Highly exposed copper oxide supported on three-dimensional porous reduced graphene oxide for non-enzymatic detection of glucose

Designing Nanocomposite-Based Electrochemical Biosensors for Diabetes Mellitus Detection: A Review

This review will unveil the development of a new generation of electrochemical sensors utilizing a transition-metal-oxide-based nanocomposite with varying morphology. There has been considerable discussion on the role of transition metal oxide-based nanocomposite, including iron, nickel, copper, cobalt, zinc, platinum, manganese, conducting polymers, and their composites, in electrochemical and biosensing applications. Utilizing these materials to detect glucose and hydrogen peroxide selectively and sensitively with the correct chemical functionalization is possible. These transition metals and their oxide nanoparticles offer a potential method for electrode modification in sensors. Nanotechnology has made it feasible to develop nanostructured materials for glucose and H2O2 biosensor applications. Highly sensitive and selective biosensors with a low detection limit can detect biomolecules at nanomolar to picomolar (10-9 to 10-12 molar) concentrations to assess physiological and metabolic parameters. By mixing carbon-based materials (graphene oxide) with inorganic nanoparticles, nanocomposite biosensor devices with increased sensitivity can be made using semiconducting nanoparticles, quantum dots, organic polymers, and biomolecules.

A sensitive and facile electrochemical paper-based sensor for glucose detection in whole blood using the Pd/CB-Ni@rGO modified electrode

We created novel Pd/CB-Ni@rGO nanomaterials for glucose detection. The as-synthesized nanomaterials were dropped on the electrode surface using the drop casting technique. The prepared electrode was then attached to a paper-based device containing the sample zone and the reaction zone, enabling plasma isolation and an enzymatic reaction for glucose detection in whole blood. The nanomaterials and surfaces of electrodes were characterized by FTIR, TEM, and SEM. The proposed approach is a disposable glucose detection method that is unaffected by protein fouling on the electrode, and it requires only one drop of human blood. Therefore, there is no need for extensive sample preparation, and there is less sample consumption. Under optimal conditions, Pd/CB-Ni@rGO can accurately measure blood glucose levels with a linear range of 7 to 7140 μM (R2 = 0.9986) and a low detection limit of 0.82 μM. Besides, the developed sensor shows excellent anti-interference capacity, stability, and satisfactory reproducibility and repeatability. Importantly, Pd/CB-Ni@rGO was successfully applied for glucose in whole blood from 4 volunteers, with results that correlated well with those obtained using an Accucheck glucometer at a 95% confidence level. Given its low cost, high accuracy, and ease of use, the blood glucose sensor holds significant potential for clinical use and broadens the area of future noninvasive sensor development.

Porous nitrogen-doped reduced graphene oxide-supported CuO@Cu2O hybrid electrodes for highly sensitive enzyme-free glucose biosensor

Constructing high-performance enzyme-free biosensors for detecting glucose is essential to preliminary diabetes diagnosis. Here, copper oxide nanoparticles (CuO@Cu₂O NPs) were anchored in porous nitrogen-doped reduced graphene oxide (PNrGO) to construct CuO@Cu₂O/PNrGO/GCE hybrid electrode for sensitive detection of glucose. Benefiting from the remarkable synergistic effects between the multiple high activation sites of CuO@Cu₂O NPs and the dramatic properties of PNrGO with excellent conductivity and large surface area with many accessible pores, the hybrid electrode possesses outstanding glucose sensing performance that is far superior to those of pristine CuO@Cu₂O electrode. The as-fabricated enzyme-free glucose biosensor displays prominent glucose sensitivity of 2,906.07 μA mM^-1 cm^-2, extremely low limit of detection of 0.13 μM, and wide linear detection of 3 μM-6.772 mM. In addition, excellent reproducibility, favorable long-term stability, and distinguished selectivity are obtained in the glucose detection. Importantly, this study provides promising results for continuous improvement of non-enzyme sensing applications.

Screen-Printed Carbon Electrodes with Macroporous Copper Film for Enhanced Amperometric Sensing of Saccharides

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L⁻¹ and 4.0–100 μmol L⁻¹) with detection limits of 0.1 μmol L⁻¹ glucose, 0.03 μmol L⁻¹ fructose, and 0.05 μmol L⁻¹ sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability.

Cost Effective Synthesis of Graphene Nanomaterials for Non-Enzymatic Electrochemical Sensors for Glucose: A Comprehensive Review

The high conductivity of graphene material (or its derivatives) and its very large surface area enhance the direct electron transfer, improving non-enzymatic electrochemical sensors sensitivity and its other characteristics. The offered large pores facilitate analyte transport enabling glucose detection even at very low concentration values. In the current review paper we classified the enzymeless graphene-based glucose electrocatalysts' synthesis methods that have been followed into the last few years into four main categories: (i) direct growth of graphene (or oxides) on metallic substrates, (ii) in-situ growth of metallic nanoparticles into graphene (or oxides) matrix, (iii) laser-induced graphene electrodes and (iv) polymer functionalized graphene (or oxides) electrodes. The increment of the specific surface area and the high degree reduction of the electrode internal resistance were recognized as their common targets. Analyzing glucose electrooxidation mechanism over Cu- Co- and Ni-(oxide)/graphene (or derivative) electrocatalysts, we deduced that glucose electrochemical sensing properties, such as sensitivity, detection limit and linear detection limit, totally depend on the route of the mass and charge transport between metal(II)/metal(III); and so both (specific area and internal resistance) should have the optimum values.

Non-Enzymatic Glucose Sensors Involving Copper: An Electrochemical Perspective

Non-enzymatic glucose sensors based on the use of copper and its oxides have emerged as promising candidates to replace enzymatic glucose sensors owing to their stability, ease of fabrication, and superior sensitivity. This review explains the theories of the mechanism of glucose oxidation on copper transition metal electrodes. It also presents an overview on the development of among the best non-enzymatic copper-based glucose sensors in the past 10 years. A brief description of methods, interesting findings, and important performance parameters are provided to inspire the reader and researcher to create new improvements in sensor design. Finally, several important considerations that pertain to the nano-structuring of the electrode surface is provided.

Sensitive and Enzyme-Free Glucose Sensor Based on Copper Nanowires/Polyaniline/Reduced Graphene Oxide Nanocomposite Ink

In this paper, we report the preparation and characterization of a sensitive and reusable nonenzymatic glucose (NEG) sensor based on copper nanowires (CuNWs)/polyaniline (PANI)/reduced graphene oxide (rGO) nanocomposite ink. The CuNWs/PANI/rGO nanocomposite ink was prepared by solvothermal mixing of CuNWs, PANI, rGO and binders. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infra-Red (FT-IR) spectroscopy techniques were used to assess the structural and morphological parameters of prepared nanocomposite ink. The cyclic voltammetry (CV) technique was used to estimate the electrochemical behavior of prepared NEG sensor. The structural, morphological and spectroscopy results confirmed the change in morphological and oxidation state of CuNWs to CuO nanostructures as a constituent of nanocomposite ink. The CuO nanostructures supported on PANI/rGO demonstrated good electrochemical stability and great electrocatalytic activity toward glucose oxidation. At a glucose oxidation potential of 0.64V, the prepared NEG sensor exhibited great electrocatalytic ability by offering a high sensitivity of 843.06[Formula: see text]AmM[Formula: see text]cm[Formula: see text] in the linear glucose range 0–4mM with a lower detection limit of 1.6mM. In addition to these outstanding performance characteristics, CuNWs/PANI/rGO nanocomposite ink-based NEG sensor has the advantages of ease of fabrication, low cost and reusability.

Shape-controlled Cu2O nanospheres as bifunctional catalysts boosting the oxidations of glucose and hydrazine

Cuprous oxide (Cu2O) nanoparticles hold promise as low-cost catalysts for the oxidations of both glucose and hydrazine (N2H4). The shape-controlled growth of Cu2O crystals can regulate effectively its catalytic activities.

Construction of a selective non-enzymatic electrochemical sensor based on hollow nickel nanospheres/carbon dots–chitosan and molecularly imprinted polymer film for the detection of glucose

A non-enzymatic glucose electrochemical sensor platform was fabricated by assembling hollow nickel nanospheres/carbon dots–chitosan and molecularly imprinted polymer film modified a glass carbon electrode.

Metal-Organic-Framework FeBDC-Derived Fe3O4 for Non-Enzymatic Electrochemical Detection of Glucose

Present-day science indicates that developing sensors with excellent sensitivity and selectivity for detecting early signs of diseases is highly desirable. Electrochemical sensors offer a method for detecting diseases that are simpler, faster, and more accurate than conventional laboratory analysis methods. Primarily, exploiting non-noble-metal nanomaterials with excellent conductivity and large surface area is still an area of active research due to its highly sensitive and selective catalysts for electrochemical detection in enzyme-free sensors. In this research, we successfully fabricate Metal-Organic Framework (MOF) FeBDC-derived Fe₃O₄ for non-enzymatic electrochemical detection of glucose. FeBDC synthesis was carried out using the solvothermal method. FeCl₂.4H₂O and Benzene-1,4-dicarboxylic acid (H₂BDC) are used as precursors to form FeBDC. The materials were further characterized utilizing X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The resulting MOF yields good crystallinity and micro-rod like morphology. Electrochemical properties were tested using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) with a 0.1 M of Phosphate Buffer Saline (PBS pH 7.4) solution as the supporting electrolyte. The measurement results show the reduction and oxidation peaks in the CV curve of FeBDC, as well as Fe₃O₄. Pyrolysis of FeBDC to Fe₃O₄ increases the peak of oxidation and reduction currents. The Fe₃O₄ sample obtained has a sensitivity of 4.67 µA mM⁻¹.cm⁻², a linear range between 0.0 to 9.0 mM, and a glucose detection limit of 15.70 µM.

A Brief Description of Cyclic Voltammetry Transducer-Based Non-Enzymatic Glucose Biosensor Using Synthesized Graphene Electrodes

The essential disadvantages of conventional glucose enzymatic biosensors such as high fabrication cost, poor stability of enzymes, pH value-dependent, and dedicated limitations, have been increasing the attraction of non-enzymatic glucose sensors research. Beneficially, patients with diabetes could use this type of sensor as a fourth-generation of glucose sensors with a very low cost and high performance. We demonstrate the most common acceptable transducer for a non-enzymatic glucose biosensor with a brief description of how it works. The review describes the utilization of graphene and its composites as new materials for high-performance non-enzymatic glucose biosensors. The electrochemical properties of graphene and the electrochemical characterization using the cyclic voltammetry (CV) technique of electrocatalysis electrodes towards glucose oxidation have been summarized. A recent synthesis method of the graphene-based electrodes for non-enzymatic glucose sensors have been introduced along with this study. Finally, the electrochemical properties such as linearity, sensitivity, and the limit of detection (LOD) for each sensor are introduced with a comparison with each other to figure out their strengths and weaknesses.

Recent advances in electrochemical non-enzymatic glucose sensors - A review

This review encompasses the mechanisms of electrochemical glucose detection and recent advances in non-enzymatic glucose sensors based on a variety of materials ranging from platinum, gold, metal alloys/adatom, non-precious transition metal/metal oxides to glucose-specific organic materials. It shows that the discovery of new materials based on unique nanostructures have not only provided the detailed insight into non-enzymatic glucose oxidation, but also demonstrated the possibility of direct detection in whole blood or interstitial fluids. We critically evaluate various aspects of non-enzymatic electrochemical glucose sensors in terms of significance as well as performance. Beyond laboratory tests, the prospect of commercialization of non-enzymatic glucose sensors is discussed.

Galvanostatic electrodeposition of copper nanoparticles on screen-printed carbon electrodes and their application for reducing sugars determination

In this work, a novel method for the galvanostatic electrodeposition of copper nanoparticles on screen-printed carbon electrodes was developed. Nanoparticles of spherical morphology with sizes between 60 and 280nm were obtained. The electrocatalytic effect of these copper nanospheres towards the oxidation of different sugars was studied. Excellent analytical performance was obtained with the nanostructured sensor: low detection limits and wide linear ranges (1-10,000µM) were achieving for the different reducing sugars evaluated (glucose, fructose, arabinose, galactose, mannose, xylose) with very similar calibration slopes, which demonstrates the possibility of total sugar detection. The reproducibility of these sensors was 4.4% (intra-electrode) and 7.2% (inter-electrode). The stability of the nanostructured electrodes was at least 30 days, even using the same device on different days. Several real samples (honey, orange juice and normal and sugar-free soft drinks) were evaluated to study the reliability of the nanostructured sensor.

Free-Standing Networks of Core-Shell Metal and Metal Oxide Nanotubes for Glucose Sensing

Nanotube assemblies represent an emerging class of advanced functional materials, whose utility is however hampered by intricate production processes. In this work, three classes of nanotube networks (monometallic, bimetallic, and metal oxide) are synthesized solely using facile redox reactions and commercially available ion track membranes. First, the disordered pores of an ion track membrane are widened by chemical etching, resulting in the formation of a strongly interconnected pore network. Replicating this template structure with electroless copper plating yields a monolithic film composed of crossing metal nanotubes. We show that the parent material can be easily transformed into bimetallic or oxidic derivatives by applying a second electroless plating or thermal oxidation step. These treatments retain the monolithic network structure but result in the formation of core-shell nanotubes of altered composition (thermal oxidation: Cu₂O-CuO; electroless nickel coating: Cu-Ni). The obtained nanomaterials are applied in the enzyme-free electrochemical detection of glucose, showing very high sensitivities between 2.27 and 2.83 A M^-1 cm^-2. Depending on the material composition, varying reactivities were observed: While copper oxidation reduces the response to glucose, it is increased in the case of nickel modification, albeit at the cost of decreased selectivity. The performance of the materials is explained by the network architecture, which combines the advantages of one-dimensional nano-objects (continuous conduction pathways, high surface area) with those of a self-supporting, open-porous superstructure (binder-free catalyst layer, efficient diffusion). In summary, this novel synthetic approach provides a fast, scalable, and flexible route toward free-standing nanotube arrays of high compositional complexity.

Recent advancements, key challenges and solutions in non-enzymatic electrochemical glucose sensors based on graphene platforms

This review elucidates the recent advances in graphene platforms in electrochemical non-enzymatic glucose sensors and provides solutions for existing bottlenecks.

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.

Advanced Mesoporous Spinel Li4Ti5O12/rGO Composites with Increased Surface Lithium Storage Capability for High-Power Lithium-Ion Batteries

Spinel Li4Ti5O12 (LTO) and reduced graphene oxide (rGO) are attractive anode materials for lithium-ion batteries (LIBs) because of their unique electrochemical properties. Herein, we report a facile one-step hydrothermal method in preparation of a nanocomposite anode consisting of well-dispersed mesoporous LTO particles onto rGO. An important reaction step involves glucose as a novel linker agent and reducing agent during the synthesis. It was found to prevent the aggregation of LTO particles, and to yield mesoporous structures in nanocomposites. Moreover, GO is reduced to rGO by the hydroxyl groups on glucose during the hydrothermal process. When compared to previously reported LTO/graphene electrodes, the newly prepared LTO/rGO nanocomposite has mesoporous characteristics and provides additional surface lithium storage capability, superior to traditional LTO-based materials for LIBs. These unique properties lead to markedly improved electrochemical performance. In particular, the nanocomposite anode delivers an ultrahigh reversible capacity of 193 mA h g(-1) at 0.5 C and superior rate performance capable of retaining a capacity of 168 mA h g(-1) at 30 C between 1.0 and 2.5 V. Therefore, the newly prepared mesoporous LTO/rGO nanocomposite with increased surface lithium storage capability will provide a new opportunity to develop high-power anode materials for LIBs.

Advances in non-enzymatic glucose sensors based on metal oxides

This review summarizes the advances in non-enzymatic glucose sensors based on different metal oxides (ZnO, CuO/Cu₂O, NiO,etc.) and their composites.