Kinetics of reduction of a resazurin-based photocatalytic activity ink

Correlation between the photocatalysed oxidation of methylene blue in solution and the reduction of resazurin in a photocatalyst activity indicator ink (Rz Paii )

“…The UV/Vis spectrophotometry results generated using this system, for a typical (non-heat-treated) piece of commercial self-cleaning Glass (Activ TM ) are illustrated in figure 3(b), along with an insert plot of the decay in the absorbance, at 608 nm, due to the photocatalysed reduction of Rz, which yielded a value for the initial rate, ri(Rz), for reaction (2). An analysis of the decays in the insert diagrams in figures 2(b) and 3(b), reveals that the photocatalysed oxidation of the MB is first order, whereas that of Rz reduction in the Rz paii is zero order, as has been noted previously [6,10,12,18].…”

Probing the activities of UV and visible-light absorbing photocatalyst powders using a resazurin-based photocatalyst activity indicator ink (Rz Paii )

“…The preparation of the Rz ink used in this work has been described elsewhere [32] and comprised: 20 g of 1.5% HEC, 2 g glycerol and 20 mg Rz. For all Rz-ink-on-SC-disc irradiations, a few drops of the Rz ink were pipetted onto the pressed semiconductor disc and spun at 2000 rpm for 30 s. The semiconductor disc, with Rz ink film coating, was then placed 3 cm away from the LED and irradiated.…”

“…In almost all previous work carried out on semiconductor films, such as self-cleaning glass and paint, using photocatalyst indicator inks, the Rz ink coating on the semiconductor film under test was irradiated in air [32]. This is in sharp contrast with all the work carried out in aqueous solution described above which was carried out under O2-free conditions.…”

“…1 mW cm -2 . However, it is known [32] that the O2 present in air is able to compete with the Rz for reduction by the photogenerated electrons, i.e. SC O2 + TiO2(e -) → O2 -+ TiO2 (5) hν ≥ Ebg and so effect a decrease in the rate of reaction (3), typically by ca.…”

Spectrophotometric and Digital Colour Colourimetric (DCC) analysis of colour-based indicators

“…The change in absorbance spectrum of the ink film recorded every 2 mins is illustrated here.The parameter t(50) in air can be determined for the UV-activated TiO 2 /thionine/glycerol ink film by plotting the change in absorbance due to the Th in the ink at its  max = 609 nm, i.e. A 609 , as a function of 'dark' time, as illustrated infigure 11, where A t=0 is the overall change in A 609 as the indicator turns from colourless to blue due to reaction(19), and t(50) is the time taken for A = 0.5A t=0 . Using the same data manipulation process as described in the previous section, the photographic images in figure 10 of the TiO 2 /thionine/glycerol ink film were used to generated the plot of AsR) vs 'dark' time, also illustrated inFigure 11.As before, a quick comparison of the two plots in figure 11, namely absorbance, Abs 609 (at  max for Th, i.e.…”