Report of Results: MVA7571
Analysis of Dust Samples for Nanotubes
Prepared for:

Respectfully Submitted by: ___________________________ Whitney B. Hill, M.S. Research Microscopist

___________________________ James R. Millette, Ph.D. Executive Director

MVA Scientific Consultants 3300 Breckinridge Boulevard Suite 400 Duluth, GA 30096

25 July 2008

7571report072508 

### ** COMPANY SANITIZED **Report of Results: MVA7571
Analysis of Air Samples for Nanotubes

INTRODUCTION

This report includes the results of analyses of dust sample filter cassettes collected by and delivered to MVA Scientific Consultants on 22 July 2008. All samples were collected using preloaded SKC Micro-Vac cassettes (0.4 m, 37mm PC filter). No areas of collection were noted. Identification numbers assigned at the laboratory of MVA Scientific Consultants are shown in Table 1. MVA Scientific Consultants was asked to determine the size of carbon nanotubes (CNT) in the dust samples. Analyses were conducted during the period 22 July through 23 July 2008.

METHODS AND EQUIPMENT

The samples were analyzed for carbon nanotubes (CNT) following the analytical procedures described as “EPA 763 / NIOSH 7402 Modified”. These procedures follow the filter preparation procedures of NIOSH 7402 and the counting procedures of the EPA AHERA transmission electron microscopy (TEM) method (EPA 763) with a modification that nanotubes are counted rather than asbestos fibers. Magnifications from 20,000 up to 100,000 times were used. Identification of particles as nanotubes was based on a comparison with known nanotube reference samples obtained by MVA Scientific Consultants from various sources including MVA’s work with the Georgia Institute of Technology (Georgia Tech). The TEM analyses were performed with a Philips CM 120 transmission electron microscope equipped with an Oxford INCA energy dispersive x-ray spectrometer.

RESULTS

No nanotubes were found in any of the samples. A summary of the CNT results is given in Table 1. Some non-nanotube particulate was found on all filters.

NOTES

Samples 1, 2 and 3 had very clean-looking filters and could be prepared directly. Sample 4 contained dust particles that had clumped together. The cassette was washed out with filtered distilled water and a portion of the resulting suspension was filtered through a 0.2 m PC filter. The filter was then prepared following standard direct preparation procedures.

7571report072508 Page 2 of 3 

### ** COMPANY SANITIZED **Table 1. Analysis Results for CNTs in Dust Samples Collected July 2008

MVA# Sample Information TEM Analysis Results T2956 #1 – Filter Prepared Directly for TEM NCNTD T2957 #2 – Filter Prepared Directly for TEM NCNTD T2958 #3 – Filter Prepared Directly for TEM NCNTD T2959 #4 – Filter Prepared Indirectly for TEM NCNTD

*NCNTD = No Carbon Nanotubes Detected

7571report072508 Page 3 of 3 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Revised Report of Results: MVA7678
Analysis of Dust Samples for Nanotubes
Prepared for:

Respectfully Submitted by: ____

_______________________ Whitney B. Hill, M.S. Research Microscopist

___________________________ James R. Millette, Ph.D. Executive Director

MVA Scientific Consultants 3300 Breckinridge Boulevard Suite 400 Duluth, GA 30096

Supercedes Report Da ted 30 October 2008

11 November 2008 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 2 of 8 Revised Report of Results: MVA7678
Analysis of Dust Samples for Nanotubes

INTRODUCTION

This revised report includes the results of analy ses of five dust sample filter cassettes and three reference samples collected by and delivered to MVA Scientific Consultants on 21 Octob er 2008. The five micro-vacuum dust samples were collected on 16 October 2008 usi ng preloaded SKC Micro-Vac cassettes (0.4 m, 37mm PC filter). No collection areas were pro vided. The three refere nce samples were provided as dry material, materi al in suspension and as a coating. Identification numbers assigned at the laboratory of MVA Scie ntific Consultants are show n in Table 1. MVA Scientific Consultants was asked to de termine the amount of carbon nanotubes (CNT) on the dust sample filters. Analyses were conducted during the period 23 October through 27 October 2008.

METHODS AND EQUIPMENT

The filters from the five dust samples (T3406 through T3410) were prepared directly for transmission electron microscopy (TEM). A thin strip was cut from each filter. This portion of the filter was c arbon coated and prepared according to the preparation procedures described in ASTM Method 6281 -04 for polycarbonate filters.

The dry reference material (Ref 1-T3411) and the suspended material (Ref 2-T3412) were prepared for TEM following the procedure described in ASTM Method D6602-03b (for carbon black and other bulk carbon nano-particles). A portion of Sample T3411 was suspended in acetone and drops of the suspension w ere allowed to dry on the carbon film of an electron microscope grid. For Sample T3412, drops of the suspension were taken directly from the bottle as received and were allowed to dry on the carbon film of an electron microscope grid. Reference 3 (T3413) could not be prepared using the same method. It was not analyzed by TEM.

The particle counting procedures involved th e careful examination of grid openings at magnifications up to 100,000 ti mes for nanotubes either as indi vidual tubes or clusters. Identification of particles as nanotubes was based on a comparison with two of the nanotube reference samples (T 3411 and T3412). The TEM analyses were performed with a Philips CM 120 transmission electron microscope equipped with an Oxford INCA energy dispersive x-ray spectrometer.

When no nanotubes structures are found, the filter loading analytical sensitivity is calculated. The filter loading analytical sensi tivity is based on the possibility of finding one structure in the sample. Th e analytical sensitivity is calculated from the following equation: 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 3 of 8 Structure/mm 2 = 1 structure # of Grid Openings x Grid Opening Area

RESULTS

No nanotubes were found in any of the dust samples. A summary of the CNT results is given in Table 1. Some non-nanotube particul ate was found on all filters. TEM images of areas of the filters prepared f rom samples T3406 through T341 0 have been included to show the presence of the non-nanotube particulate found on the filters (Figures 1 through 5). The images show particl es and evidence of th e pores that exist on the polycarbonate filters. Representative TEM images of the reference nanotubes are shown in Figures 6 and 7. 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 4 of 8 Table 1. Analysis Results for CNTs in Dust Samples Collected October 2008

MVA# Sample Information TEM Analysis Results T3406 Nano-1

– Filter Prepared Directly for TEM CNT-ND* T3407 Nano-2

– Filter Prepared Directly for TEM CNT-ND T3408 Nano-3

– Filter Prepared Directly for TEM CNT-ND T3409 Nano-4

– Filter Prepared Directly for TEM CNT-ND T3410 Nano-5

– Filter Prepared Directly for TEM CNT-ND T3411 Ref-1 - prepared acco rding to ASTM D6602 Fig 1 T3412 Ref-2

– prepared according to ASTM D6602 Fig 2 T3413 Ref-3

– Could not be prepar ed according to ASTM D6602 N/A

*CNT-ND = Carbon Nano tubes - Not Detected. The single nanotube analytical sensitivity was 11 nanotube structures per mm 2 of filter for each dust sample. 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 5 of 8 Figure 1. TEM image of a non-nanotube particle found in sample T3406.

Figure 2. TEM image of non-nanotube particl es found in sample T3407. 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 6 of 8 Figure 3. TEM image of a non-nanotube particle found in sample T3408.

Figure 4. TEM image of a non-nanotube particle found in sample T3409. 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 7 of 8 Figure 5. TEM image of non-nanotube particl es found in sample T3410.

Figure 6. TEM image of carbon nanotubes f rom reference sample T3411. The scale bar is 100 nm. 

### ** COMPANY SANITIZED **7678report103008_rev1_111108 Page 8 of 8 Figure 7. TEM image of carbon nanotubes f rom reference sample T3412. The scale bar is 250 nm. 

### ** COMPANY SANITIZED **

### Report



# Carbon Nanotube Sampling

November 20, 2008 

### ** COMPANY SANITIZED **___________________________________________________________ November 20 , 2008 2 1.0 Introduction

T.

n

c t a t Dr i t s a K zm r t pe f r a s t i i an a in sa pl ng a a f where MWCNT are handled. This report presents the methods used and results of that sampling, conducted on October 16, 2008.

2.0 Background

There were no releases of dry MWCNT or spills of liquid suspensions of MWCNT observed by on the day of his visit to However, surfaces in areas where liquid suspensions of MWCNT were observed being handled contained visible signs of dark discoloration. The appearance of the dark discoloration was consistent with the physical appearance of treated MWCNT suspensions used at those locations. The discolored areas appeared as dried deposits of droplets of a dark liquid. Upon close examination of a number of the droplet areas, there was no visible raised solid or particulate residue associated with the discolored areas. The discoloration could not be removed by gentle wiping with a dry paper towel, but appeared to remain on the surface as an adhered stain.

3.0 Objective

The objective of the sampling performed at N r on October, 16, 2008 was to evaluate the potential presence of dislodgeable particulate MWCNT on surfaces or suspended in air within the facility. 

### ** COMPANY SANITIZED **____________________________________________________________ November 20 , 2008 3 4.0 Approach and Methods

The approach applied to meeting the above project objective was to perform surface and air sampling for MWCNT particles at locations assumed to have the highest likelihood of containing a source of particulate or airborne MWCNT. Sampling was performed while routine operations involving MWCNT materials were underway.

The locations and areas sampled were selected based on a reported history of handling of MWNT and visible evidence of staining. It was assumed that areas of dark surface discoloration, reported associated with previous spills of MWCNT suspensions, as well as exterior surfaces of the glove box, had a higher likelihood of containing particulate MWCNT than non-stained areas or locations with no history of handling of pow dered or suspensions of MWCNT. Similarly, air in the vicinity of these locations was assumed to have higher likelihood of containing airborne MWCNT particles than locations within N not associated with the handling or processing of dry or liquid suspensions of MWCNT.

The following is a listing of locations sampled:

Sample ID Sample Type Nano-1 Air Sample

Nano-2 Air sample

Nano-3 Surface sample

Nano-4 Surface sample

Nano-5 Surface sample

4.1 Air sampling

Air sampling was performed using an SKC Inc. "Air Check" air sampling pump pre-calibrated to a constant flow rate of 2.0 lpm. Airborne pa rticulate was collected by filtration onto a 37 mm polycarbonate filter (0.4 um pore opening size) pre-loaded in a non-conductive styrene cassette (SKC part no. 225-9542). Sampling of air proceeded over a duration of 135 minutes, for a total air collection volume of 270 liters.

A hand-held TSI P-Track Ultrafine Particle Counter was also to deployed to collect real-timedata regarding the presence and levels of airborne particulate in various areas of The PTrak was serviced and pre-calibrated by Galson Laboratories (Galson ID PK-002). According to 

### ** COMPANY SANITIZED **_____________________________________________________________ November 20 , 2008 4 information provided by the manufacturer, the P-Trak is an alcohol vapor condensation particle counter with a reported sensitivity to particles as small as 0.02 um. The P-track unit was deployed in the survey mode, providing real-time readings, in units of particles/cc, and refreshed every ten seconds. The readings were recorded manually.

4.2 Surface Sampling

Surfaces were sampled for dislodgeable particulate material using a "micro-vac" technique. The surface sampling was accomplished by gently traversing a pre-selected designated 200 cm2 stained surface with a Tygon nozzle attached to a sampling cassette and air collection pump, while the pump was in operation. The nozzle acte d as a "vacuum', drawing particulate into the cassette and onto the filter. The entire 200 cm2 surface sampled was traversed 4 times.

The "micro vac" method utilized a non-conductive styrene cassette pre-loaded with a 37 mm polycarbonate filter (0.4 um pore opening size) identical to the cassette used for air sampling (SKC part no. 225-9542). However the opening to the cassette was fitted with a pre-cleaned Tygon tubing microvacuum nozzle. The cassette was connected to a SKC "Leland Legacy" air sampling pump operated at a flow rate of 5.0 lpm.

4.3 Analysis of samples for presence of particulate MWCNT

The cassette samples were shipped to MVA Scientific Consultants, Inc. of Duluth GA (MVA) for characterization by Transmission Electron Microscopy. The samples submitted to MVA included three sealed reference samples provided by The reference samples included the following:

REF-1: a small aliquot of the MWCNT powder as received by REF-2: a small aliquot of a liquid MWNT suspension as purified and processed at REF-3: a dry solid plate coated with the processed MWNT.

MVA was instructed to analyze the filters in the cassette samples for individual particles, fragments or clusters of MWCNT matching the reference standards. The samples were prepared for TEM following the procedure described in ASTM Method D6602-03b (for carbon black and other bulk carbon nano-particles). A representative number of randomly selected TEM grids and examined by TEM at magnification of up to 100,000 times. The attached report prepared by MVA provides additional detail as to the methods of analysis and the results.

5.0 Results

There were no MWCNT particles detected in any of the samples collected at

The limit of detection reported by MVA was 11 particles per mm2 of filter surface. This detection limit is a theoretical value, based on the hypothetical event detecting one MWCNT particle in the sum total area of all of the grids examined, reported as a value with the units of "strucures/mm2". The limit of detection of 11 structures per mm2 of filter was then used to calculate the minimum number of particles that would have been required to be present on the filter, collected from the sampled area, in order to have been detected by the method. 

### ** COMPANY SANITIZED **______________________________________________________________________________________ November 20 , 2008 5 Based on the reported TEM detection limit of 11 structures per mm2, a filter diameter of 37 mm, and a sampled surface area of 200 cm2, less than 60 MWCNT structures were collected per square centimeter of each of the sampled surfaces.

Similarly, based on the reported TEM detection limit of 11 structures per mm2, a filter diameter of 37 mm, and a total air volume collected of 270 liters (135 min @ 2.0 lpm), air in the sampled locations contained less than 0.04 structures cubic centimeter.

The results of the real-time particle readings measured by the P-Tack particle counting device are presented below:

Location P-track instrument reading (particles/cc) 8790 10,400 9,170 518 253 1390 0 35 558 241 0 35 14 147 9 4 2760 0 1

6.0 Conclusions and Discussion

While the actual level of accuracy and precision of the for detection of MWCNT is not known, the results of the hand-held P-Track dust measurements suggest that the level of airborne particulate within the Nantero laboratory areas is very low, especially if considered relative to readings representing locations outside of the laboratory.

The results of the sampling and subsequent TEM analysis document a consistent absence of detectable MWCNT particles in the surface and air samples collected at

The attached TEM report prepared by MVA includes photomicrographs of the reference standards of MWCNT as well as representative images of surfaces of the sample filters, showing the absence of MWCNT particulates. The micrographs demonstrate and document a level of magnification and resolution capable of detecting and supporting the positive identification of the reference MWCNT particles or their fragments. 

### ** COMPANY SANITIZED **_____________________________________________________________ November 20 , 2008 6 Based on the sensitivity and specificity of the TEM method, and the reported absence of detectable MWCNT, it can be concluded that there is a low likelihood that the surface stains, presumably caused by spillage of MWCNT suspensions, contain MWCNT in an easily dislodged form. The absence of MWCNT particles from air in sampled portions of the facility also suggests that the activities and conditions at those locations at the time of sampling did not contribute to detectable levels of airborne MWCNT.

It should be recognized that the sampled areas were under the control of a high volume exhaust and HEPA filtered recirculation system designed to minimize airborne particulate. The results of the hand-held particle counter indicate that airborne particulate levels in the areas sampled S l i Mi l i i M l D E L were significantly lower than common areas outside of the labs, as well adjacent locations within the lab. These areas were serviced by what was reported as a high volume HEPA filtered air exhaust and recirculation system. The absence MWCNT from the air samples analyzed by electron microscopy could have been influenced by the exhaust and recirculation system operating within the labs at the time of sampling. The results of the air sampling cannot be used to conclude that no airborne particulate MWCNT would be present in the event that lab operations were underway in the absence of active exhaust ventilation or HEPA fitration.

There is no standard or reference value against which the reported limit of detection of 60 MWCNT structures per cm2 can be compared. However, given the small size and mass of a MWCNT structure, it should be recognized that th is is an extremely low, perhaps insignificant, number of MWCNT particles. Similarly, aside from limits applicable to total nuisance dust, there are no regulatory standards or guidance values applicable to MWCNT in workplace air. However, it is notable that the limit of detection for MWCNT in this sampling (0.04 structures per cubic centimeter) is below the 0.1 structure/cc OSHA Permissible Exposure Limit for Asbestos.

7.0 Recommendations

The results of this sampling indicate the absence of detectable amounts of MWCNT in sampled air and surfaces. However, visible evidence of spillage of what was reported as MWCNT suspensions was observed at numerous locations of the facility where MWCNT are routinely handled. While the results of this sampling suggest that the spilled MWCNT suspensions are not present in a form that can release particulate to impact air in the facility, it is not known if these results apply to all stained (or unstained) areas where spills have occurred in the past. It is therefore recommended that reasonable efforts be taken to clean surfaces in the facility to remove staining and other surface deposits from accessible areas. This would also be appropriate given that is not directly aware of all past activities within the facility.

Following the general cleaning, it is recommended that a "clean as you go" policy for responding to spills be established and enforced. Removal of all "old" areas of discoloration would then provide a visual aid for identifying and initiating an immediate response to new spills, consistent with a "clean as you go" approach. 

### ** COMPANY SANITIZED **____________________________________________________________ November 20 , 2008 7 

## Attachment 1: Floor Plan ** COMPANY SANITIZED **

### ** COMPANY SANITIZED **____________________________________________________________ November 20 , 2008 9 

## Attachment 2: MVA Scien tific Consultants Electron Microscopy Report ** COMPANY SANITIZED **