Direct electrochemistry of myoglobin based on electrodeposition of Pd nanoparticles with carbon ionic liquid electrode as basic electrode

Synthesis of honeycomb Ag@CuO nanoparticles and their application as a highly sensitive and electrocatalytically active hydrogen peroxide sensor material

Copper acetate/silver nitrate/polyvinylpyrrolidone was first prepared into nano-hybrid silver-doped copper oxide by electrospinning, and then nano-honeycomb particles were produced through heat-treatment. For the first time, honeycomb Ag@CuO nanoparticles were prepared by electrospinning, and a H₂O₂ sensor was constructed by modifying the carbon paste electrode (CPE) with the honeycomb Ag@CuO nanoparticles. This work performed the structural, morphological, and phase analysis of the Ag@CuO nanoparticles by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated the synthesis of Ag@CuO hybrid nanoparticles with high purity, and cyclic voltammetry and amperometry show that the Ag@CuO modified electrode has high electrocatalytic performances with fast voltammetric responses and a notably decreased overpotential compared to that of even the CuO modified CPE. In addition, the Ag/CuO-CPE based H₂O₂ sensor has the highest sensitivity of 1982.14 μA (mmol L^-1)^-1 cm^-2, the lowest detection limit of 0.01 μmol L^-1 ((S/N) = 3), and the measured linear response for H₂O₂ oxidation ranged from 0.05 μmol L^-1 to 100 μmol L^-1 and 100 μmol L^-1 to 1.5 mmol L^-1. The proposed method was applied to the determination of H₂O₂ in coconut fruit samples from canned coconut, and the satisfactory results confirmed the applicability of this sensor in practical analysis.

Electron Transfer of Myoglobin Immobilized in Au Electrodes Modified with a RAFT PMMA-Block-PDMAEMA Polymer

Myoglobin was immobilized with poly(methyl methacrylate)-block-poly[(2-dimethylamino)ethyl methacrylate]PMMA-block-PDMAEMA polymer synthesized by reversible addition-fragmentation chain transfer technique (RAFT). Cyclic voltammograms gave direct and slow quasireversible heterogeneous electron transfer kinetics between Mb-PMMA-block-PDMAEMA modified electrode and the redox center of the protein. The values for electron rate constant (Ks) and transfer coefficient (α) were0.055±0.01·s−1and0.81±0.08, respectively. The reduction potential determined as a function of temperature (293–328 K) revealed a value of reaction center entropy ofΔS0of351.3±0.0002 J·mol−1·K−1and enthalpy change of-76.8±0.1 kJ·mol−1, suggesting solvent effects and charge ionization atmosphere involved in the reaction parallel to hydrophobic interactions with the copolymer. The immobilized protein also exhibits an electrocatalytical response to reduction of hydrogen peroxide, with an apparentKmof114.7±58.7 μM. The overall results substantiate the design and use of RAFT polymers towards the development of third-generation biosensors.