The effect of silver nanoparticles doped in PVA on the structural and optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different sizes and concentrations of silver nanoparticles. Structural properties are studied using X-ray diffraction and FTIR spectrum. Using the reflectance and transmittance of samples, the effect of doped nanoparticles and their concentration on optical parameters of PVA films include absorption coefficient, optical bandgap energy, complex refractive index, complex dielectric function, complex optical conductivity, and relaxation time is extracted and discussed. The dispersion of the refractive index of films in terms of the single oscillator Wemple-DiDomenico (WD) model is investigated and the dispersion parameters are calculated. Results show that by doping silver nanoparticles in PVA, number of Bragg’s planes in the structure of polymer and its crystallinity are increased noticeably. Ag–O bonds are formed in the films and the bandgap energy of samples is decreased. Calculations based on WD model confirm that by doping nanoparticles, the anion strength of PVA as a dielectric medium is decreased.
In this experimental study, the effect of dye concentration on the optical properties of red-BS dyedoped polyvinyl alcohol (PVA) thin films is investigated. Three thin film samples with different concentration of red-BS dye were prepared by spin-coating method on the glass substrate. Using transmission and reflection spectrum of films, their optical parameter such as refractive index, absorption coefficient, and dielectric function are extracted and the effect of dye impurity on theses parameters has been studied. The band gap energy of samples is calculated using Tauc method. Band gap energy of samples is decreased by increasing the concentration of dye impurity in PVA films.
The effect of silver nanoparticles doped in polyvinyl alcohol (PVA) on the nonlinear optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different concentrations of silver nanoparticles. Nonlinear optical properties of doped polymer films are studied experimentally employing Z-scan techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 45 mW power. The effect of nonlinear refractive index of samples is obtained by measuring the profile of propagated beam through the samples and their nonlinear refractive index is found to be negative. The nonlinear absorption coefficient is calculated using open aperture Z-scan data while its nonlinear refractive index is measured using the closed aperture Z-scan data, leads to measuring the third order susceptibility |χ (3) |. Real and imaginary parts of the third-order nonlinear optical susceptibility |χ (3) | are decrease with increasing the concentration of Ag nanoparticles in the films. The values of thermo-optic coefficient are determined at different concentrations of silver nanoparticles for samples.
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