Voltammetric determination of total dissolved iron in coastal waters using a glassy carbon electrode modified with reduced graphene oxide, Methylene Blue and gold nanoparticles

A nanocomposite, prepared from reduced graphene oxide (rGO), Methylene Blue (MB) and gold nanoparticles (AuNPs), was used to modify a glassy carbon electrode for the determination of total dissolved iron by differential pulse voltammetry. The use of rGO warrants a larger electrode surface and the presence of more active sites, while electron transfer is accelerated by incorporating AuNPs. MB acts as an electron mediator, as an anchor for the AuNPs (which were grown in situ), and also prevents the aggregation of rGO. The modified electrode displayed a remarkably improved sensitivity and selectivity for Fe(III). The kinetics of the electrode reaction is adsorption-controlled, and the reversible process involves one proton and one electron. The response to Fe(III) is linear in the 0.3 to 100 mu M concentration range, and the detection limit is 15 nM. Possible interferences by other ions were studied. The electrode was successfully applied to the determination of total dissolved iron in real coastal waters.