Microwave-enhanced electrochemical processes in micellar surfactant media |
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Authors: | Mohamed A Ghanem Frank Marken Barry A Coles Richard G Compton |
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Institution: | (1) Department of Chemistry, University of Bath, Bath, BA2 7AY, UK;(2) Physical & Theoretical Chemistry Laboratory, Oxford University, Oxford, OX1 3QZ, UK;(3) Present address: Science & Mathematics Department, Faculty of Petroleum& Mining Engineering, Suez, Egypt |
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Abstract: | High intensity microwave radiation effects are demonstrated for electron transfer processes at 25 or 50-μm diameter platinum
electrodes immersed in micellar sodium dodecylsulfate (SDS) solutions. First, a solution containing 2 mM Fe(CN)63− and 2 mM Fe(CN)64− in aqueous 0.1 M NaCl with and without SDS is employed to calibrate the electrode temperature and mass transport conditions.
Addition of 0.1 M SDS has only a small effect on the microwave enhanced voltammetry for the Fe(CN)63-/4− system. Next, two highly water-insoluble redox systems are studied. A solution of 1 mM tert-butylferrocene in aqueous 0.1 M NaCl containing 0.1 M SDS is shown to give no current response in the absence of microwaves.
In the presence of focused microwaves at a platinum disc electrode, a strong current for the one electron oxidation of tert-butylferrocene is detected presumably due to localized disruption of the micellar solution. Concentrations of tert-butylferrocene down to the micromolar level are detected. α-Tocopherol, a lipophilic vitamin and antioxidant, is soluble
in aqueous 0.1 M SDS/0.1 M NaCl. In the presence of microwave radiation, a strong and concentration dependent anodic current
response consistent with the two-electron oxidation of α-tocopherol is observed. A heptode array of seven individual 50 μm
diameter platinum microelectrodes placed in ca. 720 μm distance of each other is shown to allow microwave enhanced currents
to be increased sevenfold with each electrode exhibiting the same microwave effect. |
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Keywords: | Microwave Electrochemistry Voltammetry Surfactants Micelle Ferrocene Vitamin Antioxidants Cavitation Array electrode Heptode |
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