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A nanocomposite comprising hexagonal CoAl-layered double hydroxide nanoshales with multiwall carbon nanotubes (MWCNTs) was synthesized by reflux heating. The nanocomposite was then applied to modify a carbon paste electrode. The modified electrode was then applied to fabricate a non-enzymatic hydrogen peroxide sensor. Hydrogen peroxide was electrocatalytically oxidized on the modified electrode surface, while its electroreduction was performed by an enhanced direct electron transfer to the electrode surface. The catalytic rate constants of the hydrogen peroxide electrooxidation were processed by an active cobalt species, and the diffusion coefficient of hydrogen peroxide was reported. An amperometric method was developed for determination of hydrogen peroxide based on its electrocatalytic oxidation with a sensitivity of 118.0 mA dm 3 mol-1 cm-2 and a limit of detection of 10 mol dm-3. In addition, amperometric method based on hydrogen peroxide electroreduction had a sensitivity of 42.0 mA dm 3 mol-1 cm-2 and a limit of detection of 40 mol dm-3. The sensor had the advantages of high activity and sensitivity, with a simple fabrication method without complications of immobilization steps and using any enzyme or reagent.

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Nickel nanowrinkles were synthesized by a simple hydrothermal method in one step in the presence of fluoride ions in ethylene glycol. The nanowrinkles were then employed as the modifier of a carbon paste electrode. The kinetics of the charge transfer across the modified electrode/solution interface was studied and the modified electrode was employed to fabricate an amperometric sensor of hydrochlorothiazide. The mechanism and kinetics of the electrocatalytic oxidation of hydrochlorothiazide on the modified electrode surface were studied by cyclic voltammetry and chronoamperometry. An amperometric procedure was developed for determination of hydrochlorothiazide with a sensitivity of 13.50 mA mol-1 dm 3 cm-2 and a limit of detection of 21.2 mol dm-3. The method was used for the direct assay of hydrochlorothiazide in human serum samples and hydrochlorothiazide tablets. The sensor had the advantages of sensitivity (guaranteed by a Nafion layer on the sensor surface), high electrocatalytic activity and long-term stability toward hydrochlorothiazide.