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Preparation and study of optical properties of (polymer nickel nitrate) composite

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  • 1. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 152 Preparation and Study of Optical Properties of (Polymer-Nickel Nitrate) Composite Hind Ahmed, Bahaa H. Rabee, Hussein Hakim, Ahmed Hashim , Saba R. Salman Babylon University, College of Education, Department of Physics, Iraq E-Mail: ahmed_taay@yahoo.com ABSTRACT Polymer composite of polyvinyl alcohol (PVA), nickel nitrate have been prepared by solution cast method for different doping concentrations of nickel nitrate. The optical characterization has been done by analyzing the absorption spectra in the spectral region 200–800 nm. It was found that the optical energy gap decreases with increasing NiNO3 content. The refractive index (n), extinction coefficient (k), static dielectric constant have been calculated for the investigated films. The optical constants are changing with increase the weight percentages of nickel nitrate. Key words: composite, polymer, optical constants, nickel nitrate 1. INTRODUCTION The doped polymers may present useful applications in integrated optics or in real time holography. In order to tailor materials with improved properties within the doped polymer class, it is necessary to understand and control the electronic mechanisms involved in the optical behavior[1]. The physical properties of polymers may be affected by doping, the certain structural, optical, mechanical, electrical and magnetic properties of the selected polymer can be controllably modified owing to the type of the doping, concentration, and the way in which it penetrates and interacts with the chains of the polymer[2]. Polyvinyl Alcohol offers a combination of excellent film forming and binder characteristics, along with insolubility in cold water and organic solvents. This combination of characteristics is useful in a variety of applications . Moreover, it contains a carbon backbone with hydroxyl groups attached to methane carbons. These hydroxyl groups can be a source of hydrogen bonding, hence the assistance in the formation of polymer blends [3]. Recently, we focused our research on studying the optical properties of PVA filled with (NiNO3) fillers. 2. MATERIALS AND METHODS PVA and NiNO3 used as received. The experiment was carried out at room temperature (25o C). Different weight percentages of PVA and NiNO3 are dissolved completely in 30ml (weight of each sample 1 gm and the concentrations of nickel nitrate are 0, 0.5, 1, 1.5 wt.%) distilled under constant stirring for 1hour while the mixture was heated up till 90o C then the mixture was let to cool down to room temperature (25o C) while the stirring of the mixture was carried out to ensure a homogenous composition. To cast the film, the mixture for each NiNo3 concentrations was poured in a casting glass plate and let it dry at room temperature for 120 hours. At the expiry of this time, the films were ready which were peeled off the casting glass plate and cut into pieces for characterization by measuring optical properties using double-beam spectrophotometer. 3. RESULTS AND DISCUSSION The absorption spectra of the composite with different concentrations of nickel nitrite is shown in Fig. 1.
  • 2. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 153 Fig. 1: Absorbance of NiNO3 /PVA composite with different concentrations of nickel nitrite. It is clear from Fig 1 that as the concentration of the NiNO3 component in the polymer composition increases the absorption Fig.2 shows the variation of absorption coefficient for composite with various photon energy. The absorption coefficient (α) of composite depends on optical absorbance (A) and thickness of film (d) which is evaluated using the relation [4]: )1......(........../303.2 dA=α Fig.2 absorption coefficient for composite with various photon energy The optical energy gap (Eg) of the thin films has been determined from absorption coefficient data as a function of photon energy. According to the generally accepted non-direct transition model for amorphous semiconductors proposed by Tauc [5], )2....(..........)( r gEhBh −= υυα Where B is a constant related to the properties of the valance band and conduction band, hυ is the photon energy , Eg is the optical energy band gap, r=2,or3 for indirect allowed and indirect forbidden transition .From the linear plots of (α h ν) l/r against (h ν), the optical energy gap has been determined from the intercepts of extrapolations to zero with the photon energy axis (αhν)1/r → 0 . From the results obtained it is seen that an decrease of concentration of NiNO3 in the system leads to an increase in the optical band gap. The increase in band gap with decrease in concentration can be due to the decrease in cluster size of the parent solution. It is found that as the 0 0.5 1 1.5 2 2.5 3 3.5 4 200 300 400 500 600 700 800 Wavelength(nm) Absorbance pure 0.5 wt.% 1wt.% 1.5 wt.% 0 2 4 6 8 10 12 1 2 3 4 5 6 7 Photon energy(eV) pure 0.5 wt.% 1wt.% 1.5 wt.% α(cm)-1
  • 3. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 154 concentration of the NiNO3 decreases there is a red shift in band edge and a change in the slope of absorption spectra[6] as shown in figures (3a.and 3b.). Fig..3a. the relationship between (αhυ)1/2 (cm-1 .eV)1/2 and photon energy of composites. Fig..3b. the relationship between (αhυ)1/3 (cm-1 .eV)1/3 and photon energy of composites. Fig.4 shows the variation of extinction coefficient for composite with various wavelength. The extinction coefficient K, is related to the absorption coefficient α can be calculated by using the relation[6]: )3.....(..............................4/ παλ=K 0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 Photon energy(eV) pure 0.5 wt.% 1wt.% 1.5 wt.% (αhυ)1/2 (cm-1 .eV)1/2 0 2 4 6 8 10 12 0 1 2 3 4 5 6 7 Photon energy(eV) pure 0.5 wt.% 1wt.% 1.5 wt.% (αhυ)1/3 (cm-1 .eV)1/3
  • 4. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 155 Fig.4 extinction coefficient for composite with various wavelength The refractive index as a function of wavelength can be determined from the reflection coefficient data R and the extinction coefficient k using equation ( as shown in figure 5)[6]: )4.(.......... )1( )1( ) )1( 4 ( 2/12 2 − + −− − = R R K R R n Fig.5 the relationship between refractive index for composite with wavelength The decrease in the extinction coefficient with an increase in wavelength shows that the fraction of light lost due to scattering[6]. The high refractive index values of these composites are advantageous for strong optical confinement and enhance the optical intensities for nonlinear interactions. The real part of the dielectric constant is associated with the term that shows how much it will slow down the speed of light in the material ,can be calculated by using the relation[6]: )5(..........22 1 kn −=ε and imaginary part of the dielectric constant can be calculated by using the relation[7]: ε2 =2nk ...… …....(6) 1.E-07 1.E-06 1.E-05 1.E-04 200 300 400 500 600 700 800 k pure 0.5 wt.% 1wt.% 1.5 wt.% λ(nm) 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 200 300 400 500 600 700 800 n pure 0.5 wt.% 1wt.% 1.5 wt.% λ(nm)
  • 5. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 156 Fig.6 variation of real part of dielectric constant of composite with wavelength Fig.7 variation of imaginary part of dielectric constant of composite with wavelength The imaginary part shows how a dielectric absorbs energy from an electric field due to dipole motion. The dielectric constant (ε1) and dielectric loss (ε2) have been determined from [7]. 4. CONCLUSIONS 1. The absorbance increases with increase the concentration of nickel nitrite. 2. The absorption coefficient, extinction coefficient, refractive index and real and imaginary parts of dielectric constants are increasing with increase the weight percentages of nickel nitrite. REFERENCES [1] M. Bulinski, V. Kuncser, D. Cristea, C. Plapcianu, S. Krautwald, H. Franke, F. E. Wagner, G. Filoti,"OPTICAL AND ELECTRONIC PROPERTIES OF METAL DOPED POLYMERS FOR INTEGRATED OPTICS, J. of Optoelectronics and Advanced Materials Vol. 5, No. 1, pp. 331 - 335(2003). [2] Omed Ghareb Abdullah and Sarkawt Abubakr Hussen, "Variation of Optical Band Gap Width of PVA films Doped with Aluminum Iodide”. 2010 International Conference on Manufacturing Science and Technology (ICMST 2010). [3] A. Bhattacharya, P. Ray, “Studies on Surface Tension of Poly(Vinyl Alcohol): Effect of Concentration, Temperature, and Addition of Chaotropic Agents” Received 30 September 2003; accepted 16 December 2003. [4] C. Mwolfe, N. Holouyak and G. B. Stillman, "Physical properties of Semiconductor", prentice Hall, New York, (1989). 0 1 2 3 4 5 6 7 8 9 200 300 400 500 600 700 800 pure 0.5 wt.% 1wt.% 1.5 wt.% ε1 λ(nm) 0.E+00 2.E-05 4.E-05 6.E-05 8.E-05 1.E-04 1.E-04 1.E-04 200 300 400 500 600 700 800 pure 0.5 wt.% 1wt.% 1.5 wt.% ε2 λ(nm)
  • 6. Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) Vol.20, 2013 157 [5]Abd El-Raheem M M, J. Phys. Condens. Matter. 19, 216209 (2007). [6] R Tintu , Nampoori V P , Radhakrishnan P and Sheenu Thomas J. Appl. Phys. 108, 073525(2010). [7] R Tintu, K. Saurav, K.Sulakshna,Vpn.Nampoori,Pradhakrishnan and Sheenu thomas .” Ge28Se60Sb12 /PVA composite films for photonic application”. Journal of Non- Oxide Glasses Vol. 2, No 4, , p. 167-174, 2010.
  • 7. This academic article was published by The International Institute for Science, Technology and Education (IISTE). The IISTE is a pioneer in the Open Access Publishing service based in the U.S. and Europe. The aim of the institute is Accelerating Global Knowledge Sharing. More information about the publisher can be found in the IISTE’s homepage: http://www.iiste.org CALL FOR PAPERS The IISTE is currently hosting more than 30 peer-reviewed academic journals and collaborating with academic institutions around the world. There’s no deadline for submission. Prospective authors of IISTE journals can find the submission instruction on the following page: http://www.iiste.org/Journals/ The IISTE editorial team promises to the review and publish all the qualified submissions in a fast manner. All the journals articles are available online to the readers all over the world without financial, legal, or technical barriers other than those inseparable from gaining access to the internet itself. Printed version of the journals is also available upon request of readers and authors. IISTE Knowledge Sharing Partners EBSCO, Index Copernicus, Ulrich's Periodicals Directory, JournalTOCS, PKP Open Archives Harvester, Bielefeld Academic Search Engine, Elektronische Zeitschriftenbibliothek EZB, Open J-Gate, OCLC WorldCat, Universe Digtial Library , NewJour, Google Scholar