pH sensing characteristics and biosensing application of solution-gated reduced graphene oxide field-effect transistors.

Solution-gated reduced graphene oxide field-effect transistors (R-GO FETs) were investigated for pH sensing and biochemical sensing applications. A channel of a networked R-GO film formed by self-assembly was incorporated as a sensing layer into a solution-gated FET structure for pH sensing and the detection of acetylcholine (Ach), which is a neurotransmitter in the nerve system, through enzymatic reactions. The fabricated R-GO FET was sensitive to protons (H(+)) with a pH sensitivity of 29 mV/pH in terms of the shift of the charge neutrality point (CNP), which is attributed to changes in the surface potential caused by the interaction of protons with OH surface functional groups present on the R-GO surface. The R-GO FET immobilized with acetylcholinesterase (AchE) was used to detect Ach in the concentration range of 0.1-10mM by sensing protons generated during the enzymatic reactions. The results indicate that R-GO FETs provide the capability to detect protons, demonstrating their applicability as a biosensing device for enzymatic reactions.