**8. Conclusions**

This chapter presents an appealing alternative of a novel antibacterial material. The use of chitosan was due to its versatility, its abundance in nature, and excellent biocompatibility and nontoxicity. Through a straightforward technique, TiO2 nanoparticles dispersed onto a chitosan matrix permitted formulating a renewable and biodegradable composite film capable of excellent antibacterial properties when exposed to UV light.

The synthesis process used did not affect the crystal structure of the dioxide, which remains anatase polymorph. X-ray diffraction characterization confirmed such anatase structure.

Chitosan demonstrated to be a very good selection as a matrix able to hold in place the TiO2 nanoparticles. Incorporation of TiO2 nanoparticles onto the chitosan film via solution casting method produced the chitosan/TiO2 biocomposite films. The immobilized TiO2 exhibited good distribution in the chitosan film, as demonstrated via secondary electron microscopy. From those observations, one can infer that chitosan provides an excellent substrate to immobilize TiO2 nanoparticles. Electron microscopy also demonstrated that the nanostructured TiO2 particles dispersed homogeneously within the polymer matrix without obvious aggregation even at the highest TiO2 content, i.e., 1.5% wt.

Under UV light, TiO2 proved effective against *E. coli* and *S. aureus*. This is due to the generation of ROS from the UV excitement of the TiO2. The growth curve analysis demonstrated that the growth rate of bacteria was affected, as evidenced by the Kirby-Bauer technique. In the present experimental conditions, the best effect came from biocomposites containing 1.5% wt TiO2.

The irradiation with UV light affected the chitosan covalent bonds, as revealed by the Fourier-transform infrared spectroscopy. From the spectra of chitosan with TiO2, one could infer that more oxygen molecules were present. The degradation of the bond at 3000 cm<sup>−</sup><sup>1</sup> (C▬H) demonstrated that extensive UV light irradiation is detrimental to the biopolymer, compromising its integrity in actual applications.

The research presented for the synthesis of the films is an effective way to immobilize TiO2 while retaining the structure of the stronger photocatalytic polymorph.
