Enzymatic glucose biosensor based on bismuth nanoribbons electrochemically deposited on reduced graphene oxide

We describe the electrochemical preparation of bismuth nanoribbons (Bi-NRs) with an average length of 100 ± 50 nm and a width of 10 ± 5 μm by a potentiostatic method. The process occurs on the surface of a glassy carbon electrode (GCE) in the presence of disodium ethylene diamine tetraacetate that acts as a scaffold for the growth of the Bi-NRs and also renders them more stable. The method was applied to the preparation of Bi-NRs incorporated into reduced graphene oxide. This nanocomposite was loaded with the enzyme glucose oxidase onto a glassy carbon electrode. The resulting biosensor displays an enhanced redox peak for the enzyme with a peak-to-peak separation of about 28 mV, revealing a fast electron transfer at the modified electrode. The loading of the GCE with electroactive GOx was calculated to be 8.54 × 10⁻¹⁰ mol∙cm⁻², and the electron transfer rate constant is 4.40 s⁻¹. Glucose can be determined (in the presence of oxygen) at a relatively working potential of −0.46 V (vs. Ag|AgCl) in the 0.5 to 6 mM concentration range, with a 104 μM lower detection limit. The sensor also displays appreciable repeatability, reproducibility and remarkable stability. It was successfully applied to the determination of glucose in human serum samples.

A potentiostatic method was used to prepare reduced graphene oxide and bismuth nanoribbons nanocomposite on a glassy carbon electrode. This nanocomposite was loaded with enzyme glucose oxidase to fabricate a glucose biosensor.

     

Determination of the antioxidant propyl gallate in meat by using a screen-printed electrode modified with CoSe<Subscript>2</Subscript> nanoparticles and reduced graphene oxide

A voltammetric sensor is described for the quantitation of propyl gallate (PG). A screen-printed carbon electrode (SPCE) was modified with reduced graphene sheets that were decorated with cobalt diselenide nanoparticles (CoSe₂@rGO). The material was hydrothermally prepared and characterized by several spectroscopic techniques. The modified SPCE displays excellent electrocatalytic ability towards PG. Differential pulse voltammetry, with a peak voltage at 0.34 V (vs. Ag/AgCl) has a sensitivity of 12.84 μA·μM^?1·cm^?2 and a detection limit as low as 16 nM. The method is reproducible, selective, and practical. This method was applied to the determination of PG in spiked meat samples, and the result showed an adequate recovery.

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Graphical abstract Schematic of a new method for fast and sensitive electrochemical determination of the food additive propyl gallate in meat

     

Synthesis and characterization of manganese diselenide nanoparticles (MnSeNPs): Determination of capsaicin by using MnSeNP-modified glassy carbon electrode

A new type of manganese diselenide nanoparticles (MnSeNPs) was synthesized by using a hydrothermal method. Their surface morphology, crystallinity and elemental distribution were characterized by using transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy which scrutinize the formation of the NPs. The NPs were coated on a glassy carbon electrode (GCE), and electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were applied to study the electroanalytical properties towards the oxidation of the food additive capsaicin. The modified GCE displays lower charge transfer resistance (R _ct ?=?29.52 Ω), a larger active surface area (0.089 cm²/g, and more efficient electrochemical oxidation of capsaicin compared to a MnS₂/GCE and a bare GCE. The oxidation peak potential is 0.43 V (vs. Ag/AgCl) which is lower than that of previously reported GCEs. The sensor has a detection limit as low as 0.05 μM and an electrochemical sensitivity of 2.41 μA μM^?1 cm^?2. The method was applied to the determination of capsaicin in pepper samples.

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Graphical abstract Electrochemical determination of capsaicin in pepper extract by using MnSeNPs modified electrode.

     

Green biosynthesis of silver nanoparticles and nanomolar detection of p-nitrophenol

Green biosynthesis of nanoparticles and their applications in sensor field is of great interest to the researchers. We report herein a simple green approach for the synthesis of silver nanoparticles (Ag-NPs) using Acacia nilotica Willd twig bark and its application for the detection of 4-nitro phenol (4-NP). The synthesized Ag-NPs were characterized by Transmission electron microscopy, X-ray diffraction and elemental analysis. The size of synthesized Ag-NPs was in the range of 10–50 nm. The Ag-NPs modified electrode shows a high sensitivity and selectivity towards the sensing of 4-NP. The fabricated modified electrode shows a low detection limit of 15 nM on the wider linear response range from 100 nM to 350 μM with the sensitivity of 2.58?±?0.05 μAμM^?1 cm^?2. In addition, the fabricated sensor shows good repeatability and reproducibility.

Two-dimensional copper oxide/zinc oxide nanoflakes with three-dimensional flower-like heterostructure enhanced with electrocatalytic activity toward nimesulide detection

The strategy of building two-dimensional (2D) metal oxide nanoflakes has inspired several innovations in different fields of application on account of its tremendous significance. It includes ultrathin planar surface, large charge carrier mobility, and tunable band structures, providing unprecedented features for sensing. Moreover, the intercalation of 2D dimensions to 3D superstructures will result in improved and dual advantages of both 2D/3D. The construction of 2D/3D copper oxide zinc oxide nanocomposite as electrode material for specific detection of nimesulide (NMS) is herein reported. The conversion of 2D CZ nanoflakes to 3D CZ microflowers was possibly achieved via the self-assembly process. This simple and cost-effective development of the CZ composite was characterized for evaluating the physical, chemical, and morphological properties. The highly crystalline nature of CZ was observed from powder X-ray diffraction and X-ray photoelectron spectroscopy analysis. The formation of 2D nanoflakes of CZ was strongly confirmed from field emission scanning electron microscopy and high-resolution transmission electron microscopy images. To verify the strong attachments, Fourier transforms infrared spectroscopy spectra were analyzed. Electrochemical sensing of NMS at CZ fabricated glassy carbon electrode reflects higher electrocatalytic activity with a linear range of NMS addition from 0.299 μM to 319.15 μM. The lower detection limit was about 0.005 μM with a sensitivity of 7.152 μAμM^?1 cm². The CZ nanocomposite will be more applicable for sensing several drugs with enriched active sites, higher conductivity, and large surface area raised from low-cost metal oxides when compared with highly conducting materials.