# Cotton Terry Textiles with Photo- and Bio-Activity in a Model Study and Real Conditions
## 3 Results
The results on the self-cleaning properties of modified materials assessed on diagonal cotton wave fabric using blackcurrant juice are shown in Table 3. The color variation of stained samples was assessed using K/S values, CIE L*a*b* coordinates and the color difference \(\Delta\)E* before and after 6 h of UV/VIS irradiation. The L* value refers to sample lightness from 0 (black) to 100 (white), whereas a* and b* values characterize color variation: from green (-a*) to red (+a*) and blue (-b*) to yellow (+b*) respectively. Color difference \(\Delta\)E* is a numerical comparison between the reference color and that of the tested samples. According to the well-known Kubelka-Munk theory, K/S value is linearly related to colorant concentration in the fabric. Almost 60% reduction in K/S value after 6 h UV/VIS irradiation was observed for modified fabrics in comparison to 26% reduction for untreated fabric. Increase in L* values for control and modified blackcurrant juice stained fabrics indicated that both samples became lighter after UV/VIS irradiation. The L* value ranged from 73.38 and 73.57 to 75.44 and 80.70 for untreated and modified samples respectively. The modified sample, however, was lighter after irradiation than the untreated sample. \(\Delta\)E* indicated significant color differences after irradiation (the higher the \(\Delta\)E* value, the greater the color difference). UV/VIS irradiation significantly affected shade changes in the modified sample in comparison to the control, which was characterized by small shade changes. The b* movement from -1.86 to 6.26 and the a* movement from 9.56 to 2.52 represent a shift from red towards yellow after irradiation due to photodegradation of the color compound. This confirmed that the self-cleaning action of the fabric surface modified with ZnO/TiO\({}_{2}\) NPs has photocatalytic properties. Study in model conditions showed that microorganisms survived on textiles in both control and modified materials (Figure 6). Survival indexes on control textiles ranged from N = 33.3% (_A. niger_) to N = 1800% (_B. subtilis_), which indicates that the number of microorganisms increased after 24 h incubation on textile materials. On photocatalytically modified textile materials, the survival index was N = 22.3-123.9% and the number of microorganisms decreased by one logarithmic scale after 24 h of incubation. Biostatic activity of photocatalytically modified textiles against the tested microorganisms in model conditions was on the low and medium level A = 0.4-1.62. The lowest activity of modified materials was determined for mold _A. niger_ and the highest for bacteria _B. subtilis_. Comparing two samples of the modified textile materials with _E. coli_ under different lighting conditions (without light and under natural light), it was found that the biostatic activity of the material against this bacterium increased from A = 0.9 in conditions without light to A = 1 in natural light conditions after 24 h of incubation. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Textiles**} & \multirow{2}{*}{\
\begin{tabular}{c} **Surface** \\ **Mass (g/m2)** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Time of** \\ **Absorption (s)** \\ \end{tabular} } & \multicolumn{4}{c}{**Volor Fastness**} & \\ \cline{3-8}  & & & \multicolumn{2}{c}{**Washing in 60 \({}^{\circ}\)C**} & \multicolumn{2}{c}{**Rubbing**} \\ \cline{3-8}  & & & \multicolumn{2}{c}{**Color Change**} & **Staining** & **Dry** & **Wet** \\ \hline control & 518 & 5.21 & 5 & 5 & 5 & 5 & 5 \\ modified & 540 & 5.08 & 5 & 5 & 5 & 5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selected properties and color fastness of Terry cotton fabrics.