Novel pH-Based Photocatalyst Activity Indicator Hydrogel Film (Hpaii)

A. Mills, D. Hawthorne

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
315 Downloads (Pure)


A novel, hydrogel-supported photocatalyst activity indicator, Hpaii, is presented, based on an agar gel containing the pH indicator dye propyl red (PR), and the photoacid generator, diphenyliodonium nitrate (DPIN). The latter is broken down when the film is on an active photocatalytic film, and the acid released protonates the PR, turning the gel from a yellow colour to a red. Initially tested on a TiO2 sol-gel film, the Hpaii is also shown to be effective in indicating the activity of several different commercially available photocatalytic surfaces, including: glass, tiles and paint. This is the first example of a water-based photocatalyst activity indicator ink based on monitoring a photocatalytic process via the change in pH induced in the indicator films, as revealed by the pH-indicator, propyl red.
Original languageEnglish
Pages (from-to)390-395
JournalJournal of Photochemistry and Photobiology A: Chemistry
Early online date19 Jun 2017
Publication statusPublished - 01 Sep 2017


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