Novel Cu/CuO/ZnO hybrid hierarchical nanostructures for non-enzymatic glucose sensor application

Advances of Transition Metal-Based Electrochemical Non-enzymatic Glucose Sensors for Glucose Analysis: A Review

Glucose concentration is a crucial parameter for assessing human health. Over recent years, non-enzymatic electrochemical glucose sensors have drawn considerable attention due to their substantial progress. This review explores the common mechanism behind the transition metal-based electrocatalytic oxidation of glucose molecules through classical electrocatalytic frameworks like the Pletcher model and the Hydrous Oxide-Adatom Mediator model (IHOAM), as well as the redox reactions at the transition metal centers. It further compiles the electrochemical characterization techniques, associated formulas, and their ensuing conclusions pertinent to transition metal-based non-enzymatic electrochemical glucose sensors. Subsequently, the review covers the latest advancements in the field of transition metal-based active materials and support materials used in non-enzymatic electrochemical glucose sensors in the last decade (2014-2023). Additionally, it presents a comprehensive classification of representative studies according to the active metal catalysts components involved.

Functionalized ZnO-Based Nanocomposites for Diverse Biological Applications: Current Trends and Future Perspectives

The wide array of structures and characteristics found in ZnO-based nanostructures offers them a versatile range of uses. Over the past decade, significant attention has been drawn to the possible applications of these materials in the biomedical field, owing to their distinctive electronic, optical, catalytic, and antimicrobial attributes, alongside their exceptional biocompatibility and surface chemistry. With environmental degradation and an aging population contributing to escalating healthcare needs and costs, particularly in developing nations, there's a growing demand for more effective and affordable biomedical devices with innovative functionalities. This review delves into particular essential facets of different synthetic approaches (chemical and green) that contribute to the production of effective multifunctional nano-ZnO particles for biomedical applications. Outlining the conjugation of ZnO nanoparticles highlights the enhancement of biomedical capacity while lowering toxicity. Additionally, recent progress in the study of ZnO-based nano-biomaterials tailored for biomedical purposes is explored, including biosensing, bioimaging, tissue regeneration, drug delivery, as well as vaccines and immunotherapy. The final section focuses on nano-ZnO particles' toxicity mechanism with special emphasis to their neurotoxic potential, as well as the primary toxicity pathways, providing an overall review of the up-to-date development and future perspectives of nano-ZnO particles in the biomedicine field.

Development of MoS2-ZnO heterostructures: an efficient bifunctional catalyst for the detection of glucose and degradation of toxic organic dyes

The heterostructure catalyst MoS2-ZnO possesses binary properties and provides a novel platform for the remediation of environmental as well as health issues.

Bi-functional 3D-NiCu-Double Hydroxide@Partially Etched 3D-NiCu Catalysts for Non-Enzymatic Glucose Detection and the Hydrogen Evolution Reaction

Hydrogen production, which is in the spotlight as a promising eco-friendly fuel, and the need for inexpensive and accurate electronic devices in the biochemistry field are important emerging technologies. However, the use of electrocatalytic devices based on expensive noble metal catalysts limits commercial applications. In recent years, to improve performance and reduce cost, electrocatalysts based on cheaper copper or nickel materials have been investigated for the non-enzymatic glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER). In this study, we demonstrate a facile and easy electrochemical method of forming a cheap nickel copper double hydroxide (NiCu-DH) electrocatalyst deposited onto a three-dimensional (3D) CuNi current collector, which can effectively handle two different reactions due to its high activity for both the GOR and the HER. The as-prepared electrode has a structure comprising abundant 3D-interconnected porous dendritic walls for easy access of the electrolyte ions and highly conductive networks for fast electron transfer; additionally, it provides numerous electroactive sites. The synergistic combination of the dendritic 3D-CuNi with its abundant active sites and the self-made NiCu-DH with its excellent electrocatalytic activity toward the oxidation of glucose and HER enables use of the catalyst for both reactions. The as-prepared electrode as a glucose sensor exhibits an outstanding glucose detection limit value (0.4 μM) and a wide detection range (from 0.4 μM to 1.4 mM) with an excellent sensitivity of 1452.5 μA/cm2/mM. The electrode is independent of the oxygen content and free from chloride poisoning. Furthermore, the as-prepared electrode also requires a low overpotential of -180 mV versus reversible hydrogen electrode to yield a current density of 10 mA/cm2 with a Tafel slope of 73 mV/dec for the HER. Based on this performance, this work introduces a new paradigm for exploring cost-effective bi-functional catalysts for the GOR and HER.

Protein templated Au-CuO bimetallic nanoclusters toward neutral glucose sensing

In this study, the application of bovine serum albumin (BSA) as a carrier to glucose-sensitive materials for the detection of glucose was proposed. Au-CuO bimetallic nanoclusters (Au-CuO/BSA) were prepared using BSA as a template, the new sensing material (Au-CuO/BSA/MWCNTs) was synthesized by mixing with multi-walled carbon nanotubes (MWCNT) and applied to non-enzymatic electrochemical sensors to detect glucose stably and effectively under neutral condition. The scanning electron microscopy was used to investigate the morphology of the synthesized nanocomposite. The electrochemical properties of the sensor were studied by cyclic voltammetry. Glucose detection experiments show that Au-CuO/BSA/MWCNTs/Au electrode has good glucose detection ability, stability, accuracy, repeatability, and high selectivity in neutral environment. Unlike existing glucose-sensitive materials, due to the use of BSA, the composite material is firmly fixed to the electrode surface without a Nafion solution, which reduces the current blocking effect on the modified electrode. The composite materials can be effectively preserved for extremely long periods, higher than 80% activity is maintained at room temperature in a closed environment for 3 to 4 months, due to the special effects of BSA. In addition, the feasibility of using BSA in glucose-sensitive materials is confirmed.

Non-Enzymatic Detection of Glucose in Neutral Solution Using PBS-Treated Electrodeposited Copper-Nickel Electrodes

Transition metals have been explored extensively for non-enzymatic electrochemical detection of glucose. However, to enable glucose oxidation, the majority of reports require highly alkaline electrolytes which can be damaging to the sensors and hazardous to handle. In this work, we developed a non-enzymatic sensor for detection of glucose in near-neutral solution based on copper-nickel electrodes which are electrochemically modified in phosphate-buffered saline (PBS). Nickel and copper were deposited using chronopotentiometry, followed by a two-step annealing process in air (Step 1: at room temperature and Step 2: at 150 °C) and electrochemical stabilization in PBS. Morphology and chemical composition of the electrodes were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cyclic voltammetry was used to measure oxidation reaction of glucose in sodium sulfate (100 mM, pH 6.4). The PBS-Cu-Ni working electrodes enabled detection of glucose with a limit of detection (LOD) of 4.2 nM, a dynamic response from 5 nM to 20 mM, and sensitivity of 5.47 ± 0.45 μA cm-2/log10(mole.L-1) at an applied potential of 0.2 V. In addition to the ultralow LOD, the sensors are selective toward glucose in the presence of physiologically relevant concentrations of ascorbic acid and uric acid spiked in artificial saliva. The optimized PBS-Cu-Ni electrodes demonstrate better stability after seven days storage in ambient compared to the Cu-Ni electrodes without PBS treatment.

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.

Highly sensitive non-enzymatic electrochemical glucose sensor based on dumbbell-shaped double-shelled hollow nanoporous CuO/ZnO microstructures

A high-performance non-enzymatic glucose sensor based on hybrid metal-oxides is proposed. Dumbbell-shaped double-shelled hollow nanoporous CuO/ZnO microstructures (CuO/ZnO-DSDSHNM) were prepared via the hydrothermal method using pluronic F-127 as a surfactant. This structure is studied by various physicochemical characterizations such as scanning electron microscopy, X-ray diffraction spectroscopy, inductively coupled plasma atomic emission spectroscopy, elemental mapping techniques, X-ray photoelectron spectroscopy, and transmission electron microscopy. This unique CuO/ZnO-DSDSHNM provides both a large surface area and an easy penetrable structure facilitating improved electrochemical reactivity toward glucose oxidation. The prepared CuO/ZnO-DSDSHNM was used over the glassy carbon electrode (GCE) as the active material for glucose detection and then coated by Nafion to provide the proposed Nafion/CuO/ZnO-DSDSHNM/GCE. The fabricated glucose sensor exhibits an extremely wide dynamic range from 500 nM to 100 mM, a sensitivity of 1536.80 µA mM^-1 cm^-2, a low limit of detection of 357.5 nM, and a short response time of 1.60 s. The proposed sensor also showed long-term stability, good reproducibility, favorable repeatability, excellent selectivity, and satisfactory applicability for glucose detection in human serum samples. The achieved high-performance glucose sensing based on Nafion/CuO/ZnO-DSDSHNM/GCE shows that both the material synthesis and the sensor fabrication methods have been promising and they can be used in future researches.

Carbon-Coated Tungsten Oxide Nanospheres Triggering Flexible Electron Transfer for Efficient Electrocatalytic Oxidation of Water and Glucose

Electrocatalytic oxidation of water (i.e., oxygen evolution reaction, OER) plays crucial roles in energy, environment, and biomedicine. It is a key factor affecting the efficiencies of electrocatalytic reactions conducted in aqueous solution, e.g., electrocatalytic water splitting and glucose oxidation reaction (GOR). However, electrocatalytic OER still suffers from problems like high overpotential, sluggish kinetics, and over-reliance on expensive noble-metal-based catalysts. Herein, 15 nm thick carbon-based shell coated tungsten oxide (CTO) nanospheres are loaded on nickel foam to form CTO/NF. An enhanced electrocatalytic OER is triggered on CTO/NF, with the overpotential at 50 mA cm^-2 (317 mV) and the Tafel slope (70 mV dec^-1) on CTO/NF lower than those on pure tungsten oxide (360 mV, 117 mV dec^-1) and noble-metal-based IrO₂ catalysts (328 mV, 96 mV dec^-1). A promoted electrocatalytic GOR is also achieved on CTO/NF, with efficiency as high as 189 μA mM^-1 cm^-2. The carbon-based shell on CTO is flexible for electron transfer between catalyst and reactants and provides catalytically active sites. This improves reactant adsorption and O-H bond dissociation on the catalyst, which are key steps in OER and GOR. The carbon-based shell on CTO retains the catalyst as nanospheres with a higher surface area, which facilitates OER and GOR. It is the multiple roles of the carbon-based shell that increases the electrocatalytic efficiency. These results are helpful for fabricating more efficient noble-metal-free electrocatalysts.

A Non-Enzymatic Sensor Based on Fc-CHIT/CNT@Cu Nanohybrids for Electrochemical Detection of Glucose

Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon nanotube@ Cu (Fc-CHIT/CNT@Cu). The elemental composition of the carbon nanohybrids, morphology and structure were characterized by various techniques. Electrochemical impedance spectroscopy (EIS) was used to study the interfacial properties of the electrodes. Cyclic voltammetry (CV) and chronoamperometry methods in alkaline solution were used to determine glucose biosensing properties. The synergy effect of Cu NPs and Fc on current responses of the developed electrode resulted in good glucose sensitivity, including broad linear detection between 0.2 mM and 22 mM, a low detection limit of 13.52 μM and sensitivity of 1.256 μA mM⁻¹cm⁻². Moreover, the modified electrode possessed long-term stability and good selectivity in the presence of ascorbic acid, dopamine and uric acid. The results indicated that this inexpensive electrode had potential application for non-enzymatic electrochemical glucose detection.

Non-enzymatic sensor for determination of glucose based on PtNi nanoparticles decorated graphene

Diabetes has become a universal epidemic in recent years. Herein, the monitoring of glucose in blood is of importance in clinical applications. In this work, PtNi alloy nanoparticles homogeneously dispersed on graphene (PtNi alloy-graphene) was synthesized as a highly effective electrode material for glucose detection. Based on the modified PtNi alloy-graphene/glass carbon (PtNi alloy-graphene/GC) electrode, it is found that the PtNi alloy-graphene/GC electrode exhibited excellent electrocatalytic performance on glucose oxidation. Furthermore, the results from amperometric current–time curve show a good linear range of 0.5–15 mM with the limit of detection of 16 uM (S/N = 3) and a high sensitivity of 24.03 uAmM⁻¹ cm⁻². On account of the good selectivity and durability, the modified electrode was successfully applied on glucose detection in blood serum samples.

Mucilage-capped silver nanoparticles for glucose electrochemical sensing and fuel cell applications

A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time. Mucilage-AgNPs were synthesized through the direct chemical reduction of Ag⁺ by mucilage extracted from Opuntia ficus-indica. Mucilage-AgNPs were identified and characterized using ultraviolet-visible spectroscopy, transmission electron microscopy and square wave voltammetry. Modification of the GC with AgNPs was carried out via a transfer-sticking technique with an immobilization time of 1 h. The Mucilage-AgNPs/GC composite was studied as a possible anode for glucose oxidation in a biofuel cell. The composite resulted in glucose oxidation with a current density and power density of 85.7 μA cm⁻² and 25.7 μW cm⁻², respectively. Glucose sensing using the Mucilage-AgNPs/GC composite was achieved successfully via two pathways: glucose oxidation and AgNP inhibition. The glucose oxidation-based sensor showed a lower detection limit of 0.01 mM and a linear range of 0.01 to 2.2 mM. The AgNPs inhibition-based sensor provides an indirect determination pathway of glucose with a detection limit of 0.1 mM and a linear range of 0.1 to 1.9 mM. AgNP inhibition is a novel pathway that could be used for determining a large number of organic and inorganic molecules. Overall, the Mucilage-AgNPs/GC is considered a pioneering composite for glucose sensing and fuel cell applications.

A simple, cost-effective and green mucilage-capped silver nanoparticles (Mucilage-AgNPs) modified glassy carbon electrode (GC) composite was constructed for efficient and facile electrochemical oxidation of glucose for the first time.

A review on ZnO nanostructured materials: energy, environmental and biological applications

Zinc oxide (ZnO) is an adaptable material that has distinctive properties, such as high-sensitivity, large specific area, non-toxicity, good compatibility and a high isoelectric point, which favours it to be considered with a few exceptions. It is the most desirable group of nanostructure as far as both structure and properties. The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery, solar cells, photocatalysis, biosensors, biomedical and biological applications in the form of bulk crystal, thin film and pellets. The nanosized materials exhibit higher dissolution rates as well as higher solubility when compared to the bulk materials. This review significantly focused on the current improvement in ZnO-based nanomaterials/composites/doped materials for the application in the field of energy storage and conversion devices and biological applications. Special deliberation has been paid on supercapacitors, Li-ion batteries, dye-sensitized solar cells, photocatalysis, biosensors, biomedical and biological applications. Finally, the benefits of ZnO-based materials for the utilizations in the field of energy and biological sciences are moreover consistently analysed.

In situ formation of metal-organic framework derived CuO polyhedrons on carbon cloth for highly sensitive non-enzymatic glucose sensing

Metal-organic frameworks (MOFs) are considered promising templates for the fabrication of nanostructured materials with high porosities and high surface areas, which are important parameters for enhanced performance in sensing applications. Here, a facile in situ synthetic strategy to construct MOF-derived porous CuO polyhedrons on carbon cloth (CC) is reported. Uniform Cu(OH)2 nanorods are first synthesized on carbon cloth, followed by the conversion of Cu(OH)2 nanorods into porous CuO polyhedrons via a copper-based MOF, Cu-BTC, as the intermediate species. When evaluated as a glucose sensing electrode, the as-fabricated CuO polyhedrons/CC composite exhibits a high sensitivity of 13 575 μA mM-1 cm-2 with a fast response time (t90) of 2.3 s and a low detection limit of 0.46 μM. This work exemplifies the rational fabrication of porous nanostructures on conductive substrates for enhanced performance in glucose detection.

Metal oxide modified ZnO nanomaterials for biosensor applications

Advancing as a biosensing nanotechnology, nanohybrids present a new class of functional materials with high selectivity and sensitivity, enabling integration of nanoscale chemical/biological interactions with biomedical devices. The unique properties of ZnO combined with metal oxide nanostructures were recently demonstrated to be an efficient approach for sensor device fabrication with accurate, real-time and high-throughput biosensing, creating new avenues for diagnosis, disease management and therapeutics. This review article collates recent advances in the modified ZnO nanostructured metal oxide nanohybrids for efficient enzymatic and non-enzymatic biosensor applications. Furthermore, we also discussed future prospects for nanohybrid materials to yield high-performance biosensor devices.

Copper Nanoparticle and Nitrogen Doped Graphite Oxide Based Biosensor for the Sensitive Determination of Glucose

Copper nanoparticles with the diameter of 50 ± 20 nm decorated nitrogen doped graphite oxide (NGO) have been prepared through a simple single step carbonization method using copper metal-organic framework (MOF), [Cu₂(BDC)₂(DABCO)] (where BDC is 1,4-benzenedicarboxylate, and DABCO is 1,4-Diazabicyclo[2.2.2]octane) as precursor. The surface morphology, porosity, surface area and elemental composition of CuNPs/NGO were characterized by various techniques. The as-synthesized CuNPs/NGO nanomaterials were coated on commercially available disposable screen-printed carbon electrode for the sensitive determination of glucose. We find that the modified electrode can detect glucose between 1 μM and 1803 μM (linear range) with good sensitivity (2500 μA mM⁻¹ cm⁻²). Our glucose sensor also possesses low limits of detection (0.44 μM) towards glucose determination. The highly selective nature of the fabricated electrode was clearly visible from the selectivity studies. The practicability of CuNPs/NGO modified electrode has been validated in the human serum samples. The storage stability along with better repeatability and reproducibility results additionally substantiate the superior electrocatalytic activity of our constructed sensor towards glucose.

Recent advances in electrochemical non-enzymatic glucose sensors - A review

This review encompasses the mechanisms of electrochemical glucose detection and recent advances in non-enzymatic glucose sensors based on a variety of materials ranging from platinum, gold, metal alloys/adatom, non-precious transition metal/metal oxides to glucose-specific organic materials. It shows that the discovery of new materials based on unique nanostructures have not only provided the detailed insight into non-enzymatic glucose oxidation, but also demonstrated the possibility of direct detection in whole blood or interstitial fluids. We critically evaluate various aspects of non-enzymatic electrochemical glucose sensors in terms of significance as well as performance. Beyond laboratory tests, the prospect of commercialization of non-enzymatic glucose sensors is discussed.

Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

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. Graphical Abstract Schematic representation of electrochemical nonenzymatic glucose sensing on the nanomaterials modified electrodes. At an applied potential, the nanomaterial-modified electrodes exhibit excellent electrocatalytic activity for direct oxidation of glucose oxidation.

CeO₂ Nanorods Embedded in Ni(OH)₂ Matrix for the Non-Enzymatic Detection of Glucose

The electrode based on cerium oxide (CeO₂) nanorods embedded in nickel hydroxide (Ni(OH)₂) matrix were prepared and used for detecting glucose non-enzymatically. The materials were characterized by X-ray diffraction, transmission electron microscopy (TEM), and so on. The results indicate that the response of CeO₂/Ni(OH)₂ nanocomposite are significantly improved due to the synergetic effect between CeO₂ and Ni(OH)₂. The optimum CeO₂/Ni(OH)₂ nanocomposite electrode exhibits a detection range from 2 μM to 6.62 mM, a sensitivity of 594 μA mM-1 cm-2, an estimated detection limit of 1.13 μM, and a response time less than 5 s. In addition, this biosensor also shows good selectivity, long term stability, and accurate measurement in juice on sale.

CuCo2O4 nanowire arrays supported on carbon cloth as an efficient 3D binder-free electrode for non-enzymatic glucose sensing

CuCo₂O₄ nanowire arrays supported on carbon cloth (CuCo₂O₄ NWAs/CC) were prepared via a simple hydrothermal synthesis and subsequent calcination process and utilized as a 3D binder-free electrode for non-enzymatic glucose sensing with high performance.

Hierarchical Cu/Cu(OH)2 nanorod arrays grown on Cu foam as a high-performance 3D self-supported electrode for enzyme-free glucose sensing

Hierarchical Cu/Cu(OH)₂ nanorod arrays grown on Cu foam (Cu/Cu(OH)₂ NRA/CF) were prepared via a three-step strategy involving the synthesis of Cu(OH)₂ NRA/CF, the preparation of Cu NRA/CF, and the growth of Cu(OH)₂ nanoparticles on Cu NRA/CF.

Advances in non-enzymatic glucose sensors based on metal oxides

This review summarizes the advances in non-enzymatic glucose sensors based on different metal oxides (ZnO, CuO/Cu₂O, NiO,etc.) and their composites.

Non-enzymatic amperometric sensing of glucose by employing sucrose templated microspheres of copper oxide (CuO)

An enzymeless glucose sensor (MCSPE) based on copper oxide microspheres (CMS) prepared by hydrothermal reaction of copper nitrate and sucrose, can sense glucose in a wide linear detection range with good sensitivity and low detection limit.

Electrodeposition of a 3D hierarchical porous flower-like cobalt–MWCNT nanocomposite electrode for non-enzymatic glucose sensing

A versatile and cost-effective electrodeposition technique was adopted to synthesize cobalt and cobalt–MWCNT nanocomposite electrodes and the fabricated cobalt–MWCNT material was successfully demonstrated as a non-enzymatic glucose sensor.