Optical and structural properties enhancement of hybrid nanocomposites thin films based on polyaniline doped with Zinc Oxide embedded in bimodal mesoporous silica (ZnO@SiOx) nanoparticles

Hybrid thin films of doped polyaniline (PANI) with Zinc Oxide (ZnO) nanoparticles (NPs) embedded in bimodal mesoporous silica-forming (ZnO@SiOx) NPs were prepared. The preparation was done by spin coating techniques of the solution of a protonated PANI with TFA acid with sequential weight ratios of ZnO@SiOx NPs in the range from 15% to 60%. The prepared thin film morphologies were investigated using Scanning Electron Microscopy (SEM). The aggregation or the clustering of ZnO@SiOx) NPs in the polymer network matrix is very limited due to the silicone oxide (SiOx) which is known to limit the growth of aggregation clusters. The optical properties of hybrid thin films were studied through reflectance and transmission spectroscopy in the UV-Vis range. The optical constants such as the refractive index (n), extinction coefficient (k), real (epsilon') and imaginary (epsilon '') parts of dielectric permittivity and the absorption coefficient were deduced via analysis of the transmittance spectra using 'CODE' software. Increase of the ZnO@SiOx NPs content gives rise to a decrease of the values of these constants: The refractive index n showed a significant decrease for the highest ratio. The static dielectric permittivity constant, the gap energy E(g )and the Urbach energy were determined by using common optical models. E-g decreases with increasing ZnO@SiOx NPs content. For the nanocomposites corresponding to an amount of 45%, the value of E-g reached 2.4eV. The bonding of the ZnO@SiOx NPs to the protonated PANI by TFA doping was investigated thoroughly by FTIR spectroscopy. Based on its optical and electrical properties the novel PANI/ZnO@SiOx hybrid nanocomposite is a promising candidate for optoelectronic and photovoltaic applications.