An Electrolyte-Gated Graphene Field-Effect Transistor for Detection of Gadolinium(III) in Aqueous Media

In this work, an electrolyte-gated graphene field-effect transistor is developed for Gd3+ ion detection in water. The source and drain electrodes of the transistor are fabricated by photolithography on polyimide, while the graphene channel is obtained by inkjet-printing a graphene oxide ink subsequently electro-reduced to give reduced graphene oxide. The Gd3+-selective ligand DOTA is functionalized by an alkyne linker to be grafted by click chemistry on a gold electrode without losing its affinity for Gd3+. The synthesis route is fully described, and the ligand, the linker and the functionalized surface are characterized by electrochemical analysis and spectroscopy. The as functionalized electrode is used as gate in the graphene transistor so to modulate the source-drain current as a function of its potential, which is itself modulated by the concentration of Gd3+captured on the gate surface. The obtained sensor is able to quantify Gd3+ even in a sample containing several other potentially interfering ions such as Ni2+, Ca2+, Na+ and In3+. The quantification range is from 1 pM to 10 mM, with a sensitivity of 20 mV dec−1 expected for a trivalent ion. This paves the way for Gd3+ quantification in hospital or industrial wastewater.