A simple, inexpensive method for the rapid testing of the photocatalytic activity of self-cleaning surfaces

Abstract

A rapid, semi-quantitative, inexpensive method, using a simple digital scanner and an indicator ink, suitable for use in the laboratory, or in the field, for assessing the photocatalytic activity of commercial photocatalytic self-cleaning materials such as glass, is described. The repeatability of the current method is found to be high and better than many of the previously reported ISO photocatalyst tests.

Kinetics of reduction of a resazurin-based photocatalytic activity ink

“…This water-based Rz ink is used to coat the photocatalytic film under test so that, upon the subsequent ultra-bandgap irradiation of the photocatalytic sample/dried ink film combination, the photogenerated holes on the photocatalytic film react quickly and irreversibly with the glycerol SED (to form glyceraldehyde/glyceric acid), leaving the photogenerated electrons to reduce the blue-coloured Rz dye to pink-coloured resorufin, Rf. The overall process can be summarised as follows [11][12][13][14]:…”

Assessment of activity of ‘transparent and clear’ and ‘opaque and highly coloured’ photocatalytic samples using a fluorescent photocatalytic activity indicator ink, FPaii

“…All irradiations were carried out using 2 x 4 W UVA tubes, with a principal wavelength of 352 nm, and an irradiance of approximately 2 mW cm -2 . Paii films on the samples under test were made using the Rz ink, via a draw-down method [20], using a wire-wound bar, i.e. a K-bar, that is used regularly in the print industry to deposit ink films of known thickness [22].…”

“…However, this apparent 'limitation' to the applicability of paii technology presumes that the assessment of the concentration of the redox dye in the paii, as a function of irradiation time, t, requires the accurate measurement of the colour of the indicator film, via either UV/Vis absorbance measurements (which is only appropriate for clear samples) or diffuse reflectance/RGB analysis (usually appropriate for opaque samples) [10,20]. Note that the latter techniques are only appropriate for use with opaque, but NOT highly coloured samples.…”

Titania‐based photocatalytic coatings on stainless steel hospital fixtures

“…The radiation level was approximately four times summer sunlight. The RZ PC test ink and Kbar ink applicator from Queens University Belfast were used to spread an even coat of ink on the coated surface [27,28]. A camera with timer was used to observe the colour change of the dye from blue to pink then clear due to photocatalytic activity of the dry TiO 2 surface.…”