Dual functional nickel cobalt/MWCNT composite electrode-based electrochemical capacitor and enzymeless glucose biosensor applications: Influence of Ni/Co molar ratio

Fabrication of spinel NiCo2O4 nanoflowers by simple hydrothermal method for effective electrochemical detection of NO2- in processed food sample

This study introduces a novel, cost-effective, highly sensitive electrochemical sensor for detecting nitrite (NO2-) in processed food samples. The sensor was developed by fabricating spinel NiCo2O4 nanoflowers (NCO) using a hydrothermal method. Various characterization techniques, including XRD, FT-IR, XPS, HR-SEM, EDX, and HR-TEM, were used to analyze the structure and morphology of NCO. The obtained NCO exhibited a particle size of ∼16 nm and a flowered shape. Electrochemical impedance spectroscopy (EIS) was used to assess the electron-transfer properties. Cyclic voltammetry (CV) and chronoamperometry (CA) were employed to explore the electrocatalytic performance, revealing a high surface area and remarkable activity. The NCO electrode exhibited a remarkable sensitivity 44.16 μA mM-1 cm-2 at low concentrations and 33.51 μA mM-1 cm-2 at higher concentrations and a low detection limit of 0.99 μM. It is worth noting that the sensor displayed excellent reproducibility and repeatability, with relative standard deviation (RSD) values of 1.06 % and 1.37 %, respectively. Furthermore, the fabricated sensor was successfully applied for the detection of NO2- in milk, oranges, apple juice, wastewater, and processed foods such as chicken and sausage. The obtained results indicate that the proposed sensor is a promising candidate for practical NO2- detection applications.

Acetate-assisted in situ electrodeposited β-MnO2 for the fabrication of nano-architectonics for non-enzymatic glucose detection

Highly sensitive and low-cost electrocatalytic materials are of great importance for the commercial application of non-enzymatic glucose sensors. Herein, we fabricated a novel one-pot enzyme- and indicator-free method for the colorimetric sensing of blood glucose levels based on the direct redox reaction of β-MnO2/glucose. Owing to the introduction of ammonium acetate and the enhanced oxygen evolution reaction, the higher conductive β-MnO2 nanosheets with the larger surface area were directly grown in situ on the conductive substrate by a linear sweep voltammetry (LSV) electrodeposition method. Besides, owing to the unique tunnel-type pyrolusite MnO2, the electrolyte diffusion was facilitated and reduced the response time in the glucose detection process. Hence, the acetate-assisted MnO2 electrode exhibited a high sensitivity of 461.87 μA M-1 cm-2 toward glucose, a wide detection range from 1.0 μM to 1 mM, and a low detection limit of 0.47 μM while the electrode also maintained excellent selectivity and stability. These results clearly indicate that the new strategy we developed has great potential for practical applications.

A Facile Fabrication of Ordered Mesoporous Carbons Derived from Phenolic Resin and Mesophase Pitch via a Self-Assembly Method

Ordered and disordered mesoporous structures were synthesized by a self-assembly method using a mixture of phenolic resin and petroleum-based mesophase pitch as the starting materials, amphiphilic triblock copolymer F127 as a soft template, hydrochloric acid as a catalyst, and distilled water as a solvent. Then, mesoporous carbons were obtained via autoclave method at low temperature (60 °C) and then carbonization at a relatively low temperature (600 °C), respectively. X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) analyses revealed that the porous carbons with a mesophase pitch content of approximately 10 wt% showed a highly ordered hexagonal mesostructure with a highly uniform pore size of ca. 5.0 nm. In addition, the mesoporous carbons prepared by self-assembly and low-temperature autoclave methods exhibited the amorphous or crystalline carbon structures with higher specific surface area (SSA) of 756 m2/s and pore volume of 0.63 cm3/g, depending on the synthesis method. As a result, mesoporous carbons having a high SSA were successfully prepared by changing the mixing ratio of mesophase pitch and phenolic resin. The electrochemical properties of as-obtained mesoporous carbon materials were investigated. Further, the OMC-meso-10 electrode delivered the maximum SC of about 241 F/g at an applied current density of 1 A/g, which was higher than those of the MC-10 (~104 F/g) and OMC-20 (~115 F/g).

Glucose nano biosensor with non-enzymatic excellent sensitivity prepared with nickel-cobalt nanocomposites on f-MWCNT

NiCo (Nickel-cobalt) nanoparticles were obtained by the chemical reduction method on functionalized multi-walled carbon nanotubes. After this process, chronoamperometry, cyclic voltammetry, and amperometric methods were used to investigate the electrochemical and electrocatalytic behavior of NiCo@f-MWCNT against glucose oxidation. In addition, the NiCo@f-MWCNT nanocomposites were analyzed by characterization techniques such as X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) in terms of the morphological and atomic structure of prepared nanomaterials. The sensitivity and limit of detection the non-enzymatic glucose sensor (NiCo@f-MWCNT) were calculated as 10,015 μA/mM^-1 cm^-2 0.26 μM, respectively. As a result of these studies and experiments, the NiCo@f-MWCNT nanocomposite is a really good sensor and their stability showed that the current nanomaterials expressed to be new material for the electrochemical detection of glucose.

Curly fish scales-like Ni2.5Mo6S6.7 electrodeposited on PEDOT-rGO with uneven surface as ultrafast response electrode for electrocatalytic glucose, nitrite and hydrogen peroxide

The difficulty to achieve rapid detection is the limitation of many enzyme-free sensors today. Thus, designing tri-functionalsensors with ultra-fast and efficientdeterminationis a challenging taskin biological science. Herein, curly fish scales-like Ni_2.5Mo₆S_6.7 active materials was anchored on poly (3,4-ethylenedioxythiophene)-reduced graphene oxide (PEDOT-rGO) hybrid membranes with uneven surface (Ni_2.5Mo₆S_6.7/PEDOT-rGO) as a high-performance tri-functional catalyst for glucose, nitrite and hydrogen peroxide determination.The sensor constructed under optimal conditions exhibited ultrafast response performance towards glucose and nitrite within 2 s, and hydrogen peroxide within 1 s. Meanwhile, it provided the wide linear range with a low detection limit towards glucose (as low as 0.001 mM and up to 15.000 mM, and 0.33 μM), nitrite (as low as 0.001 mM and up to 10.000 mM, and 0.33 µM) and hydrogen peroxide (from 0.010 mM to 7.000 mM, and 0.79 μM), respectively. In addition, the sensor demonstrated satisfied selectivity, repeatability, reproducibility and stability. Furthermore, the sensor has potential application in real samples. This study may provide a new strategy for the construction of tri-functional electrode materials with the ultra-fast response.

Free-Standing PVDF/Reduced Graphene Oxide Film for All-Solid-State Flexible Supercapacitors towards Self-Powered Systems

The development of polymer-based devices has attracted much attention due to their miniaturization, flexibility, lightweight and sustainable power sources with high efficiency in the field of wearable/portable electronics, and energy system. In this work, we proposed a polyvinylidene fluoride (PVDF)-based composite matrix for both energy harvesting and energy storage applications. The physicochemical characterizations, such as X-ray diffraction, laser Raman, and field-emission scanning electron microscopy (FE-SEM) analyses, were performed for the electrospun PVDF/sodium niobate and PVDF/reduced graphene oxide composite film. The electrospun PVDF/sodium niobate nanofibrous mat has been utilized for the energy harvester which shows an open circuit voltage of 40 V (peak to peak) at an applied compressive force of 40 N. The PVDF/reduced graphene oxide composite film acts as the electrode for the symmetric supercapacitor (SSC) device fabrication and investigated for their supercapacitive properties. Finally, the self-charging system has been assembled using PVDF/sodium niobate (energy harvester), and PVDF/reduced graphene oxide SSC (energy storage) and the self-charging capability is investigated. The proposed self-charging system can create a pathway for the all-polymer based composite high-performance self-charging system.

Carbyne-enriched carbon anchored on nickel foam: A novel binder-free electrode for supercapacitor application

Carbon- and carbon derivatives are widely employed as efficient electrode materials for supercapacitor applications. Herein, we demonstrate a cost-effective dip-coating process followed by dehydrohalogenation of PVDF-Ni for the preparation of carbyne enriched carbon anchored on nickel (CEC-Ni) as high-performance electrode material. The removal of halogens in the prepared CEC-Ni were widely characterized using XRD, XPS, Laser Raman, and FT-IR analysis. The occurrence of carbon-carbon vibration in the prepared CEC-Ni foam was confirmed using FT-IR spectroscopy. Laser Raman analysis confirms that the CEC-Ni foam contains both sp and sp² hybridized carbon. The electrochemical properties of prepared carbyne enriched carbon anchored on nickel foam electrode (CEC-NiE) showed an ideal capacitive properties and delivered a maximum specific capacitance of about 106.12 F g^-1 with excellent cyclic retention. Furthermore, the mechanism of charge-storage in the CEC-NiE was analyzed using Dunn's method. In additon, the asymmetric supercapacitor device was fabricated using CEC-NiE as positive and rGO as negative electrode achieved a remarkable energy density of 33.57 Wh Kg^-1 with a maximal power density of 14825.71 W Kg^-1. These results suggested that the facile preparation of CEC-NiE could be a promising and effective electrode material for future energy storage application.