aerodynamic and chemical characteristics of six engineered

Aerosol and Air Quality Research, 14: 74–85, 2014 Copyright © Taiwan Association for Aerosol Research ISSN: 1680-8584 print / 2071-1409 online doi: 10.4209/aaqr.2013.06.0185 Aerodynamic and Chemical Characteristics of Six Engineered Nanomaterial Powders Michael R. Olson1, Jamie J. Schauer1,2,3*, Maria Powell3, Andrew P. Rutter4, Martin M. Shafer2,4

1 Department of Civil and Environmental Engineering, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA 2 Wisconsin State Laboratory of Hygiene, 2601 Agriculture Drive, Madison, WI 53718, USA 3 Nanoscale Science and Engineering Center, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA 4 Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 N. Park St, Madison, WI 53706, USA ABSTRACT

Six engineered nanomaterial (ENM) powders (nano-diamond, nano-silver, nano-titanium dioxide, single walled carbon nanotubes, multi-walled carbon nanotubes, and C60 fullerenes) were investigated to determine their aerodynamic and chemical characteristics. Materials were suspended in a controlled environmental chamber, collected on filters and cascading deposition impactors (MOUDI), and then underwent gravimetric and chemical analysis using standard atmospheric aerosol methodologies. The chemical analyses included examining elemental/organic carbon (EC/OC), soluble metals by ICP-MS, organics by TD-GCMS, and reactive oxygen species (ROS) macrophage assay. Chemical composition and toxicity were compared to urban ambient PM values to give context to the ENM results, allowing a relative assessment of aerosol characteristics and the risks associated with ENM emissions. The results show that ENM particle suspensions generally exist in the accumulation or coarse particle mode range, while large mass concentrations of Aitken-nuclei mode particles were not observed. Key findings include the following: the organic and elemental carbon analysis of the carbon structured ENM could not adequately reconstruct the mass of these carbon based materials, suggesting the carbon structure of these samples is too refractive or the carbonaceous material is not oxidized sufficiently to allow accurate quantification with standard thermal-optical EC/OC analysis; the materials exhibited very low quantities of PAHs and alkanes, with the majority of these constituents below detection limits; a select group of soluble metals were detected in concentrations similar to those observed in urban ambient samples on a mass per mass basis, and lastly, the biological activity of the ENM was found to be small (by in-vitro ROS macrophage assay), especially when compared to the activity of atmospheric PM2.5 in an urban location in the US. Keywords: Nanoparticle; ICP-MS; EC/OC; TD-GCMS; ROS. INTRODUCTION

The promise of nanotechnology has led to the rapid expansion of nanotechnology research and production of commercially available products (Aitken et al., 2006). The unique properties nanomaterials (as defined as primary particle sizes of < 100 nm in at least one dimension) may express, make them attractive for commercial applications (Maynard and Kuempel, 2005). The potential for widespread application has raised concerns for the environmental fate, transport, and transformation of these materials. * Corresponding author. E-mail address: [email protected]

(Gottschalk and Nowack, 2011; Nowack et al., 2012; Olson and Gurian, 2012) The fact that engineered nanoparticles are produced to exploit the unique properties, which occur at the atomic and near atomic scale, have led to concerns over potential impacts to the environment and human health, in particular when considering the known health effects of ultrafine ambient particulate matter(Nowack and Bucheli, 2007; Kendall and Holgate, 2012).

Quantification and characterization of ENMs airborne emissions have become some of the key points of concern for industry, regulators, and research bodies when assessing the hazards and managing exposure of ENMs (Maynard and Aitken, 2007; Hunt et al., 2013). Maynard and Aitken (2007) have noted that mass related aerosol measurements may not be sufficient to characterize ENM risks, but combining multiple measurement techniques is a powerful

Olson et al., Aerosol and Air Quality Research, 14: 74–85, 2014 75

approach to determine the physiochemical nature of airborne particles and determining the exposure to airborne nanoparticles can be a daunting task that may require new approaches, simplified by looking at specific particle attributes that can be associated with biological response. While developing new approaches to assess ENM emissions is an option to pursue, using existing methodologies, coupled together, and applying knowledge of the physiochemical characteristics of the materials of interest is another method, which we have applied in this study. Here we specifically measure particle number, mass distribution, and toxicity to assess the aerodynamic and chemical characteristics of a select set of ENM.

Previous studies have assessed airborne release of ENM, by looking at multiple material types but with limited characterization methods (Tsai et al., 2012; Evans et al., 2013), or using more detailed characterization of a single material type, either in a controlled laboratory setting or associated with a manufacturing process (Maynard et al., 2004; Maynard et al., 2007; Birch, 2011; Birch et al., 2011; Chen et al., 2011; Gottschalk and Nowack, 2011). Studies that have suspended ENM in controlled conditions have used multiple approaches to aerosolize the ENM powders. Evans et al. used a Venturi aerosolization method to create high velocity flow, suspending multiple powder samples, and concluding that it was unlikely the materials tested would exhibit a substantial sub-100 nm particle number contribution. Maynard et al. (2004) suspended materials using a fluidized bed approach, agitating SWCNT material using bronze beads in a vortex shaker and passing low flow through the sample. They showed both an increase in the number of particles and an increased number of particles below 0.1 micrometers with increased agitation, but in general, emission rates were low and the majority of the particles emitted were greater than 0.1 micrometers mobility diameter. Tsai et al. (2012) tested nano-particle powder emissions at multiple suspension energies and concluded that at low energies nano-particle concentrations generated are negligible, but with increased energies the occurrence of suspended nano-sized particles increases.

Studies also looked at specific size fraction of ENM to asses toxicity and changes in morphology (Maynard et al., 2007; Chen et al., 2011). While these studies are insightful, they do not represent the likely real-world particle morphology as they do not account for the actual PM size distribution. In addition, these studies give insight into the physiochemical properties of the ENM but do not give context to the results, where in this research we investigate the ENM properties and compare the findings to ambient aerosol measurements from urban location in the United States.

This study was conducted to determine the aerodynamic and chemical characteristics of six commercially available engineered nanomaterials, (ENM), and compare them to more commonly understood characteristics of urban ambient particulate samples. This approach furthers the understanding of how ENMs behave when emitted to the air, assesses the application of existing aerosol measurement techniques, and gives a relative assessment of risk through the comparison

to better understood urban aerosol characteristics. The study utilizes commonly applied air sampling and analysis techniques to assess the aerodynamic and chemical properties of common forms of commercially available ENMs under a controlled environment. The research investigates the application of these techniques specifically on ENMs. METHODS AND MATERIALS

The analysis determined mass and size distribution of suspended nanoparticles, in order to predict the size distribution profiles of particle agglomerates that may be emitted. The collected materials were chemically analyzed to assess chemical and agglomeration characteristics. The results were compared to ambient atmospheric concentrations of elemental and organic carbon, organic species, and soluble metals. In addition, the impact these materials might have on particulate matter toxicity was assessed through a reactive oxygen species (ROS) macrophage assay. Sample Collection

Samples were suspended in a stainless steel, sealed residence chamber with dimensions of 1.5 meters high and 0.25 meters internal diameter. Samples were introduced to the chamber through a sample flask with a controlled flow of medical air supplied from compressed gas cylinders. The suspension air was filtered through a desiccant chamber and a high efficiency particulate air (HEPA) filter. Sample materials were suspended by initiating high velocity flow, approximately 50 LPM, through a 500 mL flask containing the materials. Sample trains included both PM2.5 size selective cyclones followed by 47 mm aluminum filter holders and Micro-Orifice Uniform Deposit Impactors (MOUDI; MSP Corporation; no inline cyclone). A schematic of the resuspension chamber and the filter/impactor layout is depicted in Fig. 1. PM2.5 cut point samples were collected on 47 mm quartz and 47 Teflo® filters (Pall Corporation). The two MOUDI samplers substrates consisted of 47 mm aluminum foil impactors followed by a 37 mm quartz after-filter and 47 mm teflo® impactors followed by a 37 mm Teflo® after-filter. Teflon substrates were pre-cleaned and weighed after being equilibrated in a temperature and humidity controlled room for 24 hours. Aluminum substrates were pre-cleaned, baked, and equilibrated prior to being weighed and stored in baked aluminum lined Petri dishes. Quartz filters were baked for 12 hours and then stored in aluminum lined Petri dishes before use; quartz filters were not pre-weighed. Samples were prepared by adding pre-weighed portions of the engineered nanomaterials to a clean 500 mL flask and placed in-line in the resuspension system. The mass of material loaded for each suspension is reported in Table 1. The mass of materials were selected based on material availability and sequence of suspension. Although the system was thoroughly evacuated between suspensions of different material types, as an added QAQC procedure, we tested larger quantities sequentially to minimize the impact of any potential contamination from previous suspensions. No evidence of cross contamination was observed and all data is reported as blank subtracted


Fig. 1. Schematic of engineered nanomaterial suspension and sampling system.

Table 1. Summary of engineered nanoparticle powders physical characteristics, as reported by the manufacture, suspended for chemical and aerodynamic analysis.

Material Average Primary Particle

Size Aspect Ratio

Bulk Powder Density (g/cm3)

Source Mass

Loaded(mg)

Nano Diamonda Diameter: 4.0 nm 1:1 0.3–0.7 International

Technology Center 3.0

Nano Silvera Diameter: 10 to 60 nm 1:1 0.25 Quantum Sphere, Inc 24.5

Nano TiO2a Diameter: 21 nm 1:1 0.13 Degussa Corporation 40.2

SWC a Single Tube diameter 1.4

nm; Rope Diameter approximately 20 nm

1:175 1.7–1.9 Carbolex 36.0

SWCb Single Tube diameter 1.4

nm; Rope Diameter approximately 20 nm

1:175 1.7–1.9 Carbolex 35.6

MWCb Primary Particle diameter 2–

15 nm; Rope length 1–10 µm; 5–20 graphitic layers

1:500–1:666 2.1 Sigma Aldrich 42.2

C60 Fullereneb Primary Particle diameter approximately 1 nm

Crystal Size: 10–1000 nm

1.7–1.9 Alfa Aesar 60

a Direct transfer to sample flask. b Pulverized with mortar and pestle, direct transfer to sample flask.

values derived from system blank tests preformed intermittently between suspensions. For bulk samples, which were not friable, the sample was transferred to a 2 oz glass mortar and pestle and pulverized for approximately 30 seconds prior to weighing. Table 1 indicates which test materials were pulverized prior to suspension. Prior to suspension and sample collection, the system was purged with HEPA filtered air until particle counts stabilized at 1 to 6 pt/cm3 according to a P-TRAK® Ultrafine Particle

Counter Model 8525 (TSI, Inc. Shoreview, MN). The P-Trak® has the ability to count particles with the 0.02 to 1.0 micrometer range regardless of the particle morphology (TSI, 2013). Throughout suspension and sampling, particle counts were monitored with the P-TRAK® and sampling continued until particle counts returned to pre-suspension values, spanning a time of 12 to 20 minutes. Particle concentrations in the chamber were maintained at concentrations lower than typical ambient particle number


counts, with all tests having a maximum suspended particle concentration of less than 2,000 pt/cm3 with the exception of the titanium dioxide which a maximum residence chamber particle concentration of 10,000 pt/cm3. These concentrations are significantly lower than 106 pt/cm3 concentrations where nanometer sized particles will rapidly coagulate (Maynard and Kuempel, 2005). Materials Tested

Six engineered nanomaterials were selected for analysis: nano-diamond powder, nano-silver powder, nano-titanium dioxide powder, single walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and C60 fullerenes. Materials tested were selected to represent commonly used engineered nanomaterials that are currently commercially available and likely to be used in commercial applications into the future. Materials were either obtained directly from commercial sources or from research laboratories at the University of Wisconsin – Madison that offered samples of materials that they had obtained from commercial sources. Table 1 summarizes the materials tested. In general, materials tested were received in powder form from the suppliers, with the exception of MWCNT, which was received as a solid aggregate. Chemical Analysis

Chemical and physical characteristics were determined by applying standard atmospheric aerosol characterization methods. Analysis included: gravimetric mass determined after 24 hours of equilibration using a Mettler Toledo microbalance with robotic loading system (Bohdan Automation), elemental and organic carbon (EC/OC) determined by the NIOSH 5040 method following the ACE Asia protocol (Schauer et al., 2003), leachable metals quantified by Inductively Coupled Plasma Mass Spectrometry

(ICP-MS) (Lough et al., 2005), and toxicity by reactive oxygen species (ROS) macrophage (Landreman et al., 2008). Additionally, carbon based materials were analyzed for organic species using thermal desorption – gas chromatography mass spectrum (TD-GCMS) analysis (Sheesley et al., 2007). Table 2 describes analytical details for the analysis listed above. RESULTS AND DISCUSSION

The chemical and physical results from the ENM tested and ambient urban particulate matter concentrations were compared in order to assess the potential environmental impacts. The ambient values represent select sampling events but are not meant to be comprehensive results for urban PM physiochemical composition; they are reported only to give context to the ENM results. The comparisons were applied to two locations: St. Louis MO [particle count and organic species] and Denver, CO [soluble metals and µg ZYM equivalent ROS macrophage]. ENM results that had both corresponding ambient and nanomaterial constituent data are reported in the figures. For example, ambient phenanthrene was not available and thus was not compared to the detected nanomaterial results; a complete list of analytes is reported in the supplemental materials.

Mass Distribution

Particle size distributions are plotted for the materials tested in Fig. 2. Distributions were obtained from gravimetric mass results from the MOUDI utilizing Teflon substrates. MOUDI samples collected in parallel utilizing aluminum substrates showed excessive particle bounce, as documented in the supplemental materials to this document, and have not been included. The mass distributions are reported as log normalized concentrations (dC/·dlogDp) versus aerodynamic

Table 2. Summary of analytical analysis conducted to characterize suspended engineered nanomaterial.

Analysis Description

Gravimetric mass analysis

Teflon and aluminum foil substrates were analyzed by a high-precision scale analysis (Mettler Toledo 5) using a robotic system (Bohdan Automation). Filters were allowed to equilibrate in a temperature and humidity controlled environment for a minimum of 24 hours (21 ± 2C, RH 35 ± 3%) prior to analysis

Elemental And Organic Carbon 47 mm quartz substrates from the PM2.5 cyclone sample train were analyzed using a Thermal Optical Analyzer following the NIOSH 5040 method (Birch and Cary, 1996).

Soluble Metal Species

Water extracts from 47 mm Teflon substrates from the PM2.5 cyclone sample train were filtered through 0.22 micron polypropylene syringe filter and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) (PQ Excel, ThermoElemental).

Thermal Desorption – Gas chromatography mass spectrometry

47 mm quartz substrate from the PM2.5 cyclone sample train were analyzed using thermal desorption gas chromatography mass spectrometry (GCMS) (HP 6890N Network GC system, 5973 Mass Selective Detector, Agilent Technologies).

Macrophage assay (Reactive Oxygen Species)

Water extracts from 47 mm Teflon substrate from the PM2.5 cyclone sample train were filtered through 0.22 micron polypropylene syringe filter and analyzed by measuring the conversion of reactive oxygen species (ROS) dependant 2,7-dichlorofluorescin-diactate (DCFH-DA) to dichlorofluorescin (DCF) in rat alveolar macrophage by fluorescence intensity .


Fig. 2. Normalized aerodynamic diameter size distribution of engineered nanomaterials. Resuspended materials are normalized based on calculated total concentrations (C) obtained by summing the impactor mass loading within the reporting range. a) SWCNT – Single walled carbon nanotubes b) MWCNT – Multi-walled carbon nanotubes c) Nano-Silver – Nano Silver Powder d) Nano TiO2 – Nano-Titanium dioxide powder. Error bars represent propagated uncertainties based on the standard deviation of MOUDI stage specific system blanks run twice in-between suspension tests. Nano-diamond and C60 Fullerene samples are not reported due to the large relative uncertainty.

diameter, and are normalized to the total concentration (Ct) measured in the reporting range; resulting in unitless values of dC/Ct·dlogDp. This leads to the area under the mass distribution curve equaling one for each of the ENMs reported in Fig. 2. The first two stages of the mass distribution (18 and 10 micrometer diameter) have been omitted due to sample line configuration of the MOUDIs which led to a suspected loss of large aerodynamic diameter particles. Error bars are based on the observed standard deviation of two Teflon system blanks collected for each MOUDI stage and propagated to the reported units. A larger percent error is indicative of less total mass being collected on the MOUDI stages, a result of low system concentrations, either from a small system loading mass or loss of particulate mass within the system. This can be observed in the plots found in the supplemental materials for nano-diamond powder (low mass loading) and C60 fullerene power (elevated loss of particle mass in the system). These materials had the greatest portion of particulate matter in the nuclei mode (< 0.1 micrometer), however, it is difficult to get a clear understanding of the true fraction of particles in this size range due to the larger error associated with these samples. In addition, accumulation mode (> 0.1 and < 2.5 micrometers) particle diameter accounted for a substantial portion of the materials mass distribution. Single and multi-walled carbon nanotubes (SWCNT, MWCNT) mass distributions indicate

the majority of the particles had an aerodynamic diameter greater than one micrometer. The larger particle size is due to the formation of “ropes” as a result of Van der Waals forces that have further bundled together forming larger particles (Lam et al., 2006). The nano-silver and nano-titanium dioxide also showed the majority of the particulate matter occurred in the larger aerodynamic diameter ranges. However, these materials did demonstrate a greater portion of mass in the Aitken-nuclei and accumulation mode size ranges as compared to the SWCNT and MWCNT. It should be noted that a second mass distribution (not shown) of powdered SWCNT was analyzed in a second sample run. In this run, the sample was not prepared by pulverizing with a glass mortar and pestle, and essentially no material was detected below the 10-micron aerodynamic diameter. This indicates that without pulverization the SWCNT agglomerates exist primarily in the coarse mode. This was confirmed by P-Trak® (top diameter detection of approximately 1 micrometer) readings which logged a significant decrease of particle concentration in the non-pulverized SWCNT sample as compared to the SWCNT that was pulverized prior to suspension. Particle Size Distribution

Fig. 2 shows the normalized particle distribution of the tested ENM. The mass distributions do not show any more


significant fraction in the sub 100 nanometers size range than what would be expected in a typical urban ambient sample, nor do they show a strong multimodal characteristic with a typical minimum mass distribution in the 1 to 3 µm range that would be characteristic of urban aerosols. The ENMs exhibit less mass fraction in the sub 100 nanometer range than would be expected near an urban freeway which acts as a significant source of nuclei and accumulation mode particles, resulting from combustion and secondary aerosol materials formation (Seinfeld and Pandis, 2006). This is a result of the tested ENMs already in larger agglomerates when they get suspended. This suggests the release of nanomaterials, originating in powder form, will not lead to significant emissions of ultra-fine particle concentrations unless they are released under very high dispersion energies as suggested by Tsai et al. (2012) and Evans et al. (2013). Particle Count

P-Trak® particle counts for each of the sample runs were compared with the MOUDI size distributions in the range of the P-Trak® particle counter (0.02–1 micrometer aerodynamic diameter) and a particle number per mass of measured PM1.0 was calculated. These values are summarized in Table 3. Nano-silver and C60 Fullerene had the lowest particle count per mass (2.9 [± 1.0] × 107 and 7.5 [± 1.7] × 107 #/mg PM1.0 diameter respectively) of the materials tested. The SWCNT, MWCNT, nano-diamond and nano-titanium dioxide had larger particle counts per mass of material in this size range. This likely reflects the formation of agglomerates. A review of particle count and MOUDI mass distributions, using various particle shapes, showed the P-Trak® yielded lower particle count than those calculated using mass distribution data, with the exception of SWCNT, which showed a good correlation between P-trak® particle counts and MOUDI mass distributions. In addition, uncertainty in the ratio of particle number to the PM1.0 mass was governed by the low mass loading on the MOUDI impactors with aerodynamic diameters less than one micrometer.

Fig. 3(a) shows the comparison of particle number from the ENM particle numbers per microgram of PM1.0 to those observed over a 14 month period in St. Louis, MO from May 2001 through June 2002. The St. Louis data is the average particle concentration per mass based on a particle size distribution developed with a system consisting of a nano-Differential Mobility Analyzer (DMA), regular-DMA, and an optical particle counter (OPC). PM1.0 mass was calculated through a summation of spherical particle volume for particles 1 µm and smaller and the application of a particle density estimated using PM2.5 spherical volume and measured PM2.5 mass loadings. The results indicate particle number in ambient air at urban location such as St. Louis is significantly higher than those likely to be observed from the release of the tested powder ENMs. This discrepancy is due to the fact that nanomaterials are already in larger agglomerate forms when they become resuspended, while nucleation sized particles are being released by combustion sources or atmospheric processing in the ambient air in urban locations. It should be noted that the T

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Fig. 3. a) Comparison of # particles/µg of PM1.0 of six engineered nanomaterials to ambient PM1.0 in St. Louis, MO. Particle numbers for St. Louis, MO are averaged from May 2001 to June 2002 based five minute records of validated data (Bae et al., 2006). b) The expressed macrophage reactive oxygen species reported as µg zymosan equivalents per mg of PM2.5 activity for engineered nanomaterials compared to ambient activity in an urban location, Denver, CO.

particle morphology, in particular aerosol bulk density, is not the same for the materials represented in Fig. 3(a), however, the degree in which ambient particle number concentration outweighs the ENMs tested is substantial. ANALYTICAL RESULTS EC/OC and Soluble Metals

The EC/OC, soluble metals, and unidentified “other” faction of the tested ENMs are summarized in Table 3. Fig. 4 shows the detected mass fraction of these components

normalized to the total mass measured on the PM2.5 filters. The organic species fraction from these results were not included in the mass fraction plots, as the total detected component concentrations were at least three orders of magnitude less than the OC detection levels. The detected alkanes and PAHs (discussed in the following section) are tabulated in the supplemental materials to this report. The nano-diamond results are not included due to the low mass collected on the filter, resulting in large uncertainties relative to the mass fraction. Nano-silver and nano-titanium dioxide show little EC/OC or soluble metals fractions. It should be


Fig. 4. Mass fraction of organic carbon, elemental carbon, and soluble metals of the PM2.5 fraction of suspended engineered nanomaterials. Nano-diamond is not reported due large uncertain in the calculated mass fractions resulting from low filter loading.

noted that the nano-silver mass on the PM2.5 filter was relatively small and the larger EC/OC contributions is likely a result of higher uncertainties with the analysis. Nano-silver had the highest relative soluble metal concentration compared to any of the materials tested, as to be expected, it was primarily water soluble silver. The nano-titanium dioxide showed very low EC/OC and soluble metals concentrations, including titanium, which was below the system blank detection levels. While a statistically significant mass of water soluble titanium was not detected in the TiO2 sample, these results are not unexpected since TiO2 is insoluble; however, this also indicates that a significant mass of nano-sized colloidal form of TiO2 was not present in the extract. The SWCNT, MWCNT, and C60 fullerenes had relatively low soluble metals content. These three materials had varying EC/OC response when analyzed. In all samples the total carbon detected did not equal the total mass collected on the PM2.5 filters. The EC/OC analysis for these materials did not appear to quantify the carbon based materials fully. Review of the thermograms for the SWCNT show the majority of the organic carbon is evolved during heating in the helium atmosphere, some pyrolized organic carbon is evolved after the introduction of oxygen, however throughout the analysis the measured light absorbance remains low and unchanged, indicating the SWCNT does not effectively absorb light and is not detected as EC. The same observations were made for the C60 fullerene EC/OC analysis. MWCNT had a similar initial detection of organic carbon and a much more profound occurrence of pyrolized organic carbon. The MWCNT showed greater light absorbance throughout the analysis and a decrease of light absorbance after the introduction of oxygen at peak analysis temperatures. The light absorbance characteristics resulted in a greater detection of EC from

the MWCNT. It can be concluded that the light absorbance characteristics (limited absorbance) of these materials result in muted detection of EC and the reduced observed mass fraction as compared to the total filter mass concentration. The thermograms for each of the materials tested are located in the supplemental materials to this document. The sum of all blank corrected soluble metals detected by ICP-MS is indicated by the soluble metals fraction in Fig. 4. Only nano-silver showed an appreciable level of soluble metal contribution. This was dominated by a soluble silver concentration greater than 11,000 ng/mg of PM2.5 nano-silver powder. Elevated soluble zinc concentrations, greater than 2,300 ng/mg of PM2.5 were also noted in the nano-diamond powder. The nano-diamond powder result has a relatively large uncertainty due to the small mass loaded into the resuspension system. Tables 3 and 4 summarize the mass fraction of EC/OC and detected soluble metals.

The detected soluble fraction of metals from each of the nonmaterial’s tested was compared to annual average ambient PM2.5 soluble metals collected in Denver, CO (7.78 µg/m3; January 1, 2003 through December 31, 2003) as a means to understand the relative impact these materials may pose as emission sources. Fig. 5(c) shows a comparison of these species to ambient concentrations in ng/m3 for an equivalent mass of PM2.5. Again, each nanomaterial had a differing composition of water soluble metals detected; in comparison to ambient samples, the overall concentration for nanomaterials was on a similar scale as ambient samples. With this in mind, namomaterials have the potential to have similar impacts to soluble metals concentrations as existing ambient sources. Nine soluble metals (Titanium, Iron, Copper, Zinc, Arsenic, Yttrium, Cadmium, Lead and Silver) were detected in the materials tested; soluble silver results were not available for the Denver ambient samples. The nano-


Table 4. Summary of select blank subtracted soluble metals of engineered nanomaterials collected on PM2.5 Teflon filters. Results have been normalized to the PM2.5 mass collected on the filter.

Compound Units Nano-Diamond Nano-Silver Nano-Titanium

Dioxide SWCNT MWCNT C60 Fullerene

Arsenic ng/mg 231.2 ± 64.1 165.5 ± 45.2 1.5 ± 1.7 18.7 ± 5.2 3.5 ± 3.7 38.7 ± 5.2Yttrium ng/mg 0.0 ± 1.0 0.0 ± 0.8 0.0 ± 0.0 19.9 ± 0.5 10.3 ± 0.2 4.4 ± 0.2Silver ng/mg 0.0 ± 17.6 11062.6 ± 224.4 33.3 ± 1.3 174.4 ± 6.7 8.0 ± 1.2 18.9 ± 2.8

Cadmium ng/mg 0.0 ± 0.7 0.0 ± 0.7 0.0 ± 0.0 0.0 ± 0.1 1.2 ± 0.3 0.1 ± 0.2Lead ng/mg 47.8 ± 1.6 3.6 ± 1.0 0.0 ± 0.0 0.2 ± 0.1 2.3 ± 0.1 0.0 ± 0.1

Titanium ng/mg 133.3 ± 118.0 66.6 ± 66.3 0.0 ± 2.3 0.0 ± 7.1 0.0 ± 6.2 30.2 ± 10.5Iron ng/mg 248.1 ± 433.5 198.3 ± 306.1 5.9 ± 11.3 0.0 ± 29.7 421.9 ± 27.3 35.8 ± 36.9

Copper ng/mg 103.5 ± 11.5 59.0 ± 9.4 0.1 ± 0.2 11.4 ± 1.6 7.5 ± 1.3 6.2 ± 1.1Zinc ng/mg 2324.9 ± 1077.5 132.9 ± 787.1 21.8 ± 27.1 122.9 ± 70.8 11.0 ± 63.4 15.5 ± 88.6

diamond showed the highest level of soluble metals with estimated concentrations exceeding ambient levels of titanium (1.04 ± 0.92 ng/m3 vs 0.10 ± 0.03 ng/m3), zinc (18.09 ± 8.38 ng/m3 vs. 5.17 ± 1.87 ng/m3), and arsenic (1.79 ± 0.50 ng/m3 vs. 0.13 ± 0.04 ng/m3). SWCNT, MWCNT, and C60-fullerenes all have higher estimated Yttrium contribution than the ambient at 0.16 ± 0.004 ng/m3, 0.08 ± 0.002 ng/m3, 0.03 ± 0.001 ng/m3 vs. 0.003 ± 0.001 ng/m3, respectively. Alkanes and Polycyclic Aromatic Hydrocarbons (PAHs)

SWCNT, MWCNT, and C60 fullerenes were analyzed for PAHs and alkanes by TD-GCMS. A total of 18 organic compounds were detected above the system blank concentrations. Each of the materials showed a different organic species profile. Phenanthrene and C-23 through C-27 alkanes were detected in the SWCNT samples. MWCNT showed the highest concentration of the PAH Anthracene (39.5 ± 8.0 pg/µg PM2.5) as well as the alkane Nonacosane (8.3 ± 1.7 pg/µg PM2.5). The C60 fullerene organics species consisted primarily of C-29 through C-36 alkanes. Birch (2011) detected elevated levels of PAHs at a CNT production facility, including phenanthrene, anthracene, fluoranthene and pyrene, however these PAHs were near or below the detection limit when directly analyzing the facilities product. A summary table of the detected organic compounds is available in the supplemental materials.

The detected alkanes and PAHs from the SWCNT, MWCNT, and C60 Fullerenes were compared to annual average ambient PM2.5 organics species collected in St. Louis, MO (16.9 µg/m3 PM2.5; May 9, 2001 through April 30, 2003). Figs. 5(a) and 5(b) shows a comparison of these species as ambient concentrations in ng/m3 for an equivalent mass of PM2.5. As discussed previously, the nanomaterials had distinct groups of organic species detected, as compared to ambient samples which showed concentrations of each of the thirteen organic species (fluoranthene, pyrene, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacotane, and tetratriacontane) detected in the nanomaterials. In addition, the overall concentration of the alkanes and PAHs were several orders of magnitude greater in the ambient samples. While it is not surprising the ambient samples, composed of emissions from multiple sources, would have elevated organics species, it is noteworthy that the

relative concentration of organics species the nanomaterials possess is much less. It is not clear if the species detected on the nanomaterials are a result of the manufacturing process, and thus a potential source, or if ambient concentrations of alkanes and PAHs were preferentially adsorbed to the nanomaterial agglomerates from the time of manufacturing to the suspension testing, leading to the various profiles of organics species detected on each nanomaterial. However, as Birch (2011) suggests PAHs are formed under the conditions in which CNTs are synthesized and CNT have a high sorptive capacity, indicating CNT production could be a source of PAHs and other organic constituents. ROS Macrophage

The capacity of the nanomaterials to induce reactive oxygen species (ROS) in-vitro was evaluated with a alveolar macrophage cell line (NR 8383) (Landreman et al., 2008). Intra-cellular ROS is quantified with the broad-spectrum ROS fluorescence probe DCFH in a 96 well-plate format assay. All samples were run in triplicate and ROS activity was expressed as zymosan (ZYM) equivalents per mg of material. The macrophage ROS assay was performed on water extracts of the Teflon filter-collected PM2.5 and thus the ROS activity reflects water soluble components of the nanomaterials. The results (Table 3) indicate extremely low ROS activity (in most samples, not significantly different than zero). For reference, the ROS activity of urban atmosphere PM is commonly in the 500–4000 microgram ZYM/mg range (Shafer et al., 2009) compared with the < 50 microgram ZYM/mg observed for most nanomaterials in this study. The nano-titanium dioxide was analyzed both as a water soluble species and as a suspended material. The suspended material (filter extract was not filtered through a 0.22 micron polypropylene syringe filter) resulted in a zymosan equivalent per total mass of PM2.5 of approximately 10 times greater than the soluble titanium dioxide. This value is still substantially less than an ambient PM2.5 ROS activity, which is discussed further below. Interestingly nano-silver powder did not show a ROS response even though nano-silver is widely used as an antimicrobial agent. Bacteria experience oxidative stress, similar to the macrophage, when ROS generation leads to elevated stress as compared to that observed under steady-state oxidative species concentrations. (Quadros


Fig. 5. a) and b) Estimated concentrations of detected PAHs for an equivalent average annual mass of PM2.5 in an urban location, St. Louis, MO and c) estimated concentrations of detected soluble metals for an equivalent average annual mass of PM2.5 (7.78 µg/m3; January 1, 2003 through December 31, 2003) in an urban location, Denver, CO.


and Marr, 2010; Fang, 2011; Stoiber et al., 2011) The lack of response indicates the nano-silver remained in the particle form and did not release significant number of silver ions, likely the primary cause of molecular toxicity from sliver nanoparticles (Xiu et al., 2012).

The mass fraction of µg ZYM equivalent change in ROS activity for each of the nanomaterials was compared to the ambient PM2.5 induced ROS activity for Denver, CO. Fig. 3(b) shows the induced toxicity as measured by ROS response was minimal when compared to the ambient PM2.5 sample response. Large uncertainties associated with the reported values are a result of propagation on the error associated with the low mass filter loading; the detected ROS activity for the individual materials tested did exceed the method detection limit, as a result, the response is not quantifiable but it is likely greater than zero. Nano-diamond was the only nanomaterial that showed a significant ROS response, however this was response was still more than sixteen times less than the ambient PM2.5 sample, 233 ± 682 ROS µg ZYM equivalent/mg PM2.5 to 3757 ± 578 ROS µg ZYM equivalent/mg PM2.5. This ROS response was likely driven by the elevated soluble metals detected in the nano-diamond samples. The titanium dioxide, SWCNT, and C60 fullerenes also showed some response, however all were near zero and less the individual uncertainties. CONCLUSION

Six commercially available engineered nanomaterial powders were investigated to determine their aerodynamic and chemical characteristics. Materials were suspended in a controlled environment and collected on Teflon, quartz, and aluminum substrates for gravimetric and chemical analysis. Standard aerosol analytical techniques were applied to assess the viability of these procedures on engineered nanomaterials; materials whose unique properties make them desirable for commercial applications but may result in difficulty quantifying emissions and associated risks. The results were compared to ambient urban environment PM samples to assess the relative risk, in particular particle number and size distribution, soluble metals, organic species, and ROS macrophage response. The results showed that these engineered nanomaterials generally remained in the accumulation mode or coarse particle size range when they become suspended in air. Limited evidence was shown that nuclei mode primary particle sizes were preserved, and generally the tested materials expressed mass concentrations in the accumulation mode or larger. EC/OC analysis showed carbon structured nanomaterials such as SWCNT, MWCNT, and C60 Fullerenes were not completely quantified by NIOSH 5040 method, likely due to limited light absorption and the material not being completely oxidized under the existing temperature regime, which resulted in a decrease in quantifiable carbon mass. Additional investigation into the application of thermal-optical ECOC methods to quantify fullerene structured carbon nanomaterials is recommended. The materials tested exhibited very low quantities of PAHs and alkanes, relative to ambient samples, indicating they are not likely to be a significant source of PAHs and alkanes,

however, they may preferentially adsorb these materials affecting how these constituents are ultimately deposited. In addition, macrophage ROS response was small, especially when compared to that of ambient PM2.5 ROS response. The nanomaterials did exhibit similar levels of soluble metals to those observed in urban ambient samples, indicating they have the potential to be a source of soluble metals, such as silver, zinc, iron and arsenic. It should be noted these results are relevant to ambient emissions and may not be applicable to laboratory, or commercial setting, where the unique properties of nanomaterials may have a substantial impact on human health depending on potential exposure scenarios. In addition, more exotic nanoparticles; (for example, materials that contain cadmium or other highly toxic metals) may prove to have a greater impact than those materials analyzed as part of this research. The comparison of analytical and toxicological results indicated that in most cases the existing risks of ambient PM will outweigh all but the extreme cases of release of engineered nanoparticles to the environment. ACKNOWLEDGMENTS

The authors would like to thank University of Wisconsin-Madison Nanoscale Science and Engineering Center (NSEC) for funding this work, initiated under NSF grant DMR-0425880 and completed under NSF grant DMR-0832760; Dr. Jay Turner at Washington University for St. Louis, MO ambient Particle distribution and speciated organics data; Dr. Mike Hannigan at the University of Colorado for Denver, CO ambient WS-metals and ROS data; Dr. George Gruetzmacher for use of the P-Trak®; and the analytical staff at the Wisconsin State Laboratory of Hygiene (WSLH) for ROS, WS-ICPMS, TD-GCMS, ECOC, and gravimetric analysis. SUPPLEMENTARY MATERIALS

Supplementary data associated with this article can be found in the online version at http://www.aaqr.org. REFERENCES Aitken, R.J., Chaudhry, M.Q., Boxall, A.B.A. and Hull, M.

(2006). Manufacture and Use of Nanomaterials: Current Status in the UK and Global Trends. Occup. Med. 56: 300–306.

Birch, M.E. and Cary, R.A. (1996). Elemental Carbon-Based Method for Monitoring Occupational Exposures to Particulate Diesel Exhaust. Aerosol Sci. Technol. 25: 221–241.

Birch, M.E. (2011). Exposure and Emissions Monitoring during Carbon Nanofiber Production-Part II: Polycyclic Aromatic Hydrocarbons. Ann. Occup. Hyg. 55: 1037–1047.

Birch, M.E., Ku, B.K., Evans, D.E. and Ruda-Eberenz, T.A. (2011). Exposure and Emissions Monitoring during Carbon Nanofiber Production-Part I: Elemental Carbon and Iron-Soot Aerosols. Ann. Occup. Hyg. 55: 1016–1036.


Chen, C.H., Li, J.P., Huang, N.C., Yang, C.S. and Chen, J.K. (2011). Establishment of Airborne Nanoparticle Exposure Chamber System to Assess Nano TiO2 Induced Mice Lung Effects. AIP Conf. Proc. 1415: 167–170.

Evans, D.E., Turkevich, L.A., Roettgers, C.T., Deye, G.J. and Baron, P.A. (2013). Dustiness of Fine and Nanoscale Powders. Ann. Occup. Hyg. 57: 261–277.

Fang, F.C. (2011). Antimicrobial Actions of Reactive Oxygen Species. Mbio 2: e00141-11.

Gottschalk, F. and Nowack, B. (2011). The Release of Engineered Nanomaterials to the Environment. J. Environ. Monit. 13: 1145–1155.

Hunt, G., Lynch, I., Cassee, F., Handy, R.D., Fernandes, T., Berges, M., Kuhlbusch, T.A.J., Dusinska, M. and Riediker, M. (2013). Towards a Consensus View on Understanding Nanomaterials Hazards and Managing Exposure: Knowledge Gaps and Recommendations. Materials 6: 1090–1117.

Kendall, M. and Holgate, S. (2012). Health Impact and Toxicological Effects of Nanomaterials in the Lung. Respirology 17: 743–758.

Lam, C.W., James, J.T., McCluskey, R., Arepalli, S. and Hunter, R.L. (2006). A Review of Carbon Nanotube Toxicity and Assessment of Potential Occupational and Environmental Health Risks. Crit. Rev. Toxicol. 36: 189–217.

Landreman, A.P., Shafer, M.M., Shafer, M.M., Hemming, J.C., Hannigan, M.P. and Schauer, J.J. (2008). A Macrophage-based Method for the Assessment of the Reactive Oxygen Species (ROS) Activity of Atmospheric Particulate Matter (PM) and Application to Routine (daily-24 h) Aerosol Monitoring Studies. Aerosol Sci. Technol. 42: 946–957.

Lough, G.C., Schauer, J.J., Park, J.S., Shafer, M.M., Deminter, J.T. and Weinstein, J.P. (2005). Emissions of Metals Associated with Motor Vehicle Roadways. Environ. Sci. Technol. 39: 826–836.

Maynard, A.D. and Kuempel, E.D. (2005). Airborne Nanostructured Particles and Occupational Health. J. Nanopart. Res. 7: 587–614.

Maynard, A.D. and Aitken, R.J. (2007). Assessing Exposure to Airborne Nanomaterials: Current Abilities and Future Requirements. Nanotoxicology 1: 26–41.

Maynard, A.D., Baron, P.A., Foley, M., Shvedova, A.A., Kisin, E.R. and Castranova, V. (2004). Exposure to Carbon Nanotube Material: Aerosol Release during the Handling of Unrefined Single-Walled Carbon Nanotube Material. J. Toxicol. Environ. Health A 67: 87–107.

Maynard, A.D., Ku, B.K., Emery, M., Stolzenburg, M. and McMurry, P.H. (2007). Measuring Particle Size-dependent Physicochemical Structure in Airborne Single Walled Carbon Nanotube Agglomerates. J. Nanopart. Res. 9:

85–92. Nowack, B. and Bucheli, T.D. (2007). Occurrence, Behavior

and Effects of Nanoparticles in the Environment. Environ. Pollut. 150: 5–22.

Nowack, B., Ranville, J.F., Diamond, S., Gallego-Urrea, J.A., Metcalfe, C., Rose, J., Horne, N., Koelmans, A.A. and Klaine, S.J. (2012). Potential Scenarios for Nanomaterial Release and Subsequent Alteration in the Environment. Environ. Toxicol. Chem. 31: 50–59.

Olson, M.S. and Gurian, P.L. (2012). Risk Assessment Strategies as Nanomaterials Transition into Commercial Applications. J. Nanopart. Res. 14: 786–786.

Quadros, M.E. and Marr, L.C. (2010). Environmental and Human Health Risks of Aerosolized Silver Nanoparticles. J. Air Waste Manage. Assoc. 60: 770–781.

Schauer, J.J., Mader, B.T., Deminter, J.T., Heidemann, G., Bae, M.S., et al. (2003). ACE-Asia Intercomparison of a Thermal-optical Method for the Determination of Particle-phase Organic and Elemental Carbon. Environ. Sci. Technol. 37: 993–1001.

Seinfeld, J.H. and Pandis, S.N. (2006). Atmospheric Chemistry and Physics - From Air Pollution to Climate Change (2nd Edition), John Wiley & Sons.

Shafer, M.M., Perkins, D.A., Antkiewicz, D.S., Stone, E.A., Quraishi, T.A. and Schauer, J.J. (2009). Reactive Oxygen Species activity and Chemical Speciation of Size-fractionated Atmospheric Particulate Matter from Lahore, Pakistan: An Important Role for Transition Metals. J. Environ. Monit. 12: 704–715.

Sheesley, R.J., Schauer, J.J. Meiritz, M., DeMinter, J.T., Bae, M.S. and Turner, J.R. (2007). Daily Variation in Particle-phase Source Tracers in an Urban Atmosphere. Aerosol Sci. Technol. 41: 981–993.

Stoiber, T.L., Shafer, M.M. and Armstrong, D.E. (2011). Induction of Reactive Oxygen Species in Chlamydomonas Reinhardtii in Response to Contrasting Trace Metal Exposures. Environ. Toxicol. 28: 516–523.

Tsai, C.J., Lin, G.Y., Liu, C.N., He, C.E. and Chen, C.W. (2012). Characteristic of Nanoparticles Generated from Different Nano-powders by Using Different Dispersion Methods. J. Nanopart. Res. 14: 777.

TSI (2013). Personal Communication with Sou Vang Technical Support Specialist.

Xiu, Z.M., Zhang, Q.B., Puppala, H.L., Colvin, V.L. and Alvarez, P.J. (2012). Negligible Particle-specific Antibacterial Activity of Silver Nanoparticles. Nano Lett. 12: 4271–4275.

Received for review, June 5, 2013 Accepted, August 15, 2013

1

AerodynamicandChemicalCharacteristicsofSelectEngineeredNanomaterialsPowders

SupplementalMaterials

I.EvidenceofMOUDIParticlesBounce

II.AlkaneandPAHsTabulatedResults

III.EC/OCThermograms

IV.NormalizedTiO2andNano‐diamondsizedistributions

2

I. Evidence of MOUDI Particles Bounce: Titanium dioxide mass distributions obtained by the MOUDIs demonstrating particle bounce in the aluminum foil substrates.

Photo of MOUDI 3.2 micron orifice cut point for the aluminum foil substrate, and corresponding distribution curves for titanium dioxide powder. Particulate matter bounce is evident from missing deposition points on aluminum impactor substrate. Top photograph shows the orifice distribution. Bottom photograph shows deposition distribution.

Nano Titanium Dioxide Powder (Teflon Impactor)

Diameter, m

0.01 0.1 1 10

dC/ dl

og(D

p),

0

200

400

600

800

1000

1200

1400

1600

1800

Nano Titanium Dioxide Powder(Aluminum Foil Impactor)

Diameter, m

0.01 0.1 1 10

dC/ dl

og(D

p),

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200

400

600

800

1000

1200

1400

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3

II. Alkane and PAHs Tabulated Results

System Blank System Blank SWCNT MWCNT C60 Fullerene Run #3-003 Run #5-008 Run #9-017 Run #10-019 Run #11-021

Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter)

Phenanthrene 5591.11 6231.53 5755.80 2565.08 3511.45Anthracene 0.00 257.31 0.00 8093.34 0.00Fluoranthene 449.02 451.44 381.67 606.31 348.14Acephenanthrylene * 0.00 0.00 0.00 0.00 0.00Pyrene 550.09 726.68 758.62 1544.30 493.19Methylfluoranthene* 0.00 0.00 0.00 0.00 0.009-Methylanthracene 0.00 0.00 0.00 0.00 0.00Benzo(GHI)fluoranthene 0.00 0.00 0.00 0.00 0.00Cyclopenta(cd)pyrene 0.00 0.00 0.00 0.00 0.00Benz(a)anthracene 0.00 0.00 0.00 0.00 0.00Chrysene 0.00 0.00 0.00 0.00 0.001-Methylchrysene 0.00 0.00 0.00 0.00 0.00Retene 0.00 0.00 0.00 0.00 0.00Benzo(b)fluoranthene 0.00 0.00 0.00 0.00 0.00Benzo(k)fluoranthene 0.00 0.00 0.00 0.00 0.00Benzo(j)fluoranthene * 0.00 0.00 0.00 0.00 0.00Benzo(e)pyrene 0.00 0.00 0.00 0.00 0.00Benzo(a)pyrene 0.00 0.00 0.00 0.00 0.00Perylene 0.00 0.00 0.00 0.00 0.00Indeno(1,2,3-cd)pyrene 0.00 0.00 0.00 0.00 0.00Benzo(GHI)perylene 0.00 0.00 0.00 0.00 0.00Dibenz(ah)anthracene 0.00 0.00 0.00 0.00 0.00Picene 0.00 0.00 0.00 0.00 0.00Coronene 843.22 816.40 865.42 1447.27 750.56Dibenzo(ae)pyrene 0.00 0.00 0.00 0.00 0.0017A(H)-22,29,30-Trisnorhopane 0.00 0.00 0.00 0.00 0.0017B(H)-21A(H)-30-Norhopane 0.00 0.00 0.00 0.00 0.0017A(H)-21B(H)-Hopane 0.00 0.00 0.00 0.00 0.0022S-Homohopane * 0.00 0.00 0.00 0.00 0.0022R-Homohopane * 0.00 0.00 0.00 0.00 0.0022S-Bishomohopane * 0.00 0.00 0.00 0.00 0.0022R-Bishomohopane * 0.00 0.00 0.00 0.00 0.0022S-Trishomohopane* 0.00 0.00 0.00 0.00 0.0022R-Trishomohopane* 0.00 0.00 0.00 0.00 0.00ABB-20R-C27-Cholestane 0.00 0.00 0.00 0.00 0.00ABB-20S-C27-Cholestane 0.00 0.00 0.00 0.00 0.00AAA-20S-C27-Cholestane * 0.00 0.00 0.00 0.00 0.00ABB-20R-C28-Ergostane 0.00 0.00 0.00 0.00 0.00ABB-20S-C28-Ergostane * 0.00 0.00 0.00 0.00 0.00ABB-20R-C29-Sitostane 0.00 0.00 0.00 0.00 0.00ABB-20S-C29-Sitostane * 0.00 0.00 0.00 0.00 0.00Nonane 0.00 0.00 0.00 0.00 0.00Decane 0.00 0.00 0.00 0.00 0.00Undecane 0.00 0.00 0.00 0.00 0.00

4

System Blank System Blank SWCNT MWCNT C60 Fullerene Run #3-003 Run #5-008 Run #9-017 Run #10-019 Run #11-021

Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter) Conc

(pg/filter)

Dodecane 0.00 0.00 0.00 0.00 0.00Tridecane 0.00 0.00 0.00 0.00 0.00Tetradecane 0.00 0.00 0.00 0.00 0.00Pentadecane 0.00 0.00 0.00 0.00 0.00Hexadecane 0.00 0.00 0.00 0.00 0.00Norpristane 0.00 0.00 0.00 0.00 0.00Heptadecane 0.00 0.00 0.00 0.00 0.00Pristane 0.00 0.00 0.00 0.00 0.00Octadecane 0.00 0.00 0.00 0.00 0.00Phytane 0.00 0.00 0.00 0.00 0.00Nonadecane 0.00 0.00 0.00 0.00 0.00Eicosane 0.00 0.00 0.00 0.00 0.00Heneicosane 0.00 0.00 0.00 0.00 0.00Docosane 0.00 0.00 0.00 0.00 0.00Tricosane 357.91 0.00 497.10 0.00 0.00Tetracosane 233.99 0.00 707.37 0.00 0.00Pentacosane 120.96 0.00 439.85 0.00 0.00Hexacosane 76.45 0.00 180.09 0.00 0.00Heptacosane 297.60 0.00 578.80 0.00 0.00Octacosane 119.61 0.00 210.81 378.68 1560.16iso-nonacosane* 0.00 0.00 0.00 0.00 0.00Nonacosane 190.26 186.39 154.01 1863.25 3002.16anteiso-triacontane* 0.00 0.00 0.00 0.00 0.00Triacontane 123.28 188.74 0.00 409.06 799.79iso-hentriacontane* 0.00 0.00 0.00 0.00 0.00Hentriacontane 125.10 0.00 0.00 272.91 2125.14anteiso-dotriacontane* 0.00 0.00 0.00 0.00 0.00Dotriacontane 0.00 0.00 0.00 285.74 2395.36iso-tritriacontane* 0.00 0.00 0.00 0.00 0.00Tritriacontane 0.00 0.00 0.00 0.00 576.81Tetratriacontane 0.00 0.00 0.00 0.00 333.08Pentatriacontane 0.00 0.00 0.00 0.00 287.56Hexatriacontane 0.00 0.00 0.00 0.00 247.98

5

III. EC/OC Thermograms

Nano-diamond

6

Nano-Silver

7

Nano-titanium dioxide

8

SWCNT – not pulverized

9

SWCNT - pulverized

10

MWCNT- Pulverized

11

C60 Fullerene pulverized

12

System Blank 1

13

System Blank 2

14

Trip Blank 1

15

Trip Blank 2

16

Loading Blank

17

Nano Diamond Powder (Teflon Impactor)

Diameter, m

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p),

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0.6

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1.6

IV. Normalized Nano-diamond and C60 –Fullerene size distributions

C60 Fullerene Powder (Teflon Impactor)

Diameter, m

0.01 0.1 1 10

dC

/C d

log

(Dp),

0.0

0.2

0.4

0.6

0.8

1.0

aerodynamic and chemical characteristics of six engineered

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