In situ stabilization of hydroxylamine via electrochemical immobilization of 4-nitrophenol on GCE/MWCNT electrodes: NADH electrocatalysis at zero potential
| Autor: | Annamalai Senthil Kumar, Madhanagopal Jagannathan, Sornambikai Sundaram, Mohammed Rafiq Abdul Kadir |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Anal. Methods. 6:8894-8900 |
| ISSN: | 1759-9679 1759-9660 |
| Popis: | Electrochemical immobilization of 4-nitrophenol (4-NP) was conducted on a purified multi-walled carbon nanotube (p-MWCNT) modified glassy carbon electrode (GCE/p-MWCNT) in pH 7 phosphate buffer solution (PBS). The electrochemical reduction of 4-NP to stable in situ electrogenerated hydroxylamine (ONHOH) intermediate species within the p-MWCNT matrix may be the underlying mechanism of immobilization. The ONHOH-stabilized p-MWCNT modified electrode, GCE/ONHOH@p-MWCNT, showed stable and well-defined surface-confined redox peaks at −0.11 V (A1/C1) and 0.080 V (A2/C2) vs. Ag/AgCl over other CNT-modified GCEs. The modified electrode system suggested quasi-reversible and reversible electron transfer mechanisms for the A1/C1 and A2/C2 redox couples. TEM analysis of the ONHOH@p-MWCNT hybrid powder demonstrated the presence of ONHOH species on the surfaces, as well as on the inner walls of the p-MWCNTs. The XRD peaks exhibited shifts in 2θ values for the hybrid material compared with the unmodified materials, which confirmed the stabilization of ONHOH within the p-MWCNT via π–π interactions. Electrochemical characterization of the GCE/ONHOH@p-MWCNT revealed two electron transfer mechanisms with adsorption-controlled and Nernstian behaviours. A highly sensitive electrocatalytic oxidation of dihydronicotinamide adenine dinucleotide (NADH) at 0.02 V vs. Ag/AgCl was achieved with the GCE/ONHOH@p-MWCNT. Furthermore, the hybrid electrode successfully sensed NADH amperometrically with 2.9 nA μM−1 sensitivity, a 0.043 μM limit of detection and a linear detection range from 100 μM to 1 mM for ten successive additions of 100 μM NADH at an applied potential of 0.02 V vs. Ag/AgCl in pH 7 PBS. |
| Databáze: | OpenAIRE |
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