Significance of nanomaterials in electrochemical glucose sensors: An updated review (2016-2020).

Au and Au-Based nanomaterials: Synthesis and recent progress in electrochemical sensor applications.

Carbon-based quantum particles, especially spherical carbon quantum dots (CQDs) and nanosheets like graphene quantum dots (GQDs), are an emerging class of quantum dots with unique properties owing to their quantum confinement effect. Many reviews appeared recently in the literature highlighting their optical properties, structures, and applications. These papers cover a broad spectrum of carbon-based nanoparticles, excluding a more detailed discussion about some important aspects related to the definition of carbon-based particles and the correlation of optical and electrochemical aspects in relation to sensing and biomedical applications. A large part of this review is devoted to these aspects. It aims, in particular, to act as a bridge between optical and electrochemical aspects of carbon-based quantum particles, both of which are associated with the electronic nature of carbon-based quantum particles. A special focus will be on their use in electroanalysis, notably their benefits in redox, and in electrochemical analysis with emphasis on their application as sensors. Electroanalysis is an easy and cost-effective means of providing qualitative and quantitative information of a specific analyte in solution in a time scale of some minutes. The integration of carbon-based quantum particles into these detection schemes as well as their incorporation into composite nanomaterials have largely improved detection limits with possibilities for their integration in aspects ranging from point-of-care devices to personalized medicine. This review will focus on some of these aspects while also covering the nanomedical aspects of carbon-based quantum particles, ultimately correlated for such developments.

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Carbon-based quantum particles: an electroanalytical and biomedical perspective.

In this study, a simple and rapid analytical method development for ascorbic acid (AA) determination in food samples by using differential pulse voltammetry (DPV) method on ZnO/CNTs nanocomposite ionic liquid modified carbon paste electrode. For this, several parameters, such as ZnO/CNTs nanocomposite, ionic liquid ratio, and pH, have been studied. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgClsat), which corresponded to the oxidation of AA. Compared to common carbon paste electrode, the electrochemical response was greatly improved. Under the optimized conditions, the oxidation peak current of AA showed linear dynamic range 0.1–450 μmol l−1 with a detection limit of 0.07 μmol l−1, using the DPV method. The proposed sensor was successfully applied to the determination of AA in fresh vegetable juice, fruit juices and food supplement samples without previous preparation and was compared with a published electrochemical method.

Application of ZnO/CNTs Nanocomposite Ionic Liquid Paste Electrode as a Sensitive Voltammetric Sensor for Determination of Ascorbic Acid in Food Samples

An overview (with 376 refs.) is given here on the current state of methods for electrochemical sensing of glucose based on the use of advanced nanomaterials. An introduction into the field covers aspects of enzyme based sensing versus nonenzymatic sensing using nanomaterials. The next chapter cover the most commonly used nanomaterials for use in such sensors, with sections on uses of noble metals, transition metals, metal oxides, metal hydroxides, and metal sulfides, on bimetallic nanoparticles and alloys, and on other composites. A further section treats electrodes based on the use of carbon nanomaterials (with subsections on carbon nanotubes, on graphene, graphene oxide and carbon dots, and on other carbonaceous nanomaterials. The mechanisms for electro-catalysis are also discussed, and several Tables are given where the performance of sensors is being compared. Finally, the review addresses merits and limitations (such as the frequent need for working in strongly etching alkaline solutions and the need for diluting samples because sensors often have analytical ranges that are far below the glucose levels found in blood). We also address market/technology gaps in comparison to commercially available enzymatic sensors.

Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

A novel and sensitive non-enzymatic glucose sensor was developed based on the modification of Au@Cu2O nanocomposite on the surface of glassy carbon (Au@Cu2O/Nafion/GC) electrode. Au@Cu2O nanocomposites were prepared using a facile chemical reduction method and its core-shell structure was confirmed by transmission electron microscopy (TEM) and element analyses, in which the diameter of Au nanoparticle (NP) is about 14 nm and the thickness of shell is about 30–50 nm, being composed of Cu2O nanoparticles. Electrochemical properties of Au@Cu2O/Nafion/GC electrode were investigated by cyclic voltammetric techniques and electrochemical impedance spectroscopy (EIS). It was found that the Au@Cu2O/Nafion/GC electrode exhibited enhanced electrocatalytic activity towards glucose oxidation in alkaline medium (pH = 12.6), as compared to those of Cu2O/Nafion/GC and Au/Nafion/GC electrodes. Some influence parameters including pH value and Au@Cu2O content on electrocatalytic activity of the modified electrode have been investigated. Under the optimized conditions, the electrochemical sensor has a linear dependence over glucose concentrations from 0.05 to 2.0 mM with a sensitivity of 715 μA mM−1 Cm−2. Moreover, such a glucose sensor demonstrated good stability, reproducibility and selectivity. Our results suggest that Au@Cu2O core-shell structure could be a promising candidate for the construction of non-enzymatic sensor.

Au@Cu2O core-shell structure for high sensitive non-enzymatic glucose sensor

The authors describe the preparation of amino-functionalized carbon dots (NH2-CDs) via a one-step hydrothermal process using silver nitrate and chitosan as the precursors. The NH2-CDs have a fairly consistent size distribution with an average size of 2.8 ± 0.5 nm. This is attributed to the introduction of Ag(I) both as a catalyst and a precipitant. The NH2-CDs are highly crystalline. Their surface carries amino groups and carboxy groups which is confirmed by transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Horseradish peroxidase (HRP) was immobilized in the NH2-CDs and then placed on a glassy carbon electrode (GCE). Spectroscopic and electrochemical analyses evidenced the stability and good bioactivity of the immobilized HRP. This reveals that NH2-CD is a desirable matrix for enzyme immobilization. The modified GCE exhibits enhanced electro-catalytic activity towards hydrogen peroxide (H2O2) reduction as compared to that of plain CDs. The effects of pH value and loading on the performances of the modified GCEs were studied. Under optimized conditions, the biosensor has a linear response in the 5 to 590 nM H2O2 concentration range, with a 1.8 nM defection limit (at an S/N ratio of 3). The sensor is stable, reproducible and selective. Finally, the sensor was applied to determine H2O2 in real samples, and satisfactory recoveries were achieved.

Immobilization of horseradish peroxidase on amino-functionalized carbon dots for the sensitive detection of hydrogen peroxide.

A new electrochemical sensor has been developed for the simultaneous determination of 4-aminophenol (4-AP) and phenol (Ph) based on the defect-rich hexagonal boron nitride (D-h-BN). The D-h-BN was prepared via one-step calcination route using a single-source precursor. The obtained D-h-BN was structurally characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). Photoluminescent (PL) result suggested that the as-synthesized h-BN was highly defective. More interestingly, such D-h-BN exhibited favorable electrocatalytic activity in the redox reaction of Ph and 4-AP, which was confirmed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements. The enhanced electrocatalytic activity of D-h-BN was attributed to its large surface-active sites and fast electron transfer mediated by defect structure. Thus, D-h-BN was employed to modify glassy carbon electrode (GCE) without any binder agents and the as-fabricated sensor showed good electrochemical performances in the simultaneous determination of 4-AP and Ph. By using DPV method, the linear detection ranges between concentrations and current intensities for 4-AP and Ph were 0.01–30 and 0.1–30 μM, respectively, and their detection limits (S/N = 3) were estimated to be 0.003 and 0.035 μM. Moreover, the desirable selectivity and reproducibility make the proposed method successfully applied for real sample assay.

Yumei Long

Papers

Au@Cu2O core-shell structure for high sensitive non-enzymatic glucose sensor

Immobilization of horseradish peroxidase on amino-functionalized carbon dots for the sensitive detection of hydrogen peroxide.

Defect-rich hexagonal boron nitride for the simultaneous determination of 4-aminophenol and phenol

In situ decoration of Au nanoparticles on carbon nitride using a single-source precursor and its application for the detection of tetracycline.

Carbon-doped h-BN for the enhanced electrochemical determination of dopamine