PrFeO3-MoS2 nanosheets for use in enhanced electro-oxidative sensing of nitrite

Green Synthesis of Au Magnetic Nanocomposites Using Waste Chestnut Skins and Their Application as a Peroxidase Mimic Nanozyme Electrochemical Sensing Platform for Sodium Nitrite

An electrochemical sensor with high sensitivity for the detection of sodium nitrite was constructed based on the peroxidase-like activity of Au magnetic nanocomposites (Au@Fe3O4). The Au@Fe3O4 composite nanoparticles were green-synthesized via the reduction of gold nanoparticles (AuNPs) from waste chestnut skins combined with the sonochemical method. The nanoparticles have both the recoverability of Fe3O4 and the advantage of being able to amplify electrical signals. Furthermore, the synergistic effect of green reduction and sonochemical synthesis provides a functional approach for the preparation of Au@Fe3O4 with significant peroxidase-like activities. The physicochemical properties were characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), the Brunauer-Emmett-Teller (BET) method, and Fourier transform infrared spectroscopy (FT-IR). The electrochemical properties of sodium nitrite were determined with cyclic voltammetry (CV) and chronoamperometry (i-t). The results revealed that Au@Fe3O4 acted as a peroxidase mimic to decompose hydrogen peroxide to produce free radicals, while ·OH was the primary free radical that promoted the oxidation of sodium nitrite. With the optimal detection system, the constructed electrochemical sensor had a high sensitivity for sodium nitrite detection. In addition, the current response had a good linear relationship with the sodium nitrite concentration in the range of 0.01-100 mmol/L. The regression equation of the working curve was y = 1.0752x + 4.4728 (R2 = 0.9949), and the LOD was 0.867 μmol/L (S/N = 3). Meanwhile, the constructed detection system was outstanding in terms of recovery and anti-interference and had a good detection stability of more than 96.59%. The sensor has been successfully applied to a variety of real samples. In view of this, the proposed novel electrochemical analysis method has great prospects for application in the fields of food quality and environmental testing.

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.

Voltammetric sensor based on glassy carbon electrode modified with hierarchical porous carbon, silver sulfide nanoparticles and fullerene for electrochemical monitoring of nitrite in food samples

This paper reports the development of a voltammetric sensor using glassy carbon electrode based on hierarchical porous carbon (HPC) with silver sulfide nanoparticles (Ag₂SNP), Nafion and fullerene (C₆₀) for the determination of nitrite in foods. Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray were used to characterize the morphology and composition of the materials. The use of HPC and C₆₀ in the construction of the electrode contributed toward the enlargement of the specific surface area and the improvement of the electrochemical performance of the device. The electrochemical behavior of nitrite in different electrodes was evaluated by cyclic voltammetry in the potential range of 0.4 - 1 V. Using the optimal conditions, a linear response ranges of 4.0- 148 μmol L^-1, a limit of detection of 0.09 μmol L^-1 and a sensitivity of 0.05 μAμmol L^-1 cm^-2 were obtained. The results showed that the proposed method can selectively detect nitrite in the presence of other compounds without interference and with good stability. The proposed method was successfully applied for the detection of nitrite in food samples where it demonstrated a good degree of accuracy and satisfactory efficiency.

Mesoporous Carbon/α-Fe2O3 Nanoleaf Composites for Disposable Nitrite Sensors and Energy Storage Applications

In this work, we report a novel hydrothermal synthesis of α-Fe₂O₃ nanoleaf-incorporated mesoporous carbon-chitosan (α-Fe₂O₃@MPC-chit) as a versatile disposable sensor for selective electrochemical detection of nitrite and for supercapacitor applications. The newly synthesized α-Fe₂O₃@MPC-chit nanocomposite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy, UV, and Raman spectroscopy. The extensive physicochemical characterization reveals the strong immobilization of α-Fe₂O₃ nanoleaves within the MPC-chit composite. The electrochemical characterization with cyclic voltammetry and impedance spectroscopy using [Fe(CN)₆)]^3-/4- as a redox probe concludes good electron conductivity and efficient electron transfer behavior of α-Fe₂O₃@MPC-chit. The α-Fe₂O₃@MPC-chit modified electrode exhibits excellent electrocatalytic activity toward nitrite oxidation. The amperometric method of nitrite detection showed a linear range of up to 200 μmol L^-1 _. The current sensitivity and detection limit were found to be 0.913 μA μM^-1 and 31 nM cm^-2, respectively. The improved catalytic activity of the proposed electrode was endorsed by the synergistic effect of α-Fe₂O₃ with the MPC-chit composite. The ability of the proposed electrode was demonstrated by the successful detection of nitrite present in tap water, river water, and industrial samples with extensive recovery values. Furthermore, the α-Fe₂O₃@MPC-chit modified stainless-steel electrode showed high-performance supercapacitor application and exhibited a large specific capacitance of 380 F g^-1 at 1 A g^-1.

Homopolymerization of 3-aminobenzoic acid for enzyme-free electrocatalytic assay of nitrite ions

We describe non-enzymatic novel detection of nitrite ions in various matrices on the surface of poly-3-aminobenzoic acid.

2D Materials in Development of Electrochemical Point-of-Care Cancer Screening Devices

Effective cancer treatment requires early detection and monitoring the development progress in a simple and affordable manner. Point-of care (POC) screening can provide a portable and inexpensive tool for the end-users to conveniently operate test and screen their health conditions without the necessity of special skills. Electrochemical methods hold great potential for clinical analysis of variety of chemicals and substances as well as cancer biomarkers due to their low cost, high sensitivity, multiplex detection ability, and miniaturization aptitude. Advances in two-dimensional (2D) material-based electrochemical biosensors/sensors are accelerating the performance of conventional devices toward more practical approaches. Here, recent trends in the development of 2D material-based electrochemical biosensors/sensors, as the next generation of POC cancer screening tools, are summarized. Three cancer biomarker categories, including proteins, nucleic acids, and some small molecules, will be considered. Various 2D materials will be introduced and their biomedical applications and electrochemical properties will be given. The role of 2D materials in improving the performance of electrochemical sensing mechanisms as well as the pros and cons of current sensors as the prospective devices for POC screening will be emphasized. Finally, the future scopes of implementing 2D materials in electrochemical POC cancer diagnostics for the clinical translation will be discussed.

Recent advances in molybdenum disulfide-based electrode materials for electroanalytical applications

The primary objective of this review article is to summarize the development and structural diversity of 2D/3D molybdenum disulfide (MoS₂) based modified electrodes for electrochemical sensors and biosensor applications. Hydrothermal, mechanical, and ultrasonic techniques and solution-based exfoliation have been used to synthesize graphene-like 2D MoS₂ layers. The unique physicochemical properties of MoS₂ and its nanocomposites, including high mechanical strength, high carrier transport, large surface area, excellent electrical conductivity, and rapid electron transport rate, render them useful as efficient transducers in various electrochemical applications. The present review summarizes 2D/3D MoS₂-based nanomaterials as an electrochemical platform for the detection and analysis of various biomolecules (e.g., neurotransmitters, NADH, glucose, antibiotics, DNA, proteins, and bacteria) and hazardous chemicals (e.g., heavy metal ions, organic compounds, and pesticides). The substantial improvements that have been achieved in the performance of enzyme-based amperometry, chemiluminescence, and nucleic acid sensors incorporating MoS₂-based chemically modified electrodes are also addressed. We also summarize key sensor parameters such as limits of detection (LODs), sensitivity, selectivity, response time, and durability, as well as real applications of the sensing systems in the environmental, pharmaceutical, chemical, industrial, and food analysis fields. Finally, the remaining challenges in designing MoS₂ nanostructures suitable for electroanalytical applications are outlined. Graphical abstract • MoS₂ based materials exhibit high conductivity and improved electrochemical performance with great potential as a sensing electrode. • The role of MoS₂ nanocomposite films and their detection strategies were reviewed. • Biomarkers detection for disease identification and respective clinical treatments were discussed. • Future Challenges, as well as possible research development for "MoS₂ nanocomposites", are suggested.

Electrochemical sensor based on a nanocomposite prepared from TmPO4 and graphene oxide for simultaneous voltammetric detection of ascorbic acid, dopamine and uric acid

A nanocomposite is described that consists of TmPO₄ and graphene oxide (GO) and is used to modify a glassy carbon electrode (GCE) to obtain a sensor for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). GO and TmPO₄ were synthesized via the Hummers method and by a hydrothermal method, respectively. The nanocomposite was characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical properties of the modified GCE were studied by electrochemical impedance spectroscopy and cyclic voltammetry. The good performance of the modified GCE results from the synergistic effects between GO with its good electrical conductivity and of TmPO₄ as the electron mediator that accelerates the electron transfer rate. Compared to a bare GCE, a GO/GCE and a TmPO₄/GCE, the GO/TmPO₄/GCE exhibits three well-defined and separated oxidation peaks (at -0.05, +0.13 and + 0.26 V vs. SCE). Responses to AA, DA and UA are linear in the 0.1-1.0 mM, 2-20 μM and 10-100 μM concentration ranges, respectively. Graphical abstract Schematic presentation of a nanocomposite that consists TmPO₄ and graphene oxide (GO) and is used to modify a glassy carbon electrode (GCE) to obtain a sensor for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA).

The electrochemical applications of rare earth-based nanomaterials

This review presents a general description of the synthesis and electrochemical properties of rare earth-based nanomaterials and their electrochemical applications.