Structure, optical band gap, Urbach tail, and transparency region in isotactic polypropylene/zirconium dioxide nanocomposites

The present work studies the effect of embedded zirconia nanoparticles in polypropylene on the structure and optical absorption in the vicinity of the optical band gap. X-ray diffraction analysis, X-ray dispersion energy spectroscopy, scanning and transmission electron microscopes, IR and UV spectroscopic methods were used for investigation. It is shown that nanocomposites are comprised of two distinct phases. An increase in the filler concentration leads to a decrease in crystallinity. It has been demonstrated that the optical band gap decreases while the Urbach energy increases with increasing filler concentration. These alterations are concomitant with the establishment of novel energetic levels within the band gap, resulting in its constriction, as well as an augmentation in disorder and interaction between the nanoparticles and the matrix. Additional peaks between are also observed that due to the presence of C-C and C-H bonds in the molecular structure of polypropylene and is caused by σ→σ* type transitions. It has been observed that as the particle concentration and size increase, there is a decrease in the optical transmittance in the relatively transparent region of the composite. This phenomenon is interpreted by the theory of light absorption and scattering in the dispersed medium of nanocomposite.