Fig. 2: Epifluorescence microscopy to visualize the decomposition of organic contaminants on reactive coatings.
From: Photocatalytically reactive surfaces for simultaneous water harvesting and treatment
a, Schematic of the microscope setup. b–e, Epifluorescence image sequences of contaminated water drops (V = 5 µl) containing fluorescein (initial concentration, C0 = 25 ppm) on the different coatings on glass substrates: TiO2-PVB-PDMS surface before (b) and after (c) UV irradiation; TiO2-EC-PDMS surface before (d) and after (e) UV irradiation. The TiO2-PVB-PDMS and TiO2-EC-PDMS coatings are hydrophilic and hydrophobic, respectively, after UV activation (Table 1). In the upper left of each image in the time sequence is shown the measured Ī/Ī0 value, that is, the mean intensity value (Ī) measured in the central area of the droplet–substrate interface normalized by the initial value (Ī0). Scale bars: primary image, 200 µm; inset sequence images, 25 µm. f, Plot of Ī/Ī0 versus time (t) for the experiments in b (black square symbols) and c (blue circle symbols). We define the decay time (t*) as the moment when Ī/Ī0 = 0.001, which we assume corresponds to ~99.9% reduction of the fluorescein concentration. g, Plot of Ī/Ī0 versus t for the experiments in d (black square symbols) and e (red triangle symbols). h, Plot of t* versus V for water droplets containing fluorescein on the reactive TiO2-PVB-PDMS (blue circle symbols) and TiO2-EC-PDMS (red triangle symbols) coatings (see also Supplementary Fig. 3). The lines of best fit for estimating t* follow power law trends (as indicated by the dashed lines) of ∝ V1/3 (pre-factor = 12 min m−1) for the TiO2-PVB-PDMS reactive coating and ∝ V2/3 (pre-factor = 77 min m−2) for the TiO2-EC-PDMS reactive coating. In f–h, each data point is the average of n = 15 measurements (that is, five readings each for three separately prepared coating types) and the data are presented as the mean value ± standard deviation.
