Graphene-based field effect transistor sensors

Abstract

Graphene has attracted a large amount of attention in sensing applications due to its remarkable properties such as large surface area, high carrier mobility and sensitivity which make it ideal for the field. Graphene-based field effect transistor (GFET) in particular is an extremely sensitive platform for detecting various surface modulations and interactions. However, GFETs still have a number of challenges that hinder its full potential such as selectivity and reliability. This thesis presents two main works with GFET sensors. The first work involves fabricating a GFET device with two-dimensional paper networks (2DPN) as a component. The paper network serves as both a gate dielectric and an easy-to-fabricate vessel for containing the solution with the analyte species which are in this case DNA and glucose. The choice of paper enables a simpler alternative approach to the construction of a GFET device, which was shown to behave similarly to a solution-gated GFET with comparable electron-hole mobilities and Dirac points, and was able to produce current changes correlated with the analyte concentration. The second work involves the use of molecularly imprinted polymers (MIP), which were electrochemically grown on the surface of graphene to grant the GFET sensor high selectivity towards specific analyte molecules. The use of MIP allowed for the construction of a highly selective sensor without compromising the high mobility of pristine graphene. The polybithiophene-based MIP used in this work was electropolymerized on the surface of a CVD graphene, which was then shown to maintain the properties of graphene such as high carrier mobility as indicated by the I-V_g curves from its field-effect transistor (FET) device. Sensing studies using histamine as a model analyte demonstrated that the binding of the analyte with MIP induced current responses in the sensor where higher electron mobility was observed which was largely attributed to the electron sharing of histamine with the MIP during binding. The binding interaction of the MIP-analyte system was noted to play a crucial role in the detection where electron sharing and coordination is implicitly required to induce the current response.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology