Reversible and Irreversible Responses of Defect-Engineered Graphene-Based Electrolyte-Gated pH Sensors

Sun Sang Kwon, Jaeseok Yi, Won Woo Lee, Jae Hyeok Shin, Su Han Kim, Seunghee H. Cho, Sungwoo Nam, Won Il Park

Research output: Contribution to journalArticlepeer-review


We have studied the role of defects in electrolyte-gated graphene mesh (GM) field-effect transistors (FETs) by introducing engineered edge defects in graphene (Gr) channels. Compared with Gr-FETs, GM-FETs were characterized as having large increments of Dirac point shift (∼30-100 mV/pH) that even sometimes exceeded the Nernst limit (59 mV/pH) by means of electrostatic gating of H+ ions. This feature was attributed to the defect-mediated chemisorptions of H+ ions to the graphene edge, as supported by Raman measurements and observed cycling characteristics of the GM FETs. Although the H+ ion binding to the defects increased the device response to pH change, this binding was found to be irreversible. However, the irreversible component showed relatively fast decay, almost disappearing after 5 cycles of exposure to solutions of decreasing pH value from 8.25 to 6.55. Similar behavior could be found in the Gr-FET, but the irreversible component of the response was much smaller. Finally, after complete passivation of the defects, both Gr-FETs and GM-FETs exhibited only reversible response to pH change, with similar magnitude in the range of 6-8 mV/pH.

Original languageEnglish (US)
Pages (from-to)834-839
Number of pages6
JournalACS Applied Materials and Interfaces
Issue number1
StatePublished - Jan 13 2016


  • defect passivation
  • defect-mediated chemisorption
  • electrolyte-gated field effect transistor
  • graphene
  • graphene mesh
  • nanosensor
  • pH sensor

ASJC Scopus subject areas

  • Materials Science(all)


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