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(a and b) TEM images of MWCNTs, (c and d) TEM images of Co3O4/MWCNTs composites at various magnifications
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We report the successful formation of cobalt oxide (Co3O4) nanoparticles/multi-walled carbon nanotubes (Co3O4/MWCNTs) composites as efficient electrocatalytic materials for chemical sensing. Co3O4/MWCNTs composites were synthesized via a straightforward hydrothermal treatment and comprehensively characterized. Working as effective electron mediator...
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A comprehensive review of the electroactive materials for non-enzymatic glucose sensing and sensing devices has been performed in this work. A general introduction for glucose sensing, a facile electrochemical technique for glucose detection, and explanations of fundamental mechanisms for the electro-oxidation of glucose via the electrochemical tec...
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... To address this issue, metal oxide (MO) nano particles have been introduced into graphene which will prevent the agglomeration and increases the surface area since it is uniformly distributed on the surface of graphene. 6 It is reported that semiconductor nanoparticles such as NiO, 7 MgO, 8 Co 3 O 4 , 9 MnO, 10 ZnO, 11 and Fe 2 O 3 12 have a great deal of attraction in sensing biomolecules because of its large surface area and excellent electrical conductance. 13 Graphene can easily interact and strongly bind with transition metals and MO/RGO exhibits amazing sensing features and superior electrochemical properties as a result of the synergistic effect between conductive graphene and nano sized transition metal oxide. ...
This paper demonstrates a highly sensitive, selective, biocompatible and cost-effective method for the simultaneous determination of Epinephrine (EPN), Uric acid (UA) and Tyrosine (TYR). Superior electrochemical performance was achieved using ZnO/RGO/CPE modified electrodes compared to individual components, graphene oxide (GO) and ZnO modified electrodes. The electrochemical activity of the fabricated sensor is examined through cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). A sharp increase in anodic peak current and negative shift in the electrode potential upon modification indicates enhanced electrocatalytic activity of ZnO/RGO/CPE. Well distinguishable voltammetric peaks with base-to-base separation and better anodic current were achieved with modified electrode in a mixture of EPN, UA and TYR. The developed sensor exhibits good electrocatalytic activity and an excellent rate of electron transfer arising from the synergistic effect of ZnO and RGO. The detection limit of each biomolecule calculated using DPV is 310 pM for EPN, 340 pM for UA and 730 pM for TYR. The practical feasibility of the proposed sensor is demonstrated by recording satisfactory voltammetric responses in human urine and serum samples.
... Meanwhile, there is no such characteristics peaks were observed in the neutral electrolyte solution (PB solution, pH 7.4) which reveals the essential of OHion for the electrochemical redox reaction of Co 3 O 4 . The redox peaks O I /R I and O II /R II can result from the reversible conversion between Co 3 O 4 and CoOOH (O I /R I ) and further the conversion of CoOOH and CoO 2 (O II /R II ), respectively [28]. These reversible reactions can be expressed as the following equation: ...
An efficient, ease, and environmentally friendly method has been developed using Ocimum tenuiflorum leaf extract as reducing agent to prepare Co3O4 nanorods. The synthesized nanorods have been characterized by using various physicochemical techniques such as XRD, FTIR, TG-DTA, TEM, XPS and evaluated the biological sensing activity of Co3O4/GCE as electrocatalyst against glucose and dopamine etc. Electrochemical measurements reveal that Co3O4/GCE exhibited excellent electrocatalytic activity towards glucose with two different linear counter part, i.e., 200 nM – 110 µM (R² = 0.9996) & 160 µM – 5.91 mM (R² = 0.9873). The developed glucose sensor reveals the lowest limit of detection level and sensitivity of glucose is about 50 nM and 1301.39 µAmM–1cm⁻², respectively in short response time. The Co3O4/GCE sensor also exhibited electrocatalytic activity towards dopamine with wide response range of 500 nM to 407 µM with the correlation coefficient of R² = 0.9939 and the sensitivity of Co3O4/GCE calculated to 0.24 µAµM⁻¹cm⁻² and the sensor exhibits the detection limit to dopamine around 240 nM. The cobalt oxide nanorods show more potent fungal activity towards the Aspergillus niger and Candida albicans as the standard used.
... Number of electrons (n) involved in the electrochemical reaction is another important parameter that determines the CC oxidation rate. Henceforth, Randles-Sevcik relation [34] presented in Eq. (4) has been employed to calculate the n value. ...
Herein, we report the one-pot synthesis of WO3/RGO composite and its efficient electrochemical activity in catechol (CC) oxidation. Anchoring of 1-D WO3 microrods on 2-D RGO nanosheets were confirmed through the detailed physicochemical analyses (XRD, FESEM, XPS, Raman). Availability of large electrocatalytically active surface area yields the conductivity enrichment as well as significantly improved redox properties in WO3/RGO composite. Further, a 20-fold intensified oxidation signal in CV and a 4-fold increased sensitivity from differential pulse voltammetry (DPV) support the superior electron transfer rate at the surface of WO3/RGO composite. Oxidation of CC involving the transfer of two electrons via a diffusion controlled process was revealed by the electrochemical approaches. From density functional theory (DFT) simulations, the charge transfer from O 2p orbital of catechol to W 4d orbital of WO3 facilitate the oxidation of catechol molecule. Z-scan study explored the strong reverse saturable absorption at 532 nm excitation and the third-order nonlinear optical susceptibility χ⁽³⁾ of 9.727 x 10⁻⁸ esu was obtained for WO3/RGO. Hence, the hydrothermally prepared WO3/RGO composite with its excellent redox properties and negative nonlinearity could be a competent material to use in electrochemical sensing and optical limiting.
... Our previous work showed that the electrode reaction constant rate (Ks) of bare chrysanthemum-like Co 3 O 4 /GCE was quite low. With introduction of conducting materials, such as MWCNTs, the Ks of Co 3 O 4 /MWCNTs/GCE could be improved [13]. To further enhance the electrochemical performances of Co 3 O 4 during hydrazine detection and meantime insure the quickness of Co 3 O 4 based hydrazine sensor, it's necessary to take measure to improve the Ks value of Co 3 O 4 based electrode. ...
... Blood glucose concentration is commonly used as a marker in clinical diagnosis, which is of great significance to the evaluation of a person's health status [3]. So far, there have been many reports on the determination of blood glucose, including electrochemical analysis [4,5], electrochemiluminescence [6][7][8], chemiluminescence [9][10][11], surface-enhanced Raman scattering [12][13][14], etc. These methods generally have high sensitivity, but usually require specific instruments and equipment, which undoubtedly limits their potential. ...
A novel colorimetric and ratiometric fluorescence sensor was constructed by using carbon quantum dots (CQDs) and o-diaminobenzene (ODB). Unlike ODB by itself, ODB oxide (oxODB) not only emits fluorescence, but also produces ultraviolet (UV) absorption. Therefore, on the basis of the potential optical properties of ODB, glucose oxidase (Gox) and horseradish peroxidase (HRP) were introduced into a CQDs–ODB system for the quantitative oxidation of ODB. When glucose is present, it is oxidized by oxygen under the catalytic action of its oxidase to form hydrogen peroxide. Hydrogen peroxide is a strong oxidant that can rapidly oxidize ODB through the catalysis of horseradish peroxidase. oxODB can cause changes in the fluorescence ratio (I550/I446) and absorbance ratio (A/A0). At the same time, the color of the detection solution can also change under sunlight and ultraviolet lamps. Therefore, glucose can be quantitatively detected by ratiometric fluorescence and colorimetry simultaneously, and semi-quantitatively detected by observing the colors with sunlight and ultraviolet lamps of 365 nm. This increases not only the convenience but also the accuracy of detection. In addition, this sensor has good selectivity and can be used for the determination of glucose in serum, providing a new idea for the development of blood glucose sensors.
The development and utilization of biosensors have received a great attention from the scientific community due to their wide applications in the areas of food safety, medical diagnosis, environmental monitoring and other fields. In this paper, we report the development of a novel photoelectrochemical (PEC) sensor for glucose detection using a flexible carbon fiber/TiO 2 nanopillars electrode. The carbon fiber/TiO 2 nanopillars was prepared by two step process in which the first step is to grow TiO 2 seeds over carbon fiber by magnetron sputtering while the second step leads the growth of TiO 2 nanopillars over flexible carbon fibers substrate. Under photoexcitation, the PEC sensor showed a significant enhancement in the sensitivity for glucose detection. The detection mechanism was based on the photoelectrochemical oxidation of glucose to gluconic acid, which generated an electrical signal that was proportional to the glucose concentration. The electrochemical examinations were performed at low glucose concentrations in the range of 1–5 mM (mmol L ⁻¹ ) to investigate the corresponding photocurrent. The results showed that the photocurrent increases with increasing the glucose concentration. This is of great significance for the detection of hypoglycemia, and has good application prospects in the fields of nano-detection, biological diagnosis and wearable devices. The flexible carbon fiber/TiO 2 PEC sensor developed in this study is a promising approach for the development of wearable devices for continuous glucose monitoring.
This study presents an electrochemical sensor for detecting epicatechin (EC) in food samples (dark chocolate and apple) using cobalt oxide (Co3O4) synthesized from Carica papaya peel extract combined with multiwalled carbon nanotubes (GCE/MWCNTs/Co3O4), doped onto glassy carbon electrode. Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to examine the structural, morphological, and electrochemical properties of the electrode materials. The GCE/MWCNTs/Co3O4 electrode demonstrated excellent electron transport properties as well as excellent electrocatalytic activity towards EC, with a Rct value of 4.74 kΩ lower than that of the bare electrode. A detection limit of 0.12 µM and a sensitivity of 0.0837 µA/µM were obtained using square wave voltammetry (SWV) for EC concentrations between 47.6 - 310.3 µM. The designed sensor demonstrated good repeatability, stability, reproducibility, selectivity, and excellent recoveries (90-108%) with RSDs ranging from 0.46 to -2.52 for the detection of EC in food samples. Further, the EC's energy band gap (- 5.15 eV) and absolute hardness (- 2.57 eV) calculated at the density functional theory (DFT) level, indicate its strong chemical reactivity. Finally, the computed Monte Carlo adsorption energy confirms the strong electrostatic interaction between the surface of the GCE/MWCNTs and the Co3O4 NPs, thus contributing to the selectivity of EC detection, demonstrating the potential applications for the designed sensor in the food industry.
