Development and Production of Reference Materials Debra L. Kaiser Chief, Ceramics Division

1. Development and Production of Reference Materials Debra L. Kaiser Chief, Ceramics Division Materials Science and Engineering Laboratory

2. Material-Based Standards: Definitions • International Vocabulary of Metrology* (IVM): • Reference Material • Certified Reference Material (CRM) • NIST: • Standard Reference Material (SRM) • Reference Material (RM) *published by the International Organization for Standards (ISO) http://www.iso.org/iso/publications_and_e-products/

3. Reference Material: IVM Definition • Material or substance whose property values are sufficiently homogeneous and well established to be used for: • Calibrating an apparatus • Assessing a measurement method • Assigning values to materials • Quality control • Properties may be: • Quantitative, e.g., amount or size of substance or species • Qualitative, e.g., identity of substances or species

4. Certified Reference Material: IVM Definition • All from the previous slide for a Reference Material plus: • Accompanied by a certificate • Property values are certified as traceable to an accurate realization of the unit in which the property values are expressed • nanoparticle diameter traceable to a known wavelength of light via a step height transfer artifact • Each certified value is accompanied by an uncertainty at a stated level of confidence

5. NIST Standard Reference Material (SRM) • All from the previous slide for a CRM plus: • Meets NIST-specific certification criteria* • Issued with a Certificate of Analysis that details its characterizations and provides information regarding its appropriate uses • Certified values are usually measured by two or more independent methods at NIST • Certified values and uncertainties for which NIST has the highest confidence because it has fully investigated or accounted for all known or suspected sources of bias *NIST Special Publication 260-136

6. NIST Reference Material (RM) • All from the previous slide for a CRM plus: • Issued with a Report of Investigation that details its characterizations and provides information regarding its appropriate uses • Reference (not certified) values that are the best estimates of the true values • Associated uncertainties may reflect only measurement precision and may not include all sources of uncertainty • Reference values may be measured by only one method at NIST

7. Development Production Research Stages of NIST RM Development • Underpinning measurement science and technology • Customer needs and market assessments indicate an RM is required to address barriers to innovation • Select material and source, define reference and information values, select measurement methods, establish testing plan • Develop a prototype whose reference values are traceable • Heterogeneity testing, generate reference and information values, perform statistical analyses • Generate Report of Investigation and release RM Development and production stages typically take 1-3 years

8. RM Report of Investigation • Reference value A value best estimate of the true value provided on the NIST report of investigation, where all known or suspected sources of bias have not been fully investigated by NIST. • Information value A value that will be of interest and use to the RM user, but insufficient information is available to assess the uncertainty associated with the value or a limited number of analyses were performed. Measurement variance may be reported.

9. Material Considerations for RM • Source material • Commercially available “off-the-shelf” material • “Custom-made” by NIST or an external party • Sufficiently large, homogeneous quantity of material to produce specified number of units (“feedstock”) • Stability of RM • Ideally stable for many years; may not be possible for some materials • Periodic assessment of stability

10. Current NIST Nanoparticle SRMs and RMs • Polystyrene spheres • SRM 1963a: nominal 100 nm diameter • SRM 1964: nominal 60 nm diameter • Uses: calibration and validation of particle sizing instruments TEM image of SRM 1963a • Gold nanoparticles • RM 8011, 8012, and 8013 • Nominal 10 nm, 30 nm, and 60 nm diameter citrate-stabilized colloidal gold • In production • Available for sales by December 2007 AFM image of 30 nm gold

11. Gold Nanoparticle RMs • NCI requested that NIST provide gold nanoparticle RMs (January 2006) • NCI-NCL (Nanotechnology Characterization Laboratory) and NIST jointly defined the scope of the first-generation of RMs (June 2006) • Customers & uses • Material type – unconjugated colloidal gold • Nominal particle diameters • Size of RM unit, number of RM units • Reference and information values • NIST development stage started in July 2006; involved eight Divisions in five NIST Laboratories • NIST production stage started in February 2007 • NCI provided the majority of the funding for material and labor costs for the RM development and production TEM image of 60 nm gold

12. Intended Uses of RMs 8011, 8012, 8013 • Evaluate and qualify methodology and instrument performance related to the physical and dimensional characterization of nanoscale particles used in pre-clinical biomedical research • Development and evaluation of in vitro assays designed to assess the biological response (e.g., cytotoxicity, haemolysis) of nanomaterials • Use in interlaboratory comparisons • Widely recognized that the RMs will have value beyond the biomedical research community—early interest from NTP, EPA, NIOSH

13. G Frens, Nature Physical Science20 241 (1973) Cit- Cit- HAuCl4 Cit- H2O, 100OC Cit- RM Material and Packaging • Citrate-reduced gold in aqueous solution (0.01% HAuCl4) • Produced by BBI to NIST specifications in 8 liter batches for 3 nominal sizes: RM8011 – 10 nm RM8012 – 30 nm RM8013 – 60 nm • Gold solutions homogenized, hermetically sealed in 5 mL glass ampoules under argon, gamma-irradiated to insure sterility. • Each RM “package” will contain 2 x 5 mL ampoules • Long term stability (“shelf-life”) will be monitored by DLS/UV-Vis

14. Reference Values Dimensional reference values: mean particle diameter in solution, as an aerosol, and deposited on a substrate AFM: atomic force microscopy; SEM: scanning electron microscopy; TEM: transmission EM DLS: dynamic light scattering; DMA: differential mobility analysis; SAXS: small-angle x-ray scattering 1Traceable to a known wavelength of light via a 68.9 nm silicon step height transfer artifact 2Traceable to a calibrated AFM using a lattice transfer artifact 3Instrument calibrated using negatively stained catalase crystals 4Instrument calibrated using NIST SRM 1964, nominal 60 nm polystyrene spheres

15. Informational Values • Electro-chemical properties: • Au concentration by ICP-OES • Citrate and chloride ion concentrations by ion chromotography • pH by electrochemical methods • Electrolytic conductivity by conductometric methods • Zeta potential by electrophoretic light scattering • Optical absorption by UV-Vis spectroscopy • Chromatographic separation trace by asymmetric-flow field flow fractionation • Sterility assessment ICP-OES: inductively-coupled plasma optical emission spectrometry

16. Report of Investigation - Content

17. Report of Investigation - Content • Introductory/Summary Statement • Reference Value Statement • Reference Value Table (assigned value + uncertainty) • Expiration of Material • Maintenance of RM Value Assignment (stability evaluation) • Contribution Acknowledgements (participants, funding) • Handling and Storage • Instructions for Use & Cautions to User • Material Source and Processing • Heterogeneity Assessment • Value Assignment and Uncertainty Analysis • Information Value Statement • Informational Values/Data (footnoted methods) • Methodology for Reference Value Measurements(instrument, sample preparation procedures, measurement procedures) • References

18. Post RM Production Activities & Goals • Maintenance of RM Value Assignment Assessment of long-term stability/shelf-life DLS, UV-Vis will be used to periodically monitor RM for substantive changes that affect the reference value assignment Substantive changes will be addressed and further testing conducted as necessary. Purchasers can be notified of the change. • Peer Reviewed Publication Science-based analysis of size measurements with the goal of improving fundamental understanding of nanomaterial metrology and property assessment. Cross-OU cooperation. Public dissemination of results Enable more in-depth analysis

19. Post RM Production Activities & Goals Assay Cascade ProtocolsPhysical – In Vitro – In Vivo http://ncl.cancer.gov/working_assay-cascade.asp • Physico-Chemical Characterization • Size, Size Distribution • Topology • Molecular Weight • Aggregation • Purity • Chemical Composition • Surface Characteristics • Functionality • Zeta Potential • Stability • Solubility NIST-generated documents Public dissemination is a critical component

20. Future RM Plans • Next-Generation Gold Nanoparticles • Exploring new chemical routes for production of functionalized nanoparticles in collaboration with NCL. Some issues: • basic science underlying the technology • stability • packaging • Other Nanoparticles • Discussed options with potential partners including NTP (Nigel Walker) and FDA (Subhas Malghan) • Materials under consideration include silver, titanium dioxide

21. NIST Participants on Gold RM Project Analytical Chemistry Division Ceramics Division Measurement Services Division Metallurgy Division Polymers Division Precision Engineering Division Process Measurements Division Statistical Engineering Division