Attachment 2 - CoA_SRM-1963a.pdf

SRM 1963a Page 1 of 5

National Institute of Standards & Technology

Certificate of Analysis

Standard Reference Material® 1963a

Polystyrene Spheres

(Nominal Diameter 100 nm)

This Standard Reference Material (SRM) is intended for the calibration/validation of particle sizing instruments, including electron microscopes, differential mobility analyzers, scanning surface inspection systems, and other light scattering instruments. A unit of SRM 1963a consists of 5 mL of polystyrene spheres in deionized filtered (0.2 µm pore size) water. The particle suspension contains primary spheres (monomers) with very few agglomerates.

The spheres are present at a mass fraction of approximately 0.5 % and are supplied in a dispensing vial.

The size probability distribution is P(D) = dN/dD, where dN is the fraction of particles with diameter between D and D + dD. The modal diameter, which is the diameter where P(D) takes the largest value, also called the mode of P(D), was measured for the spheres suspended as an aerosol using differential mobility analysis (DMA) [1]. The certified value for the modal diameter of the polystyrene spheres as an aerosol is given in Table 1.

Table 1. Certified Modal Sphere Diameter and Expanded Uncertainty(a)

Modal Diameter

101.8 nm ± 1.1 nm

(a) The expanded uncertainty (95 % confidence interval) includes both Type A and Type B uncertainties calculated according to the

ISO/JCGM Guide [2].

These results are based on three repeat measurements on each of three different dates. There was one calibration measurement made either proceeding or following each of the certification measurements [3]. The measurand is the diameter for the Modal Sphere. The certified values are metrological traceable to the SI unit of length, expressed as nanometers.

The value for the combined uncertainty for the modal diameter is 0.55 nm and the number of degrees of freedom for the uncertainty is 153. This information may be used to estimate the uncertainty when using the spheres for calibrating a particle sizing instrument and estimating the effective degrees of freedom.

Expiration of Certification: The certification of SRM 1963a is valid, within the measurement uncertainty specified, until 31 March 2022, provided the SRM is handled and stored in accordance with instructions given in this certificate (see “Instructions for Handling, Storage and Use”). This certification is nullified if the SRM is damaged, contaminated, or otherwise modified.

Maintenance of Certification: NIST will monitor this SRM over the period of its certification. If substantive technical changes occur that affect the certification before the expiration of this certificate, NIST will notify the purchaser. Registration (see attached sheet or register online) will facilitate notification.

Technical direction and physical measurements were provided by T.A. Germer, NIST Sensor Science Division;

G.W. Mulholland, M.K. Donnelly, and S.R. Kukuck, NIST Fire Research Division; V.A. Hackley, NIST Materials Measurement Science Division; and D.Y.H. Pui, Particle Technology Laboratory, University of Minnesota.

LaDonna Lauren, Chief Microsystems and Nanotechnology Division

Gaithersburg, MD 20899 Steven J. Choquette, Director Certificate Issue Date: 01 May 2019 Office of Reference Materials Certificate Revision History on Last Page.

SRM 1963a Page 2 of 5

Statistical analysis was provided by C.R. Hagwood of the NIST Statistical Engineering Division.

Support aspects involved in the issuance of this SRM were coordinated through the NIST Office of Reference Materials.

Traceability: In the present certification measurements [1], the DMA was calibrated using SRM 1963. The certification of SRM 1963 [4] was based upon the certification of the 0.895 µm particle standard, SRM 1690. The certification of SRM 1690 [5], in turn, was based upon the He-Ne laser wavelength in air, 632.807 nm. Lastly, the He-Ne laser wavelength [6] has been determined with respect to the fundamental standard, SI Unit for length. All of the contributions to the uncertainty imposed by this traceability chain have been included in the Type B uncertainty expressed above.

Information Values: An information value is considered to be a value that will be of interest to the SRM user, but insufficient information is available to assess the uncertainty associated with the value. Information values cannot be used to establish metrological traceability.

Additional Information: A single measurement of the size probability distribution P(D) over an extended range of the distribution is given in Table 2 and Figure 1. The standard deviation of the size distribution near the peak is

2.5 nm, and the standard deviation of the entire distribution is 4.0 nm. The number median diameter is 101.1 nm. The number median diameter is the diameter x, at which the integral

( ) 0.5 x

P D dD =∫ where the cumulative distribution function is 0.5. The number mean diameter, the volume mean diameter, the light scattering mean diameter, and the dynamic light scattering mean diameter are given in Table 3. The extended measurement of P(D) yielded a slightly different modal diameter than the certified value, because that measurement was only obtained from a single scan on a single day; the difference between those values is statistically insignificant.

These are non-certified values with no uncertainty assessed and are provided for information purposes only.

The peak diameter is for the spheres as an aerosol. The contaminants in the suspension result in a residue layer on the spheres. The estimated thickness of this layer is 0.30 nm.

INSTRUCTIONS FOR HANDLING, STORAGE, AND USE

Handling and Use: A sample of the spheres may be obtained by squeezing a drop from the vial. Use filtered (0.2 µm pore size filter) deionized water for dilution. Care should be exercised to prevent contamination once the cap has been removed.

Storage: Refrigerate the sample (5 °C to 15 °C) but DO NOT allow the sample to become frozen. DO NOT remove the cap from the vial until the sample is used. It should be noted that no biocide was added during packaging. Once the sample is opened, there is a possibility of biological contamination leading to growth of bacteria or spores. To minimize the occurrence of this unwanted growth, replace the cap immediately after dispensing the sample drops.

Note: The polystyrene spheres may be damaged by exposure to an electron beam. This effect can be minimized by using a short exposure time and low electron flux [7].

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Table 2. Additional information values describing the size probability distribution, P(D), obtained from a single measurement scan over an extended range.

D P(D) D P(D)

(nm) (nm-1) (nm) (nm-1)

78.15 0.00095 101.02 0.14710

82.85 0.00149 101.43 0.14442

87.38 0.00368 101.83 0.14632

91.76 0.00383 102.23 0.14008

94.81 0.01651 102.64 0.13092

95.23 0.01812 103.04 0.12077

95.65 0.02420 103.44 0.10385

96.07 0.02611 103.84 0.08883

96.49 0.03227 104.24 0.07115

96.90 0.03691 104.63 0.05788

97.32 0.04591 105.03 0.04429

97.74 0.05411 105.43 0.03257

98.15 0.06523 105.82 0.02370

98.56 0.07391 106.22 0.01718

98.97 0.08900 106.61 0.01227

99.39 0.10203 108.12 0.00515

99.80 0.11510 111.98 0.00094

100.20 0.12779 115.77 0.00106

100.61 0.13759

Figure 1. Size probability distribution, P(D), of data provided in Table 2 obtained from a single measurement scan over an extended range.

70 80 90 100 110 120 0.00

0.05

0.10

0.15

P( D)

, n m

-1

D, nm

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Table 3. Information value for the weighted mean particle diameter based on the size probability distribution, P(D), given in Table 1.

Peak Diameter (a)

(nm)

〈DN〉

(b) (nm)

〈DV〉

(nm)

〈DLS〉

(nm)

〈Dh〉Z (nm) σ〈DN〉 (nm)

101.5 100.6 101.0 101.4 101.3 4.0

Number mean diameter: ( ) dND D P D D= ∫

Standard deviation of size distribution: ( ) ( ) 1/ 22 dND D P D Dσ = −

Volume or mass mean diameter:

d dV

DD P D D

D

D P D D

Light scattering weighted mean diameter (Rayleigh limit):

d dLS

DD P D D

D

D P D D

Dynamic light scattering mean diameter (c):

1 d dh Z

D P D D

DD

D P D D

(a) The peak diameter is estimated from a cubic fit for the 11 data points within 30 % of the largest value of P(D) = 0.14710.

(b) The integrals are evaluated using the trapezoidal rule.

(c) The subscript h indicates that this is the hydrodynamic diameter based on the diffusive motion of the particle.

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REFERENCES

[1] Mulholland, G.W.; Donnelly, M.K.; Hagwood, C.; Kukuck, S.R.; Hackley, V.A.; Pui, D.Y.H.; Measurement of 100 nm and 60 nm Particle Standards by Differential Mobility Analysis; J. Res. Natl. Inst. Stand. Technol., Vol. 111, Issue 4, pp. 257–312, (2006).

[2] JCGM 100:2008; Evaluation of Measurement Data — Guide to the Expression of Uncertainty in Measurement (GUM 1995 with Minor Corrections); Joint Committee for Guides in Metrology (JCGM) (2008); available at https://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf (accessed May 2019); see also Taylor, B.N.; Kuyatt, C.E.; Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results; NIST Technical Note 1297; U.S. Government Printing Office: Washington, DC (1994); available at http://www.nist.gov/pml/pubs/tn1297/index.cfm (accessed May 2019).

[3] May, W.; Parris, R.; Beck II, C.; Fassett, J.; Greenberg, R.; Guenther, F.; Kramer, G.; Wise, S.; Gills, T.;

Colbert, J.; Gettings, R.; MacDonald, B.; Definition of Terms and Modes Used at NIST for Value-Assignment of Reference Materials for Chemical Measurements; NIST Special Publication 260-136 (2000); available at http://www.nist.gov/srm/upload/SP260-136.PDF (accessed May 2019).

[4] Mulholland, G.W.; Bryner, N.P.; Croarkin, C.; Measurement of the 100 nm NIST SRM 1963 by Differential Mobility Analysis; Aerosol Sci. Technol., Vol. 31, pp. 39–55 (1999).

[5] Mulholland, G.W.; Hartman, A.W.; Hembree, G.G.; Marx, E.; Lettieri, T.R.; Development of a One Micrometer Diameter Particle Size Standard Reference Material; J. Res. NBS., Vol. 90, pp. 3–26 (1985).

[6] Mielenz, K.D.; Nefflen, K. F.; Gillilland, K.E.; Stephens, R.B.; Zipin, R.B.; Measurement of the 633-nm Wavelength of Helium-Neon Lasers; Appl. Phys. Lett., Vol. 7, p. 277 (1965) and Mielenz, K.D.; Nefflen, K.F.;

Rowley, W.R.C.; Wilson, D.C.; Engelhard, E.; Reproducibility of Helium-Neon Laser Wavelengths at 633 nm;

Appl. Opt., Vol. 7, p. 289 – 293 (1968).

[7] Jung, K.Y.; Park, B.C.; Song, W.Y.; Eom, T.B.; Eom, B.-H.O.; Measurement of 100-nm Polystyrene Sphere by Transmission Electron Microscope; Powder Technol., Vol. 126, pp. 255–265 (2002).

Certificate Revision History: 01 May 2019 (Change of expiration date; editorial changes); 06 October 2014 (Corrected Semiconductor and Dimensional Metrology Division Chief name; editorial changes); 05 June 2014 (Extension of the certification period; editorial changes);

10 January 2007 (Original certificate date).

Users of this SRM should ensure that the Certificate of Analysis in their possession is current. This can be accomplished by contacting the SRM Program: telephone (301) 975-2200; fax (301) 948-3730;

e-mail srminfo@nist.gov; or via the Internet at https://www.nist.gov/srm.

https://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf http://www.nist.gov/pml/pubs/tn1297/index.cfm http://www.nist.gov/srm/upload/SP260-136.PDF mailto:srminfo@nist.gov https://www.nist.gov/srm