Optical properties of pure and doped poly(vinyl chloride) (PVC) films, prepared by using casting technique, with different nanosize zinc oxide (ZnO) concentrations (1–20) wt% have been studied. Parameters such as extinction coefficient, refractive index, real and imaginary parts, Urbach energy, optical conductivity, infinitely high frequency dielectric constant, and average refractive index were studied by using the absorbance and transmittance measurement from computerized UV-visible spectrophotometer (Shimadzu UV-1601 PC) in the spectral range 200–800 nm. This study reveals that the optical properties of PVC are affected by the doping of ZnO where the absorption increases and transmission decreases as ZnO concentration increases. The extinction coefficient, refractive index, real and imaginary parts, infinitely high frequency dielectric constant, and average refractive index values were found to increase with increasing impurity percentage. The Urbach energy values are found to be decreasing with increasing ZnO concentration. The optical conductivity increased with photon energy after being doped and with the increase of ZnO concentration.
A nanoparticle is the most fundamental component in the fabrication of a nanostructure; metallic nanoparticles have different physical and chemical properties from bulk metals (lower melting points, higher specific surface area, specific optical properties, mechanical strength, and specific magnetization) properties that might prove to be attractive in various industrial applications. The optical property is one of the fundamental attraction and characteristic of nanoparticle [
Science the introduction of metal nanoparticles in transparent polymer matrix, polymeric nanocomposites have attracted the attention of researches as advanced technological materials because of their unique optical, electronic, mechanical, and structural characteristics. These characteristics are obtained from the unique combination of the inherent characteristics of polymers and metal nanoparticles. The characteristics of these nanocomposite films can be manipulated by varying the polymer matrix, nanoparticles, and their composition. Polymer nanocomposites have been fabricated with different polymers and nanoparticles. The incorporation of the nanoparticles into polar polymers can induce significant changes in the ultimate properties of polymers and improve their properties [
Polymer material is widely being used in various devices as insulating material and for optoelectronic applications. This is due to their unique properties such as light weight, high flexibility, and ability to be fabricated at low temperature and low cost [
Recently, electrical conductivity of polyaniline doped PVC-PMMA polymer blends, Deshmukh et al. [
Analysis of the absorption spectra in the lower energy part gives information about atomic vibrations, while the higher energy part of the spectrum gives knowledge about the electronic states in the atom. There are many researches on the optical properties of polyvinyl alcohol doped PVC-PVA thin films [
Poly(vinyl chloride) (PVC) is powder supplied by BDH, doped with nano ZnO at room temperature by using casting technique in this work. The PVC was dissolved in THF and heated gently in water bath to prevent thermal decomposition of polymer. The polymer was stirred using a magnetic stirrer until completely dissolved. Nano ZnO material with different weights (1, 5, 10, 15, and 20) wt% was added to the polymer solution and heated for a while until completely dissolved. The solution was poured into a clean glass plate and left to dry for 24 hr to remove any residual solvent. The thickness of the produced films was 20
The UV-VIS absorbance spectra in the region 200–800 nm for doped and undoped films are shown in Figure
Absorption spectra of all PVC samples.
The optical transmission spectra of the PVC thin films with different concentrations of nano ZnO are shown in Figure
Transmission spectra of all PVC samples.
This figure shows that the transmittance intensity increases with the increasing of the wavelength, and as the concentration of doped material nano ZnO increases, the transmittance decreases. The reason for this behavior is that the increases of concentration of ZnO lead to increases the localized state density which reduces the transmittance values. The transmission spectrum increases and it is approximately constant at 71%, 57%, 55%, 42%, and 37% for the concentrations 1, 5, 10, 15, and 20%, respectively. It is noticed that the composite films after doped have new peaks where appear in the short wavelengths, So higher transmission values in the higher wavelengths of the spectrum.
The dependence of the extinction coefficient
Variation of the extinction coefficient as a function of wavelength.
Formation of new peaks for all samples after the doping and broadening of those peaks with increasing ZnO is an indication of change in the molecular structure (degradation, polymer fragments, or free radicals) of PVC and/or PVC/ZnO film samples by doping [
The refractive index
Variation of the refractive index as a function of wavelength.
The real
The dependence of the real part on the wavelength is shown in Figure
Variation of the real part of dielectric constant as a function of wavelength.
The imaginary part of dielectric constant as a function of wavelength is shown in Figure
Variation of the imaginary part of dielectric constant as a function of wavelength.
Pure PVC sample values is very few change up to 300 nm to 800 nm. After adding nano ZnO impurity for samples 1, 5, 10, 15, and 20%, the imaginary part increases for all wavelengths up to 200 nm to 800 nm and with increasing impurity percentage. New peaks appear which indicate that the samples have the no same structure. Hence, the change in the doped percentage gave change in the chemical composition of the polymer [
The absorption spectra clarify an extending tail for lower photon energies below the band edge, which can be described by [
The values of optical parameters for different concentrations.
Wt% |
|
|
|
---|---|---|---|
Pure | 0.2011 | 1.2638 | 1.1241 |
1 | 0.1072 | 3.1482 | 1.7743 |
5 | 0.0914 | 4.1028 | 2.0255 |
10 | 0.1453 | 4.6396 | 2.1539 |
15 | 0.2004 | 4.6905 | 2.1657 |
20 | 0.1677 | 4.3221 | 2.0789 |
Variation of the Urbach plot of (ln
Figure
The optical conductivity as a function of photon energy.
Observe increasing in the optical conductivity with impurity percentage cases to moving curves vertex to low photon energies and new peaks appear in these samples.
Analysis of the obtained data of refractive index can be used to obtain the infinitely high frequency dielectric constant
Dielectric constant as a function of square wavelength.
The results indicate that nanosize zinc oxide ZnO can effectively dope PVC and enhance its optical properties. The presence of ZnO leads to an increase in the absorption and to a decrease in the transmission as ZnO concentration increases. The extinction coefficient, refractive index, real and imaginary partes, optical conductivity, infinitely high frequency dielectric constant, and average refractive index values show dependence on ZnO concentration where they increase after being doped and with the increase of ZnO concentration. The Urbach energy decreased with increasing impurity concentration.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors thank the Universiti Kebangsaan Malaysia for the funding (Codes AP-2011 17, DPP-2013-054, UKM-MI-OUP-2011, AP-2012-017, and DLP 2013-002).