Electrocatalytic activity of 6,7-dihydroxy-3-methyl-9-thia-4,4a-diazafluoren-2-one/multi-wall carbon nanotubes immobilized on carbon paste electrode for NADH oxidation: Application to the trace determination of NADH

Simultaneous Electrochemical Determination of Nicotinamide Adenine Dinucleotide and Ascorbic Acid at Carbon Nanotube Electrode

Simultaneous electrochemical determination of nicotinamide adenine dinucleotide (NADH) and ascorbic acid (AA) at a carbon nanotube electrode is presented. The discrimination of NADH and AA is conducted with the difference of peak potential by differential pulse voltammetry. Two well-distinguished anodic peaks, +0.56 and +0.26 V, due to NADH and AA are observed. The characteristics of those peaks were independent from each other. The attained characteristics for simultaneous determination of NADH and AA are (i) NADH measurement at the concentration range of 0.030 - 2.0 mM in the presence of 1.2 mM AA, and (ii) AA measurement at the concentration range of 0.030 - 2.0 mM in the presence of 2.0 mM NADH.

Electrocatalytic activity of nickel oxide nanoparticles as mediatorless system for NADH and ethanol sensing at physiological pH solution

The glassy carbon (GC) electrode modified by nickel oxide nanoparticles (NiOxNPs) is proposed as a novel electrocatalytic system for the oxidation of NADH without using any electron transfer mediator. Here, chronoamperometry was used not only as a simple method for the deposition of NiOxNPs onto the GC electrode but also as an efficient tool in the controlling of nanoparticles size and efficient electrocatalytic activity. The surface morphology and electrochemical properties of the NiOxNPs/GC electrode was investigated using scanning electron microscopy and cyclic voltammetry techniques, respectively. The NPs are deposited uniformly across the GC surface and the size of NiOxNPs varies from 20 to less than 100 nm. The NiOxNPs/GC electrode shows excellent electrocatalytic activity toward oxidation of NADH at reduced overvoltage. The detection limit and sensitivity of the modified electrode toward NADH were estimated to be 106 nM (S/N=3) and 0.052 μAμM(-1), respectively at a concentration range up to 1mM. Due to the biocompatibility of NiOxNPs toward biomolecules, this modified electrode can be used as an efficient transducer in the design of an ethanol biosensor based on the coupled alcohol dehydrogenase enzyme(ADH). Hydrodynamic amperometric detection of ethanol on the ADH-Nafion/NiOxNPs/GC modified electrode gives linear responses over the concentration range of 0.2-6mM with a detection limit of 6.4 μM and sensitivity of 36 nA mM(-1). Applicability of the proposed biosensor for ethanol detection in real samples, easy and simple preparation, being mediator free, high sensitivity and biocompatibility are the major advantages of the proposed biosensor.