Highly Sensitive pH Sensors of Extended-Gate Field-Effect Transistor With the Oxygen-Functionalized Reduced Graphene Oxide Films on Reverse Pyramid Substrates

The oxygen-plasma-treated reduced graphene oxide films (OPT-RGOFs) as the pH sensing membranes for the extended-gate field-effect transistors were demonstrated to achieve the higher pH sensitivity of 52 mV/pH and better linearity of 0.996 in a wide sensing range of pH 1–13 than those without plasma treatment. It was attributed to the oxygen-containing functional groups on the RGOF induced from the plasma treatment. In addition, the OPT-RGOFs sprayed on the reverse pyramid substrates were also proposed to further enhance the sensing sites, leading to a superior pH sensitivity of 57 mV/pH with an excellent linearity of 0.996.