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Table 1 Physico-chemical parameters of the test materials

From: Comparative inhalation toxicity of multi-wall carbon nanotubes, graphene, graphite nanoplatelets and low surface carbon black

Property MWCNT Graphene Graphite nanoplatelets Carbon black
Representative images (SEM) See Figure 1 See Figure 1 See Figure 1 See Figure 1
Particle size Distribution (SEM)primary structure 15 nm, fiber shape Up to 10,000 nm diameter, flakes Up to 30,000 nm diameter, flakes 50-100 nm, globular
State of agglomeration ~20,000 nm, bundles ~40,000 nm, ‘crumpled napkin’ >50,000, ‘crumpled cardboard’ >20,000 nm
Crystallite size (XRD) Dominatingly amorphous in XRD Dominatingly amorphous in XRD Contains amorphous material, but has sharp diffraction peak corresponding to 19 nm crystallite size Dominatingly amorphous in XRD
Crystalline phase (XRD) Graphite, C hexagonal with modified lattice const. Possibly graphite, sync –C– hexagonal or carbon –C– hexagonal, or carbon –C– cubic or carbon - C Graphite, sync– C - hexagonal Graphite, C hexagonal with modified lattice const.
Pore sizes (Hg intrusion) 25 nm, 400 nm, 150,000 nm 9 nm, 100 nm, 40,000 nm 6,000 nm, 30,000 nm, 150,000 nm 100 nm, 150,000 nm
Surface area (Hg) [mg/m2] 161 131 74 32
Apparent density (g/mL) 0.15 0.02 0.04 0.52
Agglomerate density (g/mL) 0.39 0.29 0.89 1.05
Surface chemistry (%) (XPS) C 99 C 84.1 C 84.3 C 98
O 1 O 8.8 O 9.0 O 1
   S 5.4 S 1.7 S 1
   Na 0.6 Na 3.0 Cl <<1
   Si 0.4 Ca 1.5   
   Cl 0.6 Si 0.6   
Raman peak positions (cm-1) (Laser spectroscopy) G 1574   1574   1573   1590
D 1338   1338   1348   1348
D/G 1.16 ± 0.04   1.40 ± 0.05   0.01 ± 0.01   -
Dispersability (by AUC) agglomerated agglomerated agglomerated agglomerated
In water <0.01 wt% below 100 nm <0.01% below 100 nm <0.01% below 100 nm 1,920 nm
In DMEM/FCS agglomerated at several μm    Dispersed below 100 nm
Purity (combined assessment from XRD, ICP-MS, XPS data) 99% < 85% < 85% 98%
Identified impurities None significant Sulfur impurity (presumably from acid intercalation before exfoliation) Na-, Ca, Si-containing minerals None significant
3D-Graphite (not 2D-Graphene) impurities 3D-Graphite (not 2D-Graphene) impurities