# Graphene sensors and optoelectronics

> Graphene sensing and optoelectronics in six panels: single NO₂ molecules detected as resistance steps, a metal–graphene–metal photodetector and its frequency response, a flexible transparent electrode and transparent neural electrodes that neurons are imaged through.

- Page: https://www.labcanvas.com/templates/graphene-research/graphene-sensors-optoelectronics
- Open in the LabCanvas editor (LabCanvas account): https://www.labcanvas.com/editor.html?template=graphene-sensors-optoelectronics
- Updated: 2026-10-14
- Category: Graphene research
- Method: Sensors
- Starting materials: Exfoliated and CVD graphene on SiO₂/Si or PET
- Product: Gas sensors, photodetectors and transparent electrodes
- Key result: Devices drawn in 3D after the cited papers, heights exaggerated; resistance steps and frequency response computed from the cited values
- Figure: 1920 × 1080 px, 45 editable layers (6 generated objects with settings)

## Steps

1. **Single-molecule sensor**: Micrometre-size graphene sensors detect single gas molecules: each one that attaches or detaches changes the local carrier concentration by one electron (Schedin et al. 2007); NO₂ is a strong acceptor, its dimer N₂O₄ dopes only weakly (Wehling et al. 2008)
2. **Resistance steps**: Each attachment or detachment is a step in the resistance; graphene is exceptionally low in noise (Schedin et al. 2007); resist residue dopes graphene and concentrates analyte (Dan et al. 2009)
3. **Photodetector**: Graphene on SiO₂ over a Si back gate with Ti/Au contacts; at the metal–graphene junction the local field separates electrons and holes, so it works without a source–drain bias (Xia et al. 2009; Park et al. 2009)
4. **How fast**: No degradation up to 40 GHz (Xia et al. 2009); an intrinsic response time of 2.1 ps, a bandwidth of ≈ 262 GHz (Urich et al. 2011)
5. **Transparent electrode**: Roll-to-roll, predominantly monolayer 30-inch CVD films: sheet resistance as low as ≈ 125 Ω/sq at 97.4 % transmittance; doped four-layer films ≈ 30 Ω/sq at ≈ 90 % (Bae et al. 2010)
6. **See through the electrode**: Neurons in hippocampal slices were imaged through transparent graphene electrodes by confocal and two-photon microscopy with no light-induced artefacts in the recordings (Kuzum et al. 2014)

## Strengths

- Every atom is on the surface
- Fast, unbiased photodetection (Xia et al. 2009)
- Transparent and flexible (Bae et al. 2010)

## Limitations

- Residues and substrates change the response (Dan et al. 2009)
- About 2 % absorption limits the responsivity (Xia et al. 2009)

## Uses

- Gas and chemical sensors
- Optical communications
- Touch screens and bioelectronics

## References

1. Schedin et al., “Detection of individual gas molecules adsorbed on graphene”, Nat. Mater. 2007. https://doi.org/10.1038/nmat1967 (primary)
2. Xia et al., “Ultrafast graphene photodetector”, Nat. Nanotechnol. 2009. https://doi.org/10.1038/nnano.2009.292 (primary)
3. Urich, Unterrainer & Mueller, “Intrinsic response time of graphene photodetectors”, Nano Lett. 2011. https://doi.org/10.1021/nl2011388 (primary)
4. Bae et al., “Roll-to-roll production of 30-inch graphene films for transparent electrodes”, Nat. Nanotechnol. 2010. https://doi.org/10.1038/nnano.2010.132 (primary)
5. Kuzum et al., “Transparent and flexible low noise graphene electrodes for simultaneous electrophysiology and neuroimaging”, Nat. Commun. 2014. https://doi.org/10.1038/ncomms6259 (primary)
6. Wehling et al., “Molecular doping of graphene”, Nano Lett. 2008. https://doi.org/10.1021/nl072364w (further reading)
7. Dan et al., “Intrinsic response of graphene vapor sensors”, Nano Lett. 2009. https://doi.org/10.1021/nl8033637 (further reading)
8. Park, Ahn & Ruiz-Vargas, “Imaging of photocurrent generation and collection in single-layer graphene”, Nano Lett. 2009. https://doi.org/10.1021/nl8029493 (further reading)
9. Echtermeyer et al., “Surface plasmon polariton graphene photodetectors”, Nano Lett. 2016. https://doi.org/10.1021/acs.nanolett.5b02051 (further reading)

Credit: Drawn and computed by LabCanvas after Schedin et al., Nat. Mater. 2007 (doi:10.1038/nmat1967), Xia et al., Nat. Nanotechnol. 2009, Urich et al., Nano Lett. 2011, Bae et al., Nat. Nanotechnol. 2010, Kuzum et al., Nat. Commun. 2014, and the papers in the details.

## Questions

**What does the “Graphene sensors and optoelectronics” template show?** Graphene sensing and optoelectronics in six panels: single NO₂ molecules detected as resistance steps, a metal–graphene–metal photodetector and its frequency response, a flexible transparent electrode and transparent neural electrodes that neurons are imaged through.

**What are the steps shown in “Graphene sensors and optoelectronics”?** 1. Single-molecule sensor: Micrometre-size graphene sensors detect single gas molecules: each one that attaches or detaches changes the local carrier concentration by one electron (Schedin et al. 2007); NO₂ is a strong acceptor, its dimer N₂O₄ dopes only weakly (Wehling et al. 2008). 2. Resistance steps: Each attachment or detachment is a step in the resistance; graphene is exceptionally low in noise (Schedin et al. 2007); resist residue dopes graphene and concentrates analyte (Dan et al. 2009). 3. Photodetector: Graphene on SiO₂ over a Si back gate with Ti/Au contacts; at the metal–graphene junction the local field separates electrons and holes, so it works without a source–drain bias (Xia et al. 2009; Park et al. 2009). 4. How fast: No degradation up to 40 GHz (Xia et al. 2009); an intrinsic response time of 2.1 ps, a bandwidth of ≈ 262 GHz (Urich et al. 2011). 5. Transparent electrode: Roll-to-roll, predominantly monolayer 30-inch CVD films: sheet resistance as low as ≈ 125 Ω/sq at 97.4 % transmittance; doped four-layer films ≈ 30 Ω/sq at ≈ 90 % (Bae et al. 2010). 6. See through the electrode: Neurons in hippocampal slices were imaged through transparent graphene electrodes by confocal and two-photon microscopy with no light-induced artefacts in the recordings (Kuzum et al. 2014).

**What are the starting materials and the product?** Starting materials: Exfoliated and CVD graphene on SiO₂/Si or PET. Product: Gas sensors, photodetectors and transparent electrodes.

**Which papers is “Graphene sensors and optoelectronics” based on?** Schedin et al., “Detection of individual gas molecules adsorbed on graphene”, Nat. Mater. 2007 (doi:10.1038/nmat1967); Xia et al., “Ultrafast graphene photodetector”, Nat. Nanotechnol. 2009 (doi:10.1038/nnano.2009.292); Urich, Unterrainer & Mueller, “Intrinsic response time of graphene photodetectors”, Nano Lett. 2011 (doi:10.1021/nl2011388); Bae et al., “Roll-to-roll production of 30-inch graphene films for transparent electrodes”, Nat. Nanotechnol. 2010 (doi:10.1038/nnano.2010.132); Kuzum et al., “Transparent and flexible low noise graphene electrodes for simultaneous electrophysiology and neuroimaging”, Nat. Commun. 2014 (doi:10.1038/ncomms6259); Wehling et al., “Molecular doping of graphene”, Nano Lett. 2008 (doi:10.1021/nl072364w); Dan et al., “Intrinsic response of graphene vapor sensors”, Nano Lett. 2009 (doi:10.1021/nl8033637); Park, Ahn & Ruiz-Vargas, “Imaging of photocurrent generation and collection in single-layer graphene”, Nano Lett. 2009 (doi:10.1021/nl8029493); Echtermeyer et al., “Surface plasmon polariton graphene photodetectors”, Nano Lett. 2016 (doi:10.1021/acs.nanolett.5b02051).

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