Microwave-enhanced voltammetric detection of copper(II) at gold nanoparticles-modified platinum microelectrodes

In this work, in situ microwave activation of electrochemical detection of copper(II) at a gold nanoparticles-modified Pt microelectrode (Au-NPs/Pt) was investigated. Self-focusing of the microwave radiation creates an extreme localized heating at the electrode/solution (electrolyte) interface within the diffusion layer of the electrode with an inverted thermal gradient and convective flow. The temperature at the electrode/solution interface is calibrated with reversible one electron redox system Fe (CN)₆^{3 - / 4 -} in aqueous K₂SO₄ solution (pH 3). Significantly increased currents were observed at the Au-NPs/Pt electrode compared to that at bare Pt electrode under the low microwave power. The Cu(II) detection at the Au-NPs/Pt microelectrode by cyclic voltammetry is also shown to be strongly enhanced by microwave radiation, which triggers Cu(II) current response orders of magnitude higher than those expected values in conventional conditions. The limit of detection by cyclic voltammetry is found to be 0.1 μM and 1.0 μM with and without microwave radiation. The effect of surfactant, which blocks the electrochemical Cu(II) signal under conventional conditions, is discussed on the Cu(II) response under the in situ microwave radiation of electrochemical process.