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Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24 IWNEST PUBLIHER

Mathematics and Statistics Journal (ISSN: 2077-4591) Journal home page: http://www.iwnest.com/MSJ/

The Effect of Magnesium Oxide Nanoparticles on Optical Properties of Polystyrene 1Hussein 1

Hakim, 2Ahmed Hashim, 3Shurooq Sabah and 4Najlaa Mohammad

Babylon University, College of Science, Department of Physics, Iraq. Babylon University, College of Education of Pure Science, Department of Physics, Iraq.

2,3,4

ARTICLE INFO Article history: Received 22 February 2015 Accepted 2 April 2015 Keywords: Magnesium Oxide Nanoparticles Optical Properties Polystyrene

ABSTRACT The optical properties of polymer nanocomposites consisting of polystyrene and magnesium oxide nanoparticles have been studied. Films of nanocomposites are prepared by casting technique. The optical properties were measured in range wavelength (300-800)nm. It was found that the optical absorption is due to indirect allowed transitions for pure and nanocomposites polymer films, while the energy gaps decrease with the increase of the concentration of MgO nanoparticles. The optical constants (refractive index, extinction coefficient, the real and the imaginary parts of the dielectric constant) have been calculated. The optical constants are changed with the increase of the concentration of MgO nanoparticles.

© 2015 IWNEST Publisher All rights reserved. To Cite This Article: Hussein Hakim, Ahmed Hashim, Shurooq Sabah and Najlaa Mohammad, The Effect of Magnesium Oxide Nanoparticles on Optical Properties of Polystyrene. Math. Stat. J., 1(1), 19-24, 2015

INTRODUCTION This new class of organic inorganic composites or hybrid materials may afford potential applications in molecular electronics, optics, photoelectron chemical cells, solvent-free coatings, etc [1]. Transparent films can be used as optical filters, polarizers, total re-flectors, narrow pass-band filters etc. Films of dielectric materials have been successfully used in some optical devices and materials [2]. Polymer composites are used as electrical conductive adhesives and circuit elements in microelectronics and have been reported to possess anticorrosive behavior as metal components coatings [3]. Polystyrene has wide applications mainly used in the packaging industry; optical of polystyrene is used in manufacture of unbreakable glasses for gauges, windows and lenses, as well as in countless specialties and novelties and also for edge lighting of indicators and dials [2]. Its major characteristics include rigidity, transparency, high refractive index, good electrical insulation characteristics, low water absorption, and ease of coloring and processing [4]. 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 [5] Hence, the aim of this work is to study the optical parameters of polymer nanocomposites based on PS-MgO system. Experimental Detail: Polystyrene and MgO nanoparticles have been used as the raw materials in this work to prepare the solid polymer nanocomposites by using the solution cast technique. For this purpose, 0.5 gm of polystyrene was dissolved in 15 mL of chloroform. The mixture was stirred continuously with a magnetic stirrer for several hours at room temperature until the polystyrene has completely dissolved. The concentrations of the MgO nanoparticles which added to the polystyrene are (1.5, 3 and 4.5) wt.% .The solutions were then cast into different clean and dry glass and allowed to evaporate at room temperature until solvent free films were obtained. The optical properties were measured by using UV/1800/ Shimadzu spectrophotometer in range of wavelength (200-800) nm.

Corresponding Author: Ahmed Hashim, Babylon University, College of Education of Pure Science, Department of Physics, Iraq E-mail: [email protected]

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Ahmed Hashim et al, 2015 Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24

RESULTS AND DISCUSSIONS The transmission of composites: The transmission spectra of the (PS-MgO) nanocomposites with different concentrations of nanoparticles are presented in Fig 1.. Iit is clear from Fig 1. as the concentration of the MgO nanoparticles component in the polymer composition increase the transmission decrease. 1 Pure 1.5 wt.%

0.9

3 wt.%

Transmittance

4.5 wt.%

0.8 0.7 0.6 0.5 0.4 300

400

500

600

700

800

Wavelength(nm)

Fig. 1: The variation transmittance for (PS-MgO) nanocomposites with wavelength. The absorbance of composites: Fig. 2 shows the relationship between absorbance of (PS-MgO) nanocomposites with wavelength, from the figure it was appeared that the absorbance tends to decrease with the wavelength increasing. It clear from the Fig. 2 that as the concentration of the MgO component in the polymer 0.9 Pure

0.8

1.5 wt .% 3 wt .%

Absorbance

0.7

4.5 wt .%

0.6 0.5 0.4 0.3 0.2 0.1 0 300

400

500

600

700

800

Wavelength(nm )

Fig. 2: The variation Absorbance for (PS-MgO) nanocomposites with wavelength. Composition increase the absorbance increase this increasing may be refer to consist a new energy level between the valance band and conduction band . The Absorption coefficient and energy gap of composite: The absorption coefficient (α) was calculated in the fundamental absorption region from the following equation[6]: d  2.303A...........................(1) (1) Where: A is absorbance and (d) is the thickness of sample

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Ahmed Hashim et al, 2015 Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24

Fig 3. shows the optical absorption spectrum of (PS-MgO) nanocomposites for different impurities quantities, it was found that the nanocomposites have a low absorption coefficient at a small photon energy then increase at different rates dependence on the nanocomposites structure; the pure sample had low absorption coefficient this may be as a result of low crystalinity. The optical energy gap Eg of the films has been determined from absorption coefficient data as a function of photon energy according to the nondirect transition model [7]:for higher values of absorption coefficient where the absorption is associated with interband transitions. (αhυ)/B = (hυ - Eg )m (2) Where: hυ = the energy of the incidence photon ,h = The Planck constant Eg = The optical energy band gap ,B = a constant known as the disorder parameter which is nearly independent of the photon energy, r = depends on type of transition. 7.0E+01

Pure 1.5 wt .% 3 wt .%

6.0E+01

4.5 wt .%

α(cm)-1

5.0E+01 4.0E+01 3.0E+01 2.0E+01 1.0E+01 0.0E+00 1

2

3

4

5

Eph(eV)

Fig. 3: the variation Absorption coefficient for (PS-MgO) nanocomposites with photon energy. 18

Pure 1.5 wt.%

16

4.5 wt.%

14

1/2

-1

(αhυ) (cm .eV)

1/2

3 wt.%

12 10 8 6 4 2 0 1

1.5

2

2.5

3

3.5

4

4.5

Eph (eV)

Fig. 4: The variation (  hv)1/2for (PS-MgO) nanocomposites with photon energy. The indirect optical band gap can be evaluated from the linear plots of (αhυ)1/2 versus hυ as illustrated in Fig. 4 represented the indirect transition , the energy gab values dependence in general on the crystal structure of the nanocomposites and on the arrangement and distribution way of atoms in the crystal lattice . From Fig. 4 the energy gab shift to lower energy with increasing the concentration of MgO nanoparticles compare with the pure polystyrene.

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Ahmed Hashim et al, 2015 Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24

Refractive Index and Extinction Coefficient: The refractive index (n) and extinction coefficient (k) are important parameters characterizing photonic materials. The refractive index (n) as a function of wavelength can be determined from the reflection coefficient data R and the extinction coefficient K using equation:

n(

4R ( R  1)  K 2 )1 / 2  .......... .(3) 2 ( R  1) (1  R )

(3)

Pure

2.6

1.5 wt.% 3 wt.%

2.4

4.5 wt.%

2.2

n

2 1.8 1.6 1.4 1.2 1 300

400

500

600

700

800

Wavelength(nm)

Fig. 5: the variation Refractive index for (PS-MgO) nanocomposites with wavelength. The extinction coefficient (k) was calculated using the following equation: K=αλ/4π Where (λ) is the wavelength and (α )the absorption coefficient.

(4)

1.0E-03

Pure 1.5 wt .% 3 wt .%

k

4.5 wt .%

1.0E-04

1.0E-05 300

400

500

600

700

800

Wavelength(nm)

Fig. 6: The variation extinction coefficient for (PS-MgO) nanocomposites with wavelength. The fraction of light lost due to scattering increase with the concentration of MgO nanoparticles therefore the extinction coefficient increase. Dielectric constant: The dielectric constant of compound (ε) is divided into two parts real(ε 1), and imaginary (ε 2).The real parts of dielectric constant is associated with the term that shows how much will slow down the speed of light in the material and the imaginary parts shows how a dielectric absorbs energy from an electric field due to dipole motion . (ε 1and ε 2) can be calculated by using equations [8,9]:

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Ahmed Hashim et al, 2015 Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24

ε = ε1 – i ε2 ε 1=n2-k2 ε 2=2nk

(5) (6) (7) 7

Pure 1.5 wt .%

6.5

3 wt .% 4.5 wt .%

6

ε1

5.5 5 4.5 4 3.5 3 2.5 2

300

400

500

600

700

800

Wavelength(nm)

Fig. 7: The variation real dielectric constant for (PS-MgO) nanocomposites with wavelength. Pure

1.E-03

1.5 wt.% 3 wt.%

ε2

4.5 wt.%

1.E-04

1.E-05 300

400

500

600

700

800

Wavelength(nm )

Fig. 8: The variation Imaginary dielectric constant for (PS-MgO) nanocomposites with wavelength. Conclusion: The optical studies showed that the addition of MgO to the polystyrene films has clear effect on these properties. The transition were found to be indirect type .the energy band gap decrease with increase the concentration of MgO nanoparticles. The optical constants of polystyrene increase with the increase of the concentration of MgO nanoparticles. It was shown from the studies that additive of MgO nanoparticles into the polymer results in fabrication of new nanpcomposite films. It will contribute to produce a new material that might potentially be used as an alternative or substitute material for many other application . REFERENCES [1] [2]

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Ahmed Hashim et al, 2015 Mathematics and Statistics Journal, 1(1) January 2015, Pages: 19-24

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