Synergistic coupling of NiCo2O4 nanorods onto porous Co3O4 nanosheet surface for tri-functional glucose, hydrogen-peroxide sensors and supercapacitor

Recent progress in nanomaterial-based electrochemical biosensors for hydrogen peroxide detection & their biological applications

The electrochemical biosensor has brought a paradigm shift in the field of sensing due to its fast response and easy operability. The performance of electrochemical sensors can be modified by coupling them with various metal oxides, nanomaterials, and nanocomposites. Hydrogen peroxide is a short-lived reactive oxygen species that plays a crucial role in various physiological and biological processes. Therefore, its monitoring is of paramount importance. With this, the research fraternity has developed various nanomaterial-based superlative sensors that have enhanced the sensing performance towards H2O2 in terms of sensitivity, detection limit, and linear range. The integration of nanocomposite materials has allowed for the synergistic combination of different components, leading to improved sensor stability, selectivity, and detection limits. The precious metal alloys, metal oxides, semiconductor nanomaterials, carbon cloth, multi-walled carbon nanotubes, graphene oxide, and nanoparticles demonstrate effective catalytic performance for detecting H2O2 electrochemically. These advanced materials possess extraordinary properties and structures, rendering them highly advantageous for diverse applications. These biosensors aid in monitoring H2O2 levels secreted by MCF-7, HeLa cells, NIH-3T3, and A549 cells in real-time. Further, this type of biosensor identified alterations in H2O2 levels in the lungs, bronchoalveolar lavage fluid (BALF) of mice with pulmonary fibrosis, activated hepatic stellate cells, and the livers of mice with liver fibrosis. The current review highlights the recent advancements in compositions, morphology, limit of detection, sensitivity, biological applications, etc. properties of the electrochemical biosensors for H2O2 detection.

Constructing Co3O4 Nanowire@NiCo2O4 Nanosheet Hierarchical Array as Electrode Material for High-Performance Supercapacitor

The Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo2O4 nanosheet could self-assemble on the Co3O4 nanowire. The structure and morphology of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge-discharge, charge-discharge cycle, and electrochemical impedance and then compared with the Co3O4 nanowire. The results show that the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could reach a high value of 2034 F g-1 at a current density of 2.5 A g-1. After 5000 galvanostatic charge-discharge cycles, the specific capacitance of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor.

Electrochemical and Photoelectrochemical Detection of Hydrogen Peroxide Using Cu2O/Cu Nanowires Decorated with TiO2-x Deriving from MXenes

H₂O₂ is a major transmitter of redox signals in electrochemical processes, whose detection is relevant for various industries. Herein, we developed a new fabrication method for a Cu₂O/Cu nanowire-based nonenzymatic H₂O₂ electrochemical sensor that was decorated with irregular TiO_2-x nanoparticles deriving form Ti₃C₂ MXene. The TiO_2-x/Cu₂O/Cu-NW electrodes possess excellent selectivity, stability, and reproducibility for H₂O₂ detection in both EC and PEC operational modes. In the EC detection of H₂O₂, the TiO_2-x/Cu₂O/Cu-NW electrode shows a linear relationship in the range from 10 μM to 42.19 mM and a low detection limit of 0.79 μM (S/N = 3), which has a similar sensitivity but a much broader linear range compared with the commercial H₂O₂ analyzer (0-5.88 mM, Q45H/84, US-QContums). It also shows excellent recovery in detecting H₂O₂ in the real orange juice and milk samples with the recovery ranging from 96.9 to 105%, indicating the potential for practical applications. In the PEC detection of H₂O₂, the TiO_2-x/Cu₂O/Cu-NW electrode shows a lower detection limit of 59 nM (S/N = 3), which is 13 times more sensitive than the EC electrode. The enhanced PEC performance can be attributed to the formation of p-n heterojunction between TiO_2-x and Cu₂O, which improves light utilization and inhibits the recombination of photo-induced electrons and holes. This work illuminates the extraordinary potential of MXene-derived TiO₂ in electrochemical and photoelectrochemical applications.

Fabrication of platinum-doped NiCo2O4 nanograss modified electrode for determination of carbendazim

In this study, a platinum-doped nickel cobaltite nanograss (Pt-doped NiCo₂O₄ NG) with its own unique structural features was initially synthesized, utilizing a simple hydrothermal method and then applied as a novel platform for the detection of carbendazim (C₉H₉N₃O₂; CBZ). To this end, the CBZ electrochemical signals were evaluated by means of differential pulse voltammetry (DPV), demonstrating the acceptable catalytic effect of the Pt-doped NiCo₂O₄ NG/screen-printed electrode (SPE) on the CBZ oxidation signal. Under the optimized conditions, CBZ was subsequently quantified by the Pt-doped NiCo₂O₄ NG/SPE with a wide linear range (0.03-140 μM) and a low limit of detection (LOD) value (0.005 μM). The proposed sensor was thus characterized by good anti-interference ability, selectivity, and stability. The analysis of the real samples, viz. tomato and lettuce, also confirmed that the given sensor had good recoveries and relative standard deviation (RSD). Ultimately, a comparison between liquid chromatography-mass spectrometry (LC-MS) and this method established no significant difference in the results.

Well-designed sophisticated structure of sandwich-like CC@NiAl-LDH@GO@NiCo-LDH material with unique advantages for high performance and practicality hybrid quasi-solid-state supercapacitors

A sandwich-like flexible architecture electrode material composed of NiAl-LDH nanoplates grown on carbon cloths (CC), coupled with GO interlayer and NiCo-LDH nanowire on the interlayer was successfully assembled via hydrothermal and chemical bath deposition (denoted as CC@NiAl-LDH@GO@NiCo-LDH). The promising combination of NiAl-LDH, graphene and NiCo-LDH forming a multilayer structure through electrostatic absorption and in-situ growth process which endow a high mass loading superiority and synergistic effect for supercapacitors. In addition, the interspace inside the sandwich-like architecture constructed by the graphene and the NiAl-LDH/ NiCo-LDH nano-flakes contribute to alleviate of the volume expansion during the cycling process and promote the diffusion rate of ions. The CC@NiAl-LDH@GO@NiCo-LDH material demonstrates excellent electrochemical performance which exhibit remarkable specific capacitance of 2359.8F·g^-1 (14.2F·cm^-2) at 1 A·g^-1 (6 mA·cm^-2) and outstanding capacitance retentions of 93.1% after 1500 cycles. Subsequently, the CC@NiAl-LDH@GO@NiCo-LDH material was used as cathode material to fabricate a hybrid quasi-solid-state supercapacitor that exhibits a high energy density of 52.0 Wh·kg^-1 at 796.7 W·kg^-1 and 38.4 Wh·kg^-1 at 12015 W·kg^-1, revealing its potential and viability for commercial applications. Furthermore, the hybrid quasi-solid-state supercapacitor can be applied under different extreme operating conditions such as bending, twisting, sour/alkali soaking, ice bathing, warm bathing, hammering and cutting conditions. It is predictable that the unique sandwich-like structure will be an extremely promising electrode material for high-performance supercapacitors.

Nanosized CuO encapsulated Ni/Co bimetal Prussian blue with high anti-interference and stability for electrochemical non-enzymatic glucose detection

Non-enzymatic glucose sensors based on metal oxides are receiving remarkable attention owing to their outstanding characteristics of being easy-to use, low cost, and reusability. However, the disadvantage of weak anti-interference associated with poor selectivity significantly restricts their applicability. Herein, we report a two-step in situ fabrication of nanosized CuO encapsulated Ni/Co bimetal Prussian blue (PB) with a typical core-shell structure, which can be efficiently used for non-enzymatic glucose detection, ascribing to the permeability and abundant active sites of out-shelled crystalline porous Ni/Co PB and the high catalytic activity and conductivity of embedded CuO nanoparticles, afforded by their mutual synergistic interactions. The glassy carbon electrode modified with the hybrid of the CuO-encapsulated Ni/Co PB (simplified as the Ni/Co-PB/CuO/GCE electrode) exhibited a high glucose sensitivity of 600 μA mM-1 cm-2 with a low detection limit of 0.69 μM (S/N = 3), a fast response time (less than 3 s), and excellent long-term stability. In addition, the CuO-encapsulated Ni/Co PB showed favorable anti-interference ability in the presence of ascorbic acid (AA), L-lysine (Lys), dopamine (DA), cysteine (Cys), dopamine (DA), and KCl interferences. The reusability and long-term stability, as well as the practicability of the Ni/Co-PB/CuO/GCE sensing electrode verified by testing real serum samples were also investigated, and the experimental results demonstrated the applicability of the core-shell NiCo-PB/CuO based flexible electrochemical sensor for non-enzymatic glucose sensing in practical applications.

Design of ZIF-67 MOF-derived Co3O4/NiCo2O4 nanosheets for supercapacitor electrode materials

Binary transition metal oxides exhibit improved properties including good redox potentials and electrical conductivities compared with single metal oxides as electrode materials in energy storage. Herein, ZIF-67 is prepared by a one-step method using Co2+ as the central metal ion, 2-methylimidazole as the organic ligand, and methanol as an organic solvent at room temperature. Hollow NiCo2O4 and sheet-like Co3O4/NiCo2O4 derived from bimetallic imidazolate framework precursors were synthesized by adding cobalt and nickel ions in appropriate proportions. A hollow and porous structure is achieved for the reaction between a nickel salt and ZIF-67, and this unique nanostructure provides a high active surface area, which is beneficial to the electrochemical properties. Several samples are prepared and used as electrode materials for electrochemical tests in 6 M KOH. As a result, the Co3O4/NiCo2O4 electrode with a sheet nanostructure showed a high specific capacitance of 846 F g−1 at a current density of 0.5 A g−1. This Co3O4/NiCo2O4 electrode material is promising for future studies on high-performance supercapacitors to solve emerging energy-related problems.

[Formula: see text]

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.

Ni and Co synergy in bimetallic nanowires for the electrochemical detection of hydrogen peroxide

The development of a highly sensitive and selective non-enzymatic electrode catalyst for the detection of a target molecule was remained a great challenge. In this regard, bimetallic nanowires (BMNWs) are considered as promising electrode material for their fascinating physical/chemical properties superior to a single system. In this article, nickel cobalt (Ni _x -Co) BMNWs with tunable stoichiometry were prepared by a template assisted electrodeposition method and their catalytic performance was investigated for the detection of hydrogen peroxide (H₂O₂). It has been found that Ni-Co (0.5:1) BMNWs/PC electrode exhibits superior non-enzymatic sensing ability toward H₂O₂ detection with a high selectivity. The electrode shows fast response within ∼3 s and an excellent reproducible sensitivity of 2211.4 μAmM^-1 cm^-2, which is the best compared to the individual Ni, Co, Ni-Co (0.3:1) BMNWs and previously reported electrodes. In addition, the electrode shows a linear response in the wide concentration range from 0.005 mM to 9 mM, low detection limit of 0.5 μM (S/N = 3.2) and a relatively long-term storage (50 d). Moreover, the sensor reveals excellent results for H₂O₂ detection in the real samples. The enhanced sensitivity of the Ni-Co (0.5:1) BMNWs based electrode may be due to the stable structure and synergy of Ni and Co. The results demonstrate that the catalytic activity of the electrode binary catalyst towards H₂O₂ detection can be improved by adjusting the Ni/Co ratio in BMNWs. The excellent performance of the electrode suggests that Ni-Co BMNWs are promising candidate for the construction of cost-effective electrochemical sensors for medical and industrial applications.

In situ construction of multi-dimensional Co3O4/NiCo2O4 hierarchical flakes on self-supporting carbon substrate with ultra-high capacitance for hybrid supercapacitors

Research on environmentally friendly energy storage devices is an important strategy to solve the energy crisis and environmental pollution. Herein, a novel self-supporting electrode based on multi-dimensional Co₃O₄/NiCo₂O₄ hierarchical flakes coating on graphene/carbon sphere (rGO/CS) conductive substrate is reasonably designed. Firstly, a simple hydrothermal method is used to synthesize NiCo₂O₄ with both flake and nanoneedle morphology on the rGO/CS substrate. Subsequently, Co₃O₄/NiCo₂O₄@rGO/CS is obtained by in-situ growth of metal organic frameworks polyhedrons on the surface of NiCo₂O₄ flakes followed by calcination. In the unique structure, benefitting from the synergy between the substrate and multi-element transition metal oxides, the integrated film shows good conductivity, high specific surface area and abundant active sites. Thus, the binder-free electrode exhibits an ultra-high specific capacitance of 3876.6 F g^-1 (538.4 mA h g^-1) at 1 A g^-1. A hybrid supercapacitor is assembled with activated carbon as the negative electrode and Co₃O₄/NiCo₂O₄@rGO/CS as the positive electrode, the device shows a highest energy density of 56.5 Wh kg^-1 at a power density of 800 W kg^-1. After 6000 charge-discharge cycles, 92.5% of the initial capacitance can be still maintained, indicating its good application prospects in energy storage materials.

Ultrasensitive Detection of Hydrogen Peroxide Using Bi2Te3 Electrochemical Sensors

Electrochemical sensors, with high accuracy, good selectivity, and linear response, have been widely used for environmental protection, health monitoring, and disease treatment. However, to date, these sensors still have limit sensitivity or otherwise require the use of high-cost materials such as noble metals and enzymes. Here, we report a novel electrochemical sensor using a topological insulator, Bi₂Te₃. Through liquid-phase exfoliation, we prepared nano- and microflakes of Bi₂Te₃ and measured their performance in hydrogen peroxide sensing via electrocatalytic reduction processes. Our devices exhibit a sensitivity of ∼4900 μA mM^-1 cm^-2 and a detection limit of ∼10^-8 molar, both of which are superior to typical noble metal-based electrochemical sensors. Through electrochemical analysis and microkinetic simulations, we extracted the kinetic parameters and gained insights into the reaction mechanism. We attribute the ultrahigh sensitivity to the facile electron transfer at the Bi₂Te₃-aqueous solution interface.

NiCo2O4 Nano-/Microstructures as High-Performance Biosensors: A Review

Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo2O4 mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo2O4 materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein. Comparative analysis reveals better electrochemical sensing of bioanalytes by one-dimensional and two-dimensional NiCo2O4 nano-/microstructures than other morphologies. Better biosensing efficiency of NiCo2O4 as compared to corresponding individual metal oxides, viz. NiO and Co3O4, is attributed to the close intrinsic-state redox couples of Ni3+/Ni2+ (0.58 V/0.49 V) and Co3+/Co2+ (0.53 V/0.51 V). Biosensing performance of NiCo2O4 is also significantly improved by making the composites of NiCo2O4 with conducting carbonaceous materials like graphene, reduced graphene oxide, carbon nanotubes (single and multi-walled), carbon nanofibers; conducting polymers like polypyrrole (PPy), polyaniline (PANI); metal oxides NiO, Co3O4, SnO2, MnO2; and metals like Au, Pd, etc. Various factors affecting the morphologies and biosensing parameters of the nano-/micro-structured NiCo2O4 are also highlighted. Finally, some drawbacks and future perspectives related to this promising field are outlined.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.