Enhanced molecular structure, thermal stability, and linear/nonlinear optical characteristics of chitosan/titanium dioxide nanocomposite films

Abstract

This study sought to fabricate and characterize novel nanocomposite films of chitosan and titanium dioxide in terms of molecular structure, thermal, and optical properties for usage in food packaging and optoelectronic applications. Fourier transform infrared analysis confirmed that TiO2-NPs interacted with chitosan and demonstrated good compatibility. Differential scanning calorimetry and thermogravimetric analysis revealed that increasing the concentration of TiO2-NPs improved the thermal stability of the nanocomposites. The linear optical properties in the UV-Vis range (200–800 nm) were measured spectrophotometrically. Below 400 nm, the transmittance spectra of the nanocomposites show decreased degrees of transparency, indicating their capacity to entirely block UV-light transmission. Tauc's model was used to identify the types of electronic transitions in the samples. The single-oscillator model was utilized to investigate the dispersion energy and parameters. Nonlinear optical properties were also investigated. UV-Vis analysis revealed that increasing the concentration of TiO2-NPs from 0 to 12 wt% reduced the absorption edge from 2.716 to 2.043 eV, decreased the direct (3.282 to 2.798 eV) and indirect (2.417 to 1.581 eV) energy band gaps, increased the Urbach energy from 0.692 to 1.295 eV, decreased the dispersion energy from 11.324 to 5.621 eV, decreased the single oscillator energy from 6.308 to 5.393 eV, and improved the other linear and nonlinear parameters. The findings support the usage of CS/TiO2 nanocomposite films in the packaging industry and a variety of optical applications.