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

Kafizas, A; Adriaens, D; Mills, A; Parkin, IP; (2009) Simple method for the rapid simultaneous screening of photocatalytic activity over multiple positions of self-cleaning films. PHYS CHEM CHEM PHYS , 11 (37) 8367 - 8375. 10.1039/b905222d.

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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 (TM) 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 (TM) 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 (c). 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 (TM) 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.

Type:Article
Title:Simple method for the rapid simultaneous screening of photocatalytic activity over multiple positions of self-cleaning films
DOI:10.1039/b905222d
Keywords:CHEMICAL-VAPOR-DEPOSITION, TITANIA THIN-FILMS, STEARIC-ACID, SEMICONDUCTOR PHOTOCATALYSIS, PILKINGTON ACTIV(TM), VISIBLE-LIGHT, TIO2 FILMS, GLASS, DEGRADATION, COATINGS
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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