AVS 58th Annual International Symposium and Exhibition
    Graphene and Related Materials Focus Topic Friday Sessions
       Session GR+MS+EM-FrM

Paper GR+MS+EM-FrM8
Potassium-Ion Sensors Based on Valinomycin-Modified Graphene Field-Effect Transistors

Friday, November 4, 2011, 10:40 am, Room 208

Session: Graphene Device Physics and Applications
Presenter: Yasuyuki Sofue, The Institute of Scientific and Industrial Research, Osaka University, Japan
Authors: Y. Sofue, The Institute of Scientific and Industrial Research, Osaka University, Japan
Y. Ohno, The Institute of Scientific and Industrial Research, Osaka University, Japan
K. Maehashi, The Institute of Scientific and Industrial Research, Osaka University, Japan
K. Inoue, The Institute of Scientific and Industrial Research, Osaka University, Japan
K. Matsumoto, The Institute of Scientific and Industrial Research, Osaka University, Japan
Correspondent: Click to Email
Highly sensitive ion sensors based on valinomycin-modified graphene field-effect transistors (VGFETs) have been developed to selectively detect K ions, which are an essential element for biological activity including human life. Graphene single-layers were obtained by mechanical exfoliation. Graphene FETs were fabricated by conventional e-beam lithography and lift-off method on a thermally grown SiO2 layer. To demonstrate selective detection of K ions, the graphene channels were covered with ion selective membrane, which consisted of polyvinyl chloride and valinomycin. Transfer characteristics of VGFETs in a 100 mM Tris-HCl buffer solution with various KCl concentrations over the range from 10 nM to 1.0mM. With increasing K ion concentration, the solution-gated voltage at the Dirac point shifted toward negative direction. The shifts are due to the accumulation of positively charged K ions surrounded by valinomycin on the graphene surfaces. The electrostatic potential of graphene surfaces exhibit a rather linear dependence on log[K]. These results indicate that VGFETs effectively detected K ions with concentration from 10 nM to 1.0 mM. To investigate selectivity in VGFETs, Na-ion concentration dependence was also measured. The transfer characteristic in VGFETs remained almost constant over the Na ion concentration range between 10 nM and 1.0 mM. These results indicate that VGFET selectively detected K ions with high sensitivity.