The synthesis of the bare and SiO2-coated nanoparticles was performed using the Flame Spray Pyrolysis (FSP) based Harvard Versatile Engineered Nanomaterial Generation system (VENGES27 (link), 28 (link)). In brief, Fe2O3, Ag, ZnO and CeO2 and core particles were synthesized by combustion of organometallic precursors listed in Table 2 . Precursor solutions were fed to the FSP nozzle through a stainless steel capillary at 5 ml/min, dispersed by 5 l/min O2 (Air Gas, purity >99%, pressure drop at nozzle tip: pdrop = 2 bar) and combusted to form the desired nanomaterials. A premixed stoichiometric methane-oxygen (1.5 l/min, 3.2 l/min) supporting flame was used along with 40 l/min O2 (Air Gas, purity >99%) sheath gas.
The FSP burner was enclosed with a 200 mm quartz glass tube (i.d. 45 mm). On top of this tube, HMDSO (Sigma Aldrich) vapor was swirl-injected through a torus ring with 16 equidistant and of equal size (dinner = 0.6 mm) openings. A total gas flow of 16 l/min, consisting of N2 carrying HMDSO vapor (VN2,coat) and pure N2 (VN2,swirl) for mixing, was injected through the torus ring jets. The torus ring jet injection angles were 20° in the downstream direction, in order to avoid stagnation flow, and 10° away from the centerline, in order to induce the necessary mixing swirl.67 The reactor was terminated by a 200–400 mm quartz tube. HMDSO vapor was obtained by bubbling N2 (VN2,coat) gas through liquid HMDSO (500 ml), maintained at a controlled temperature using a temperature-controlled water bath. At saturated conditions, the HMDSO content within the N2,coat flow is determined by the HMDSO partial vapor pressure, which is a function of the bubbler temperature and can be estimated using the Antoine equation.31 We define the molar ratio of injected HMDSO to synthesized core particles as ṅHMDSO/ṅCore. A theoretical coating thickness (TCT) for the individual particles was estimated based on ṅHMDSO/ṅCore, assuming full HMDSO conversion to SiO2 coatings (no separate SiO2 formation)31 as well as monodisperse spherical primary particles of a known diameter (dXRD).
The bare nanoparticles were synthesized at identical conditions, in the absence, however, of the HMDSO vapor. For the purpose of evaluating ENM-bio interactions, bare Ag was cooxidized with SiO2, in order to provide sufficient control over Ag primary particle size.18 After synthesis, particles were collected for physico-chemical characterization and in-vitro toxicity assessments on a water-cooled glass fiber filter (Whatman) located 800 mm above the reactor.27 (link), 28 (link) A schematic of the coating reactor used is provided inFigure 1 .
The FSP burner was enclosed with a 200 mm quartz glass tube (i.d. 45 mm). On top of this tube, HMDSO (Sigma Aldrich) vapor was swirl-injected through a torus ring with 16 equidistant and of equal size (dinner = 0.6 mm) openings. A total gas flow of 16 l/min, consisting of N2 carrying HMDSO vapor (VN2,coat) and pure N2 (VN2,swirl) for mixing, was injected through the torus ring jets. The torus ring jet injection angles were 20° in the downstream direction, in order to avoid stagnation flow, and 10° away from the centerline, in order to induce the necessary mixing swirl.67 The reactor was terminated by a 200–400 mm quartz tube. HMDSO vapor was obtained by bubbling N2 (VN2,coat) gas through liquid HMDSO (500 ml), maintained at a controlled temperature using a temperature-controlled water bath. At saturated conditions, the HMDSO content within the N2,coat flow is determined by the HMDSO partial vapor pressure, which is a function of the bubbler temperature and can be estimated using the Antoine equation.31 We define the molar ratio of injected HMDSO to synthesized core particles as ṅHMDSO/ṅCore. A theoretical coating thickness (TCT) for the individual particles was estimated based on ṅHMDSO/ṅCore, assuming full HMDSO conversion to SiO2 coatings (no separate SiO2 formation)31 as well as monodisperse spherical primary particles of a known diameter (dXRD).
The bare nanoparticles were synthesized at identical conditions, in the absence, however, of the HMDSO vapor. For the purpose of evaluating ENM-bio interactions, bare Ag was cooxidized with SiO2, in order to provide sufficient control over Ag primary particle size.18 After synthesis, particles were collected for physico-chemical characterization and in-vitro toxicity assessments on a water-cooled glass fiber filter (Whatman) located 800 mm above the reactor.27 (link), 28 (link) A schematic of the coating reactor used is provided in
