Spectroscopic characterization of optical and thermal properties of (PMMA-PVA) hybrid thin films doped with SiO2 nanoparticles

Doped polymeric hybrid thin films based on Poly-Methyl-Meth-Acrylate (PMMA) and Poly-vinyl-alcohol (PVA) doped with silica nanoparticles (SiO2 NPs) are synthesized using the dip-coating technique. The as-prepared (PMMA-PVA)/SiO2 nanocomposite (wt% of SiO2 NPs = 2%, 4%, 8%, and 16%) are deposited on glass substrates. Transmittance (T%) and reflectance (R%) are measured using a UV-Vis spectrometer. Furthermore, other related optical parameters such as absorption coefficient (alpha), optical constants (n and k), and optical dielectric functions (epsilon(1) and epsilon(2)) are calculated using experimental transmittance, reflectance spectra and well-established classical models such as Tauc, Urbach and Spitzer-Fan and Drude models. The Tauc model is used to estimate the optical bandgap energy. Incorporation of specific concentrations of SiO2 NPs into PMMA-PVA polymeric matrix leads to a noticeable decrease of the optical bandgap. The optical bandgap of un-doped PMMA-PVA thin-film is estimated to be 4.069 eV. Consequently, bandgap engineering and manipulation of optical properties are possible. Additionally, refractive indices (n) of undoped PMMA-PVA polymeric thin films are calculated to be in the range (1.48-1.72). To elucidate and identify vibrational modes of thin films, Fourier-transform infrared spectroscopy (FTIR) is employed in the spectral range (500 cm(-1)-4000 cm(-1)). The results obtained are useful for a better understanding of the lattice dynamics. Moreover, thermal stability of thin films is investigated using thermogravimetric (TGA) technique. Remarkably, TGA thermograms reveal that doped thin films are thermally stable below 110C. Consequently, investigated thin films may have the potential to be key candidates for realtime optical and optoelectronic devices.