenzymatic sensors using functional nanomaterials. Drawbacks due to costly and cumbersome process, however, hamper the practicality. Here, we report the facile preparation of Cu/Ni bimetallic nanocatalyst toward glucose electrooxidation. Carboxylated multi-walled carbon nanotubes were chemically grafted onto indium tin oxide glass via silanization reaction and amide coupling reaction, providing distinct nucleation sites for Cu/Ni bimetallic electrocatalyst prepared by in-situ succinct electrodeposition, which synthetically created a three-dimensional electron transfer network. The surface morphology and chemical constituents were characterized by scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy and atomic force microscopy. The prepared electrocatalyst displayed ultrahigh electrochemical activity; the catalytic current density for glucose oxidation was found to be over 6.7 mA mM-1 cm-2. The linear response spanned three orders of magnitude of glucose concentration ranging from 1 µM to 1 mM. Analytical parameters such as accuracy, reproducibility, specificity and stability have also been validated. Importantly, we reveal that Ni plays a dominant role over Cu in electrocatalytic oxidation of glucose, thus bettering our understanding and strategy for nonenzymatic glucose sensor design. Advantages of the glucose sensor presented include easy bulk preparation, low cost, and ready-to-use.

Enzyme-free glucose sensor based on layer-by-layer electrodeposition of multilayer films of multi-walled carbon nanotubes and Cu-based metal framework modified glassy carbon electrode.

A high-performance nonenzymatic glucose sensor was successfully prepared by a layer by layer strategy through electrodeposition assembling multilayer films of Cu-metal-organic frameworks/multi-walled carbon nanotubes (Cu-MOF/MWNTs) modified glassy carbon electrodes (GCE). Different multilayer films of Cu-MOF/MWNTs modified GCE (Cu-MOF/MWNTs/GCE) were prepared by repeating the electrodeposition of MWNTs onto the GCE in an MWNTs solution (MWNTs/GCE) and electrodeposition of the Cu-MOF layer onto the MWNTs film surface to form a Cu-MOF/MWNTs composite layer in the crystallization solution of Cu-MOF. Results confirmed that this method to fabricate multilayer composite films on the GCE was fast and convenient, and that multilayer composite films were stable and unified. The electrode modified by the multilayer composite films could effectively increase the exposure of active sites and increase the surface area of reactive contact. The GCE modified by eight layers (four multilayers Cu-MOF/MWNTs films) showed the optimum catalytic performance in the oxidation of glucose. The novel glucose sensor exhibited a wider detection linear range of 0.5 µM-11.84 mM, with a detection limit of 0.4 µM and a sensitivity of 3878 µA cm-2 mM-1. Moreover, the electrochemical response of the sensor on glucose was fast (within 0.3 s) and stable, exhibited good selectivity and was free of interference.

Co3O4 nanostructures on flexible carbon cloth for crystal plane effect of nonenzymatic electrocatalysis for glucose.

This work accounts the influence of facet effect of Co3O4 nanocrystals towards nonenzymatic electrocatalysis of glucose induced by different crystal planes modified on carbon cloth (CC) electrode. Tuning the molar ratio of precursor compounds during hydrothermal synthesis of Co3O4, followed by thermal decomposition protocols, different crystal structure including nanocubes, nanothorns, nanooctahedrons and nanosheets were obtained with respective {001}, {110}, {111} and {112} facets. The electrochemical results of these different Co3O4 crystals demonstrate that the nanooctahedron with crystal plane of {111} displays the best nonenzymatic electro-catalytic glucose activity with widest linear range (0.5-1000 µM), highest sensitivity (246.8 µA mM-1) and detection limit of 0.012 µM (S/N = 3). Interestingly, the electrocatalytic activity for nonenzymatic electro-catalytic glucose is ranked in the order of {111} > {112} > {110} > {001}.

Multifunctional Nickel Phosphate Nano/Microflakes 3D Electrode for Electrochemical Energy Storage, Nonenzymatic Glucose, and Sweat pH Sensors.

Multifunctional, low-cost electrodes and catalysts are desirable for next-generation electrochemical energy-storage and sensor applications. In this study, we demonstrate the fabrication of Ni3(PO4)2·8H2O nano/microflakes layer on nickel foam (NF) by a facile one-pot hydrothermal approach and investigate this electrode for multiple applications, including sweat-based glucose and pH sensor as well as hybrid energy-storage device, e.g., supercapattery. The electrode displays a specific capacity of 301.8 mAh g-1 (1552 F g-1) at an applied current of 5 mA cm-2 and can retain 84% of its initial capacity after 10 000 cycles. Furthermore, the supercapattery composed of Ni3(PO4)2·8H2O/NF as positive electrode and activated carbon as negative electrode can offer a high specific energy of 33.4 Wh kg-1 with the power of 165.5 W kg-1. As an electrocatalyst for nonenzymatic glucose sensor, Ni3(PO4)2·8H2O/NF shows an exceptional sensitivity (24.39 mA mM-1cm-2) with a low detection limit of 97 nM (S/N = 3). Moreover, as a sweat-based pH sensor, the electrode is capable of detecting human sweat pH values ranging from 4 to 7. Therefore, this three-dimensional nanoporous Ni3(PO4)2·8H2O/NF electrode, due to its excellent electrochemical performance, can be successfully applied in electrochemical energy-storage and biosensor applications.

Nonenzymatic glucose sensor based on Ag&Pt hollow nanoparticles supported on TiO2 nanotubes.

This study was dedicated to develop a nonenzymatic glucose sensor based on Ag&Pt hollow nanoparticles supported on TiO2 nanotubes. The Ag&Pt-TiO2/(500°C) was synthesized by a simple reduction and galvanic replacement method in an aqueous solution. The surface morphology and structure of Ag&Pt-TiO2/(500°C) could be examined by transmission electron microscopy, scanning electron microscopy and energy dispersive spectrometer. The mechanical behavior was measured by nanoindentation test and the hydropathy property was measured by contact angle test. It can be observed that Ag&Pt hollow structures with a particle size of 100nm and a wall thickness of 27nm were deposited on TiO2 nanotubes. The electrochemical properties were investigated by Electrochemical Workstation with three-electrode system. Ag&Pt(6h)-TiO2/(500°C) electrode exhibited excellent catalytic ability from cyclic voltammetry and fast electron transfer rate according to the electron transfer resistance of 330Ω from impedance spectroscopy. Differential pulse voltammetry results showed the sensitivity to glucose was 3.99µA∗cm-2∗mM-1, the linearity increased to 180mM and the detection limit was 22.6µM. The prepared nonenzyme glucose sensor with good analytical performance and simple preparation method looks promising in accurate glucose detection applications.

Eggshell membrane-templated synthesis of 3D hierarchical porous Au networks for electrochemical nonenzymatic glucose sensor.

Sensitive and accurate test of blood glucose levels is necessary to monitor and prevent diabetic complications. Herein, we developed a novel and sensitive non-enzymatic glucose sensing platform by employing 3D hierarchical porous Au networks (HPANs) as electrocatalyst for glucose oxidization. The HPANs were prepared through a bio-inspired synthesis method, in which the natural eggshell membrane (ESM) was introduced as template. The structure and properties of the as-prepared HPANs were characterized by a set of techniques, including scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (XRD) and cyclic voltammetry (CV). The HPANs showed high catalytic activity towards glucose oxidization due to the unique structure. Inspiringly, the HPANs-based electrochemical glucose sensor could be driven at low potential (+0.1V) and showed an outstanding performance for glucose determination with two linear ranges of 1-500µM and 4.0-12mM, a limit of detection (LOD) of 0.2µM (3σ), and fast response time (less than 2s). Moreover, the stability and anti-interference performance of developed sensor was also excellent, enabling its preliminary application in clinical sample (human serum) test. Significantly, this work offered an environmentally friendly method for fabricating 3D nanostructure by using ESM (a biowaste) as template, setting up a typical example for producing new value-added nanomaterials with sensing application.

Vertically Aligned TiO2 Nanotube Arrays Decorated with CuO Mesoclusters for the Nonenzymatic Sensing of Glucose.

Highly ordered titanium dioxide (TiO2) nanotubes were modified with CuO mesoclusters through electrodeposition followed by electrooxidation. Field Emission Scanning Electron Microscopy (FESEM) revealed the presence of vertically aligned TiO2 nanotubes with a diameter of 60 nm and CuO mesoclusters of ~500 nm in diameter. Glucose oxidation on the CuO modified TiO2 electrode occurred at +0.55 V. The electrode exhibited a sensitivity of 1836 and 1416 µA mmol⁻¹ L cm−2 for glucose concentrations ranging from 0.625 to 6.25 mmol L⁻¹ and 6.87 to 12.5 mmol L⁻¹ respectively, a limit of detection of 3.4 µmol L⁻¹ (S/N = 3) and a rapid response time of ≤2 s. Physiological concentrations of ascorbic acid, uric acid and dopamine had no effect on the glucose oxidation. Interference from other sugars (lactose and galactose) was negligible. Result obtained from the estimation of blood glucose was found to be in good agreement with those obtained from commercially available glucose sensor strips.

Self-assembly of palladium nanoparticles on functional TiO2 nanotubes for a nonenzymatic glucose sensor.

Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO2 nanotubes (TiO2 NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at -0.05 V in the presence of 0.1 M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO2 NTs/GCE was electrochemically treated with H2SO4 and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4×10(-7)-8×10(-4)M) with a detection limit of 8×10(-8)M (S/N=3) was obviously good enough for clinical application.

Printing graphene-carbon nanotube-ionic liquid gel on graphene paper: Towards flexible electrodes with efficient loading of PtAu alloy nanoparticles for electrochemical sensing of blood glucose.

The increasing demands for portable, wearable, and implantable sensing devices have stimulated growing interest in innovative electrode materials. In this work, we have demonstrated that printing a conductive ink formulated by blending three-dimensional (3D) porous graphene-carbon nanotube (CNT) assembly with ionic liquid (IL) on two-dimensional (2D) graphene paper (GP), leads to a freestanding GP supported graphene-CNT-IL nanocomposite (graphene-CNT-IL/GP). The incorporation of highly conductive CNTs into graphene assembly effectively increases its surface area and improves its electrical and mechanical properties. The graphene-CNT-IL/GP, as freestanding and flexible substrates, allows for efficient loading of PtAu alloy nanoparticles by means of ultrasonic-electrochemical deposition. Owing to the synergistic effect of PtAu alloy nanoparticles, 3D porous graphene-CNT scaffold, IL binder and 2D flexible GP substrate, the resultant lightweight nanohybrid paper electrode exhibits excellent sensing performances in nonenzymatic electrochemical detection of glucose in terms of sensitivity, selectivity, reproducibility and mechanical properties.

Leaf-templated synthesis of 3D hierarchical porous cobalt oxide nanostructure as direct electrochemical biosensing interface with enhanced electrocatalysis.

A novel three-dimensional (3D) hierarchical porous cobalt oxide (Co3O4) architecture was first synthesized through a simple, cost-effective and environmentally friendly leaf-templated strategy. The Co3O4 nanoparticles (30-100 nm) with irregular shapes were interconnected with each other to form a 3D multilayer porous network structure, which provided high specific surface area and numerous electrocatalytic active sites. Subsequently, Co3O4 was successfully utilized as direct electrochemical sensing interface for non-enzymatic detection of H2O2 and glucose. By using chronoamperometry, the current response of the sensor at +0.31 V was linear with H2O2 concentration within 0.4-200 µM with a low limit of detection (LOD) of 0.24 µM (S/N=3) and a high sensitivity of 389.7 µA mM(-1) cm(-2). Two linear ranges of 1-300 µM (with LOD of 0.1 µM and sensitivity of 471.5 µA mM(-1) cm(-2)) and 4-12.5 mM were found at +0.59 V for glucose. In addition, the as-prepared sensor showed excellent stability and anti-interference performance for possible interferents such as ascorbic acid, uric acid, dopamine, acetaminophen and especially 0.15 M chloride ions. Similarly, other various metal oxide nanostructures may be also prepared using this similar strategy for possible applications in catalysis, electrochemical sensors, and fuel cells.