Sensitive Electrochemical Detection of Bioactive Molecules (Hydrogen Peroxide, Glucose, Dopamine) with Perovskites-Based Sensors

Perovskite-modified electrodes have received increasing attention in the last decade, due to their electrocatalytic properties to undergo the sensitive and selective detection of bioactive molecules, such as hydrogen peroxide, glucose, and dopamine. In this review paper, different types of perovskites involved for their electrocatalytic properties are described, and the proposed mechanism of detection is presented. The analytical performances obtained for different electroactive molecules are listed and compared with those in terms of the type of perovskite used, its nanostructuration, and its association with other conductive nanomaterials. The analytical performance obtained with perovskites is shown to be better than those of Ni and Co oxide-based electrochemical sensors. Main trends and future challenges for enlarging and improving the use of perovskite-based electrochemical sensors are then discussed.

Developments of the Electroactive Materials for Non-Enzymatic Glucose Sensing and Their Mechanisms

A comprehensive review of the electroactive materials for non-enzymatic glucose sensing and sensing devices has been performed in this work. A general introduction for glucose sensing, a facile electrochemical technique for glucose detection, and explanations of fundamental mechanisms for the electro-oxidation of glucose via the electrochemical technique are conducted. The glucose sensing materials are classified into five major systems: (1) mono-metallic materials, (2) bi-metallic materials, (3) metallic-oxide compounds, (4) metallic-hydroxide materials, and (5) metal-metal derivatives. The performances of various systems within this decade have been compared and explained in terms of sensitivity, linear regime, the limit of detection (LOD), and detection potentials. Some promising materials and practicable methodologies for the further developments of glucose sensors have been proposed. Firstly, the atomic deposition of alloys is expected to enhance the selectivity, which is considered to be lacking in non-enzymatic glucose sensing. Secondly, by using the modification of the hydrophilicity of the metallic-oxides, a promoted current response from the electro-oxidation of glucose is expected. Lastly, by taking the advantage of the redistribution phenomenon of the oxide particles, the usage of the noble metals is foreseen to be reduced.

An improved non-enzymatic electrochemical sensor amplified with CuO nanostructures for sensitive determination of uric acid

This study displays the facile and fluent electrochemical determination of uric acid (UA) through exceptional copper oxide nanostructures (CuO), as an effective sensing probe. The copper oxide nanostructures were fabricated via an aqueous chemical growth method using sodium hydroxide as a reducing agent, which massively hold hydroxide source. Copper oxide nanostructures showed astonishing electrocatalytic behavior in the detection of UA. Different characterization techniques such as XRD, FESEM, and EDS were exploited to determine crystalline nature, morphologies, and elemental composition of synthesized nanostructures. The cyclic voltammetry (CV) was subjected to investigate the electrochemical performance of UA using copper oxide nanostructures modified glassy carbon electrode CuO/GCE. The CV parameters were optimized at a scan rate of 50 mV/s with −0.7 to 0.9 potential range, and the UA response was investigated at 0.4 mV. PBS buffer of pH 7.4 was exploited as a supporting electrolyte. The linear dynamic range for UA was 0.001–351 mM with a very low limit of detection observed as 0.6 µM. The proposed sensor was successfully applied in urine samples for the detection of UA with improved sensitivity and selectivity.

Hierarchical cage-frame type nanostructure of CeO2 for bio sensing applications: from glucose to protein detection

Self-assembled hierarchical nanostructures are slowly superseding their conventional counterparts for use in biosensors. These morphologies show high surface area with tunable porosity and packing density. Modulating the interfacial interactions and subsequent particle assembly occurring at the water-and-oil interface in inverse miniemulsions, are amongst the best strategies to stabilize various type of hollow nanostructures. The paper presents a successful protocol to obtain CeO₂ hollow structures based biosensors that are useful for glucose to protein sensing. The fabricated glucose sensor is able to deliver high sensitivity (0.495 μA cm^-2 nM^-1), low detection limit (6.46 nM) and wide linear range (0 nM to 600 nM). CeO₂ based bioelectrode can also be considered as a suitable candidate for protein sensors. It can detect protein concentrations varying from 0 to 30 µM, which is similar or higher than most reports in the literature. The limit of detection (LOD) for protein was ∼0.04 µM. Therefore, the hollow CeO₂ electrodes, with excellent reproducibility, stability and repeatability, open a new area of application for cage-frame type particles.

Nickel sulfide-incorporated sulfur-doped graphitic carbon nitride nanohybrid interface for non-enzymatic electrochemical sensing of glucose

A nickel sulfide-incorporated sulfur-doped graphitic carbon nitride (NiS/S-g-C₃N₄) nanohybrid was utilized as an interface material for the non-enzymatic sensing of glucose in an alkaline medium (0.1 M NaOH). The precursors used in the preparation of NiS/S-g-C₃N₄ hybrid were thiourea and nickel nitrate hexahydrate as the sulfur and nickel sources, respectively. The HRTEM results reveal that NiS nanoparticles incorporated on the S-g-C₃N₄ nanosheet surface could enhance the electrocatalytic activity and electrical conductivity. The prepared NiS/S-g-C₃N₄ crystalline nature, surface functionalities, graphitic nature, thermal stability and surface composition were investigated using XRD, FT-IR, Raman spectroscopy, TGA and XPS analyses. The NiS/S-g-C₃N₄ modified electrode was used for the non-enzymatic sensing of glucose at an applied potential of 0.55 V vs. Ag/AgCl with a detection limit of 1.5 μM (S/N = 3), sensitivity of 80 μA mM^-1 cm^-2 and the response time of the fabricated sensor was close to 5 s. Different inorganic ions and organic substances did not interfere during glucose sensing. The NiS/S-g-C₃N₄ nanohybrid material could be extended for a real sample analysis and open the way for diverse opportunities in the electrochemical sensing of glucose.

A practical non-enzymatic urea sensor based on NiCo2O4 nanoneedles

We propose a new facile electrochemical sensing platform for determination of urea, based on a glassy carbon electrode (GCE) modified with nickel cobalt oxide (NiCo₂O₄) nanoneedles.

Hydrothermal and plasma nitrided electrospun carbon nanofibers for amperometric sensing of hydrogen peroxide

Nitrogen-doped carbon nanofibers (CNFs) were prepared by an electrospinning method, this followed by a hydrothermal reaction or nitrogen plasma treatment to obtain electrode for non-enzymatic amperometric sensing of H₂O₂. The hydrothermally treated electrode performs better. Its electrochemical surface is 3.7 × 10^-3 mA cm^-2, which is larger than that of a nitrogen plasma treated electrode (8.9 × 10^-4) or a non-doped CNF (2.45 × 10^-4 mA cm^-2). The hydrothermally treated CNF with rough surface and a complex profile with doped N has a higher sensitivity (357 μA∙mM^-1∙cm^-2), a lower detection limit (0.62 μM), and a wider linear range (0.01-0.71 mM) than N-CNF_P at a working potential of -0.4 V (vs. Ag/AgCl). The electrode gave high recoveries when applied to the analysis of milk samples spiked with H₂O₂. Graphical abstract Nitrogen-doped carbon nanofibers prepared by an electrospinning method followed by a hydrothermal reaction (N-CNF_ht) or nitrogen plasma treatment (N-CNF_P) are directly used as non-enzymatic amperometric H₂O₂ sensors.

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.

A comparison of nitrogen-doped sonoelectrochemical and chemical graphene nanosheets as hydrogen peroxide sensors

Nitrogen-doped graphene nanosheet (N-SEGN) with pyrrolic nitrogen and 5-9 vacancy defects has been successfully prepared from a hydrothermal reaction of tetra-2-pyridinylpyrazine and sonoelectrochemistry-exfoliated graphene nanosheet, with point defects. Additionally, based on the same reaction using chemically reduced graphene oxide, nitrogen-doped chemically reduced graphene oxide (N-rGO) with graphitic nitrogen was prepared. The N-SEGN and N-rGO were used as a non-enzymatic H₂O₂ sensors. The sensitivity of the N-SEGN was 231.3 μA·mM^-1·cm^-2, much greater than 57.3 μA·mM^-1·cm^-2 of N-rGO. The N-SEGN showed their potential for being a H₂O₂ sensor.

A CuNi/C Nanosheet Array Based on a Metal-Organic Framework Derivate as a Supersensitive Non-Enzymatic Glucose Sensor

Bimetal catalysts are good alternatives for non-enzymatic glucose sensors owing to their low cost, high activity, good conductivity, and ease of fabrication. In the present study, a self-supported CuNi/C electrode prepared by electrodepositing Cu nanoparticles on a Ni-based metal-organic framework (MOF) derivate was used as a non-enzymatic glucose sensor. The porous construction and carbon scaffold inherited from the Ni-MOF guarantee good kinetics of the electrode process in electrochemical glucose detection. Furthermore, Cu nanoparticles disturb the array structure of MOF derived films and evidently enhance their electrochemical performances in glucose detection. Electrochemical measurements indicate that the CuNi/C electrode possesses a high sensitivity of 17.12 mA mM^-1 cm^-2, a low detection limit of 66.67 nM, and a wider linearity range from 0.20 to 2.72 mM. Additionally, the electrode exhibits good reusability, reproducibility, and stability, thereby catering to the practical use of glucose sensors. Similar values of glucose concentrations in human blood serum samples are detected with our electrode and with the method involving glucose-6-phosphate dehydrogenase; the results further demonstrate the practical feasibility of our electrode.

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.

A Robust, Enzyme-Free Glucose Sensor Based on Lysine-Assisted CuO Nanostructures

The production of a nanomaterial with enhanced and desirable electrocatalytic properties is of prime importance, and the commercialization of devices containing these materials is a challenging task. In this study, unique cupric oxide (CuO) nanostructures were synthesized using lysine as a soft template for the evolution of morphology via a rapid and boiled hydrothermal method. The morphology and structure of the synthesized CuO nanomaterial were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The prepared CuO nanostructures showed high potential for use in the electrocatalytic oxidation of glucose in an alkaline medium. The proposed enzyme-free glucose sensor demonstrated a robust response to glucose with a wide linear range and high sensitivity, selectivity, stability, and reproducibility. To explore its practical feasibility, the glucose content of serum samples was successfully determined using the enzyme-free sensor. An analytical recovery method was used to measure the actual glucose from the serum samples, and the results were satisfactory. Moreover, the presented glucose sensor has high chemical stability and can be reused for repetitive measurements. This study introduces an enzyme-free glucose sensor as an alternative tool for clinical glucose quantification.

Muti-component nanocomposite of nickel and manganese oxides with enhanced stability and catalytic performance for non-enzymatic glucose sensors

A muti-component nanocomposite of nickel and manganese oxides with a uniformly dispersed microspherical structure has been fabricated by a hydrothermal synthesis method. The as-prepared nanocomposite has been employed as a sensing material for non-enzymatic glucose detection and shown excellent electrocatalytic activity, such as high sensitivities of 82.44 μA mM(-1) cm(-2) and 27.92 μA mM(-1) cm(-2) over the linear range of 0.1-1 mM and 1-4.5 mM, respectively, a low detection limit of 0.2 μM and a fast response time of <3 s. Moreover, satisfactory specificity and excellent stability have also been achieved. The results demonstrate that a muti-component nanocomposite of nickel and manganese oxides has great potential applications as glucose sensors.

A novel cage-like CdTe film with enhanced photoelectrochemical performance

A novel cage-like CdTe film with even porosity size and good connectivity among particles is successfully prepared by a simple technique for the first time.

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.

Simpler and highly sensitive enzyme-free sensing of urea via NiO nanostructures modified electrode

In this study, NiO nanostructures were synthesized via a hydrothermal process using ascorbic acid as doping agent in the presence of ammonia.

Nanorod-aggregated flower-like CuO grown on a carbon fiber fabric for a super high sensitive non-enzymatic glucose sensor

A novel flexible non-enzymatic glucose sensor based on nanorod-aggregated flower-like CuO grown on a carbon fiber fabric is developed, which displays an excellent electrocatalytic activity and a super high sensitivity due to its multichannels and high conductivity.

A highly selective and sensitive electrochemical determination of melamine based on succinic acid functionalized copper oxide nanostructures

This study presents the development of a highly selective and sensitive electrochemical sensor for the determination of melamine from aqueous environments.