Electroactive magnetic nanoparticles under magnetic attraction on a microchip electrochemical device
Résumé
This work focused on the introduction of electrochemical moieties (electroactive molecules) onto the surface of magnetic nanoparticles (NPs) based on carbodiimide coupling chemistry and the influence of magnetic attrac- tion at the working electrode surface on their electrochemical behaviour. The magnetic NPs were first func- tionalized with polyamidoamine (PAMAM) dendrimer generation 0 and then with ferrocenecarboxylic acid (Fc) as electroactive molecule. Colorimetric titration, zeta potential measurements and infrared spectroscopy proved the effective conjugation of PAMAM and Fc onto NPs. The conjugation of Fc onto the NPs was also evidenced by voltammetry as it resulted in a half-peak potential shift from 0.328 V for free Fc to 0.590 V after coupling. A transition from a reversible to an irreversible behaviour was also observed. Finally, an external magnetic field was applied on Fc-conjugated NPs to attract them onto the working electrode of a microchip electrochemical device, and the resulting modifications of the electrochemical behaviour were studied. Compared to Fc dispersed in solution, the current peak height of Fc-conjugated NPs was 2-fold higher under magnetic attraction. The mechanism of electrochemical reaction was investigated and was found to be irreversible. Surprisingly, the reaction was diffusion-controlled upon attraction.