Synthesis of Co3O4-NiO nano-needles for amperometric sensing of glucose

P-incorporated CuO/Cu2S heteronanorods as efficient electrocatalysts for the glucose oxidation reaction toward highly sensitive and selective glucose sensing

Currently, tremendous efforts have been made to explore efficient glucose oxidation electrocatalysts for enzymeless glucose sensors to meet the urgent demands for accurate and fast detection of glucose in the fields of health care and environmental monitoring. In this work, an advanced nanostructured material based on the well-aligned CuO/Cu2S heteronanorods incorporated with P atoms is successfully synthesized on a copper substrate. The as-synthesized material shows high catalytic behavior accompanied by outstanding electrical conductivity. This, combined with the unique morphology of unstacked nanorod arrays, which endow the entire material with a greater number of exposed active sites, make the proposed material act as a highly efficient electrocatalyst for the glucose oxidation reaction. Density functional theory calculations demonstrate that P doping endows P-doped CuO/Cu2S with excellent electrical conductivity and glucose adsorption capability, significantly improving its catalytic performance. As a result, a non-enzymatic glucose sensor fabricated based on our proposed material exhibits a broad linear detection range (0.02-8.2 mM) and a low detection limit (0.95 μM) with a high sensitivity of 2.68 mA mM-1 cm-2 and excellent selectivity.

Progress on the influence of non-enzymatic electrodes characteristics on the response to glucose detection: a review (2016–2022)

Glucose sensing devices have experienced significant progress in the last years in response to the demand for cost-effective monitoring. Thus, research efforts have been focused on achieving reliable, selective, and sensitive sensors able to monitor the glucose level in different biofluids. The development of enzyme-based devices is challenged by poor stability, time-consuming, and complex purification procedures, facts that have given rise to the synthesis of enzyme-free sensors. Recent advances focus on the use of different components: metal-organic frameworks (MOFs), carbon nanomaterials, or metal oxides. Motivated by this topic, several reviews have been published addressing the sensor materials and synthesis methods, gathering relevant information for the development of new nanostructures. However, the abundant information has not concluded yet in commercial devices and is not useful from an engineering point of view. The dependence of the electrode response on its physico-chemical nature, which would determine the selection and optimization of the materials and synthesis method, remains an open question. Thus, this review aims to critically analyze from an engineering vision the existing information on non-enzymatic glucose electrodes; the analysis is performed linking the response in terms of sensitivity when interferences are present, stability, and response under physiological conditions to the electrode characteristics.

Property and Reactivity Relationships of Co3O4 with Diverse Nanostructures for Soot Oxidation

Cobalt oxide (Co₃O₄) nanostructures with different morphologies (nanocubes, nanoplates, and nanoflowers) were synthesized by a simple hydrothermal method and used for catalytic oxidation of soot particles. Through the study of the physicochemical properties of the catalysts, the key factors affecting the performance of soot oxidation were investigated. The results showed that all three kinds of Co₃O₄ nanocrystals exhibited excellent low-temperature activity in catalytic oxidation of soot, and the Co₃O₄ nanoflowers showed higher oxidation activity of soot compared with Co₃O₄ nanocubes and Co₃O₄ nanoplates, whose T _m was only 370 °C. The excellent activity of Co₃O₄ nanoflowers was due to the large amount of Co³⁺ and lattice oxygen on their surface and highly defective structure, which promoted the adsorption and activation of oxygen species. The large crystallite size and few surface defects were the main reasons for the poor catalytic performance of Co₃O₄ nanocubes. During soot oxidation, the crystallite size of the catalysts and the contact between the catalysts and soot played a significant role in the catalytic performance.

A photoelectrochemical biosensor based on SnO2 nanoparticles for phosphatidylcholine detection in soybean oil

A photoelectrochemical (PEC) biosensor based on SnO₂ nanoparticles (SnO₂ NPs) was developed and applied for phosphatidylcholine (PC) detection in soybean oil. SnO₂ NPs were grown on an indium tin oxide (ITO) electrode, polythionine (PTh) was electropolymerized on the surface of ITO/SnO₂ NPs, and choline oxidase (ChO_x) was immobilized to prepare the ITO/SnO₂ NPs/PTh/ChO_x electrode. The developed PEC biosensor can detect PC under visible light irradiation. The experimental conditions for PC detection were as follows: 1.8 mg mL^-1 ChO_x concentration, 0.5 V bias voltage, 18 mW cm^-2 light intensity, and pH 6. The PEC biosensor had a detection limit of 0.005 mM (S/N = 3) and a detection range from 0.03 mM to 4 mM. This PEC biosensor based on SnO₂ NPs was applied to detect PC in soybean oil. The recovery rate tested by the standard addition method was 95.2-107.4%. These findings were consistent with the results obtained by high-performance liquid chromatography (HPLC). Therefore, the proposed PEC biosensor based on SnO₂ NPs has excellent reproducibility, stability, and great potential applications in the PEC analysis of PC in soybean oil.

Construction of heterojunction photoanode via facile synthesis of CoOx/CN nanocomposites for enhanced visible-light-driven photoelectrochemical degradation of clofibric acid

Visible-light-driven photoelectrocatalytic (PEC) oxidation has been explored extensively to develop highly active materials. Herein, a visible-light-active p-Co₃O₄ and n-g-C₃N₄ heterojunction (CoOx/CN) photoanode, constructed by simple one-pot calcination, was shown to remove clofibric acid (CA) from water through a PEC process. Compared with pristine g-C₃N₄, the optimal photoanode (15%-CoOx/CN) exhibited stable and effective PEC performance and CA degradation performance, a 100-fold enhancement in photocurrent density, and around 1.5-fold decreased efficiency over 6 h. The p-n heterojunctions were shown to increased the charge density and conductivity of g-C₃N₄ for rapid charge transfer. Furthermore, interface contact broadened the visible light absorption and accelerated charge carrier transfer. Notably, the catalysts established p-n heterojunctions, which hindered the bulk recombination of photoinduced carriers and improved the charge separation efficiency. The CoOx/CN photoanodes showed a pair of redox peaks at a potential of 0.3 V vs. Ag/AgCl, indicating good Co₃O₄ redox behavior under alkaline conditions. The 15%-CoOx/CN photoanode displayed excellent PEC performance of up to 0.16 mA cm^-2 in 0.1 M KOH solution at 1.23 V vs. RHE (reversible hydrogen electrode) and long-term stability for up to 12 h. The CoOx/CN photoanodes maintained excellent PEC activities for CA removal, even under acidic and alkaline conditions conditions (pH 3-10). Probable degradation pathway of CA was proposed according to the main degradation intermediates. This study shows that the synergistic effect of p-n heterojunctions in photoelectrodes provides a new approach to the rational application of new photoanode candidates and PEC performance optimization.

Excellent electrochemical stability of Co3O4array with carbon hybridization derived from metal-organic framework

Hybrid supercapacitors have attracted considerable attention for the use in the energy storage systems due to the simultaneous possession of high power and energy. Herein, Co₃O₄array with amorphous carbon on Ni foam has been derived from the Co-MOF. The electrochemical dynamics and energy storage mechanism of the prepared electrode have been investigated, which reveals the enhancement of the capacitive behavior with the scan rate. The electrochemically active specific surface area (ECSA) of our sample is calculated as 1416 cm²for per square centimeter of electrode. The prepared material exhibits an excellent electrochemical performance (3.17 F · cm^-2at 1 mA · cm^-2and 2.076 F · cm^-2at 30 mA · cm^-2). Further, the long-term life shows 96.7% capacity retention at 50 mV · s^-1after 20 000 cycles in KOH aqueous electrolyte. The Coulomb efficiency is noted to range from 95% to 100% even after 20 000 cycles. Further, the symmetrical solid-state supercapacitor represents a wide operating voltage range and high scan rate for practical applications. Three charged solid-state supercapacitors are observed to lit 160 parallel green LEDs (20 mA, 2.2V) for approximately 50 s. These findings from this study confirm the potential of Co₃O₄array with carbon hybridization as an effective supercapacitor electrode material.

Selective determination of epinephrine using electrochemical sensor based on ordered mesoporous carbon / nickel oxide nanocomposite

A nanocomposite of ordered mesoporous carbon/nickel oxide (OMC-NiO) was synthesized by hard-templating method. The nanocomposite remained ordered mesostructure and high surface area with the NiO nanocrystals embedded in the wall of the OMC. A sensitive sensor for electrochemical detection of epinephrine (EP) was developed with GCE modified by OMC-NiO nanocomposite. Cyclic voltammogram (CV) and differential pulse voltammetry (DPV) were used as the techniques to explore the electrochemical behavior of EP on OMC-NiO/GCE surface. The result showed that the electrode demonstrated better electrocatalytic performance to EP compared to that seen at OMC/GCE. Under the optimum condition, DPV measurements of the electrode response displayed a linear detection range for 8.0 × 10^-7 to 5.0 × 10^-5 M with a detection limit of 8.5 × 10^-8 M (S/N = 3). It is worth noting that the electrocatalytic redox mechanism of EP on the electrode have studied through experiments and calculations (cyclic voltammetry and molecular electrostatic potential distribution). Moreover, the electrocatalytic behavior for the oxidation of EP and uric acid (UA) on OMC-NiO/GCE surface was investigated. The result showed that the sensor can be used to selectively determinate EP in the presence of an excesses of UA. Finally, the developed sensor was successfully applied to the determination of EP in spiked human blood serum and EP injection with satisfactory results.

The facile synthesis of a Co3O4-NiNP composite as an electrochemical non-enzymatic sensing platform for small chemical molecules

In this paper, a new Co3O4-Ni nanocomposite-modified glassy carbon electrode (Co3O4-NiNPs/GCE) was successfully constructed and used to detect glucose and hydrogen peroxide (H2O2). The morphologies and structures of the Co3O4 and Co3O4-Ni nanocomposites were characterized via transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The construction process of the modified electrode was characterized via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Co3O4-NiNPs/GCE shows more excellent electrocatalytic activity for the detection of glucose and H2O2 compared with Co3O4/GCE and NiNPs/GCE. The amperometric i-t method was used for the quantitative analysis of glucose and H2O2. The plots of current difference versus concentration of glucose and H2O2 were linear in the range of 0.3-550 μM and 0.5-89 μM, respectively. The corresponding limits of detection (LODs) were 0.086 μM and 0.23 μM for glucose and H2O2, respectively. This recommended sensor was successfully applied for the quantitative analysis of glucose in fruit and H2O2 in water samples.

Enhanced non-enzymatic glucose sensing based on porous ZIF-67 hollow nanoprisms

Porous ZIF-67 hollow nanoprisms based non-enzymatic glucose sensor was successfully prepared using Co₅(OH)₂(OAc)₈·2H₂O as a precursor by a diffusion-controlled strategy, which exhibited wide linear range and high sensitivity.

Interface engineering of Co3O4 nanowire arrays with ultrafine NiO nanowires for high-performance rechargeable alkaline batteries

Interface engineering multi-component core-shell nanostructures with highly efficient and reversible faradaic reactions for energy conversion storage devices is still a challenge. Here, Co₃O₄ nanowires@NiO ultrafine nanowires on Ni foam were well fabricated via coating the NiO ultrafine nanowires on porous Co₃O₄ nanowire arrays. The combination of structural and compositional advantages endows the Co₃O₄@NiO core-shell composites with excellent electrochemical performance, such as a favorable specific capacity of 0.71 mA h cm^-2 at 3 mA cm^-2, excellent rate capability and 85% retention rate up to 10,000 cycles. Rechargeable alkaline batteries with the Co₃O₄@NiO core-shell composites and AC as cathode and anode, respectively, had a high specific capacity of 0.51 mA h cm^-2 and stable cycling ability (81% retention after 5000 cycles). The hierarchical core-shell heterostructure electrode exhibits excellent electrochemical performance, making it a very promising material for next-generation energy storage device applications.

Self-template formation of porous Co3O4 hollow nanoprisms for non-enzymatic glucose sensing in human serum

A novel type of porous Co₃O₄ hollow nanoprism (HNP) was successfully prepared using tetragonal cobalt acetate hydroxide [Co₅(OH)₂(OAc)₈·2H₂O] as precursor by a facile solvothermal process and a subsequent calcination treatment. The morphology and structure of the Co₃O₄ HNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and N₂ adsorption–desorption measurements. An enzyme-free glucose sensor was constructed based on the Co₃O₄ HNPs, and the electrochemical performance was tested by cyclic voltammetry (CV) and chronoamperometry. The as-prepared sensor exhibited a good electrocatalytic activity for glucose oxidation at the applied potential of 0.6 V in alkaline solution, with a high sensitivity of 19.83 μA mM⁻¹ cm⁻² and a high upper limit of 30 mM, which provide the potential for direct determination of blood glucose without any dilution pretreatment. The Co₃O₄ HNPs had a porous and tubular structure with a large amount of accessible active sites, which enhanced the mass diffusion and accelerated the electron transfer. Moreover, the sensor also demonstrated a desirable stability, selectivity and reproducibility, and could verify the non-enzymatic analysis of glucose in real samples.

Co₃O₄ hollow nanoprisms based non-enzymatic glucose sensor were prepared by a self-template process, exhibiting wide linear range, good selectivity and stability, which can directly monitoring blood glucose without any dilution pretreatment.

Label-free electrochemical immunosensor based on biocompatible nanoporous Fe3O4and biotin–streptavidin system for sensitive detection of zearalenone

In this study, a sensitive label-free electrochemical immunosensor was designed based on nanoporous Fe₃O₄and a biotin–streptavidin system to specifically detect zearalenone (ZEN).

A good-performance glucose sensor fabricated via rationally designing a new cobalt–metal–organic framework precursor

A good-performance glucose sensor based on Co₃O₄ has been first synthesized by rationally designing a new cobalt–metal–organic framework precursor.