Site resolved optical detection of photocatalysis on building materials

Ehm, Clemens; Stephan, Dietmar

doi:10.1016/j.jphotochem.2018.01.020

Cited by 5 publications

(3 citation statements)

References 15 publications

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“…These studies showed that the equipment designed and built by Ehm and Stephan [22] may be used for measuring the photocatalytic activity of photoactive gypsum materials and it is possible to cut the measurement time to 5 min. Measuring the photocatalytic activity of the same type of samples during NOx decomposition requires at least one hour of measurements, and dye decomposition measured by using colorimetry or UV-Vis/DR spectroscopy need several hours of irradiation.…”

Section: Discussionmentioning

confidence: 99%

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Fast Method for Testing the Photocatalytic Performance of Modified Gypsum

et al. 2019

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The measurement of the photocatalytic activity of building materials is quite time-consuming. Up until now, researchers have mainly used the equipment described in ISO 22197-1 to ISO 22197-4 for the determination of air purification activity, although other apparatus such as colorimeters, UV-Vis/DR spectroscopes and equipment for contact angle measurements have also been used. Usually, photocatalytic activity measurements take from one hour up to several hours. In this study, we present a very fast method for the measurement of the photocatalytic activity of gypsum. A specially designed printer with a modified bubblejet cartridge was used to apply a special ink on the surface of gypsum plates. Then the surface was irradiated by UV-A light and every 3 s a picture of the surface was taken. The results showed that the discoloration of the dye occurs after a few seconds of irradiation and the time depends on the amount of photocatalyst used as well as the number of printed ink layers. It was concluded that it is possible to use this method for a quick comparison of the photocatalytic activity of different types of modified gypsum materials.

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Section: Discussionmentioning

confidence: 99%

“…The theoretical ink layer height was 1.6 µm. A 2D CNC movement system with an x and y-stepping resolution of 50 mm, described fully by Ehm and Stephan [22], was used for printing. The printhead we used, a HP C6602A is capable of a printing resolution of 96 dpi that equals 250 mm between the printing nozzles.…”

Section: Dye Decompositionmentioning

confidence: 99%

Fast Method for Testing the Photocatalytic Performance of Modified Gypsum

et al. 2019

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“…Photocatalyst activity indicator inks, in particular the Rz paii , have proved popular for assessing the photocatalytic activity of new materials. Table provides some examples of the reported uses of the Rz ink. − One of the more innovative uses of the Rz ink comes from the group of Parkin at University College London, in their studies of photocatalyst films generated by CVD . These workers used combinatorial atmospheric chemical vapor deposition to generate a graduating substitutional/interstitial N-doped anatase TiO 2 thin film on a 50 mm × 225 mm × 3.2 mm standard float glass plate.…”

Section: Applications Of Paiismentioning

confidence: 99%

Photocatalyst Activity Indicator Inks, paiis, for Assessing Self-Cleaning Films

2021

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Conspectus Semiconductor photocatalysis, usually referred to simply as “photocatalysis” is a relatively new and yet still a growing subject area, which has led to a billion-dollar industry, mostly focused on the production of self-cleaning architectural materials, such as glass, paint, tiles, fabric, plastic and concrete. All such materials need to be tested for activity, but for self-cleaning activity there are few appropriate tests; the International Standards Organization, ISO, for example, have at present only two, both of which are slow and largely ineffective for most commercial self-cleaning products. The photocatalyst community in general, and the manufacturers of self-cleaning photocatalytic products in particular, need a fast, simple, easy to use method of assessing photocatalytic activity, which can also be used to demonstrate the efficacy of self-cleaning materials in minutes, i.e., a quantitative and qualitative test. In this account we highlight our work on photocatalyst activity indicator inks, i.e., paiis, which address the above need and work via the photocatalyzed reduction of a dye, usually resazurin, Rz, and concomitant oxidation of an organic, almost always glycerol. We describe our early work on the Rz ink which showed that, when used to assess photocatalytic film activity, the measured rate of change in color is directly proportional to the measured rate of photocatalyzed mineralization of the popular test pollutants stearic acid, SA, and methylene blue, MB, by O2. We show that photography, coupled with digital color analysis, is just as effective and much less expensive at measuring the rate of color change exhibited by paiis as UV/vis spectrophotometry and also can be used for testing clear and opaque photocatalytic samples in the laboratory and in situ. We demonstrate how the Rz ink can be used to assess the activities of both UV and Visible light absorbing photocatalytic powders and thin films, and highly colored samples. The kinetics of the photocatalyzed color change are outlined, which are zero-order with respect to the initial dye concentration and ink film thickness. We describe the basic features of the recently published Rz-ink based ISO for the qualitative and quantitative assessment of activity of nonporous, flat photocatalytic films. Although the Rz ink is best suited for assessing films of moderate photocatalytic activity, such as found in most examples of commercial self-cleaning glass, other paiis are described which can be used to assess commercial products that have much higher or lower, activities, such as photocatalytic paints and tiles, respectively. Examples of how paiis have been used in research over recent years are given, a highlight of which is their use in the search for a suitable, visible light absorbing photocatalyst alternative to TiO2, that can compete with the latter in terms of cost, durability, stability, and activity. Finally, the novel, photocatalyst-based inks that have been developed as a consequence of the works on paiis are discussed briefly, inclu...

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