Influence of Incorporation of Gallium Oxide Nanoparticles on the Structural and Optical Properties of Polyvinyl Alcohol Polymer

In the present work, gallium oxide nanoparticles (nGa2O3) are synthesized via the thermal microwave combustion method, while nanocomposites of polyvinyl alcohol (PVA) polymer with various concentrations of nGa2O3 (0, 1, 2, 3, 4, and 5 wt%) are prepared by the casting technique. The structural characterization of nGa2O3, PVA, and films of PVA-Ga2O3 nanocomposites are studied using X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), and Fourier-transform infrared spectroscopy. The HRTEM and XRD examinations showed that the prepared nGa2O3 has an average crystallite size of ~ 5.6 nm and particle size of ~ 0.9 µm. On another side, the optical transmission spectra were performed in the spectral range 250 to 2500 nm at room temperature. The refractive index, absorption coefficient, and optical bandgap (Eg) were determined using the Wemple-DiDomenico single oscillator model. It was shown that Eg slightly reduced from 3.61 to 3.55 eV with increasing the Ga2O3 content to 3 wt%, while raised again up to 3.58 eV for 5 wt% Ga2O3. Other optical characteristics such as the optical density, extinction coefficient, refractive index, optical susceptibility, thermal emissivity, optical sheet resistance for the PVA-Ga2O3 nanocomposites are investigated. The linear and nonlinear optical parameters together with their dependencies on the doping ratio reveals the qualification of PVA-Ga2O3 nanocomposites for nonlinear optical applications.

Synthesis of PVA/CeO2 Based Nanocomposites with Tuned Refractive Index and Reduced Absorption Edge: Structural and Optical Studies

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO2 on optical properties of PVA. On the insertion of CeO2 nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO2 nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO2 content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ɛ” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.

Temperature Dependence of the Refractive Index of Vitreous Alloys of the Ag-As-S System

The temperature coefficient of refractive index dn/dT is determined for glassy allous of the system along the(Ag2S)x(As2S3)100-x, direction (0 < x <20) in the spectral interval of 1–5 μm at temperature of 77– 400 K theglasses in question are shown to take negative values of dn/dT depending on the composition and wavelength.The dependence of the coefficient on spectrum and temperature is studied using a single oscillator model.

Estimation of optical parameters of silicon single crystals with different orientations

Optical properties of Si single crystals with different orientations (1 0 0) and (1 1 1) were investigated using spectrophotometric measurements in a spectral range of 200 nm to 2500 nm. The data of optical absorption revealed an indirect allowed transition with energy gap of 1.1 ± 0.025 eV. An anomalous dispersion in refractive index. The normal dispersion of the refractive index was discussed according to Wemple-DiDomenico single oscillator model. The oscillator energy Eo, dispersion energy Ed, high frequency dielectric constant ∈∞, lattice dielectric constant ∈L and electronic polarizability αe were estimated. The real ∈1 and imaginary ∈2 parts of dielectric constant were also determined.

Influence of Bath Temperature and Deposition Time on Topographical and Optical Properties of Nanoparticles ZnS Thin Films Synthesized by a Chemical Bath Deposition Method

In this paper, zinc sulfide nanoparticle (ZnS-NP) thin films were deposited onto glass substrates by chemical bath deposition using zinc sulfate as the cation precursor and thiourea as the anionic precursor. Different bath temperatures (65, 70, 75, and 80°C) and different deposition times (20, 30, 40, and 50 min) were selected to study the performance of ZnS thin films. Topographical and optical characterizations of the films were studied using the atomic force microscope (AFM) and UV-Vis spectroscope. The best ZnS thin films were deposited at a bath temperature (70°C) and a deposition time (30 min) with homogeneous distribution, high density, and small average diameter (106 nm). The energy gap (Eg) was found to be in the range of 4.05-3.97 eV for the ZnS films. Optical constants (refractive index, n, extinction coefficient, k, and dielectric constant, ε) of the films were obtained in the wavelength range 300-500 nm by using spectrophotometric measurement. The dispersion of the refractive index is analyzed by using a single oscillator model. The oscillator energy E0 and dispersion energy Ed were determined using the Wemple-DiDomenico single oscillator model. Urbach’s energy increases from 0.907 eV to 2.422 eV with increasing of deposition time. The calculated radius of nanoparticles using Brus equation was 1.9, 2.3, 2.45, and 2.51 nm at deposition times 20, 30, 40, and 50 min, respectively.

STRUCTURAL, OPTICAL, ELECTRICAL AND DIELECTRIC PROPERTIES OF PVA-YCl3 FILMS

Polyvinyl alcohol (PVA) films doped with 10[Formula: see text]wt.% of yttrium chloride (YCl[Formula: see text] have been made by casting from their aqueous solutions. The structure of un-annealed and annealed PVA-YCl3 films was studied using X-ray diffraction (XRD) patterns and Fourier-transform infrared spectroscopy (FTIR). Both FTIR and XRD revealed that the crystalline ratio of the studied samples increased due to the effect of annealing. The effect of annealing on the optical properties has been studied. Dispersion of the refractive index was described using the single oscillator model. The single oscillator energy and the dispersion energy were estimated. The calculated optical band gap of all PVA-YCl3 films was 5.0[Formula: see text]eV. The behavior of ac conductivity showed that the conduction mechanism of PVA-YCl3 films was correlated barrier hopping model. The dielectric constant and dielectric loss index were decreased with the increase of the field frequency. The electric modulus granted a straightforward technique for assessing the dielectric relaxation time. The calculated activation energy obtained from the electric modulus mechanism was 0.172[Formula: see text]eV.

Effect of gamma irradiation on structural, morphological and optical properties of p-quaterphenyl thin films

Para-quaterphenyl thin films were deposited onto glass and quartz substrates by thermal evaporation method. p-quaterphenyl thin films wereexposed to gamma radiation of Cobat-60 radioactive source at room temperature with a dose of 50 kGy to study the effect of ?-irradiation onthe structure and the surface morphology as well as the optical properties of the prepared films. The crystalline structure and the surface morphology of the as-deposited and ?-irradiated films were examined using the X-ray diffraction and the field emission scanning electron microscope. The optical constants (n & k) of the as-deposited and ?-irradiated films were obtained using the transmittance and reflectance measurements, in the wavelength range starting from 250 up to 2500 nm. The analysis of the absorption coefficient data revealed an allowed direct transition with optical band gap of 2.2 eV for the as-deposited films, which decreased to 2.06 eV after exposing film to gamma irradiation. It was observed that the Urbach energy values change inversely with the values of the optical band gap. The dispersion of the refractive index was interpreted using the single oscillator model. The nonlinear absorption coefficient spectra for the as-deposited and ?-irradiated p-quaterphenyl thin films were obtained using the linear refractive index.