## 3 Results
### Antibacterial Activity of CPD/PU and C\({}_{60}\)/PU Polymer Composite Films  
The antibacterial activity of CPD/PU and C\({}_{60}\)/PU composite films was investigated against seven bacteria strains (_K. pneumoniae, P. mirabilis, S. enterica, E. faecalis, S. epidermidis, S. flexneri, P. aeruginosa_) and fungi (A. niger). Table 3 presents the results of the antibacterial activity of these composites with and without blue light irradiation for 1 h. The results in Table 3 show that the most sensitive bacteria on CPDs/PU were _K. pneumoniae, P. mirabilis, S. enterica, E. faecalis, E. epidermidis_ and _P. aeruginosa_ under blue light irradiation for 1 h.  
The results in Table 3 show that all tested bacteria and fungi were sensitive on the C\({}_{60}\)/PU composite films under blue light irradiation for 1 h. Some bacteria strains are sensitive on the C\({}_{60}\)/PU composite films in the absence of blue light irradiation: _K. pneumoniae, P. mirabilis, S. enterica, E. faecalis_ and _P. aeruginosa_. Fungi A. niger_ was sensitive on the C\({}_{60}\)/PU composite films in both conditions: with or without blue light irradiation.  
The results presented in Table 3 indicate that both types of tested polymer composites are potent antibacterial agents. Under blue light irradiation, the C\({}_{60}\)/PU composite films eradicated Shigella flexneri completely, whereas the CPD composite films eradicated 75% of these bacteria strains. _K. pneumoniae_ and _S. epidermidis_ were sensitive on the CPD/PU composite films both with and without blue light irradiation. The C\({}_{60}\)/PU composite films  
Figure 5: (a) PL intensity spectra of h-TA at time intervals of 0–90 min and (b) PL intensity spectra of h-TA at time intervals of 0–10 min under excitation of 330 nm. Both samples were irradiated with blue light at 470 nm, 3 W.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Bacteria Strains**} & **Irradiated** & \multicolumn{2}{c}{**Nonirradiated,**} & \multicolumn{2}{c}{**Irradiated,**} & \multicolumn{2}{c}{**Nonirradiated,**} & \multirow{2}{*}{**R**} \\  & **Incubated** & **Incubated** & & & **Incubated** & & **Incubated** \\  & **N (cell/cm\({}^{2}\))** & **N (cell/cm\({}^{2}\))** & & & **N (cell/cm\({}^{2}\))** & & \\ \hline \multicolumn{7}{c}{**CPDs/PU**} & \multicolumn{7}{c}{**C\({}_{60}\)/PU**} \\ \hline _K. pneumoniae_ & 0 & 0 & 5.45 & 0 & 0 & 5.45 \\ _P. mirabilis_ & 0 & \(20\times 10^{6}\) & 5.52 & 0 & 0 & 5.52 \\ _S. enterica_ & 0 & \(5\times 10^{7}\) & 4.81 & 0 & \(2\times 10^{7}\) & 4.81 \\ _E. faecalis_ & 0 & \(10\times 10^{5}\) & 5.53 & 0 & \(6\times 10^{5}\) & 5.53 \\ _E. epidermidis_ & 0 & 0 & 4.55 & 0 & \(2\times 10^{6}\) & 0.11 \\ _S. flexneri_ & \(64\times 10^{2}\) & \(82\times 10^{4}\) & 2.10 & \(7.6\times 10^{3}\) & \(9.8\times 10^{5}\) & 2.12 \\ _P. aeruginosa_ & 0 & \(70\times 10^{5}\) & 4.95 & 0 & \(1\times 10^{5}\) & 4.95 \\ _A. niger_ & \(8.7\times 10^{2}\) & \(1\times 10^{5}\) & 2.06 & 0 & 0 & 5.47 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Number of viable bacteria colonies after treatment with the CPD/PU and C\({}_{60}\)/PU composite films in the presence and absence of blue light irradiation.  
acted very strongly on _K. pneumoniae, P. mirabilis, S. enterica_ and _P. aeruginosa_, both with and without blue light irradiation.  
The mechanism of their antibacterial activity is the following: both samples generated reactive oxygen species based on the data presented in Figures 4 and 5. The CPD/PU composite films produced singlet oxygen and hydroxyl radicals, whereas C\({}_{60}\)/PU generated only singlet oxygen under blue light irradiation. The produced ROS induced bacterial membrane damage and further oxidative stress [48]. Compared with the results presented in Table 3, we can conclude that C\({}_{60}\)/PU composite films were more toxic on a wide range of tested bacteria.