## 3 Results and Discussions
### DNA Identification on Recycled PET Composites
For example, the peak situated at 499 cm\({}^{-1}\) for the M6 4 sample was shifted at 490 cm\({}^{-1}\) in the DNA-contaminated sample, while the peak at 418 cm\({}^{-1}\) for bare M7_4 could be found at 426 cm\({}^{-1}\) after DNA attachment, and at 418 cm\({}^{-1}\) to 425 cm\({}^{-1}\) in the case of M11_4_DNA. The additional representative absorption signals for the PP chemical groups and their vibrational modes existing in the M6_4 and M7_4 samples from the ATR-FTIR spectra (Figure 6) are detailed as follows: 2916 cm\({}^{-1}\) for the asymmetric stretching of \(-\)CH\({}_{2}\), 2837 cm\({}^{-1}\) for the symmetric stretching of the methyl group (\(-\)CH\({}_{3}\)), and sharper peaks at 1453 cm\({}^{-1}\) and 1375 cm\({}^{-1}\) attributed to \(-\)CH\({}_{2}-\) and \(-\)CH\({}_{3}\) bending, respectively. These results are in good agreement with those obtained by [PERSON], et al. [38], who used FTIR spectra to study the differences between pure PP, pure PET, and a PET-PP blend. Figure 4: ATR–IR spectra for isolated DNA from experimental animals. Figure 5: ATR–IR spectra of the bare PET sample (M1_4), Al nanopowder PET sample (M2_4), and DNA—contaminated samples (M1_4_DNA and M2_4_DNA). Figure 6: _Cont_. The increased flexibility and light weight of M11_4 and M12_4 was obtained with the incorporation of HDPE into the PET composite substrate; therefore, the absorption \"fingerprint\" [39] that characterizes HDPE can be visualized as shown in Figure 7. The ATR-FTIR spectra of the PET/HDPE and PET/HDPE/Al nanopowder composites (samples M11_4 and M12_4, respectively) also display the optical responses of the HDPE surface  
Figure 6: ATR–IR spectra of the bare PET and PP blended sample (M6_4), Al nanopowder PET and PP blended sample (M7_4), and DNA\(-\)contaminated samples (M6_4_DNA and M7_4_DNA). Figure 7: ATR-IR spectra of the bare PET and HDPE blended sample (M11_4), Al nanopowder PET and HDPE blended sample (M12_4), and DNA\(-\)contaminated samples (M11_4_DNA and M12_4_DNA). functional groups next to the PET absorption bands. The absorption bands located at 2916/2914 cm\({}^{-1}\) and 2852/2847 cm\({}^{-1}\) correspond to the CH\({}_{2}\)- stretching vibration, while the sharper peak around 724/722 cm\({}^{-1}\) can be attributed to the CH\({}_{2}\) rocking mode of the CH\({}_{2}\) groups. Some of the HDPE signals are overlapped with the PET peaks, with significant intensities. The modifications of the IR spectra of substrate composites after 2 h of DNA treatment are also shown in Figures 5-7. The spectra show significant increases in the intensity of characteristic peaks of DNA due to the contamination process, as follows:  
* The appearance of the specific stretching vibrations for the OH and NH bonds of the amino acid at 3337 cm\({}^{-1}\) in the M1_4_DNA sample, at 3335 cm\({}^{-1}\) for M2_4_DNA, 3381 cm\({}^{-1}\) for M6_4_DNA, 3346 cm\({}^{-1}\) for M7_4_DNA, 3348 cm\({}^{-1}\) for M11_4_DNA, and 3368 cm\({}^{-1}\) for M12_4_DNA;
* The overlapping of the 1634 cm\({}^{-1}\) group assigned to the baFe vibrations with the deformation of the ester carbonyl bond of the PET compound for all samples: from 1713 to 1711 cm\({}^{-1}\) in M1_4_DNA, 1712 to 1711 cm\({}^{-1}\) in M2_4_DNA, 1714 to 1715 cm\({}^{-1}\) in M7_4_DNA, and 1714 to 1712 cm\({}^{-1}\) in the M11_4_DNA and M12_4_DNA samples;
* The presence of a new peak at 1634/1639 cm\({}^{-1}\) allocated to the same base region as observed in the case of the M1_4_DNA, M2_4_DNA, M7_4_DNA, M11_4_DNA, and M12_4_DNA samples, with a more intense signal, and weak in the case of the M6_4_DNA sample;
* The C-O deoxyribose stretching observed at 1035 cm\({}^{-1}\) in the spectrum of M7_4_DNA (absent in the bare M7_4 sample), at 1042 cm\({}^{-1}\) in M11_4_DNA, at 1042 cm\({}^{-1}\) in M11_4_DNA, and at 1040 cm\({}^{-1}\) in the M12_4_DNA substrate, which is more intense and sharp when compared with the peaks in the same position for DNA-free samples.