spore: profile
id: graphene-oxide
spore_version: 0.2
family: carbon-materials
name: Graphene oxide and reduced graphene oxide
abbreviation: GO, rGO
role: Oxidised graphene sheet (GO) and its reduced form (rGO), used as membranes, composites and coatings
category: carbon
type: Graphene
summary: |
  Graphene oxide (GO) is a graphene sheet carrying oxygen groups (epoxy, hydroxyl, carbonyl and carboxyl), made by oxidising graphite. It sits in the same category and type as graphene, but it is not graphene: the oxygen groups make GO an electrical insulator, lower its heat conduction and let it disperse in water. Reduced graphene oxide (rGO) has had some of those groups removed and conducts electricity far better, though still much less than graphene. The values come from a 2019 review, a 2026 review, a 2012 membrane paper, a USGS report, a supplier safety data sheet, HSE guidance and an encyclopedia entry, all read in this run.
best_for: Water-permeable membranes, polymer composites and films where an insulating or water-dispersible carbon sheet is wanted
weakest_at: 'Electrical and thermal performance: GO is an insulator, and reduced GO depends on the reduction route, so no single value describes it'
identity:
  formula: Carbon sheet with variable epoxy, hydroxyl, carbonyl and carboxyl groups; no fixed formula
  cas: ''
  crystal_system: Two-dimensional sheet, usually stacked; no fixed crystal system
  space_group: ''
  source: go-synthesis
  where: Introduction, passage on GO structure with oxygen groups in variable ratios
tags:
  environments: []
  stresses: []
  applications:
    - structures
    - thermal-control
    - electronics-and-chips
    - habitats-and-suits
properties:
  - benchmark: elastic_modulus
    label: Young's modulus, bulk GO paper
    value: 6
    value_high: 42
    bound: range
    unit: GPa
    scope: material
    conditions:
      basis: GO paper (stacked sheets); range printed in the review for different oxidation degrees and thicknesses
      test: not stated in the review
    method: Range quoted in an open-access review, which cites ref 13 of that review
    status: ground
    source: huang2019
    where: Introduction, paragraph on mechanical properties of GO
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, bulk GO paper (the review calls it intrinsic strength)
    value: 76
    value_high: 293
    bound: range
    unit: MPa
    scope: material
    conditions:
      basis: GO paper (stacked sheets); range printed in the review
    method: Range quoted in the review, in the same paragraph as the modulus
    status: ground
    source: huang2019
    where: Introduction, paragraph on mechanical properties of GO
  - benchmark: elastic_modulus
    label: Young's modulus, GO monolayer (review value)
    value: 250
    unit: GPa
    scope: material
    conditions:
      basis: GO monolayer; printed as 250 ± 150 GPa
      test: not stated in the review
    method: Value quoted in the review, citing ref 11 of that review
    status: ground
    note: The printed spread is ± 150 GPa, so this single value is a wide estimate, not a measured range.
    source: huang2019
    where: Introduction, paragraph on mechanical properties of GO
  - benchmark: intrinsic_strength
    label: Intrinsic strength, GO monolayer (review value)
    value: 30
    value_high: 50
    bound: range
    unit: GPa
    scope: material
    conditions:
      basis: GO monolayer; range printed in the review, paired with the monolayer modulus above
    method: Range quoted in the review, citing ref 11 of that review
    status: ground
    note: Snake-case name, not in the property canon; see gaps.
    source: huang2019
    where: Introduction, paragraph on mechanical properties of GO
  - benchmark: elastic_modulus
    label: Young's modulus, GO modified with polyvinyl alcohol
    value: 8
    unit: GPa
    scope: material
    conditions:
      basis: GO modified with polyvinyl alcohol (ref 133 of the review); the unmodified GO in the same row is 5 GPa
      form: modified GO film or paper; form not stated in the row
    method: Value printed in Table 1 of the review
    status: ground
    source: huang2019
    where: Table 1 (Young's modulus and tensile strength of GO modified by ions and molecules), row polyvinyl alcohol, ref 133
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, GO modified with polyvinyl alcohol
    value: 125
    unit: MPa
    scope: material
    conditions:
      basis: GO modified with polyvinyl alcohol (ref 133 of the review); the unmodified GO in the same row is 25 MPa
    method: Value printed in Table 1 of the review
    status: ground
    source: huang2019
    where: Table 1 (Young's modulus and tensile strength of GO modified by ions and molecules), row polyvinyl alcohol, ref 133
  - benchmark: elastic_modulus
    label: Out-of-plane Young's modulus, conventional GO at 25 percent relative humidity
    value: 35
    unit: GPa
    scope: material
    conditions:
      basis: conventional porous GO at relative humidity 25 percent, out-of-plane direction
    method: Experimental value quoted in the review and matched by DFT with intercalated water
    status: ground
    note: Printed as 35 ± 10 GPa at ambient humidity. The modulus changes with humidity, so it is not a fixed value.
    source: huang2019
    where: Section on out-of-plane elasticity, text on conventional GO at RH 25 percent (Fig. 13)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, GO (lowest value cited)
    value: 0.0486
    unit: S/m
    scope: material
    conditions:
      basis: GO; the review gives this as the lowest GO conductivity it cites
      test: sample form and method not stated
    method: Value quoted in an open-access 2026 review
    status: ground
    source: monir2026
    where: Section 2.1 (electrical properties of GO and rGO)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, rGO monolayer after chemical reduction
    value: 0.052
    unit: S/m
    scope: material
    conditions:
      basis: chemically reduced rGO monolayer on a silicon substrate, room temperature (298 K)
    method: Value quoted in the review, citing Gomez-Navarro et al. (ref 189 of the review)
    status: ground
    note: The review says this is still about three orders of magnitude below pristine graphene.
    source: huang2019
    where: Section on electronic transport of GO and RGO (Fig. 23a)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, rGO reduced by Shewanella
    value: 55.32
    unit: S/m
    scope: material
    conditions:
      basis: rGO made by microbial reduction with Shewanella oneidensis
    method: Value quoted in an open-access 2026 review
    status: ground
    source: monir2026
    where: Section 2.1 (electrical properties of rGO)
  - benchmark: electrical_conductivity
    label: Electrical conductivity, rGO reduced by hydrazine (comparison case)
    value: 216.56
    unit: S/m
    scope: material
    conditions:
      basis: rGO made by hydrazine reduction, quoted as the comparison case in the review
    method: Value quoted in an open-access 2026 review
    status: ground
    source: monir2026
    where: Section 2.1 (electrical properties of rGO), hydrazine comparison
  - benchmark: thermal_conductivity
    label: Thermal conductivity, GO and rGO papers or thin films (upper bound)
    value: 10
    bound: upper
    unit: W/(m·K)
    scope: material
    conditions:
      basis: GO or rGO paper or thin film; test temperature not stated in the review
    method: Statement in the review, citing two experimental papers (refs 316 and 317 of the review)
    status: ground
    note: The review attributes the low value to phonon scattering at the junctions between GO nanoplatelets.
    source: huang2019
    where: Thermal properties section, opening paragraph on GO and RGO papers
  - benchmark: thermal_conductivity
    label: Thermal conductivity, epoxy-functionalised GO (simulation)
    value: 35
    unit: W/(m·K)
    scope: material
    conditions:
      basis: GO with epoxy groups at O:C ratio 0.1, sample length 300 nm
    method: Non-equilibrium molecular dynamics result quoted in the review; a simulation, not a measurement
    status: calculated
    source: huang2019
    where: Thermal properties section, NEMD results at O:C 0.1 and L = 300 nm
  - benchmark: thermal_conductivity
    label: Thermal conductivity, hydroxyl-functionalised GO (simulation)
    value: 85
    unit: W/(m·K)
    scope: material
    conditions:
      basis: GO with hydroxyl groups at O:C ratio 0.1, sample length 300 nm
    method: Non-equilibrium molecular dynamics result quoted in the review; a simulation, not a measurement
    status: calculated
    source: huang2019
    where: Thermal properties section, NEMD results at O:C 0.1 and L = 300 nm
  - benchmark: thermal_conductivity
    label: Thermal conductivity, ether-functionalised GO (simulation)
    value: 29
    unit: W/(m·K)
    scope: material
    conditions:
      basis: GO with ether groups at O:C ratio 0.1, sample length 300 nm
    method: Non-equilibrium molecular dynamics result quoted in the review; a simulation, not a measurement
    status: calculated
    source: huang2019
    where: Thermal properties section, NEMD results at O:C 0.1 and L = 300 nm
  - benchmark: interlayer_distance
    label: Interlayer distance of a GO membrane
    value: 10
    unit: Å
    scope: material
    conditions:
      basis: GO membrane as printed (about 10 Å); hydration state not stated
    method: X-ray analysis, as stated in the paper
    status: ground
    note: Snake-case name, not in the property canon; see gaps. Printed as approximately 10 Å.
    source: nair2012
    where: Results, paragraph on annealed GO membranes (Fig. 2a)
  - benchmark: interlayer_distance
    label: Interlayer distance of GO after annealing at 300 C in hydrogen and argon
    value: 4
    unit: Å
    scope: material
    conditions:
      basis: GO annealed at 300 C in a hydrogen and argon atmosphere; printed as about 4 Å for reduced GO
    method: X-ray analysis, as stated in the paper
    status: ground
    note: The same annealing made the membranes about 100 times less permeable to water.
    source: nair2012
    where: Results, paragraph on annealed GO membranes (Fig. 2a)
  - benchmark: thermal_decomposition
    label: Temperature above which GO oxygen groups decompose
    value: 1000
    bound: lower
    unit: K
    scope: material
    conditions:
      basis: thermodynamic stability limit for the oxygen groups, as stated in the review
    method: Statement in the review
    status: ground
    note: Snake-case name, not in the property canon. The review gives a stated limit, not a measured onset.
    source: huang2019
    where: Section 2.1 (thermodynamic and kinetic stabilities)
  - benchmark: c_o_ratio
    label: C/O ratio of rGO reduced with hydrazine
    value: 9.82
    unit: '-'
    scope: material
    conditions:
      basis: rGO made by hydrazine reduction; ratio as printed
    method: Value printed in the review text on chemical reduction
    status: ground
    note: A higher C/O ratio means fewer oxygen groups. The review gives no numeric C/O ratio for untreated GO.
    source: monir2026
    where: Section 3.1.1 (chemical reduction of GO)
corrosion:
  - environment: Water and humidity (hydration and ageing)
    headline: Water content changes GO stiffness and layer spacing
    effect: The review says the out-of-plane stiffness of conventional GO depends on intercalated water, peaking near RH 25 percent. It also says ageing of GO gathers oxygen groups into highly oxidised domains, so the material changes over time. No ageing rate, time or temperature was read in a source.
    rating: unknown
    conditions:
      basis: qualitative statements in the review; no exposure time or temperature stated
    source: huang2019
    where: Section 2.1 (ageing statement) and out-of-plane elasticity section
  - environment: Water (aqueous dispersion)
    headline: GO disperses in water; rGO tends to restack
    effect: The review says GO forms stable colloidal dispersions in water because its oxygen groups make it highly reactive and hydrophilic. Reduced GO has a strong tendency to agglomerate and restack in aqueous solution.
    rating: unknown
    conditions:
      basis: qualitative statements in the review; dispersion concentration not stated
    source: monir2026
    where: Section 2.4
  - environment: Heat above about 1000 K
    headline: Oxygen groups break down at high temperature
    effect: The review says the oxygen-containing groups decompose above about 1000 K, and that thermal exfoliation of graphite oxide needs a suggested minimum of 550 C to give RGO. The groups break down into gases during that step.
    rating: moderate
    conditions:
      basis: decomposition of oxygen groups; no heating time or atmosphere stated
    source: huang2019
    where: Section 2.1 and synthesis section (thermal exfoliation)
risks:
  hazards:
    - text: A supplier safety data sheet for a 0.5 mg/mL graphene oxide dispersion in water classifies it under OSHA HCS as eye irritation (Category 2A, H319) and respiratory system (H335), with the signal word None.
      ghs:
        - H319
        - H335
      source: samaterials-sds
      where: Section 2 (hazards identification)
    - text: The same sheet lists CNT and graphite CAS numbers in its composition section, so the CAS number of the product itself is not established. Check the sheet for the exact product you handle.
      ghs: []
      source: samaterials-sds
      where: Section 3 (composition)
    - text: No UK statutory workplace exposure limit is set for nanomaterials. HSE says the ACGIH threshold for graphite (2 mg/m3 respirable dust) is not an appropriate limit for graphene, and treats nanomaterials as substances of high concern.
      ghs: []
      source: hsg272
      where: Workplace exposure limits section, paragraphs 25 to 27; paragraph 38
  failure_risks:
    - mode: Oxygen groups decompose on heating
      trigger: Heating above about 1000 K
      consequence: The oxygen groups break down, so the material is no longer GO in its as-made form. A design that relies on the as-made oxygen content will fail.
      severity: moderate
      source: huang2019
      where: Section 2.1 (thermodynamic and kinetic stabilities)
    - mode: Membrane becomes fragile and much less permeable after annealing
      trigger: Annealing GO membranes at 300 C in hydrogen and argon
      consequence: The membranes became fragile and needed care to avoid cracks, and became about 100 times less permeable to water.
      severity: moderate
      source: nair2012
      where: Results, paragraph on annealed GO membranes (Fig. 2a)
    - mode: Stiffness shifts with humidity
      trigger: Change in relative humidity or water content
      consequence: The out-of-plane modulus of conventional GO depends on water content, with a maximum near RH 25 percent, so a film's stiffness is not fixed.
      severity: low
      source: huang2019
      where: Section on out-of-plane elasticity
  side_effects:
    - text: During thermal exfoliation the epoxy and hydroxyl groups decompose into gases, and a suggested minimum of 550 C is needed for the product to be RGO.
      affects: Sheet size and yield of the product
      source: huang2019
      where: Synthesis section, thermal exfoliation paragraph
    - text: Reduced GO has a strong tendency to agglomerate and restack in water, so its dispersions can lose their state.
      affects: Processing of dispersions and films
      source: monir2026
      where: Section 2.4
  handling:
    - text: Keep dust-generating work under local exhaust ventilation, and where possible keep the material wet or damp or use slurries.
      source: hsg272
      where: Good practice section (wet handling) and LEV section
    - text: Weigh powders over a damp sheet of absorbent material, and wipe spills with a damp sheet rather than dry sweeping.
      source: hsg272
      where: Good practice section on weighing and spillages
    - text: Avoid dust formation and provide exhaust ventilation where dust forms. Keep the container tightly closed in a dry, well-ventilated place.
      source: samaterials-sds
      where: Sections 7 and 6
    - text: Wear safety glasses to EN166 and gloves that pass ASTM F-1671 for dry particulate or an aqueous suspension, plus impervious clothing.
      source: samaterials-sds
      where: Section 8 (personal protection)
  mitigations:
    - text: Examine and test local exhaust ventilation plant at least every 14 months, and keep a record of each check.
      source: hsg272
      where: LEV section (examination and testing paragraph)
uses:
  - application: structures
    device: GO and polyvinyl alcohol composite (laboratory)
    example: In the review's Table 1, GO modified with polyvinyl alcohol (ref 133) has a Young's modulus of 8 GPa against 5 GPa for the unmodified GO in the same row, and a tensile strength of 125 MPa against 25 MPa.
    source: huang2019
    where: Table 1, row polyvinyl alcohol, ref 133
  - application: electronics-and-chips
    device: Reduced GO films as transparent conductors and in field-effect transistors (research)
    example: The review lists transparent and flexible conductors and field-effect transistors among the device applications of GO and reduced GO. These are research demonstrations, not product uses.
    source: huang2019
    where: Abstract, list of device applications
  - application: thermal-control
    device: GO and rGO films as low-conductivity thermal layers (research)
    example: The review cites GO and rGO papers and films below 10 W/(m·K), and names thermoelectric materials as a use that needs suppressed heat conduction.
    source: huang2019
    where: Thermal properties section; abstract (thermoelectrics)
  - application: habitats-and-suits
    device: GO laminate membrane for water separation (laboratory test, not a space system)
    example: In a laboratory test, GO membranes stopped helium while letting water permeate at least 10^10 times faster than helium. The paper does not address space or life-support use.
    source: nair2012
    where: Abstract
supply:
  - subject: Natural graphite (feedstock for graphite oxide)
    abundance: USGS gives China 100000000 t of graphite reserves in its 2025 table; world reserve total is not in the excerpt read.
    producers:
      - country: China
        share_percent: 82
        year: 2025
        note: share of world natural graphite production, 2025 estimate
    critical_lists: []
    import_reliance: 100 percent of US apparent consumption (2021 to 2025e)
    source: usgs-graphite-2026
    where: 'Mineral Commodity Summaries 2026, Graphite (Natural): Events, Trends and Issues; World Mine Production and Reserves table; Salient Statistics'
  - subject: Natural graphite imports to the United States
    abundance: US net import reliance for natural graphite is 100 percent.
    producers:
      - country: China
        share_percent: 46
        year: 2024
        note: 2021 to 2024 import share
      - country: Canada
        share_percent: 13
        year: 2024
        note: 2021 to 2024 import share
      - country: Mozambique
        share_percent: 13
        year: 2024
        note: 2021 to 2024 import share
      - country: Mexico
        share_percent: 12
        year: 2024
        note: 2021 to 2024 import share
    critical_lists: []
    source: usgs-graphite-2026
    where: 'Mineral Commodity Summaries 2026, Graphite (Natural): Import Sources (2021 to 2024)'
media: []
documents:
  - title: Physical properties and device applications of graphene oxide (arXiv:1912.07956)
    type: paper
    url: https://arxiv.org/pdf/1912.07956
    year: 2019
  - title: Unimpeded permeation of water through helium-leak-tight graphene-based membranes (Science 335, 442, arXiv:1112.3488)
    type: paper
    url: https://arxiv.org/pdf/1112.3488
    year: 2012
  - title: 'Towards greener reduced graphene oxide: a critical review of environmentally driven reduction strategies (RSC Advances 16, 2044, PMC12776586)'
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12776586/
    year: 2026
  - title: Structure and Synthesis of graphene oxide (arXiv:1901.02274)
    type: paper
    url: https://arxiv.org/pdf/1901.02274
    year: 2019
  - title: 'USGS Mineral Commodity Summaries 2026: Graphite (Natural)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-graphite.pdf
    year: 2026
  - title: 'Stanford Advanced Materials safety data sheet: Graphene Oxide Dispersion (0.5 mg/mL in water)'
    type: sds
    url: https://samaterials.com/tds/1697119733-178-graphene-oxide-05mgml-dispersion-in-water-sds.pdf
    year: 2022
  - title: 'HSE HSG272: Using nanomaterials at work'
    type: report
    url: https://www.hse.gov.uk/pubns/books/hsg272.pdf
    year: 2013
gaps:
  - No product datasheet for GO or rGO was read with a stated C/O ratio, sheet resistance, lateral size or layer count. Commercial values are not included.
  - No numeric C/O ratio for untreated GO was read in a fetched source. The review gives O:C ratios only as simulation inputs.
  - Thermal conductivity of GO papers was not given at a stated temperature in the fetched text.
  - Oxidation temperature in air (thermogravimetry) for GO or rGO was not read from a fetched primary source.
  - Ageing and shelf life of GO powder, paste and dispersion were not quantified in any fetched source. The review gives only qualitative ageing statements.
  - Radiation, atomic-oxygen, vacuum and thermal-cycling tests of GO or rGO were not found. The space use is not established.
  - No corrosion test of GO on metal or on a current collector was found.
  - No PubChem compound record for graphene oxide was found. Search results gave vendor pages and the elemental carbon entry (CID 5462310), which are not used. PubChem GHS classification was not read.
  - The CAS number of GO is not established. The Stanford sheet's composition section lists CNT and graphite CAS numbers, so it was not used for a CAS value.
  - Supply of the Hummers oxidants (sulfuric acid, potassium permanganate, sodium nitrate) and of hydrazine was not read. No critical-mineral status for graphite was read in this run.
  - 'Non-canonical property names used: electrical_conductivity, intrinsic_strength, interlayer_distance, thermal_decomposition and c_o_ratio. None is in spores/property-canon.yaml.'
  - Two reduction results from the 2026 review's search snippets (Guex 2017, NaBH4 with C/O from 2.2 to 6.9; Compton 2011, solvent-dependent reduction) were not opened, so their numbers are not used.
  - Water-permeation result (Nair 2012) is a laboratory membrane test. No space or life-support test was found.
  - Recipe process details rest on the review and the Hummers paper. Reaction conditions for a commercial GO product were not read.
sources:
  huang2019:
    title: Physical properties and device applications of graphene oxide
    id: arXiv:1912.07956; Huang, Liu, Zhou and Zhao
    url: https://arxiv.org/pdf/1912.07956
    year: 2019
    kind: paper
    license: arXiv, as listed
  nair2012:
    title: Unimpeded permeation of water through helium-leak-tight graphene-based membranes
    id: Science 335, 442 to 444 (2012); arXiv:1112.3488; Nair, Wu, Jayaram, Grigorieva and Geim
    url: https://arxiv.org/pdf/1112.3488
    year: 2012
    kind: paper
    license: arXiv, as listed
  monir2026:
    title: 'Towards greener reduced graphene oxide: a critical review of environmentally driven reduction strategies'
    id: RSC Advances 16(3), 2044 to 2061; PMC12776586
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12776586/
    year: 2026
    kind: paper
    license: CC BY 3.0 (as printed on the page)
  go-synthesis:
    title: Structure and Synthesis of graphene oxide
    id: arXiv:1901.02274
    url: https://arxiv.org/pdf/1901.02274
    year: 2019
    kind: paper
    license: arXiv, as listed
  usgs-graphite-2026:
    title: 'Mineral Commodity Summaries 2026: Graphite (Natural)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-graphite.pdf
    year: 2026
    kind: report
    license: public domain (US government)
  samaterials-sds:
    title: Safety data sheet, Graphene Oxide Dispersion (0.5 mg/mL in water), Stanford Advanced Materials
    id: Revised 03/12/2022
    url: https://samaterials.com/tds/1697119733-178-graphene-oxide-05mgml-dispersion-in-water-sds.pdf
    year: 2022
    kind: datasheet
    license: supplier document, linked not reproduced
  hsg272:
    title: Using nanomaterials at work, including carbon nanotubes (CNTs) and other biopersistent high aspect ratio nanomaterials (HARNs), HSG272
    id: HSE HSG272
    url: https://www.hse.gov.uk/pubns/books/hsg272.pdf
    year: 2013
    kind: report
    license: Open Government Licence
  wiki-graphite-oxide:
    title: Graphite oxide (Wikipedia), used for composition and history only
    id: Wikipedia article Graphite oxide
    url: https://en.wikipedia.org/wiki/Graphite_oxide
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (Wikipedia)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 19
  unreachable: 2
  caveats: 3
  note: 'Written by an assistant on 2026-10-26 from pages read in this run: arXiv 1912.07956, arXiv 1112.3488, PMC12776586, arXiv 1901.02274, USGS MCS 2026 graphite, the Stanford Advanced Materials SDS, HSE HSG272 and Wikipedia (composition and history only). Search snippets were not used as values. Commercial GO and rGO products were not verified.'
story:
  recipe:
    line: Graphene oxide is made by oxidising graphite, usually with the Hummers method (sulfuric acid and potassium permanganate), and then exfoliating the oxidised graphite in water. The sheet keeps a carbon lattice with epoxy bridges, hydroxyl groups on its faces, and carbonyl and carboxyl groups at its edges. Reduced graphene oxide has lost some of those groups, for example by thermal exfoliation at a suggested minimum of 550 C or by chemical reduction with hydrazine.
    parts:
      - name: Carbon
        symbol: C
        role: Forms the sheet. Oxidised areas hold carbon bonded to oxygen, which breaks the flat sp2 lattice locally.
      - name: Oxygen
        symbol: O
        role: Sits in epoxy bridges, hydroxyl, carbonyl and carboxyl groups. Its amount sets the C/O ratio and how far the conductivity is suppressed.
      - name: Hydrogen
        symbol: H
        role: Sits on hydroxyl and carboxyl groups. Hydrogen species in as-made GO are thought to make the film metastable, according to the review.
  risk_groups:
    - title: For people
      level: 1
      verdict: Handle as a precaution
      lead: The supplier sheet for a dispersion classifies it as an eye and airway irritant, and no exposure limit is set for graphene oxide.
      points:
        - label: Eyes and airways
          line: A supplier sheet for a 0.5 mg/mL dispersion gives serious eye irritation (H319) and respiratory irritation (H335), with no signal word.
        - label: Dust
          line: Keep dust out of the air with local exhaust ventilation. HSE says nanomaterials are substances of high concern, and graphite's threshold is not an appropriate limit for graphene.
  why: Graphene oxide is graphene carrying oxygen groups. The groups make the sheet an electrical insulator and cut its heat conduction, but they also let it disperse in water and bind to other materials. Reduction removes some of the groups and raises conductivity. The useful numbers depend on the oxidation level, the form (paper, film or monolayer) and humidity, so most values here are ranges.
  uses:
    - where: Polymer composites
      line: A review table lists GO modified with polyvinyl alcohol at a Young's modulus of 8 GPa, against 5 GPa for the unmodified GO in the same row. The tensile strength in that row is 125 MPa against 25 MPa.
    - where: Membranes
      line: In a laboratory test, GO membranes stopped helium while letting water through at least 10^10 times faster than helium. This is a research result and not a space system.
    - where: Films and devices
      line: The review lists transparent and flexible conductors and field-effect transistors as device applications of GO and reduced GO. These are research demonstrations.
  can_do:
    - label: Stiffness
      benchmark: elastic_modulus
      line: Bulk GO paper is cited at 6 to 42 GPa in Young's modulus. A GO monolayer is quoted at 250 GPa, with a printed spread of 150 GPa. Measured values depend on oxidation, water content and test method.
    - label: Electrical conduction
      benchmark: electrical_conductivity
      line: 'GO is an insulator, cited as low as 0.0486 S/m. Reduction raises the value: 0.052 S/m for a reduced monolayer, 55.32 S/m for a Shewanella-reduced rGO, and 216.56 S/m for a hydrazine-reduced rGO used as the comparison.'
    - label: Heat conduction
      benchmark: thermal_conductivity
      line: GO and rGO papers and films are cited below 10 W/(m·K). Simulations at an O:C ratio of 0.1 give 35, 85 and 29 W/(m·K) for epoxy, hydroxyl and ether groups, which are not measurements.
    - label: Water permeation
      benchmark: interlayer_distance
      line: GO membranes let water through much faster than helium. Annealing at 300 C in hydrogen and argon shrinks the interlayer distance from about 10 Å to about 4 Å and makes the membrane about 100 times less permeable to water.
  compare: Graphene oxide and reduced graphene oxide are not graphene. Graphene is quoted in the review at 1 TPa in stiffness and with far higher thermal conduction at room temperature, both for ideal sheets. GO has oxygen on those sheets, so its electrical conductivity drops to 0.0486 S/m as the lowest value cited, and its films conduct heat below 10 W/(m·K). Reduction recovers some conductivity, to between 0.052 and 216.56 S/m across the cited cases, depending on the reductant. The comparison is with graphene's ideal values, not with a commercial graphene product.
  compare_rows:
    - label: Electrical conductivity
      benchmark: electrical_conductivity
    - label: Young's modulus
      benchmark: elastic_modulus
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Keep dust-generating work under local exhaust ventilation, and keep powders damp or in slurry where possible.
    - Wipe spills with a damp sheet, and weigh powders over a damp sheet. Do not dry sweep.
    - Wear safety glasses, gloves that pass ASTM F-1671, and impervious clothing. Check the supplier sheet for the product you use.
  good_for:
    - Water-permeable membranes and laminates at laboratory stage, where a gas-tight but water-passing layer is the goal.
    - 'Polymer composites: the review''s polyvinyl alcohol example raises Young''s modulus from 5 GPa to 8 GPa.'
    - Low-conductivity films where heat must not spread, such as thermoelectric research.
  watch_out:
    - Pure GO is electrically insulating. Reduction changes conductivity by orders of magnitude, and the result depends on the reductant.
    - Stiffness and strength values span wide ranges. The monolayer value of 250 GPa carries a printed spread of 150 GPa.
    - Humidity changes the out-of-plane stiffness and the layer spacing, so properties drift with moisture.
    - Above about 1000 K the oxygen groups decompose, which changes the material.
  verdict: GO suits laboratory work on water-permeable membranes and polymer composites. For electrical and thermal use, the reduction route and the form decide the result. No space or flight data were found.