Solid-Contact Ion-Selective Electrodes (ISEs) based on Ligand Functionalised Gold Nanoparticles

Gold nanoparticles (Au-NPs) functionalised with lipoic acid (LAc) or lipoic amide (LAm) have been investigated as solid-contact in disposable lead and sodium selective electrodes. In Pb2+ and Na+ solutions, electrodes incorporating LAm Au-NPs displayed super-Nernstian and Nernstian behaviour whereas electrodes incorporating LAc Au-NPs showed Nernstian and sub-Nernstian responses. During calibration, the response of solid-contact ion-selective electrodes (SC-ISEs) was found to depend on the particular ion-analyte/Au-NP ligand pair, suggesting that the ligand decorating the NPs has an important role in regulating the overall electrode response function. Insights into the underlying trans-membrane and the Au-NPs/membrane interface processes have been obtained by means of electrochemical impedance spectroscopy.