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 Gd 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 Gd-selective ligand DOTA is functionalized by an alkyne linker to be grafted by click chemistry on a gold electrode without losing its affinity for Gd. 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 Gdcaptured on the gate surface. The obtained sensor is able to quantify Gd even in a sample containing several other potentially interfering ions such as Ni, Ca, Na and In. The quantification range is from 1 pM to 10 mM, with a sensitivity of 20 mV dec expected for a trivalent ion. This paves the way for Gd quantification in hospital or industrial wastewater.