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Peer-reviewedCC BY 4.0ACS Nano

High-Throughput In-Operando Terahertz Time-Domain Spectroscopy of Chemical Vapor Deposited Graphene for pH Sensing

  • Oliver J. Burton1
  • Sebastian Engelbrecht2
  • Thomas Goepfert2
  • Ibtisam Hammad Abbasi1
  • Linyuan Xin1
  • Bernd M. Fischer2
  • Hannah Joyce1
  • Stephan Hofmann1
  • Hungyen Lin3
  1. 1Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom
  2. 2French-German Research Institute of Saint-Louis, 5 Rue du Général Cassagnou, 68301 Saint-Louis Cedex, France
  3. 3School of Engineering, University of Warwick, Coventry CV4 7AL, United Kingdom
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Abstract

Reliable pH sensing in liquid environments underpins applications in energy storage, biosensing, and process monitoring, yet conventional graphene-based electrical devices introduce ohmic contacts, encapsulation layers, and electrochemical artifacts that can obscure intrinsic behavior. These approaches also fail to capture the strong spatial variability of commercial CVD graphene. Here, we present a fully contactless methodology for quantifying pH-dependent conductivity of large-area CVD graphene using through-substrate reflection terahertz time-domain spectroscopy (THz-TDS). A customized liquid cell with a THz transparent window preserves unrestricted access to the graphene–electrolyte interface while enabling centimeter-scale conductivity mapping and in-operando single-point monitoring during sequential pH modulation. By integrating spatially registered Raman mapping with automated quality-metric filtering, we extract statistically robust trends across thousands of pixels rather than isolated device regions. We show that pristine monolayer graphene exhibits the highest baseline conductivity and strongest pH sensitivity, whereas O2-plasma-introduced defects systematically suppress both. This scalable, remote, and inert probing approach establishes THz-TDS as a powerful platform for high-throughput characterization and robust liquid-phase sensing in thin films and 2D systems.

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Cite

BibTeXRIS
BibTeX
@article{burton2026highthroughput,
  title = {{High-Throughput In-Operando Terahertz Time-Domain Spectroscopy of Chemical Vapor Deposited Graphene for pH Sensing}},
  author = {Oliver J. Burton and Sebastian Engelbrecht and Thomas Goepfert and Ibtisam Hammad Abbasi and Linyuan Xin and Bernd M. Fischer and Hannah Joyce and Stephan Hofmann and Hungyen Lin},
  journal = {ACS Nano},
  year = {2026},
  month = oct,
  doi = {10.1021/acsnano.6c03948},
  url = {https://doi.org/10.1021/acsnano.6c03948},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - High-Throughput In-Operando Terahertz Time-Domain Spectroscopy of Chemical Vapor Deposited Graphene for pH Sensing
AU  - Oliver J. Burton
AU  - Sebastian Engelbrecht
AU  - Thomas Goepfert
AU  - Ibtisam Hammad Abbasi
AU  - Linyuan Xin
AU  - Bernd M. Fischer
AU  - Hannah Joyce
AU  - Stephan Hofmann
AU  - Hungyen Lin
PY  - 2026
DA  - 2026/10/21
JO  - ACS Nano
DO  - 10.1021/acsnano.6c03948
UR  - https://doi.org/10.1021/acsnano.6c03948
AB  - Reliable pH sensing in liquid environments underpins applications in energy storage, biosensing, and process monitoring, yet conventional graphene-based electrical devices introduce ohmic contacts, encapsulation layers, and electrochemical artifacts that can obscure intrinsic behavior. These approaches also fail to capture the strong spatial variability of commercial CVD graphene. Here, we present a fully contactless methodology for quantifying pH-dependent conductivity of large-area CVD graphene using through-substrate reflection terahertz time-domain spectroscopy (THz-TDS). A customized liquid cell with a THz transparent window preserves unrestricted access to the graphene–electrolyte interface while enabling centimeter-scale conductivity mapping and in-operando single-point monitoring during sequential pH modulation. By integrating spatially registered Raman mapping with automated quality-metric filtering, we extract statistically robust trends across thousands of pixels rather than isolated device regions. We show that pristine monolayer graphene exhibits the highest baseline conductivity and strongest pH sensitivity, whereas O2-plasma-introduced defects systematically suppress both. This scalable, remote, and inert probing approach establishes THz-TDS as a powerful platform for high-throughput characterization and robust liquid-phase sensing in thin films and 2D systems.
SN  - 1936-0851
SN  - 1936-086X
ER  -