Copper Hydroxide Nanorods Decorated Porous Graphene Foam Electrodes for Non-enzymatic Glucose Sensing

Laser-Induced Carbon Nanofibers as Permeable Nonenzymatic Sensor for Biomarker Detection in Breath Aerosol

A novel breathable electrochemical enzyme-free sensor made from laser-induced carbon nanofibers embedding Ni nanocatalysts (Ni-LCNFs) is proposed for the capture and detection of biomarkers in breath aerosol. The permeable Ni-LCNF electrodes were fabricated on filter paper where a hydrophobic wax barrier was created to confine the device's working area. The device was tested with aerosolized glucose, which was collected on the porous Ni-LCNF electrode. After a subsequent drying step, 0.1 M NaOH was dropped onto the device, and the electrocatalytic reaction of the captured glucose enabled by a Ni nanocatalyst was monitored via cyclic voltammetry (CV). Taking the oxidation/reduction peak ratios from CV as analytical signals improves the reliability and reproducibility of the glucose measurement. In the measurement step, closing the sensing area with adhesive tape, named closed device, enhances the detection sensitivity and enables the detection limit of 0.71 μM, which is 11.5 and 50 times, respectively, better when compared to the open device configuration. Measurements with simulated glucose aerosols containing clinically relevant glucose levels and comparison to screen-printed electrodes demonstrated the device's superiority for breath analysis. Although in vivo validation studies must be conducted in future work, the proposed device results in a captivating point-of-care device integratable in breathing masks and breath analysis devices.

Hierarchical Structures Composed of Cu(OH)2 Nanograss within Directional Microporous Cu for Glucose Sensing

Cu(OH)₂ nanomaterials are widely investigated for non-enzymatic glucose sensors due to their low-cost and excellent performance. Cu(OH)₂ nanomaterials usually grow on substrates to form sensor electrodes. Reported works mainly focus on structure adjusting of the Cu(OH)₂ nanostructures, while the optimization of substrates is still lacking. In the present work, directional porous Cu (DPC) was applied as the substrate for the growth of Cu(OH)₂ nanograss (NG), and hierarchical structures of Cu(OH)₂@DPC were prepared by alkaline oxidation. The morphology and microstructure evolution of the prepared hierarchical structures was investigated, and the non-enzymatic glucose sensing performance was evaluated. Cu(OH)₂@DPC exhibits enhanced comprehensive non-enzymatic glucose sensing performance compared to the reported ones, which may benefit from both the effective adsorption of the Cu(OH)₂ NG with a relatively high surface area and the high solute exchange of the DPC by a channel effect. This work provides new insights into the further improvement of the non-enzymatic glucose sensing performance of Cu(OH)₂ nanostructures by optimizing the substrate structure.

A bibliometric analysis of graphene in acetaminophen detection: Current status, development, and future directions

Acetaminophen is a widely used analgesic throughout the world. Detection of acetaminophen has particular value in pharmacy and clinics. Electrochemical sensors assembled with advanced materials are an effective method for the rapid detection of acetaminophen. Graphene-based carbon nanomaterials have been extensively investigated for potential analytical applications in the last decade. In this article, we selected papers containing both graphene and acetaminophen. Bibliometrics was used to analyze the relationships and trends among these papers. The results show that the topic has grown at a high rate since 2009. Among them, the detection of acetaminophen by an electrochemical sensor based on graphene is the most important direction. Graphene has moved from being a primary sensing material to a substrate for immobilization of other active ingredients. In addition, the degradation of acetaminophen using graphene-modified electrodes is also an important direction. We analyzed the research history and current status of this topic through bibliometrics. Authors, institutions, countries, and key literature were discussed. We also proposed perspectives for this topic.

Graphene and Its Derivatives: Synthesis and Application in the Electrochemical Detection of Analytes in Sweat

Wearable sensors and invasive devices have been studied extensively in recent years as the demand for real-time human healthcare applications and seamless human-machine interaction has risen exponentially. An explosion in sensor research throughout the globe has been ignited by the unique features such as thermal, electrical, and mechanical properties of graphene. This includes wearable sensors and implants, which can detect a wide range of data, including body temperature, pulse oxygenation, blood pressure, glucose, and the other analytes present in sweat. Graphene-based sensors for real-time human health monitoring are also being developed. This review is a comprehensive discussion about the properties of graphene, routes to its synthesis, derivatives of graphene, etc. Moreover, the basic features of a biosensor along with the chemistry of sweat are also discussed in detail. The review mainly focusses on the graphene and its derivative-based wearable sensors for the detection of analytes in sweat. Graphene-based sensors for health monitoring will be examined and explained in this study as an overview of the most current innovations in sensor designs, sensing processes, technological advancements, sensor system components, and potential hurdles. The future holds great opportunities for the development of efficient and advanced graphene-based sensors for the detection of analytes in sweat.

Quasi-aligned Cu2S/Cu(OH)2nanorod arrays anchored on Cu foam as self-supported electrode for non-enzymatic glucose detection

Self-supported Cu₂S/Cu(OH)₂composite nanorods for highly sensitive non-enzymatic glucose sensing werein situgrown on Cu foam by simple hydrothermal treatment of aligned Cu(OH)₂nanorods. The physicochemical and electrochemical properties of the as-fabricated Cu₂S/Cu(OH)₂composite nanorods were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Raman spectroscope, x-ray photoelectron spectroscope, cyclic voltammetry, electrochemical impedance spectroscopy, amperometrici-tmeasurements. The mechanism of the composite nanorods produced on conductive substrates was also explored. The electrode exhibits a sensitivity of 9626.88μA mM^-1cm^-2towards glucose with good anti-interference ability, indicating it a promising electrode material for the enhanced non-enzymatic glucose detection.

Screen-Printed Carbon Electrodes with Macroporous Copper Film for Enhanced Amperometric Sensing of Saccharides

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L⁻¹ and 4.0–100 μmol L⁻¹) with detection limits of 0.1 μmol L⁻¹ glucose, 0.03 μmol L⁻¹ fructose, and 0.05 μmol L⁻¹ sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability.

The influence of drinking water constituents on the level of microplastic release from plastic kettles

Microplastic (MP) release from household plastic products has become a global concern due to the high recorded levels of microplastic and the direct risk of human exposure. However, the most widely used MP measurement protocol, which involves the use of deionized (DI) water, fails to account for the ions and particles present in real drinking water. In this paper, the influence of typical ions (Ca²⁺/HCO₃^-, Fe³⁺, Cu²⁺) and particles (Fe₂O₃ particles) on MP release was systematically investigated by conducting a 100-day study using plastic kettles. Surprisingly, after 40 days, all ions resulted in a greater than 89.0% reduction in MP release while Fe₂O₃ particles showed no significant effect compared to the DI water control. The MP reduction efficiency ranking is Fe³⁺ ≈ Cu²⁺ > Ca²⁺/HCO₃^- > > Fe₂O₃ particles ≈ DI water. Physical and chemical characterization using SEM-EDX, AFM, XPS and Raman spectroscopy confirmed Ca²⁺/HCO₃^-, Cu²⁺ and Fe³⁺ ions are transformed into passivating films of CaCO₃, CuO, and Fe₂O₃, respectively, which are barriers to MP release. In contrast, there was no film formed when the plastic was exposed to Fe₂O₃ particles. Studies also confirmed that films with different chemical compositions form naturally in kettles during real life due to the different ions present in local regional water supplies. All films identified in this study can substantially reduce the levels of MP release while withstanding the repeated adverse conditions associated with daily use. This study underscores the potential for regional variations in human MP exposure due to the substantial impact water constituents have on the formation of passivating film formation and the subsequent release of MPs.

Self-Therapeutic Cobalt Hydroxide Nanosheets (Co(OH)2 NS) for Ovarian Cancer Therapy

High-grade serous ovarian cancer (HGSOC) is one of the major life-threatening cancers in women, with a survival rate of less than 50%. So far, chemotherapy is the main therapeutic tool to cure this lethal disease; however, in many cases, it fails to cure HGSOC even with severe side effects. Self-therapeutic nanomaterials could be an effective alternative to chemotherapy, facilitated by their diverse physicochemical properties and the ability to generate reactive species for killing cancer cells. Herein, inorganic cobalt hydroxide nanosheets (Co(OH)₂ NS) were synthesized by a simple solution process at room temperature, and morphological, spectroscopic, and crystallographic analyses revealed the formation of Co(OH)₂ NS with good crystallinity and purity. The as-prepared Co(OH)₂ NS showed excellent potency, comparable to the FDA-approved cisplatin drug to kill ovarian cancer cells. Flow cytometric analysis (nnexin V) revealed increased cellular apoptosis for Co(OH)₂ NS than cobalt acetate (the precursor). Tracking experiments demonstrated that Co(OH)₂ NS are internalized through the lysosome pathway, although relocalization in the cytoplasm has been observed. Hence, Co(OH)₂ NS could be an effective self-therapeutic drug and open up an area for the optimization of self-therapeutic properties of cobalt nanomaterials for cancer treatment.

Carbon nanomaterial hybrids via laser writing for high-performance non-enzymatic electrochemical sensors: a critical review

Non-enzymatic electrochemical sensors possess superior stability and affordability in comparison to natural enzyme-based counterparts. A large variety of nanomaterials have been introduced as enzyme mimicking with appreciable sensitivity and detection limit for various analytes of which glucose and H2O2 have been mostly investigated. The nanomaterials made from noble metal, non-noble metal, and metal composites, as well as carbon and their derivatives in various architectures, have been extensively proposed over the past years. Three-dimensional (3D) transducers especially realized from the hybrids of carbon nanomaterials either with metal-based nanocatalysts or heteroatom dopants are favorable owing to low cost, good electrical conductivity, and stability. In this critical review, we evaluate the current strategies to create such nanomaterials to serve as non-enzymatic transducers. Laser writing has emerged as a powerful tool for the next generation of devices owing to their low cost and resultant remarkable performance that are highly attractive to non-enzymatic transducers. So far, only few works have been reported, but in the coming years, more and more research on this topic is foreseeable.

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.

Co(OH)2 nanosheets decorated Cu(OH)2 nanorods for highly sensitive nonenzymatic detection of glucose

Co(OH)₂ nanosheets/Cu(OH)₂ nanorods composite electrodes for non-enzymatic glucose detection were fabricated by electrodepositing Co(OH)₂ nanosheets on Cu(OH)₂ nanorods substrate grown directly on the copper sheet via a simple one-step reaction. The Co(OH)₂ nanosheets/Cu(OH)₂ nanorods composite electrode was characterized by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction and x-ray photoelectron spectroscopy. The glucose sensing performance of the composite electrode was investigated by cyclic voltammetry and chronoamperometry. The composite electrode shows high sensitivity of 2366 µA mM^-1 cm^-2 up to 2 mM with a lower detection limit of 0.17 mM (S/N = 3). The composite electrode is highly selective to glucose in the presence of various substances that always co-exist with glucose in real blood samples. The response of the composite towards human blood serum was in good agreement with that of commercially available glucose sensors, suggesting that a promising electrode material for highly sensitive and selective non enzymatic detection of glucose can be envisioned.

A Brief Description of Cyclic Voltammetry Transducer-Based Non-Enzymatic Glucose Biosensor Using Synthesized Graphene Electrodes

The essential disadvantages of conventional glucose enzymatic biosensors such as high fabrication cost, poor stability of enzymes, pH value-dependent, and dedicated limitations, have been increasing the attraction of non-enzymatic glucose sensors research. Beneficially, patients with diabetes could use this type of sensor as a fourth-generation of glucose sensors with a very low cost and high performance. We demonstrate the most common acceptable transducer for a non-enzymatic glucose biosensor with a brief description of how it works. The review describes the utilization of graphene and its composites as new materials for high-performance non-enzymatic glucose biosensors. The electrochemical properties of graphene and the electrochemical characterization using the cyclic voltammetry (CV) technique of electrocatalysis electrodes towards glucose oxidation have been summarized. A recent synthesis method of the graphene-based electrodes for non-enzymatic glucose sensors have been introduced along with this study. Finally, the electrochemical properties such as linearity, sensitivity, and the limit of detection (LOD) for each sensor are introduced with a comparison with each other to figure out their strengths and weaknesses.

Surfactant-free liquid-exfoliated copper hydroxide nanocuboids for non-enzymatic electrochemical glucose detection

To facilitate printable sensing solutions particles need to be suspended and stabilised in a liquid medium. Hansen parameters were used to identify that alcohol-water blends are ideal for stabilising colloidal copper hydroxide in dispersion. The suspended material can be further separated in various size fractions with a distinct cuboid geometry which was verified using atomic force microscopy. This facilitates the development of Raman spectroscopic metrics for determining particle sizes. This aspect ratio is related to the anisotropic crystal structure of the bulk crystallites. As the size of the nanocuboids decreases electrochemical sensitivity of the material increases due to an increase in specific surface area. Electrochemical glucose sensitivity was investigated using both cyclic voltammetry and chronoamperometry. The sensitivity is noted to saturate with film thickness. The electrochemical response of 253 mA M^-1 cm^-2 up to 0.1 mM and 120 mA cm^-2 up to 0.6 mM allow for calibration of potential devices. These results indicate suitability for use as a glucose sensor and, due to the surfactant-free, low boiling point solvent approach used to exfoliate the nanocuboids, it is an ideal candidate for printable solutions. The ease of processing will also allow this material to be integrated in composite films for improved functionality in future devices.

A Flexible Portable Glucose Sensor Based on Hierarchical Arrays of Au@Cu(OH)2 Nanograss

Flexible physiological medical devices have gradually spread to the lives of people, especially the elderly. Here, a flexible integrated sensor based on Au nanoparticle modified copper hydroxide nanograss arrays on flexible carbon fiber cloth (Au@Cu(OH)2/CFC) is fabricated by a facile electrochemical method. The sensor possesses ultrahigh sensitivity of 7.35 mA mM-1 cm-2 in the linear concentration range of 0.10 to 3.30 mM and an ultralow detection limit down to 26.97 nM. The fantastic sensing properties can be ascribed to the collective effect of the superior electrochemical catalytic activity of nanograss arrays with dramatically enhanced electrochemically active surface area as well as mass transfer ability when modified with Au and intimate contact between the active material (Au@Cu(OH)2) and current collector (CFC), concurrently supplying good conductivity for electron/ion transport during glucose biosensing. Furthermore, the device also exhibits excellent anti-interference and stability for glucose detection. Owing to the distinguished performances, the novel sensor shows extreme reliability for practical glucose testing in human serum and juice samples. Significantly, these unique properties and the soft structure of silk fabric can provide a promising structure design for a flexible micro-device and a great potential material candidate of electrochemical glucose sensor.

Electrochemical glucose sensing characteristics of two-dimensional faceted and non-faceted CuO nanoribbons

We present faceted and non-faceted crystal cupric oxide (CuO) nanoribbons synthesized by different processes for glucose-sensing applications.

Recent advancements, key challenges and solutions in non-enzymatic electrochemical glucose sensors based on graphene platforms

This review elucidates the recent advances in graphene platforms in electrochemical non-enzymatic glucose sensors and provides solutions for existing bottlenecks.

Enhanced amperometric sensing using a NiCo2O4/nitrogen-doped reduced graphene oxide/ionic liquid ternary composite for enzyme-free detection of glucose

Schematic illustration of the fabrication of NiCo₂O₄/N-rGO/ILs/GCE.

The promoting effect of tetravalent cerium on the oxygen evolution activity of copper oxide catalysts

A new catalyst is based on cerium-modified copper oxide demonstrated the promoting effect of tetravalent Ce toward oxygen evolution activity.

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.