Photocatalytic activity indicator inks for probing a wide range of surfaces

Andrew Mills*, James Hepburn, David Hazafy, Christopher O'Rourke, Nathan Wells, Josef Krysa, Michal Baudys, Martin Zlamal, Hana Bartkova, Claire E. Hill, Kim R. Winn, Morten E. Simonsen, Erik G. Søgaard, Swagata Banerjee, Rachel Fagan, Suresh C. Pillai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Three photocatalyst inks based on the redox dyes, Resazurin (Rz), Basic Blue 66 (BB66) and Acid Violet 7 (AV7), are used to assess the photocatalytic activities of a variety of different materials, such as commercial paint, tiles and glass and laboratory made samples of sol-gel coated glass and paint, which collectively exhibit a wide range of activities that cannot currently be probed by any one of the existing ISO tests. Unlike the ISO tests, the ink tests are fast (typically <10 min), simple to employ and inexpensive. Previous work indicates that the Rz ink test at least correlates linearly with other photocatalytic tests such as the photomineralisation of stearic acid. The average time to bleach 90% of the key RGB colour component of the ink, red for Rz and BB66 inks and green for AV7 ink, is determined, ttb(90), for eight samples of each of the different materials tested. Five laboratories conducted the tests and the results revealed an average repeatability and reproducibility of: ca. 11% and ca 21%, respectively, which compare well with those reported for the current ISO tests. Additional work on commercial self-cleaning glass using an Rz ink showed that the change in the red component of the RGB image of the ink correlated linearly with that of the change of absorbance at 608 nm, as measured using UV/vis spectroscopy, and the change in the a* component of the Lab colour analysis of the ink, as measured using diffuse reflectance spectroscopy. As a consequence, all three methods generate the same ttb(90). The advantages of the RGB digital image analysis method are discussed briefly.

Original languageEnglish
Pages (from-to)63-71
Number of pages9
JournalJournal of Photochemistry and Photobiology A: Chemistry
Issue number1
Publication statusPublished - Sept 15 2014
Externally publishedYes


  • Acid Violet 7
  • Basic Blue 66
  • Inks
  • Photocatalysis
  • Resazurin
  • Standards

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • General Physics and Astronomy


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