Three dimensional monolayer graphene foam for ultra-sensitive pH sensing

In this work, we present liquid gated three-dimensional graphene transistor for pH sensing. The sensor is made of three-dimensional network of graphene coated with hafnium oxide (HfO 2 ) operating as a pH-sensitive liquid gated field effect transistor with super-nerstian sensitivity. We attribute high sensitivity in this device to the coating of HfO 2 which provides increased interaction with hydrogen ions in the solution and on the three dimensional foam-like structure of the graphene transistor which provides very high surface-to-volume ratio.