Table 1.
Morphological, structural, physical, chemical and biological properties of metal oxide ENMs studied.
| Characterization parameters | Method | Citrate-capped Au (in suspension) | Silver supported on Silica (15% Ag-SiO2) | Copper Oxide (CuO) |
|---|---|---|---|---|
| Synthesis method by ERCC/manufacturer | Hydrothermal | Flame Spray Pyrolysis | Sigma Aldrich | |
| Primary particle size | ||||
| • Specific surface area (SSA) (m2/g) | BET | – | 333.1 ± 3.1 | 13.77 ± 0.68 |
| • dBETb (nm) | BET | – | 6.4 (Ag), 6.1 (SiO2) | 70.9 ± 3.54 |
| • dTEM (nm) | TEM | 18.36 ± 1.84e | 7.9 ± 4.3 (Ag) | 50.24 ± 10.99 |
| • dXRDa (nm) | X-Ray Diffraction | – | 5.8 (Ag) | 25.8 |
| Colloidal properties | Dynamic Light Scattering | |||
| • dHYDc (nm) | (DLS) | 21.1 ± 0.3 | 135.2 ± 2.0 | 505.6 ± 51.1 |
| • PDI | 0.056 ± 0.011 | 0.287 ± 0.027 | 0.130 ± 0.018 | |
| • Zeta potential (mV) | −38.7 ± 2.9 | 22.2 ± 1.5 | −19.0 ± 1.5 | |
| • pH | 5.64 | – | – | |
| • Conductance (mS/cm) | 0.229 ± 0.013 | 0.027 ± 0.0006 | 0.0184 ± 0.0002 | |
| Crystal structure | X-Ray Diffraction | |||
| • Crystal system | – | Cubic, 87% (Ag) | Monoclinic Tenorite | |
| • Crystallinity | Polycrystallined | Amorphous, 0% (SiO2) | Crystallinity: 73.1% | |
| Shape factors | ||||
| • Aspect ratio ξ | TEM | 1.12 ± 0.07 | 1.12 ± 0.14 | 1.35 ± 0.20 |
| • Circularity ψ | TEM | 0.96 ± 0.02 | 0.97 ± 0.09 | 0.93 ± 0.04 |
| • Roundness ζ | TEM | 0.90 ± 0.05 | 0.89 ± 0.11 | 0.76 ± 0.11 |
| Porosity | ||||
| • Total pore volume (cm3/g) | BET | – | 0.46 | 1.87 × 10−4 |
| • Average pore size (nm) | BET | – | 3.7 | 2.65 |
| Raw density (g/cm3) | Pycnometrye | 19.3 (raw material density) | 3.58 ± 0.25 | 6.1531 ± 0.0027 |
| Particle purity | ICP-MSf | 99.99 ± 0.31% (Au) | 99.98 ± 0.03 (Ag) | 98.21% ± 6.11% (Cu) |
| Endotoxin levels | ||||
| • Concentration per mass of ENM (EU/mg) | Recombinant Factor | 4.87 | 23.93 | 2.141 |
| Sterility (bacteria/mg) | Suspension tested at 50 μg/mL | No growth | No growth | 0 |
| ERCC reference reporting on characterization data | Zimmerman et al. 2019, Dong et al., 2020 | Beltran-Huarac et al., 2018 | (Eweje et al., 2019) | |
NA: not applicable.
a
dXRD: particle diameter of ENMs determined from X-ray diffraction (XRD).
b
dBET: particle diameter of ENMs determined from Brunauer-Emmett teller (BET).
c
dHYD: hydrodynamic particle diameter.
d
TEM Selected Area Electron Diffraction (SAED).
e
Picnometry: the raw density of ENMs determined by nitrogen volume displacement (pycnometry).
f
ICP-MS: inductively coupled plasma mass spectrometry.