Detection of mercury(II) ion in water using an organic field-effect transistor with a cysteine-immobilized gold electrode

In this note, we report on the electrical detection of a mercury(II) ion (Hg2+) in water using an organic field-effect transistor (OFET). The fabricated OFET device possesses an extended-gate gold electrode functionalized with l-cysteine (known as a Hg2+ ligand). We have investigated the detection ability of the OFET by immersing the extended-gate electrode in an aqueous solution with various Hg2+ concentrations. As a result, we have successfully observed the decrease in the drain current of the OFET upon the addition of incremental amounts of Hg2+ in water. The limit of detection for Hg2+ in this device is estimated to be 31 ppb.