Tristar 3000

SiO₂, Fe₂O₃, CeO₂, and the composite Ag/SiO₂ ENM, consisting of 10 percent silver supported on SiO₂ particles, were produced by flame spray pyrolysis using the Harvard Versatile Engineered Nanomaterial Generation System (VENGES) as previously described [41 (link),42 (link),47 (link)]. TiO₂ and ZnO ENM powders were purchased from EVONIK (Essen, Germany), and Alfa Aesar (Ward Hill, MA, USA), respectively. ENMs were tested for endotoxin with a Limulus Amebocyte Lysate (LAL) chromogenic quantitation kit from ThermoFisher (Waltham, MA, USA) using 10 μg ml⁻¹ suspensions of ENMs in water and following manufacturers instructions. Specific surface area, SSA, was determined by the nitrogen adsorption/Brunauer-Emmett-Teller (BET) method using a Micrometrics Tristar 3000 (Micrometrics, Inc., Norcross, GA, USA). Equivalent primary particle diameter, d_BET, was calculated, assuming spherical particles, as
$$d_{\mathit{BET}}=\frac{6}{\mathit{SSA}\times {\rho }_{\mathrm{p}}},$$ where ρ_p is the particle density, which was obtained for each particle from the densities of component materials, at 20°C, reported in the CRC handbook of Chemistry and Physics [48 ]. Particle crystal size and diameter was also determined by X-ray diffraction using a Scintag XDS2000 powder diffractometer (Scintag Inc., Cupertino, CA, USA), reported here as d_XRD.