▎ 摘　　要

We present a simple, low-cost, large area, and contamination-free monolayer graphene field-effect transistor for liquid-gated sensing applications. The graphene surface does not require any photoresist including the commonly used polymethylmethacrylate, thus avoiding possible contamination and mobility degradation. We also examine the effects of different etching solutions and concentrations on the Dirac point of graphene. With optimal device fabrication recipe, we demonstrate the device's capability to sense different KCl concentrations and pH values under liquid gating configuration. Additionally, using polydimethylsiloxane as substrates holds an advantage of enabling simple integration between microfluidic systems and graphene for chemical and biological sensor applications. (C) 2013 AIP Publishing LLC.