Super-Nernstian pH Sensor Based on Anomalous Charge Transfer Doping of Defect-Engineered Graphene
Su-Ho Jung1, Young-Min Seo2, Taejun Gu2
1SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University, Suwon 440-746, South Korea.
Nano Letters
|November 2, 2020
Summary
This study introduces a novel proton-permeable graphene pH sensor that surpasses the Nernst limit. The defect-engineered nanocrystalline graphene (nc-Gr) achieves super-Nernstian pH sensitivity, enabling ultrasensitive aqueous solution pH detection.
Area of Science:
- Materials Science
- Nanotechnology
- Electrochemistry
Background:
- Conventional graphene ion-sensitive field-effect transistor (Gr-ISFET) pH sensors are limited by the Nernstian sensitivity of ~59 mV/pH.
- Ultrasensitive pH detection requires sensors that can exceed this theoretical limit for accurate aqueous solution analysis.
Purpose of the Study:
- To develop a novel Gr-ISFET-based pH sensor with enhanced sensitivity.
- To engineer defect-rich graphene for improved proton interaction and pH sensing capabilities.
Main Methods:
- Fabrication of a novel pH sensor using proton-permeable, defect-engineered nanocrystalline graphene (nc-Gr).
- Analysis of pH sensitivity by tuning graphene grain boundary density and SiO2 surface functional groups (OH-, NH2-, CH3-).
- Investigation of the charge-neutral point (CNP) shift in response to varying pH levels.
Main Results:
- The nc-Gr ISFET exhibits an unusual negative shift in CNP with increasing pH.
- Optimized nc-Gr ISFETs demonstrate a super-Nernstian pH response of approximately -140 mV/pH.
- Proton permeability through graphene grain boundaries enhances interaction with the underlying dopant layer.
Conclusions:
- Defect-engineered nc-Gr enables ultrasensitive pH sensing beyond the Nernst limit.
- The developed sensor offers a promising platform for high-accuracy aqueous solution pH monitoring.
- Tailoring graphene's microstructure and surface chemistry is key to achieving super-Nernstian performance.
