- Author
- Watson, S. S. | Forster, A. | Tseng, I. H. | Sung, L. P.
- Title
- Assessment of Spectrophotometric Assay Methods on Nanostructured Pigments.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Report
- ACS Symposium Series 1008; Chapter 17
- Book or Conf
- Nanotechnology Applications in Coatings. American Chemical Society (ACS) Symposium Series 1008. Chapter 17, American Chemical Society, Washington, DC, Fernando, R. H.; Sung, L. P., Editors, 349-372 p., 2009
- Keywords
- coatings | nanotechnology | pigments | titanium doxide | building construction | mechanical properties | sealers | plastics | paper | methyl viologen | hydrogen peoxide | alchols | equations | solvents | uncertainty | photoreactivity
- Identifiers
- methyl viologen assay; hydrogen peroxide assay with leuo-crystal violet (LCV); isopropyl alcohol test; Dynamic Light Scattering (DLS) data
- Abstract
- Titanium dioxide (Ti02) is used in building and construction applications as a pigment or filler for polymeric products to improve their appearance and mechanical properties. Ti02 pigments exhibit a wide range of photoreactivity including reactivities that would be detrimental to the service life of polymeric materials. The lack of a simple, inexpensive metrology for measuring photoreactivity has hindered innovation and acceptance of new pigments, especially nanostructured pigments. Spectrophotometric assays, which monitor specific reactions within the photoreactivity mechanism, show promise as a reliable diagnostic method for ranking pigment reactivity and for understanding variations in the photoreactivity mechanisms in Ti02. In this study, spectrophotometric assays were investigated on an array of Ti02 pigments of different crystal phases, particle sizes, and metal oxide encapsulants as a function of assay experimental parameters, such as buffer composition and buffer pH. Assays include the reduction of methyl viologen, in which electron production from the Ti02 particles is measured, and the oxidation of leuco-crystal violet with horseradish peroxidase to measure the production of peroxide, a common reaction product in the photoreactivity mechanism. Light scattering measurements were used to follow Ti02 particle flocculation in the assays upon changing experimental conditions of assay matrix to determine pigment cluster size and to ascertain the contribution that pigment clusters have on pigment photoreactivity.