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Issue 37, 2009
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Simple method for the rapid simultaneous screening of photocatalytic activity over multiple positions of self-cleaning films

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Abstract

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 viaUV-visible absorption spectroscopy and indicative of reaction kinetics. A 3 × 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 × 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 × 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.

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

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Publication details

The article was received on 13 Mar 2009, accepted on 27 May 2009 and first published on 30 Jun 2009


Article type: Paper
DOI: 10.1039/B905222D
Citation: Phys. Chem. Chem. Phys., 2009,11, 8367-8375
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    Simple method for the rapid simultaneous screening of photocatalytic activity over multiple positions of self-cleaning films

    A. Kafizas, D. Adriaens, A. Mills and I. P. Parkin, Phys. Chem. Chem. Phys., 2009, 11, 8367
    DOI: 10.1039/B905222D

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