Fabrication of selective and sensitive chemical sensor development based on flower-flake La2ZnO4 nanocomposite for effective non-enzymatic sensing of hydrogen peroxide by electrochemical method

Study of a Nanostructured Co-Doped SnO2 Sensor for Hydrogen Peroxide Vapor Detection Using Impedance Spectroscopy

A hydrogen peroxide vapor (HPV) sensor based on SnO2 doped with 1.3 at. % Co thin film has been fabricated using the high-frequency magnetron sputtering method. The thickness of the SnO2 ⟨Co⟩ thin film was measured and the surface morphology was examined using the thickness measurement profilometer and scanning electron microscopy, respectively. The crystalline properties of the sensing material were revealed by transmission electron microscopy. The response, current-voltage, and impedance characteristics of the sensor were measured in the air and in the presence of various concentrations of HPV at 25-200 °C. An equivalent electrical circuit for the manufactured sensor structure was proposed, and the parameters of its constituent elements were determined. Furthermore, fitting frequency dependences of impedance were calculated. It was shown that charge transfer in the SnO2 ⟨Co⟩ thin film was regulated by the processes mainly occurring at the grain boundaries of the gas-sensing film.

Regulation of the coordination number of Zn single atoms to boost electrochemical sensing of H2O2

Compared with transition metals with partially occupied 3d orbitals, Zn has a filled 3d10 configuration, which severely restricts electron mobility and hence usually renders Zn2+ intrinsically inactive for electrochemical sensing. Metal single-atom catalysts are a new kind of sensing material. Owing to their unique coordination structure and high atomic utilization rate, metal single-atom catalysts show unique properties, which makes them promising for use in the field of electrochemical sensing. However, whether Zn single atoms are active sites remains to be elucidated. In this study, we prepared nitrogen-doped carbon (NC) materials by pyrolyzing ZIF-8 at high temperatures and reported that when the pyrolysis temperature was 800 °C, many Zn single atoms with Zn-N4 coordination structures remained in the NC material. Even when the pyrolysis temperature is increased to 1000 °C, a small number of Zn single atoms remain, and the coordination structure changes from Zn-N4 to Zn-N3. Furthermore, unexpectedly, both residual Zn single atoms showed electrocatalytic activity for H2O2 reduction. In particular, the electrocatalytic activity was significantly enhanced after the coordination structure was changed from Zn-N4 to Zn-N3. Density functional theory (DFT) calculations indicate that the coordination structure of Zn-N3 optimizes the adsorption and desorption strength of oxygen-containing species in the electrocatalytic reaction process, which lowers the energy barrier of the rate-determining step and increases the detection sensitivity of H2O2 nearly 4.1 times. This study revealed new properties of Zn single atoms for the electrocatalytic reduction of H2O2 and developed a strategy to increase the electrocatalytic activity of metal single-atom catalysts through coordination number regulation, which lays the foundation for the use of Zn single atoms in the field of electrochemical sensing and provides ideas for the design of new highly active sensing materials.

Sensitive and Rapid Detection of Aspartic Acid with Co3O4-ZnO Nanorods Using Differential Pulse Voltammetry

Herein, the detection of aspartic acid by doped Co₃O₄-ZnO nanorod materials was proposed using differential pulse voltammetry. The nano-composite metal oxide was synthesized by the wet precipitation method in basic media. Aspartic acid is a non-essential amino acid naturally synthesized in the body with lot of health significance, including as a biomarker for several health deficiencies. The synthesized composite Co₃O₄-ZnO nanorod was well-investigated by using FESEM, XRD, XPS, FTIR, UV/vis., EIS, and CV. The synthesized composite exhibited a low limit of detection (0.03 µM, high sensitivity (0.0014 µA µM^-1 cm^-2) and wide linear range (0.05-50 µM) for aspartic acid. The substrate, the Co₃O₄-ZnO nanorod, enhanced the electro-catalytic oxidation of aspartic acid as a result of its catalytic and conductivity properties. The developed sensor based on Co₃O₄-ZnO has a repeatable, reproducible and stable current response for aspartic acid. Additionally, other electroactive compounds did not interfere with the sensor's current response. The suitability of the developed sensor for real sample analysis was also established. Therefore, this study proposed the potential use of Co₃O₄-ZnO nanorod material in healthcare management for the maintenance of human well-being.

Electrochemical detection of hydrogen peroxide using micro and nanoporous CeO2 catalysts

In this research work, focus has been made on a glassy carbon electrode (GCE) modified commercial micro and synthesized nano-CeO₂ for the detection of hydrogen peroxide (H₂O₂). Firstly, CeO₂ nanoleaves were prepared by solvothermal route. Both commercially available micro CeO₂ and synthesized nano-CeO₂ structures were analyzed by different characterization techniques. The Raman spectra of synthesized nano CeO₂ has more oxygen vacancies than micro CeO₂. SEM images revealed that the synthesized CeO₂ acquired leaf-like morphology. The catalyst nano CeO₂ offered mesoporosity from nitrogen adsorption-desorption isotherms with massive sites of activation for increasing efficiency. Experiments on determining H₂O₂ using micro CeO₂ or nano-CeO₂/GCE was conducted using cyclic voltammetry (CV) and amperometry. Enhanced H₂O₂ reduction peak current with lower potential was observed in nano-CeO₂/GCE. The influence of scan rate and H₂O₂ concentration on the performance of nano-CeO₂/GCE were also studied. The obtained results have indicated that nano-CeO₂/GCE showed improved electrochemical sensing behavior towards the reduction of H₂O₂ than micro-CeO₂/GCE and bare GCE. A linear relationship was obtained over 0.001 μM-0.125 μM concentration of H₂O₂, with good sensitivity 141.96 μA μM^-1 and low detection limit of 0.4 nM. Hence, the present nano-CeO₂ system will have a great potential with solvothermal synthesis approach in the development of electrochemical sensors.

Development of Cd (II) Ion Probe Based on Novel Polyaniline-Multiwalled Carbon Nanotube-3-aminopropyltriethoxylsilane Composite

Cadmium belongs to the group of potentially toxic metals that have high health and environmental significance. Due to its adverse effects on the environment, this study develops an effective electrochemical sensor for detecting a polyaniline-multiwalled carbon nanotube-3-aminopropyltriethoxysilane (PANI-MWCNT-APTES) substrate cast on the GCE. The as-prepared PANI-MWCNT-APTES was prepared by a wet chemical method, and its formation was investigated using several techniques. As a result, the prepared material exhibited a limit of detection of 0.015 µM for cadmium ions (Cd²⁺) in the linear dynamic range of 0.05 µM to 50 µM. Furthermore, the PANI-MWCNT-APTES-modified GCE current response was stable, repeatable, reproducible, and short. In addition, PANI-MWCNT-APTES/GCE was harnessed for the first time for cadmium detection in real water samples, and the result was satisfactory. Therefore, the recorded results suggest that the newly designed PANI-MWCNT-APTES is a promising material for detecting Cd in the near future for human health and environmental protection.

An Electrochemical Approach for the Selective Detection of Cancer Metabolic Creatine Biomarker with Porous Nano-Formulated CMNO Materials Decorated Glassy Carbon Electrode

The facile wet-chemical technique was used to prepare the low-dimensional nano-formulated porous mixed metal oxide nanomaterials (CuO.Mn2O3.NiO; CMNO NMs) in an alkaline medium at low temperature. Detailed structural, morphological, crystalline, and functional characterization of CMNO NMs were performed by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDS) analyses. An efficient and selective creatine (CA) sensor probe was fabricated by using CMNO NMs decorated onto glassy carbon electrode (GCE) as CMNO NMs/GCE by using Nafion adhesive (5% suspension in ethanol). The relation of current versus the concentration of CA was plotted to draw a calibration curve of the CMNO NMs/GCE sensor probe, which was found to have a very linear value (r2 = 0.9995) over a large dynamic range (LDR: 0.1 nM~0.1 mM) for selective CA detection. The slope of LDR by considering the active surface area of GCE (0.0316 cm2) was applied to estimate the sensor sensitivity (14.6308 µAµM-1 cm-2). Moreover, the detection limit (21.63 ± 0.05 pM) of CMNO MNs modified GCE was calculated from the signal/noise (S/N) ratio at 3. As a CA sensor probe, it exhibited long-term stability, good reproducibility, and fast response time in the detection of CA by electrochemical approach. Therefore, this research technique is introduced as a promising platform to develop an efficient sensor probe for cancer metabolic biomarker by using nano-formulated mixed metal oxides for biochemical as well as biomedical research for the safety of health care fields.