2D materials 2d material Conducting polymers Cross sensitivity Diffusion barriers Electrochemical electrodes Electrolytes Field effect transistors Gate electrodes Gold deposits Graphene Ion-sensitive field effect transistors Ionic strength PEDOT:PSS Performance Poly(3,4-ethylene dioxythiophene): poly(styrene sulphonic acid) Poly(styrene sulfonic acid) Pseudo reference electrodes Reference electrodes Refractory metal compounds Silicon compounds Silicon nanowire field-effect transistors Styrene biosensor diffusion barrier gate electrode stability