## 3 Results
### Chemical Composition
The following peaks were identified in the spectrum of neat PU: the peak at 3335 cm\({}^{-1}\) was due to O-H stretching vibrations, the peaks at 2962 and 2866 cm\({}^{-1}\) stemmed from stretching vibrations of the CH\({}_{3}\) groups; the peaks at 1738 and 1701 cm\({}^{-1}\) were assigned to C=O bonds; the peak at 1594 cm\({}^{-1}\) was due to C=C bonds; the peak at 1525 cm\({}^{-1}\) originated from N-O stretching vibrations; the peaks at 1414 and 1313 cm\({}^{-1}\) corresponded to O-H bending vibrations; the peaks at 1228, 1169 and 1073 cm\({}^{-1}\) were assigned to C-O stretching vibrations; the peaks at 818 and 770 cm\({}^{-1}\) stemmed from C-H bending vibrations. In the case of CPD/PU composite films (red curve), we identified the following peaks: the peak at 3206 cm\({}^{-1}\) was due to O-H stretching vibrations; the peaks at 2956, 2919 and 2850 cm\({}^{-1}\) stemmed from C-H stretching vibrations; the peaks at 1734 and 1695 cm\({}^{-1}\) were assigned to C=O bonds, whereas the peak at 1598 cm\({}^{-1}\) was due to C=C bonds; the peak at 1636 cm\({}^{-1}\) originated from C=N stretching vibrations and was down-shifted by 30 cm\({}^{-1}\) compared with the same peak of CPDs nanoparticles; the peak at 1524 cm\({}^{-1}\) originated from N-O stretching vibrations; the peaks at 1412 and 1313 cm\({}^{-1}\) were due to \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Characteristic Bond** & **Binding Energy (eV)** & **Relative** & **Characteristic Bond** & **Binding Energy (eV)** & **Relative** \\  & & **Concentration (\%)** & & & **C\({}_{60}\)** & **Concentration (\%)** \\ \hline C 1 s peak C-C/C-H & 284.5 & 80 & C 1 s peak C-C/C-H & 284.5 & 79 \\ C 1 s peak C=O & 286.5 & 20 & C 1 s peak C-O/C-OH & 285.9 & 20 \\ O 1 s peak C=O & 531.4 & 100 & C 1 s peak C-O/C-OH & 288.7 & 1 \\ N 1 s peak pyridine & 398.7 & 45 & O 1 s peak O-H & 532.2 & 87 \\ N 1 s peak pyrrolic & 399.9 & 49 & O 1 s peak C-O/H\({}_{2}\)O & 533.3 & 13 \\ N 1 s peak C=N-C & 396.4 & 6 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristic bonds detected in the CPD and C\({}_{60}\) samples and relative concentration of these bonds %. O-H bending vibrations; the peak at 1369 cm\({}^{-1}\) stemmed from N-O symmetric stretching vibrations, and there was an up-shift by 2 cm\({}^{-1}\) compared with the same peak of CPD nanoparticles; the peaks at 1225, 1108 and 1073 cm\({}^{-1}\) were assigned to C-O; the peaks at 818 and 770 cm\({}^{-1}\) could be detected as C-H bending vibrations. The peak at 1290 cm\({}^{-1}\) identified in the FTIR spectrum of CPD nanoparticles could not be detected in the polymer composite film sample. The FTIR spectrum of C\({}_{60}\)/PU composite films (green curve) showed the following peaks: the peak at 3302 cm\({}^{-1}\) was due to O-H stretching vibrations; the peaks at 2919 and 2850 cm\({}^{-1}\) stemmed from C-H stretching vibrations, whereas the peaks at 1732 and 1698 cm\({}^{-1}\) were due to C=O bonds; the peak at 1634 cm\({}^{-1}\) originated from C=C vibrations and was up-shifted by 10 cm\({}^{-1}\) compared with the same peak of C\({}_{60}\); the peak at 1525 cm\({}^{-1}\) originated from N-O stretching vibrations; the peaks at 1412, 1371 and 1312 cm\({}^{-1}\) originated from O-H bending vibrations; the peaks at 1222, 1105 and 1068 cm\({}^{-1}\) were due to C-O bonds, whereas the peaks at 813 and 770 cm\({}^{-1}\) stemmed from C-H bending vibrations. Table S1 lists the position of the characteristic bonds and shifts (\(\Delta\)) identified in all samples in cm\({}^{-1}\). From this table, we can observe the position shifts of the characteristic peaks in both composite film samples. The obtained results indicate the encapsulation of certain fillers into the polymer matrix.