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Graphene based pH sensing with extremely high sensitivity

ORAL

Abstract

We have reported pH sensors based on two-dimensional (2D) MoS2 dual-gated field-effect transistors (2D-MoS2 dual-FETs) with sensitivity that greatly surpasses the Nernst limit of 59 mV/pH [1]. To further improve device performance, we replaced the 2D-MoS2 channel with graphene which has a higher maximum quantum capacitance, higher current drive, and lower contact resistance. Our graphene dual-FETs featured asymmetric front-gate (ionic liquid) and back-gate (300 nm SiO2) capacitances which allowed a quantum capacitance limited signal amplification of up to ~500, a record result for a dual-FET with the given back-gate oxides. The low contact resistance of the graphene dual-FETs enables the devices to operate with two orders of magnitude lower drain voltage than comparable MoS2 devices. We benchmark graphene dual-FETs against 2D-MoS2 dual-FETs in sensitive pH measurements. The higher sensitivity, combined with a lower limit of detection make graphene dual-FETs a powerful tool for field monitoring of pH with wide ranging applications in biology, environmental monitoring and agriculture.
[1] Son T. Le et al., Nanoscale 11 (33), 15622-15632 (2019).

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Presenters

  • Son Le

    Physical Measurement Laboratory, National Institute of Standards and Technology, National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology & Theiss Research, Theiss Research, Inc., La Jolla, CA and NIST, Gaithersburg, MD

Authors

  • Son Le

    Physical Measurement Laboratory, National Institute of Standards and Technology, National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology & Theiss Research, Theiss Research, Inc., La Jolla, CA and NIST, Gaithersburg, MD

  • Seulki Cho

    National Institute of Standards and Technology, Biophysical and Biomedical Measurements Group, Physical Measurement Laboratory, National Institute of Standards and Technology

  • Arvind Balijepalli

    National Institute of Standards and Technology, Biophysical and Biomedical Measurements Group, Physical Measurement Laboratory, National Institute of Standards and Technology

  • Curt Richter

    National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology, Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD