Simple method for the rapid simultaneous screening of photocatalytic activity over multiple positions of self-cleaning films

A. Kafizas, D. Adriaens, A. Mills, I.P. Parkin

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


An intelligent ink, previously shown to be capable of rapidly assessing photocatalytic activity, was simply applied via a felt-pen onto a commercially available piece of Activ self-cleaning glass. The ink, comprising of redox dye resazurin and the sacrificial electron donor glycerol within an aqueous hydroxy ethyl cellulose (HEC) polymer media, was photocatalytically degraded in a two-step process. The key initial stage was the photo-reductive conversion of resazurin to resorufin, whereby a colour change from blue to pink occurred. The latter stage was the subsequent photo-reduction of the resorufin, where a slower change from pink to colourless was seen. Red and green components of red-green-blue colour extracted from flat-bed scanner digital images of resazurin ink coated photocatalytic films at intervals during the photocatalysis reaction were inversely proportional to the changes seen via UV-visible absorption spectroscopy and indicative of reaction kinetics. A 3 x 3 grid of intelligent ink was drawn onto a piece of Activ and a glass blank. The photocatalysis reaction was monitored solely by flat-bed digital scanning. Red-green-blue values of respective positions on the grid were extracted using a custom-built program entitled RGB Extractor. The program was capable of extracting a number of 5 x 5 pixel averages of red-green-blue components simultaneously. Allocation of merely three coordinates allowed for the automatic generation of a grid, with scroll-bars controlling the number of positions to be extracted on the grid formed. No significant change in red and green components for any position on the glass blank was observed; however, the Activ film displayed a homogenous photo-reduction of the dye, reaching maxima in red and minima in green components in 23 +/- 3 and 14 +/- 2 min, respectively. A compositionally graded N-doped titania film synthesised in house via a combinatorial APCVD reaction was also photocatalytically tested by this method where 247 positions on a 13 x 19 grid were simultaneously analysed. The dramatic variation in photocatalysis observed was rapidly quantified for all positions (2-3 hours) allowing for correlations to be made between thicknesses and N : Ti% compositions attained from Swanepoel and WDX analysis, respectively. N incorporation within this system was found to be detrimental to film activity for the photocatalysis reaction of intelligent ink under 365 nm light.
Original languageEnglish
Pages (from-to)8367-8375
Number of pages8
JournalPhysical Chemistry Chemical Physics
Issue number37
Publication statusPublished - 30 Jun 2009


  • binary compound
  • incorporation
  • composition
  • thickness
  • correlation
  • test method
  • combinatorial chemistry
  • synthesis
  • transition element compounds
  • titanium oxide
  • kinetics
  • ultraviolet visible spectrum
  • digital image
  • chemical reduction
  • conversion
  • polymer
  • cellulose
  • glycerol
  • electron donor
  • dyes
  • glass
  • ink
  • film
  • cleaning
  • photocatalysis


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