Coral-like Cu-Co-mixed oxide for stable electro-properties of glucose determination

An integrated smartphone-based electrochemical detection system for highly sensitive and on-site detection of chemical oxygen demand by copper-cobalt bimetallic oxide-modified electrode

A portable and integrated electrochemical detection system has been constructed for on-site and real-time detection of chemical oxygen demand (COD). The system mainly consists of four parts: (i) sensing electrode with a copper-cobalt bimetallic oxide (CuCoOx)-modified screen-printed electrode; (ii) an integrated electrochemical detector for the conversion, amplification, and transmission of weak signals; (iii) a smartphone installed with a self-developed Android application (APP) for issuing commands, receiving, and displaying detection results; and (iv) a 3D-printed microfluidic cell for the continuous input of water samples. Benefiting from the superior catalytic capability of CuCoOx, the developed system shows a high detection sensitivity with 0.335 μA/(mg/L) and a low detection limit of 5.957 mg/L for COD determination and possessing high anti-interference ability to chloride ions. Moreover, this system presents good consistency with the traditional dichromate method in COD detection of actual water samples. Due to the advantages of cost effectiveness, portability, and point-of-care testing, the system shows great potential for water quality monitoring, especially in resource-limited remote areas.

Recent advances in perovskite oxides for non-enzymatic electrochemical sensors: A review

Non-enzymatic electrochemical sensors with significant advantages of high sensitivity, long-term stability, and excellent reproducibility, are one promising technology to solve many challenges, such as the detection of toxic substances and viruses. Among various materials, perovskite oxides have become a promising candidate for use in non-enzymatic electrochemical sensors because of their low cost, flexible structure, and high intrinsic catalytic activity. A comprehensive overview of the recent advances in perovskite oxides for non-enzymatic electrochemical sensors is provided, which includes the synthesis methods of nanostructured perovskites and the electrocatalytic mechanisms of perovskite catalysts. The better sensing performance of perovskite oxides is mainly due to the lattice O vacancies and superoxide oxygen ions (O₂^2-/O^-), which are generated by the transfer of lattice oxygen to adsorbed -OH and have performed excellent properties suitable for electrooxidation of analytes. However, the limited electron transfer kinetics, stability, and selectivity of perovskite oxides alone make perovskite oxides far from ready for scientific development. Therefore, composites of perovskite oxides with other materials like graphitic carbon, metals, metal compounds, conducting organics, and biomolecules are summarized. Furthermore, a brief section describing the future challenges and the corresponding recommendation is presented in this review.

Prism-like bimetallic (Ni-Co) alkaline carboxylate-based non-enzymatic sensor capable of exceptionally high catalytic activity towards glucose

In this study, we fabricated a novel non-enzymatic glucose sensor based on prism-like bimetallic alkaline carboxylate (CoNi-MIM). The morphology and structure of CoNi-MIM were carefully investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical glucose oxidation of the synthesized sensor was then explored by cyclic voltammetry (CV) and chronoamperometry in alkaline medium. It was found that CoNi-MIM is the optimal choice with a remarkably high sensitivity of 5024.4 μA mM^-1 cm^-2, low detection limit of 56.1 nM (S/N = 3), linear response of up to 14.3 mM and excellent selectivity compared to Co-MIM, CoFe-MIM and CoMn-MIM. Furthermore, the as-fabricated sensor demonstrated appreciable practicality for the determination of glucose in real samples. These results indicate that CoNi-MIM holds a good application prospect in non-enzymatic glucose sensing.

In-situ catalytic degradation of sulfamethoxazole with efficient CuCo-O@CNTs/NF cathode in a neutral electro-Fenton-like system

In this paper, a CuCo-O@CNTs/NF electrode was successfully prepared and used for in-situ degradation of sulfamethoxazole (SMX) in an electro-Fenton-like system. Carbon nanotubes (CNTs) and coral-like copper-cobalt oxides were successively loaded on nickel foam (NF). CNTs contributed to improving the dispersibility and stability of copper-cobalt oxides, and the coral-like copper-cobalt oxide catalyst was anchored on CNTs without any adhesive. In the electro-Fenton-like system, dissolved oxygen can be reduced to superoxide anions in a one-electron step, which could be further transformed into hydrogen peroxide and then reacted with the active components on the electrode to generate reactive oxygen species (ROS) to participate in the degradation of SMX. Almost 100% SMX removal was obtained within 60 min in a wide near-neutral pH range (5.6-9.0), and the electrode could still achieve a 90.4% removal rate after ten recycle runs. Radical-quenching results showed that superoxide anions were the main species in the degradation of SMX. In addition, a possible degradation pathway of SMX was proposed. According to the result of toxicological simulations, the toxicity of the pollutant solution during the degradation process exhibited a decreasing trend. This study provides new insights for in-situ catalysis of electrodes with bimetallic active components to generate ROS for high-efficiency degradation of refractory organic pollutants.

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.

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.

Facile synthesis of CuCo2O4@NiCo2O4 hybrid nanowire arrays on carbon cloth for a multicomponent non-enzymatic glucose sensor

The design of hierarchical heterogeneous structures with rational components is considered as a promising method to enhance the properties of electrocatalyst. Binary metal oxides, with high electrochemical activity, have attracted considerable interest in glucose determination. In this work, we synthesized the CuCo₂O₄@NiCo₂O₄ hybrid structure on conductive carbon cloth (CC) via a simple two-step hydrothermal process and investigated its catalytic ability toward glucose. The two individual components that make up this hybrid electrode have good electrical conductivity and excellent catalytic properties for glucose, so the smart combination of these two active materials can provide more catalytic sites and sufficient redox couples for the glucose oxidation. As a result, the CuCo₂O₄@NiCo₂O₄ modified CC presented superior glucose sensing properties, including ultrahigh sensitivity, fast response time, wide linear range and acceptable detection limit. Besides, the sample also exhibited good selectivity for substances in human blood that interfere with glucose detection, such as UA, AA, fructose, sucrose and KCl. The potential of the CuCo₂O₄@NiCo₂O₄/CC electrode for practical application was investigated by measuring the glucose concentration in real serum samples. These results prove that the construction of hierarchical ordered structure is conducive to the improvement of glucose sensor.

Flexible Free-Standing CuxO/Ag2O (x = 1, 2) Nanowires Integrated with Nanoporous Cu-Ag Network Composite for Glucose Sensing

To improve glucose electrocatalytic performance, one efficient manner is to develop a novel Cu-Ag bimetallic composite with fertile porosity and unique architecture. Herein, the self-supported electrode with Cu_xO/Ag₂O (x = 1, 2) nanowires grown in-situ on a nanoporous Cu-Ag network (Cu_xO/Ag₂O@NP-CuAg) has been successfully designed by a facile two-step approach. The integrated hierarchical porous structure, the tip-converged Cu_xO/Ag₂O nanowires combined with the interconnected porous conductive substrate, are favorable to provide more reactive sites and improve ions or electrons transportation. Compared with monometallic Cu₂O nanowires integrated with nanoporous Cu matrix (Cu₂O@NP-Cu), the bimetallic Cu_xO/Ag₂O@NP-CuAg composites exhibit the enhanced electrocatalytic performance for glucose. Moreover, the higher sensitivity of ~1.49 mA mM⁻¹ cm⁻² in conjunction with a wider linear range of 17 mM for the Cu_xO/Ag₂O@NP-CuAg electrode anodized for 10 min are attributed to the synergistic effect of porous structure and bimetallic Cu_xO/Ag₂O nanowires. Particularly, the integrated Cu_xO/Ag₂O@NP-CuAg composites possess good flexibility, which has been reported for the first time. Accordingly, the Cu_xO/Ag₂O@NP-CuAg with excellent glucose electrocatalytic performance and good flexibility is promising to further develop as a candidate electrode material of glucose sensors.

Fabrication of porous NiMn2O4 nanosheet arrays on nickel foam as an advanced sensor material for non-enzymatic glucose detection

In this work, porous NiMn₂O₄ nanosheet arrays on nickel foam (NiMn₂O₄ NSs@NF) was successfully fabricated by a simple hydrothermal step followed by a heat treatment. Porous NiMn₂O₄ NSs@NF is directly used as a sensor electrode for electrochemical detecting glucose. The NiMn₂O₄ nanosheet arrays are uniformly grown and packed on nickel foam to forming sensor electrode. The porous NiMn₂O₄ NSs@NF electrode not only provides the abundant accessible active sites and the effective ion-transport pathways, but also offers the efficient electron transport pathways for the electrochemical catalytic reaction by the high conductive nickel foam. This synergy effect endows porous NiMn₂O₄ NSs@NF with excellent electrochemical behaviors for glucose detection. The electrochemical measurements are used to investigate the performances of glucose detection. Porous NiMn₂O₄ NSs@NF for detecting glucose exhibits the high sensitivity of 12.2 mA mM⁻¹ cm⁻² at the window concentrations of 0.99–67.30 μM (correlation coefficient = 0.9982) and 12.3 mA mM⁻¹ cm⁻² at the window concentrations of 0.115–0.661 mM (correlation coefficient = 0.9908). In addition, porous NiMn₂O₄ NSs@NF also exhibits a fast response of 2 s and a low LOD of 0.24 µM. The combination of porous NiMn₂O₄ nanosheet arrays and nickel foam is a meaningful strategy to fabricate high performance non-enzymatic glucose sensor. These excellent properties reveal its potential application in the clinical detection of glucose.

Cu nanowires paper interlinked with cobalt oxide films for enhanced sensing and energy storage

A Cu-NWs paper synthesized by a one-step method is first presented. Owing to its good conductivity, it is an effective framework to interlink TMOs and prevent aggregation. For a practical application, the core-shell Cu NWs@ultrathin CoO_x delivers good performance for the catalytic oxidation of glucose and energy storage, with a sensitivity of 396.57 μA mM^-1 cm^-2 and a capacitance of 797.7 F g^-1 (1 A g^-1).

A portable micro glucose sensor based on copper-based nanocomposite structure

A sensor device based on a copper-based nanocomposite structure is achieved and presents excellent sensing performance for glucose.