Graphene Nanoplatelet–Au Nanoparticle Hybrid as a Capacitive-Metal–Oxide–Semiconductor pH Sensor

pH sensors, with high sensitivity, durability, and low cost, are considered to be essential tools in several applications such as laboratory experiments, water quality, agriculture, and healthcare. Because of their unique properties, carbon allotropes have attracted a lot of attention during the last decade to be utilized in several applications, in which pH sensing is one of them. In this work, a hybrid film of graphene nanoplatelets (GPs) and gold nanoparticles (GNPs), where the GNPs are embedded in the GP layer, was used as an active layer in an electronic pH senor based on a capacitive metal oxide semiconductor. Capacitance–voltage measurements have shown a change in the flatband voltage with changing the applied pH. The sensitivity of the GP–Au nanoparticle hybrid (GAH) film has been enhanced by a factor of 26.7% compared to the GP film. We refer the higher sensitivity to the increase in the surface potential of the GAH, which became n-doped by the Au nanoparticles, resulting in a change of the Fermi level of the GP layer. This sensor is easy to fabricate and demonstrates sensitivity that is higher than previously reported electronic pH sensitivities using different configurations.