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N-Heterocyclic Carbene–Graphene Nanotransistor Based on Covalent Bond for Ultrastable Biosensors

A graphene biosensor affected by environmental exposure, ensuring environmental stability through covalent bonding of interfacing compounds

SKKU Advanced Institute of Nano Technology
Prof. KWON, OH SEOK
KIM KYUNGHO, SEO SUNGEUN

  • N-Heterocyclic Carbene–Graphene Nanotransistor Based on Covalent Bond for Ultrastable Biosensors
  • N-Heterocyclic Carbene–Graphene Nanotransistor Based on Covalent Bond for Ultrastable Biosensors
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This study was conducted to develop a highly sensitive and stable biosensor for pathogen detection. To address the low sensitivity and specificity of conventional electric-based point-of-care test (PoCT) devices in detecting specific biomarkers, a graphene-based nanotransistor biosensor was proposed.


A novel surface modification technique was developed to form a self-assembled monolayer (SAM) of N-heterocyclic carbene (NHC) compounds on the graphene channel of a finely patterned field-effect transistor. This technique enhanced the chemical stability and bio-receptor attachment efficiency of the graphene surface.


Using density functional theory (DFT) simulations, various derivative compounds were identified, and the bonding of different carbene compounds was validated both theoretically and experimentally. The most stable and optimal compound was selected and applied, demonstrating a robust and stable surface binding structure.


Notably, the carbene compounds were designed to incorporate hydrophilic and hydrophobic layers, enhancing stability and reducing interference from non-target substances.


By functionalizing the graphene nanotransistor surface with antibodies or protein receptors, the biosensor achieved highly sensitive detection of O. tsutsugamushi (the causative agent of scrub typhus), E. coli (a foodborne pathogen), and SARS-CoV-2 (COVID-19 virus) at concentrations as low as 100 cfu/mL and 10 pg/mL. Furthermore, tests using clinical samples demonstrated approximately 100-fold higher sensitivity compared to commercially available diagnostic kits, along with excellent reproducibility and performance.


This study highlights the potential of this technology for rapid diagnostics in the era of emerging pandemics and high-transmission infectious diseases.



A Monolayer (SAM) of N-heterocyclic carbene (NHC) compounds on the graphene channel






DFT Simulation-Based Carbene Compound Library





  • Top: Detection results for Orientia tsutsugamushi (scrub typhus bacteria) and foodborne pathogens


  • Bottom: Detection results for COVID-19 in cultured and clinical samples






On-Site Hospital Validation Using a Portable Device

  • Top: Negative pressure room testing, portable device, disposable kit
  • Bottom: Performance comparison with LFA rapid diagnostic kit








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