Conductometric graphene sensors decorated with nanoclusters for selective detection of Hg2+ traces in water

Mercury ion (Hg2+) sensors based on graphene and gold nanoclusters are presented in this work. The sensors follow the structure of field-effect transistor (FET), and their sensing mechanism relies on the change in conductance of graphene and gold nanocluster percolating film. Each sensor was fabricated by deposition of interdigitated metal electrodes on the surface of graphene by thermal evaporation through a shadow mask. Next, gold nanoclusters are generated by magnetron discharge sputtering and inert-gas condensation inside an ultra-high compatible system, and they are self-assembled on the surface of graphene. The sensitivity and selectivity of graphene to Hg2+ are vastly enhanced by incorporating the nanoclusters on its surface. The detection limit of the present sensors is below the safe concentration of Hg2+ in drinking water set by different universal agencies. In addition, those sensors are practical and easy to operate in field for real life applications.