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magnetite nanocomposite for photovoltaic applications
Synthetic Metals 231 (2017) 34–43
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Research paper
Conductive thin films based on poly (aniline-co-o-anthranilic acid)/ magnetite nanocomposite for photovoltaic applications
MARK
⁎
M. Sh. Zorombaa,b, , A.F. Al-Hossainyc,d, M.H. Abdel-Aziza,e a
Chemical and Materials Engineering Department, King Abdulaziz University, Rabigh 21911, Saudi Arabia Chemistry Department, Faculty of Science, Port-Said University, 42521 Port-Said, Egypt c Chemistry Department, Faculty of Science – New valley, Assiut University, 71516 Assiut, Egypt d Chemistry Department, Faculty of Science, North boarder University, Arar, 1321, Saudi Arabia e Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt b
A R T I C L E I N F O
A B S T R A C T
Keywords: Thin film Magnetic nanocomposite Conducting polymers Thermal evaporation Optical properties
In this research, magnetite particles in a nanoscale were coated with three various weight percentages of poly (aniline co-o-anthranilic acid) copolymer. Aniline and o-anthranilic acid monomers were copolymerized in the presence of Fe3O4 nanoparticles via surface initiated polymerization method. Characterization of nanocomposites was carried out by several analysis techniques including; FT-IR, FE-SEM, TEM, XRD, TGA and UV–vis-Near infrared. FT-IR results showed that pended COOH groups of PANAA are physically interacted to magnetite nanoparticles. Magnetite nanoparticles enhanced the thermal strength of the nanocomposites in the range of 300–800 °C. The XRD analysis revealed that the average crystallite size ranges from 7.59 to 11.14 nm depending on PANAA weight percentage. Thin films of uniform spherical shape of PANAA/magnetite nanocomposite were fabricated by thermal evaporation technique. The values of Eg(direct) and Eg(indirect) decreased with increasing the thickness of PANAA, while the conductivity increased with increasing of PANAA thickness coated magnetite particles. The conductivity value ranged from 3.73 to 26.98 Ω−1 cm−1 at a photon energy 3.65 eV. Using the nanocomposites in photovoltaic applications was highlighted.
1. Introduction Optically transparent and electrically conductive polymers have been attractive in the past two decades due to their benefits in various applications including solar cells, electrostatic dissipation, electromagnetic shielding, sensors, touch-sensitive screens, and alarm devices [1,2]. Furthermore, conducting polymers/magnetic nanocomposite have attracted great attention of the scientific community currently due to its high potential of technological industrial applications in various areas, such as electromagnetic interference shielding [3], rechargeable batteries [4], corrosion protection coatings [5], electrodes [6], gas separating membranes [7,8], microwave absorption [9], sensors [10–12], and microelectronic devices [13,14]. PANI as any conjugated polymer has some characteristics related to its molecular structure and bond alternation make the polymer infusible, insoluble in organic solvents and cannot be handled like thermoplastic polymers [15,16]. The problem of difficult solubility in organic solvent has been solved by using various functionalized dopants [15–18]. Other researchers enhanced the PANI solubility by introducing another o-anthranilic acid monomer through PNAI backbones [19–21]. Unique magnetic and electrical
⁎
properties can be achieved by preparing PANI/Fe3O4 nanocomposites where polyaniline nanocomposites can be reinforced with different weights of Fe3O4 nanoparticle. Wet chemical method and surface initiated polymerization (SIP) method have been used for this purpose. The resulting magnetic polyaniline nanocomposites have a higher saturation magnetization of 72 emu/g and a conductivity around 10–4 S/ cm. PANI and its nanocomposites display a negative permittivity [22–25]. Poly(aniline co-o-anthranilic acid)/Fe3O4 nanocomposites have prepared by applying surface initiated polymerization (SIP) method for wastewater applications [26]. In the current study the aim is to cover magnetite nanoparticles with different amounts of PANAA using surface initiated polymerization method (SIP) and to prepare PANAA/magnetite nanocomposite thin films. The nanocomposite consists of organic (PANAA) and inorganic (magnetite) parts, the presence of magnetite in the composite will improve the dielectric constant and improve the efficiency if the material is used in photovoltaic cells. The study aims also to investigate the applicability of the thin films in photovoltaic applications. Photovoltaic material must fulfil two conditions, namely: (i) absorb incident photons through the promotion of electrons to higher energy levels, and (ii) contain an internal electric
Corresponding author at: Chemical and Materials Engineering Department, King Abdulaziz University, Rabigh 21911, Saudi Arabia. E-mail address: [email protected] (M.S. Zoromba).
http://dx.doi.org/10.1016/j.synthmet.2017.06.021 Received 25 April 2017; Received in revised form 22 June 2017; Accepted 28 June 2017 0379-6779/ © 2017 Elsevier B.V. All rights reserved.
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Nomenclature A Ao a, b, c B C D Dm Dc d Eg EI EU H hv h, k, l K kB ke
M Ms m nr R T α αo εo ε1 ε2 θ λ μ ρ σ σ1 σ2 ω
Absorbance Energy-independent constant Lattice constants Full width at half maximum intensity Speed of light Magnetic particle diameter Magnetic domain size Crystal size Interplanar spacing Band gap Constant Urbach energy Magnetic field strength Photon energy Miller indices Constant (0.94) Boltzmann constant Extinction coefficient
field that accelerates the promoted electrons in a particular direction, resulting in an electrical current. To this end the optical and electrical properties of the nanocomposites were studied.
Magnetization Saturation magnetization Constant Refractive index Reflectance Temperature Absorption coefficient Constant Free space dielectric constant Real dielectric constant Imaginary dielectric constant Bragg angle X-ray wavelength True magnetic moment Nanocomposite density Optical conductivity Real part of optical conductivity Imaginary part of optical conductivity Angular frequency
700 rpm at room temperature. Separately, 1.37 g o-anthranilic acid was dissolved in 30 ml ethanol then added to aniline solution. 40 ml purified water were added to the co-monomers. The co-monomers’ solution was directly mixed to the magnetite dispersion obtained from the previous step. The magnetite/co-monomers mixture was kept in an ice box to maintain the temperature 0–5 °C under magnetic stirring at 700 rpm for 30 min. 60 ml 1 M K2Cr2O7 initiator was added drop wisely to the magnetite/co-monomers mixture for 1 h under the above conditions. During the polymerization process the copolymer was gradually observed to coat the magnetite nanoparticles. The resulting PANAA/ magnetite nanocomposite was filtrated using a Buchner funnel and washed with distilled water frequent times, followed by ethanol to remove excess oxidant, unreacted monomers and oligomer. Washing continued until the filtrate (liquid) become almost colorless and then the sample was oven dried at 80 ° C for 24 h. The resulting composite was labeled by L1. The second weight of PANAA prepared to coat magnetite nanoparticles was obtained according to the same procedure of the first weight except using twofold amount of the aniline and oanthranilic acid in comparing with the first weight (1.86 g aniline and 2.74 g o-anthranilic acid) and subsequently the twofold amounts of HCl and initiator used as well. The resulting PANAA/magnetite composite was labeled by L2. The third weight of PANAA was also obtained according to the same previous procedure of the first weight except using twofold amounts of the aniline and o-anthranilic acid as for the second weight to be (3.72 g aniline and 5.48 g o-anthranilic acid) and of course, twofold of amounts HCl and an initiator was used as well. The resulting nanocomposite was labeled by L3. The typical composition of the three nanocomposites are listed in Table 1.
2. Experimental 2.1. Materials All chemical substances were used as received without any additional treatment excluding aniline. Double distillations of aniline were carried out before use and it was kept in a dark bottle. Aniline and oanthranilic acids were bought from Aldrich, potassium dichromate (Merck), ammonia solution and hydrochloric acid (Aldrich). Iron (II) chloride tetrahydrate, iron (III) chloride hexahydrate, hydrochloric acid (HCl) and ethanol of analytical grade were purchased from Shanghai chemicals. 2.2. Synthesis of magnetite nanoparticles Typically, 50 ml of 0.2 M FeCl3·6H2O were mixed with 25 ml of 0.2 M FeCl2·4H2O solution under magnetic stirring. Separately, 40 ml (33%v/v) ammonia solution was diluted with 20 ml distilled water. Subsequently, diluted ammonia solution was added to previous iron (Fe3+/Fe2+) salts drop by drop at room temperature and 800 rpm. Gradually, a black precipitate of magnetite was gradually appeared. The resulting magnetite dispersion was diluted with additional 200 ml of distilled water. The obtained dispersion was left to settle down under gravitational force. Washing process was carried out by decantation method for several times. A magnetite nanoparticle was kept in the mother liquor (total volume 40 ml distilled water) as a dispersion. The magnetite dispersion in the mother liquor was kept for using in the next step of the polymerization process with aniline and o-anthranilic acid co-monomers. A separate experiment to estimate the weight of magnetite was conducted following the same aforementioned procedure and the resulting magnetite was separated by filtration and then dried. The weight of the resulting magnetite (blank sample) was found to be 1.4 g.
2.4. Preparation of PANAA/magnetite nanocomposite thin films Thin films of PANAA/magnetite nanocomposites were fabricated by thermal evaporation method using a high vacuum coating unit Table 1 Composition of three different PANAA/magnetite nanocomposites. Co-polymer
Ratio (aniline and oanthranilic acid)
Weight of the resulting polymer composite (gram)
% weight of Fe3O4
PANAA (L1) PANAA (L2) PANAA (L3)
(0.93 g and 1.37 g) (1.86 g and 2.74 g) (3.72 g and 5.48 g)
2.43 3.12 4.76
36.55% 30.97% 22.73%
2.3. Synthesis of PANAA/Magnetite nanocomposite Three different weights of PANAA were polymerized onto the magnetite surface. The first weight of PANAA was obtained as follows: 8 ml conc. HCl was added to 0.93 g aniline under magnetic stirring at 35
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(Edwards E 306 A, England). The vacuum through the deposition process is adjusted at 1 × 10−4 Pa. Optical flat quartz substrates were used for thin films deposition. The substrates were washed carefully by chromic acid for 15 min followed by rinsing with deionized water. The powder of PANAA/magnetite was sublimated from a quartz crucible heated gradually by molybdenum boat shaped filament. A built-in quartz crystal thickness monitor (Model TM-350 MAXTEK, Inc. USA) was used to measure the deposition rate and the film thickness. The thickness of PANAA/magnetite nanocomposites films were 205, 230, 215 nm for L1, L2 and L3 respectively. Two repeated series of PANAA/ magnetite nanocomposite thin films were placed onto optically flat quartz substrates for examination by spectrophotometric and X-ray diffractometer.
located at 1585 cm−1 and 1514 cm−1. These peaks can be ascribed to the C ] C vibrations of quinoid and benzenoid units through the copolymer chains [26]. The existence of the absorption band at 1398–1402 cm−1 can be attributed to CeN stretching vibrations of benzenoid-quinoid-benzenoid sequence [28,29]. The absorption band at 1670–1676 cm−1 for all PANAA/magnetite can be attributed to C] O group. The strong band at 1150 cm−1 is a characteristic for emeraldine salt (doped with chloride ion). The absorption bands at 1502, 1500, 1496 cm−1 for L1, L2 and L3 respectively, can be attributed to the stretching band of quinoid structure through the copolymer backbone. The bands of symmetric vibrations s(OCO) at 1390–1337 cm−1 were detected for all nanocomposites.
2.5. Characterization
3.2. Thermal analysis of PANAA/magnetite nanocomposite powders
2.5.1. FTIR Infrared spectra were recorded on a Perkin–Elmer FT-IR type 1650 spectrophotometer in a wave number range 4000–400 cm−1.
Fig. 2 shows that the thermal decomposition of PANAA/magnetite nanocomposites were carried out through four stages. The first stage within the temperature range of 50–125 °C. The weight loss of around 8% for all nanocomposites L1, L2 and L3 which can be attributed to the loss of water molecules, trapped in the copolymer chains in the nanocomposite. The second stage within the temperature range of 300–400 ° C is due to the removal of CO2 molecules from the copolymer chains loaded onto magnetite (L1, L2 and L3). In the third stage, the weight loss was observed in the three composites after 640 °C which corresponds to the thermo-oxidative degradation of the polymer chain, similar results was reported by Challier et al. [30]. The thermal stability of the composites increases through the first and second stages taking the following order L1 < L2 < L3. This means that by amount of PANAA around magnetite nanoparticles, the thermal stability was significantly improved. This can be attributed to increasing hydrogen bonding and Van Der Waals interactions between the carboxylic, imine groups from PANAA chains with magnetite nanoparticles. The remaining percentages of the magnetite nanocomposites in the third decomposition stage takes the following order L3 < L2 < L1 which can be ascribed to the high contents of iron oxide in the nanocomposites as shown previously in Table 1. The Dr.TGA curves for PANAA/magnetite nanocomposites are shown in Fig. 2. The water is evolved at 92.4, 123.62 and 110.67 °C for L1, L2 and L3 respectively. No water vapor is lost above 130 °C. Decomposition takes place in three steps with the loss of water in the first step, 395.56, 368.81 and 378.54 °C for L1, L2 and L3, respectively, this may be attributed to the removal of carbon dioxide in the second step. However, the endothermic peaks at 753.08, 711.79 and 720.95 °C in the third step may be attributed to thermo-oxidative degradation of the polymer chain for L1, L2 and L3 respectively.
2.5.2. TGA Thermal stability was studied by TGA (TA Instruments − Q50, USA). Thermal decomposition process was applied under N2 atmosphere from 30 to 800 ° C (heating rate was 20 ° C/min). 2.5.3. Magnetic properties Magnetic properties of PANAA/magnetite nanocomposite powders were evaluated by using a Micro-Sense Easy VSM Software Version Easy VSM 20150927-01, in an applied field range of 0–18 kOe. Magnetic particle diameter was calculated by fitting the magnetization curve to the Langevin function of magnetization [27]:
μH ⎞ ⎛ kB T ⎞ M = coth ⎛ −⎜ ⎟, k Ms ⎝ B T ⎠ ⎝ μH ⎠ ⎜
⎟
(1)
where M is the magnetization for a field strength H, Ms is the saturation magnetization, kB is the Boltzmann constant, the true magnetic moment of each particle μ = MsπD3/6 and D is the magnetic particle diameter. Magnetic measurements were conducted in the solid state at room temperature. 2.5.4. XRD The structure of the composites was investigated by a Philips X-ray diffractometer (model X’pert) with monochromatic Cu Kα radiation operated at 40 kV and 25 mA. Powder diffractometers typically used the Bragg Brentano geometry. The diffraction patterns were recorded with 6° per minute in the range 0–80° of 2θ range. Divergence slit (DS) and the receiving slit (RS) were adjusted at 1° and 0.2 mm, respectively. 2.5.5. Morphology study The morphology of the prepared composite surfaces was determined by scanning electron microscopy (SEM; Inspect S, FEI, Holland), operated at an accelerating voltage of 3.0 kV. The samples were coated by platinum under vacuum. 2.5.6. UV–vis-near infrared measurements The spectra measurements of the thin films were recorded in the range 200–900 nm by using SHIMADZU UV-3101 UV–vis–NIR pc spectrophotometer at room temperature. 3. Results and discussion 3.1. FTIR of PANAA/magnetite nanocomposite powders The FT-IR spectra of PANAA/Fe3O4 nanocomposites are presented in Fig. 1. The spectra of L1, L2 and L3 have two major absorption peaks
Fig. 1. FTIR spectra PANAA/magnetite nanocomposite powders (L1, L2 and L3).
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Fig. 2. TGA and Dr. TGA of PANAA/magnetite nanocomposite powders (L1, L2 and L3).
The cell constants (a, b and c), d-spacing (d) and crystallite size (Dc) were calculated by the formulae [42]:
3.3. Magnetic VSM properties of synthesized PANAA/magnetite composite powders Fig. 3 shows the magnetization (M–H) curve of PANAA/magnetite. The magnetization curve of PANAA/magnetite composites showed nonlinear, reversible characteristics without hysteresis, and exhibiting only superparamagnetic behavior [30]. The value of the magnetic saturation based on VSM data, Ms were found to be 278.70 × 10−2, 186.39 × 10−2 and 885.20 × 10−3 emu g−1 for L1, L2 and L3 respectively. With increasing the contents PANAA around magnetite particles, the magnetization of the resulting composites decreased (pure magnetite has 84.5 emu g-1) [31–35]. The average magnetic particle size obtained by fitting the slope of magnetization near zero-field region, dM/DH)H→0 from the M–H curve as shown in Fig. 3. The magnetic domain size, Dm was calculated from magnetization curve with the equation [36–38]:
(3)
2dsinθ = nλ
(4)
Kλ Bcosθ
(5)
⎜
Dc =
⎟
where K is a constant and equals to 0.94, λ is the X-ray wavelength, B full width at half maximum intensity. The values of lattice constants (a, b and c) of nanocomposites powder are shown in Fig. 4. The results show that the formation of monoclinic crystal system with non-centrosymmetric space group of P21 of the crystal and the estimated cell parameters are, a = 8.832 Å, b = 9.178 Å, c = 11.576 Å, γ = α = 90°, β = 104.52°. The Bragg reflection peaks are relatively broad due to the small
1/3
18kB T (dM / dH ) H → 0 ⎞ Dm = ⎜⎛ ⎟ ρMs2 ⎝ π ⎠
1 1 ⎛ h2 k 2sin2B l2 2hlcosB ⎞ l2 = + + 2 − + 2 d2 sin2B ⎝ a2 b2 c ac ⎠ c
(2)
where kB is the Boltzmann constant T is absolute temperature, ρ is the density of the nanocomposite (4.5 g cm−3) and the Ms represents the saturation magnetization value. The values of Dm for the synthesized composites were found to be 10.92, 8.50 and 7.38 nm for L1, L2 and L3 respectively. The values of magnetic moment decreases with decreasing of magnetite percentage. The decrease in the magnetic moment value is due to the reduction in saturation magnetization as the magnetic moment and saturation magnetization are directly related to each other. The saturation magnetization and magnetic moment data are in agreement with each other [38,39]. 3.4. XRD of PANAA/magnetite composite thin films Fig. 4 shows the WXRD patterns of PANAA/magnetite nanocomposites thin film. The thin film particles has several relatively strong well-defined reflection peaks in the 2θ region of 10–80°. Similar results of pure-phase magnetite particles were reported in previous studies [40]. Based on the Joint Committee on Powder Diffraction Standards (JCPDS) No. 19-0629, the resulting peaks confirm the formation of magnetite (Fe3O4) [41].
Fig. 3. Magnetization curve of PANAA/magnetite nanocomposite powders (L1, L2 and L3).
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Fig. 4. X-Ray diffraction patterns of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
3.5. Morphology study of PANAA/magnetite nanocomposite thin films
dimensions of the nanostructure thin films (Eq. (4)), where (n) is a positive integer, (λ) is the wavelength of incident wave and d is the spacing between layers of atoms. The crystallite size (Dc) of the nanocomposites thin films were determined using the Scherer’s equation (Eq. (5)). The average crystallite size of nanostructured thin films are 11.14, 8.75, and 7.59 nm for L1, L2 and L3, respectively. The crystallite domain size of the nanocomposites particles based on the breadth of (111), (220), (311), (400), (422), (511) and (440) reflection was determined by Debye–Scherer formalism of WXRD results. The average crystallite size of PANAA/magnetite thin film decreased with increasing copolymer contents around the magnetite particles from L1 to L3.
Fig. 5 shows FE-SEM images of the nanostructured thin film. The particles within the deposited film have a uniform spherical shape and display highly monodisperse with an average diameter of 40 nm. 3.6. Optical properties of the PANAA/magnetite nanocomposite thin films The UV–vis absorption spectra of PANAA/magnetite nanocomposite thin films are shown in Fig. 6. The absorbance increases with increasing PANAA thickness around the magnetite particles. An absorption band is located at 340 nm, which assigned to π-π* electronic transition of copolymer PANAA thin film [43,44]. Fig. 5. FE-SEM image of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 6. The absorption spectra of the PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
Table 2 Optical properties of PANAA/magnetite nanocomposite thin films (λ = 450 nm). Film
Thickness, nm
%T
Eg(direct)(eV)
Eg(indirect)(eV)
Eu (eV)
nr
ke
L1 L2 L3
205 230 275
93.33 79.43 73.88
3.21 3.11 2.91
3.38 3.44 3.41
2.52 5.97 7.52
1.84 1.81 1.67
5.24 × 10−4 1.56 × 10−3 6.12 × 10−3
Fig. 7. The extinction coefficient (ke) and the refractive index distributions (nr) of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 8. The allowed direct band gap for PANAA/magnetite nanocomposite thin films (L1, L2 and L3). Fig. 10. The variation of ln (α) versus hν for PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
The extinction coefficient (ke) was calculated using the relation: (6)
ke = αλ /4π
R was calculated using the relation [46]:
where α is the absorption coefficient, defined as the absorbance (A) divided by the film thickness. The values of measured film thickness were 205, 230, and 275 nm for L1, L2 and L3 respectively. The percentages of transmittance (%T) at λ = 450 nm are given in Table 2. The data show that the%T of the PANAA/magnetite nanocomposite films decreases with increasing PANAA coated layer thickness. Fig. 7 displays the plots of (ke) versus the wavelength (λ) and the refractive index (nr) versus the wavelength (λ). The refractive index (nr) was calculated by using the reflectance (R) and the extinction coefficient (ke) of the considered films [45]:
nr = [(1 + R)/(1 − R)] +
⎡ 4R ⎤ − k 2 e 2 ⎢ ⎣ (1 − R) ⎥ ⎦
R=1−
(Texp (A)
(8)
The values of nr at λ = 450 nm are listed in Table 2. The nr value increases with increasing of PANAA layer thickness. The band gap (Eg) values of the produced films were calculated from the optical absorption spectra based on the equation [47]:
αh ν = Ao (h ν − Eg )m
(9)
where hν is the photon energy, m is assumed values of 1/2 and 2 for allowed direct and allowed indirect transitions, respectively [48,49]. Aois an energy independent constant having values between 1 × 105 and 1 × 106 (cm eV)−1 [50,51]. The values of the allowed direct Eg(direct) and the allowed indirect Eg(indirect) optical band gaps were
(7)
Fig. 9. The allowed indirect band gap for PANAA/ magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 11. The real and imaginary parts of the dielectric constant of PANAA/magnetite thin films (L1, L2 and L3).
Fig. 12. Spectral dependence of the real and imaginary parts of optical conductivity of the PANAA/ magnetite nanocomposite thin films (L1, L2 and L3).
calculated by extrapolating the linear portion of the plots of (αhν)2 versus hν and that of square root (αhν) versus hν to (αhν)2 = 0 and square root (αhν) = 0, respectively. Figs. 8 and 9 show the plots of allowed direct and indirect band gap for the PANAA/magnetite nanocomposite films. The linear dependence of both (αhν)2 and (αhν)1/2 on (hν) at higher photon energies indicates to both the direct and indirect optical transitions are possible for the films. The straight-line portion of the curves is extrapolated to zeros to give the optical band gap, Eg(direct) and Eg(indirect), and the resulting values are listed in Table 2. Both Eg(direct) and Eg(indirect) decreased with
increasing the amount of PANAA copolymer, and accordingly the conductivity increases with increasing of PANAA amount around magnetite particles. Urbach energy (EU) refers to the width of the exponential absorption edge. The EU is calculated using the relation [52]:
α = αo exp[(h ν − EI )/ EU ]
(10)
where EI and αo are constants. Fig. 10 shows the variation of ln(α) versus hν for PANAA/magnetite thin films. The EU values were calculated from the slopes of Fig. 10 using the relationship: 41
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EU = (d(ln α)/dhν)−1
(11)
PANAA around magnetite particles leads to increasing the conductivity and decreasing the percentage of transmittance (%T) and Both Eg(direct) and Eg(indirect). The real part of the optical dielectric constants ε1 (ω) was found to be 59 times of the imaginary part of dielectric constants ε2 (ω) . The loss factor ranged from 5.05 × 10−3 to 34.37 × 10−3 indicating low power dissipation of the PANAA/magnetite nanocomposite. The imaginary part of the optical conductivity of the PANAA/magnetite nanocomposite films was found to be 63 times of the real part.
and the obtained EU values are listed in Table 2. EU values of the PANAA/magnetite thin films increased with increasing of the PANAA layer thickness. The increase of EU value leads to a rearrangement of states from band to tail, and thus allows for a large number of possible bands to tail and tail-to-tail transitions [53]. 3.7. Dielectric properties and optical conductivity The dielectric constant is an essential inherent characteristic of photovoltaic material. The real part of the dielectric constant ε1 (ω) gives an indication to how considerable it will sluggish the speed of light in the material and the imaginary part ε2 (ω) gives an indication to how a dielectric absorbs energy from an electric field due to dipole motion. The knowledge of the values of real and imaginary parts of the dielectric constant make it possible to estimate the loss factor which is the ratio ε2 (ω) and is a measure of the loss of energy in a dielectric material
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.synthmet.2017.06.021. References [1] R.G. Gordon, Criteria for choosing transparent conductors, MRS bulletin 25 (2000) 52–57. [2] Y. Wang, X. Jing, Transparent conductive thin films based on polyaniline nanofibers, Mater. Sci. Eng.: B 138 (2007) 95–100. [3] T. Mäkelä, S. Pienimaa, T. Taka, S. Jussila, H.H. Isotalo, Thin polyaniline films in EMI shielding, Synth. Met. 85 (1–3) (1997) 1335–1336. [4] S. Kuwabata, S. Masui, H. Yoneyama, Charge–discharge properties of composites of LiMn2O4 and polypyrrole as positive electrode materials for 4 V class of rechargeable Li batteries, Electrochim. Acta 44 (1999) 4593–4600. [5] N. Ahmad, A.G. MacDiarmid, Inhibition of corrosion of steels with the exploitation of conducting polymers, Synth. Met. 78 (1996) 103–110. [6] J.M.G. Laranjeira, W.M. De Azevedo, M.C. Ugulino de Araújo, A conductimetric system based on polyaniline for determination of ammonia in fertilizers, Anal. Lett. 30 (1997) 2189–2209. [7] M.R. Anderson, B.R. Mattes, H. Reiss, R.B. Kaner, Gas separation membranes: a novel application for conducting polymers, Synth. Met. 41 (1991) 1151–1154. [8] B.R. Mattes, M.R. Anderson, J.A. Conklin, H. Reiss, R.B. Kaner, Morphological modification of polyaniline films for the separation of gases, Synth. Met. 57 (1993) 3655–3660. [9] T.L. Rose, S. D'Antonio, M.H. Jillson, A.B. Kon, Rajendran Suresh, F. Wang, A microwave shutter using conductive polymers, Synth. Met. 85 (1997) 1439–1440. [10] A.P.L. Pacheco, E.S. Araujo, W.M. de Azevedo, Polyaniline/poly acid acrylic thin film composites: a new gamma radiation detector, Mater. Charact. 50 (2003) 245–248. [11] A.H. Parente, E.T.A. Marques, W.M. Azevedo, F.B. Diniz, E.H.M. Melo, J.L. Lima Filho, Glucose biosensor using glucose oxidase immobilized in polyaniline, Appl. Biochem. Biotechnol. 37 (1992) 267–273. [12] F.B. Diniz, K.C. de Freitas, W.M. de Azevedo, Salinity measurements with polyaniline matrix coated wire electrodes, Electrochem. Commun. 1 (1999) 271–273. [13] J.M.G. Laranjeira, H.J. Khoury, W.M. de Azevedo, E.F. da Silva Jr., E.A. de Vasconcelos, Conducting polymer/silicon heterojunction diode for gamma radiation detection, Radiat. Prot. Dosim. 101 (2002) 85–88. [14] J.M.G. Laranjeira, H.J. Khoury, W.M. de Azevedo, E.F. da Silva Jr, E.A. de Vasconcelos, Fabrication of high quality silicon–polyaniline heterojunctions, Appl. Surf. Sci. 190 (2002) 390–394. [15] T. Olinga, A. Pron, J. Travers, Use of sulphonic and phosphonic acids as dopants of conductive polyaniline films and conductive composite material based on polyaniline, U.S. Patent 7,014,794, issued March 21, 2006. [16] M.G. Han, Y.J. Lee, S.W. Byun, S.S. Im, Physical properties and thermal transition of polyaniline film, Synth. Met. 124 (2001) 337–343. [17] M.M. Ayad, E.A. Zaki, Doping of polyaniline films with organic sulfonic acids in aqueous media and the effect of water on these doped films, Eur. Polym. J. 44 (2008) 3741–3747. [18] M. Sniechowski, D. Djurado, B. Dufour, P. Rannou, A. Pron, Direct analysis of lamellar structure in polyaniline protonated with plasticizing dopants, Synth. Met. 143 (2004) 163–169. [19] N.M. Hosny, N. Nowesser, A.S. Al Hussaini, M. Sh Zoromba, Solid state synthesis of hematite nanoparticles from doped poly o-aminophenol (POAP), J. Inorg. Organomet. Polym. Mater. 26 (2016) 41–47. [20] M. Sh. Zoromba, N.M. Hosny, Synthesis of Fe2O3, Co3O4 and NiO nanoparticles by thermal decomposition of doped polyaniline precursors, J. Therm. Anal. Calorim. 119 (2015) 605–611. [21] M. Sh Zoromba, A.A.M. Belal, A.E.M. Ali, F.M. Helaly, A.A. Abd El-Hakim, A.S. Badran, Preparation and characterization of some NR and SBR formulations containing different modified kaolinite, Polym.-Plast. Technol. Eng. 46 (2007) 529–535. [22] N.M. Hosny, N. Nowesser, A.S. Al-Hussaini, M. Sh. Zoromba, Doped copolymer of polyanthranilic acid and o-aminophenol (AA-co-OAP): synthesis, spectral characterization and the use of the doped copolymer as precursor of α-Fe2O3 nanoparticles, J. Mol. Struct. 1106 (2016) 479–484. [23] J. Deng, C. He, Y. Peng, J. Wang, X. Long, P. Li, A.S.C. Chan, Magnetic and conductive Fe3O4–polyaniline nanoparticles with core–shell structure, Synth. Met. 13 (2003) 295–301.
ε1 (ω)
through conduction. The real and imaginary dielectric constants ε1 (ω) and ε2 (ω) are related to the refractive index nr (ω) and the extinction coefficient ke (ω) by the equations [54]:
ε1 (ω) = nr2 (ω) − ke2 (ω)
(12)
and
ε2 (ω) = 2nr (ω) ke (ω)
(13)
Fig. 11 shows the variation of both ε1 (ω) and ε2 (ω) values for the PANAA/magnetite thin films as a function of photon energy. The spectrum of ε2 (ω) is characterized by the presence of one peak at 0.015, 0.043 and 0.055 for L1, L2 and L3 films respectively at a photon energy 3.65 eV. The values of ε1 (ω) were 2.97, 2.12 and 1.60 for L1, L2 and L3 films respectively at the same photon energy values. The ε2 (ω) values of the PANAA/magnetite composite thin films increased with increasing the PANAA contents. On contrary, the ε1 (ω) values decreased with increasing the PANAA contents. Fig. 12 displays the dependence of the real and imaginary parts of the optical conductivity on the incident photon energy. The optical conductivity gives an indication to the optical response of the material is defined by the equation: σ (ω) = σ1 (ω) + i σ2 (ω) (14) The data show that at a photon energy 3.65 eV, the relationship between the real optical conductivity σ1 (ω) with photon energy (hν) is characterized by existing one peak at 3.73, 20.99 and 26.98 Ω−1 cm−1 for L1, L2 and L3 film respectively. While, σ2 (ω) the imaginary part of the optical conductivity decreases with increasing PANAA layer thickness. The values of σ2 (ω) are 1458.75, 1037.87 and 784.09 Ω−1 cm−1 for L1, L2 and L3 films, respectively, at a photon energy 3.65 eV. The optical conductivity increases with increasing PANAA thickness at all values of photon energy. The increase in optical conductivity may be attributed to the high absorbance coefficient associated with increasing film thickness as shown in Fig. 10. The optical conductivity is directly proportional to the absorption coefficient and are related by the equation [55]: αn C σ = 4πr (15)where C is speed of light,α is the absorption coefficient, and nr is the refractive index. The optical and electrical properties of the prepared PANAA/magnetite nanocomposite films allow the material for promising photovoltaic applications, solar cells and optoelectronic devices. 4. Conclusions PANAA/magnetite nanocomposites were successfully fabricated by using surface initiated polymerization method (SIP). Thermal stability of PANAA was remarkably enhanced in the presence of magnetite nanoparticles in the range of 300–800 ° C. Increasing the amount of 42
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hybridization to DNA-functionalized surfaces, Langmuir 21 (2005) 3096–3103. [41] B.Y. Yu, S. Kwak, Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structure, J. Mater. Chem. 20 (2010) 8320–8328. [42] M.J. Iqbal, M.N. Ashiq, I.H. Gul, Physical, electrical and dielectric properties of Casubstituted strontium hexaferrite (SrFe12O19) nanoparticles synthesized by co-precipitation method, J. Magn. Magn. Mater. 322 (2010) 1720–1726. [43] A. Ibrahim, A.F. Al-Hossainy, Thickness dependence of structural and optical properties of novel 2- ((1,1-bis(diphenylphosphino)-2-phenylpropan-2-yl)-chromiumtetracarbonyl-amino)-3-phenyl-propanoic acid copper (II) (DPP-Cr-Palan-Cu) nanocrystalline thin film, Synth. Met. 209 (2015) 389–398. [44] H. B-Senturk, J. Choi, E. Oral, J.H. Kung, C.E. Macias, G. Braithwaite, O.K. Muratoglu, The effect of polyethylene glycol on the stability of pores in polyvinyl alcohol hydrogels during annealing, Biomaterials 29 (2008) 141–149. [45] A.M. Badr, A.A. EL-Amin, A.F. Al-Hossainy, Synthesis and optical properties for crystals of a novel organic semiconductor [Ni(Cl)2{(Ph2P)2CHC(R1R2)NHNH2}], Eur. Phys. J. B – Condens. Matter Complex Syst. 53 (2006) 439–448. [46] A.M. Badr, A.A. El-Amin, A.F. Al-Hossainy, Elucidation of charge transport and optical parameters in the newly 1CR-dppm organic crystalline semiconductors, J. Phys. Chem. C 112 (2008) 14188–14195. [47] A.F. Al-Hossainy, Synthesis, spectral, thermal, optical dispersion and dielectric properties of nanocrystalline dimer complex (PEPyr–diCd) thin films as novel organic semiconductor, Bull. Mater. Sci. 39 (2016) 209–222. [48] W.E. Mahmoud, A.A. Al-Ghamdi, S. Al-Heniti, S. Al-Ameer, The influence of temperature on the structure of Cd-doped ZnO nanopowders, J. Alloys Compd. 491 (2010) 742–746. [49] R. Wen, L. Wang, X. Wang, G.H. Yue, Y. Chen, D.L. Peng, Influence of substrate temperature on mechanical, optical and electrical properties of ZnO:Al films, J. Alloys Compd. 508 (2010) 370–374. [50] M. Dutta, S. Mridha, D. Basak, Effect of sol concentration on the properties of ZnO thin films prepared by sol–gel technique, Appl. Surf. Sci. 254 (2008) 2743–2747. [51] E.F. Keskenler, G. Turgut, S. Dogan, Investigation of structural and optical properties of ZnO films co-doped with fluorine and indium, Superlatt Microstruct. 52 (2012) 107–115. [52] I. Studenyak, M. Kranjčec, M. Kurik, Urbach rule in solid state physics, Int. J. Opt. Appl. 4 (2014) 76–83. [53] A.E. Kandjani, M.F. Tabriz, O.M. Moradi, H.R. Mehr, S.A. Kandjan, M.R. Vaezi, An investigation on linear optical properties of dilute Cr doped ZnO thin films synthesized via sol–gel process, J. Alloys Compd. 509 (2011) 7854–7860. [54] A.F. Al-Hossainy, A. Ibrahim, Structural, optical dispersion and dielectric properties of novel chromium nickel organic crystalline semiconductors, Mater. Sci. Semicond. Process. 38 (2015) 13–23. [55] P. Sharma, S.C. Katyal, Determination of optical parameters of a-(As2Se3) 90Ge10 thin film, J. Phys. D: Appl. Phys. 40 (7) (2007) 2115–2120.
[24] M. Sh Zoromba, S. Alghool, S.M.S. Abdel-Hamid, M. Bassyouni, M.H. Abdel-Aziz, Polymerization of aniline derivatives by K2Cr2O7 and production of Cr2O3 nanoparticles, Polym. Adv. Technol. 28 (2017) 842–848. [25] Z. Zhang, M. Wan, Nanostructures of polyaniline composites containingnanomagnet, Synth. Met. 132 (2003) 205–212. [26] M. Sh. Zoromba, M.I.M. Ismail, M. Bassyouni, M.H. Abdel-Aziz, N. Salah, A. Alshahrie, A. Memic, Fabrication and characterization of poly (aniline-co-o-anthranilic acid)/magnetite nanocomposites and their application in wastewater treatment Colloids and Surfaces A: Physicochem, Eng. Aspects 520 (2017) 121–130. [27] B.D. Cullity, C.D. Graham, Ferromagnetism, Introduction to magnetic materials, 2nd ed., John Wiley, Hoboken, NJ, 2009. [28] M. Wan, W. Zhou, J. Li, Composite of polyaniline containing iron oxides with nanometer size, Synth. Met. 78 (1996) 27–31. [29] M. Sh Zoromba, M.H. Abdel-Aziz, Ecofriendly method to synthesize poly (ο-aminophenol) based on solid state polymerization and fabrication of nanostructured semiconductor thin film, Polymer 120 (2017) 20–29. [30] T. Challier, R.C. Slade, Nanocomposite materials: polyaniline-intercalated layered double hydroxides, J. Mater. Chem. 4 (1994) 367–371. [31] S. Wan, J. Huang, H. Yan, K. Liu, Size-controlled preparation of magnetite nanoparticles in the presence of graft copolymers, J. Mater. Chem. 16 (2006) 298–303. [32] B.Y. Yu, S.-Y. Kwak, Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structure, J. Mater. Chem. 20 (2010) 8320–8328. [33] Y. Hou, H. Kondoh, M. Shimojo, E.O. Sako, N. Ozaki, T. Kogure, T. Ohta, Inorganic nanocrystal self-assembly via the inclusion interaction of β-cyclodextrins: toward 3D spherical magnetite, J. Phys. Chem. B 109 (2005) 4845–4852. [34] D. Yu, X. Sun, J. Zou, Z. Wang, F. Wang, K. Tang, Oriented assembly of Fe3O4 nanoparticles into monodisperse hollow single-crystal microspheres, J. Phys. Chem. B 110 (2006) 21667–21671. [35] C. Cheng, Y. Wen, X. Xu, H. Gu, Tunable synthesis of carboxyl-functionalized magnetite nanocrystal clusters with uniform size, J. Mater. Chem. 19 (2009) 8782–8788. [36] R. Massart, Preparation of aqueous magnetic liquids in alkaline and acidic media, IEEE Trans. Magn. 17 (1981) 1247–1248. [37] T. Ozkaya, M.S. Toprak, A. Baykal, H. Kavas, Y. Köseoğlu, B. Aktaş, Synthesis of Fe3O4 nanoparticles at 100C and its magnetic characterization, J. Alloys Compd. 472 (2009) 18–23. [38] D.K. Kim, Y. Zhang, J. Kehr, T. Klason, B. Bjelke, M. Muhammed, Characterization and MRI study of surfactant-coated superparamagnetic nanoparticles administered into the rat brain, J. Magn. Magn. Mater. 225 (2001) 256–261. [39] Y. Cha, M. Kim, Y. Choa, J. Kim, B. Nam, J. Lee, D.H. Kim, K.H. Kim, Synthesis and characterizations of surface-coated superparamagentic magnetite nanoparticles, IEEE Trans. Magn. 46 (2010) 443–446. [40] D.B. Robinson, H.H.J. Persson, H. Zeng, G. Li, N. Pourmand, S. Sun, S.X. Wang, DNA-functionalized MFe2O4 (M = Fe, Co, or Mn) nanoparticles and their
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Research paper
Conductive thin films based on poly (aniline-co-o-anthranilic acid)/ magnetite nanocomposite for photovoltaic applications
MARK
⁎
M. Sh. Zorombaa,b, , A.F. Al-Hossainyc,d, M.H. Abdel-Aziza,e a
Chemical and Materials Engineering Department, King Abdulaziz University, Rabigh 21911, Saudi Arabia Chemistry Department, Faculty of Science, Port-Said University, 42521 Port-Said, Egypt c Chemistry Department, Faculty of Science – New valley, Assiut University, 71516 Assiut, Egypt d Chemistry Department, Faculty of Science, North boarder University, Arar, 1321, Saudi Arabia e Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt b
A R T I C L E I N F O
A B S T R A C T
Keywords: Thin film Magnetic nanocomposite Conducting polymers Thermal evaporation Optical properties
In this research, magnetite particles in a nanoscale were coated with three various weight percentages of poly (aniline co-o-anthranilic acid) copolymer. Aniline and o-anthranilic acid monomers were copolymerized in the presence of Fe3O4 nanoparticles via surface initiated polymerization method. Characterization of nanocomposites was carried out by several analysis techniques including; FT-IR, FE-SEM, TEM, XRD, TGA and UV–vis-Near infrared. FT-IR results showed that pended COOH groups of PANAA are physically interacted to magnetite nanoparticles. Magnetite nanoparticles enhanced the thermal strength of the nanocomposites in the range of 300–800 °C. The XRD analysis revealed that the average crystallite size ranges from 7.59 to 11.14 nm depending on PANAA weight percentage. Thin films of uniform spherical shape of PANAA/magnetite nanocomposite were fabricated by thermal evaporation technique. The values of Eg(direct) and Eg(indirect) decreased with increasing the thickness of PANAA, while the conductivity increased with increasing of PANAA thickness coated magnetite particles. The conductivity value ranged from 3.73 to 26.98 Ω−1 cm−1 at a photon energy 3.65 eV. Using the nanocomposites in photovoltaic applications was highlighted.
1. Introduction Optically transparent and electrically conductive polymers have been attractive in the past two decades due to their benefits in various applications including solar cells, electrostatic dissipation, electromagnetic shielding, sensors, touch-sensitive screens, and alarm devices [1,2]. Furthermore, conducting polymers/magnetic nanocomposite have attracted great attention of the scientific community currently due to its high potential of technological industrial applications in various areas, such as electromagnetic interference shielding [3], rechargeable batteries [4], corrosion protection coatings [5], electrodes [6], gas separating membranes [7,8], microwave absorption [9], sensors [10–12], and microelectronic devices [13,14]. PANI as any conjugated polymer has some characteristics related to its molecular structure and bond alternation make the polymer infusible, insoluble in organic solvents and cannot be handled like thermoplastic polymers [15,16]. The problem of difficult solubility in organic solvent has been solved by using various functionalized dopants [15–18]. Other researchers enhanced the PANI solubility by introducing another o-anthranilic acid monomer through PNAI backbones [19–21]. Unique magnetic and electrical
⁎
properties can be achieved by preparing PANI/Fe3O4 nanocomposites where polyaniline nanocomposites can be reinforced with different weights of Fe3O4 nanoparticle. Wet chemical method and surface initiated polymerization (SIP) method have been used for this purpose. The resulting magnetic polyaniline nanocomposites have a higher saturation magnetization of 72 emu/g and a conductivity around 10–4 S/ cm. PANI and its nanocomposites display a negative permittivity [22–25]. Poly(aniline co-o-anthranilic acid)/Fe3O4 nanocomposites have prepared by applying surface initiated polymerization (SIP) method for wastewater applications [26]. In the current study the aim is to cover magnetite nanoparticles with different amounts of PANAA using surface initiated polymerization method (SIP) and to prepare PANAA/magnetite nanocomposite thin films. The nanocomposite consists of organic (PANAA) and inorganic (magnetite) parts, the presence of magnetite in the composite will improve the dielectric constant and improve the efficiency if the material is used in photovoltaic cells. The study aims also to investigate the applicability of the thin films in photovoltaic applications. Photovoltaic material must fulfil two conditions, namely: (i) absorb incident photons through the promotion of electrons to higher energy levels, and (ii) contain an internal electric
Corresponding author at: Chemical and Materials Engineering Department, King Abdulaziz University, Rabigh 21911, Saudi Arabia. E-mail address: [email protected] (M.S. Zoromba).
http://dx.doi.org/10.1016/j.synthmet.2017.06.021 Received 25 April 2017; Received in revised form 22 June 2017; Accepted 28 June 2017 0379-6779/ © 2017 Elsevier B.V. All rights reserved.
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Nomenclature A Ao a, b, c B C D Dm Dc d Eg EI EU H hv h, k, l K kB ke
M Ms m nr R T α αo εo ε1 ε2 θ λ μ ρ σ σ1 σ2 ω
Absorbance Energy-independent constant Lattice constants Full width at half maximum intensity Speed of light Magnetic particle diameter Magnetic domain size Crystal size Interplanar spacing Band gap Constant Urbach energy Magnetic field strength Photon energy Miller indices Constant (0.94) Boltzmann constant Extinction coefficient
field that accelerates the promoted electrons in a particular direction, resulting in an electrical current. To this end the optical and electrical properties of the nanocomposites were studied.
Magnetization Saturation magnetization Constant Refractive index Reflectance Temperature Absorption coefficient Constant Free space dielectric constant Real dielectric constant Imaginary dielectric constant Bragg angle X-ray wavelength True magnetic moment Nanocomposite density Optical conductivity Real part of optical conductivity Imaginary part of optical conductivity Angular frequency
700 rpm at room temperature. Separately, 1.37 g o-anthranilic acid was dissolved in 30 ml ethanol then added to aniline solution. 40 ml purified water were added to the co-monomers. The co-monomers’ solution was directly mixed to the magnetite dispersion obtained from the previous step. The magnetite/co-monomers mixture was kept in an ice box to maintain the temperature 0–5 °C under magnetic stirring at 700 rpm for 30 min. 60 ml 1 M K2Cr2O7 initiator was added drop wisely to the magnetite/co-monomers mixture for 1 h under the above conditions. During the polymerization process the copolymer was gradually observed to coat the magnetite nanoparticles. The resulting PANAA/ magnetite nanocomposite was filtrated using a Buchner funnel and washed with distilled water frequent times, followed by ethanol to remove excess oxidant, unreacted monomers and oligomer. Washing continued until the filtrate (liquid) become almost colorless and then the sample was oven dried at 80 ° C for 24 h. The resulting composite was labeled by L1. The second weight of PANAA prepared to coat magnetite nanoparticles was obtained according to the same procedure of the first weight except using twofold amount of the aniline and oanthranilic acid in comparing with the first weight (1.86 g aniline and 2.74 g o-anthranilic acid) and subsequently the twofold amounts of HCl and initiator used as well. The resulting PANAA/magnetite composite was labeled by L2. The third weight of PANAA was also obtained according to the same previous procedure of the first weight except using twofold amounts of the aniline and o-anthranilic acid as for the second weight to be (3.72 g aniline and 5.48 g o-anthranilic acid) and of course, twofold of amounts HCl and an initiator was used as well. The resulting nanocomposite was labeled by L3. The typical composition of the three nanocomposites are listed in Table 1.
2. Experimental 2.1. Materials All chemical substances were used as received without any additional treatment excluding aniline. Double distillations of aniline were carried out before use and it was kept in a dark bottle. Aniline and oanthranilic acids were bought from Aldrich, potassium dichromate (Merck), ammonia solution and hydrochloric acid (Aldrich). Iron (II) chloride tetrahydrate, iron (III) chloride hexahydrate, hydrochloric acid (HCl) and ethanol of analytical grade were purchased from Shanghai chemicals. 2.2. Synthesis of magnetite nanoparticles Typically, 50 ml of 0.2 M FeCl3·6H2O were mixed with 25 ml of 0.2 M FeCl2·4H2O solution under magnetic stirring. Separately, 40 ml (33%v/v) ammonia solution was diluted with 20 ml distilled water. Subsequently, diluted ammonia solution was added to previous iron (Fe3+/Fe2+) salts drop by drop at room temperature and 800 rpm. Gradually, a black precipitate of magnetite was gradually appeared. The resulting magnetite dispersion was diluted with additional 200 ml of distilled water. The obtained dispersion was left to settle down under gravitational force. Washing process was carried out by decantation method for several times. A magnetite nanoparticle was kept in the mother liquor (total volume 40 ml distilled water) as a dispersion. The magnetite dispersion in the mother liquor was kept for using in the next step of the polymerization process with aniline and o-anthranilic acid co-monomers. A separate experiment to estimate the weight of magnetite was conducted following the same aforementioned procedure and the resulting magnetite was separated by filtration and then dried. The weight of the resulting magnetite (blank sample) was found to be 1.4 g.
2.4. Preparation of PANAA/magnetite nanocomposite thin films Thin films of PANAA/magnetite nanocomposites were fabricated by thermal evaporation method using a high vacuum coating unit Table 1 Composition of three different PANAA/magnetite nanocomposites. Co-polymer
Ratio (aniline and oanthranilic acid)
Weight of the resulting polymer composite (gram)
% weight of Fe3O4
PANAA (L1) PANAA (L2) PANAA (L3)
(0.93 g and 1.37 g) (1.86 g and 2.74 g) (3.72 g and 5.48 g)
2.43 3.12 4.76
36.55% 30.97% 22.73%
2.3. Synthesis of PANAA/Magnetite nanocomposite Three different weights of PANAA were polymerized onto the magnetite surface. The first weight of PANAA was obtained as follows: 8 ml conc. HCl was added to 0.93 g aniline under magnetic stirring at 35
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(Edwards E 306 A, England). The vacuum through the deposition process is adjusted at 1 × 10−4 Pa. Optical flat quartz substrates were used for thin films deposition. The substrates were washed carefully by chromic acid for 15 min followed by rinsing with deionized water. The powder of PANAA/magnetite was sublimated from a quartz crucible heated gradually by molybdenum boat shaped filament. A built-in quartz crystal thickness monitor (Model TM-350 MAXTEK, Inc. USA) was used to measure the deposition rate and the film thickness. The thickness of PANAA/magnetite nanocomposites films were 205, 230, 215 nm for L1, L2 and L3 respectively. Two repeated series of PANAA/ magnetite nanocomposite thin films were placed onto optically flat quartz substrates for examination by spectrophotometric and X-ray diffractometer.
located at 1585 cm−1 and 1514 cm−1. These peaks can be ascribed to the C ] C vibrations of quinoid and benzenoid units through the copolymer chains [26]. The existence of the absorption band at 1398–1402 cm−1 can be attributed to CeN stretching vibrations of benzenoid-quinoid-benzenoid sequence [28,29]. The absorption band at 1670–1676 cm−1 for all PANAA/magnetite can be attributed to C] O group. The strong band at 1150 cm−1 is a characteristic for emeraldine salt (doped with chloride ion). The absorption bands at 1502, 1500, 1496 cm−1 for L1, L2 and L3 respectively, can be attributed to the stretching band of quinoid structure through the copolymer backbone. The bands of symmetric vibrations s(OCO) at 1390–1337 cm−1 were detected for all nanocomposites.
2.5. Characterization
3.2. Thermal analysis of PANAA/magnetite nanocomposite powders
2.5.1. FTIR Infrared spectra were recorded on a Perkin–Elmer FT-IR type 1650 spectrophotometer in a wave number range 4000–400 cm−1.
Fig. 2 shows that the thermal decomposition of PANAA/magnetite nanocomposites were carried out through four stages. The first stage within the temperature range of 50–125 °C. The weight loss of around 8% for all nanocomposites L1, L2 and L3 which can be attributed to the loss of water molecules, trapped in the copolymer chains in the nanocomposite. The second stage within the temperature range of 300–400 ° C is due to the removal of CO2 molecules from the copolymer chains loaded onto magnetite (L1, L2 and L3). In the third stage, the weight loss was observed in the three composites after 640 °C which corresponds to the thermo-oxidative degradation of the polymer chain, similar results was reported by Challier et al. [30]. The thermal stability of the composites increases through the first and second stages taking the following order L1 < L2 < L3. This means that by amount of PANAA around magnetite nanoparticles, the thermal stability was significantly improved. This can be attributed to increasing hydrogen bonding and Van Der Waals interactions between the carboxylic, imine groups from PANAA chains with magnetite nanoparticles. The remaining percentages of the magnetite nanocomposites in the third decomposition stage takes the following order L3 < L2 < L1 which can be ascribed to the high contents of iron oxide in the nanocomposites as shown previously in Table 1. The Dr.TGA curves for PANAA/magnetite nanocomposites are shown in Fig. 2. The water is evolved at 92.4, 123.62 and 110.67 °C for L1, L2 and L3 respectively. No water vapor is lost above 130 °C. Decomposition takes place in three steps with the loss of water in the first step, 395.56, 368.81 and 378.54 °C for L1, L2 and L3, respectively, this may be attributed to the removal of carbon dioxide in the second step. However, the endothermic peaks at 753.08, 711.79 and 720.95 °C in the third step may be attributed to thermo-oxidative degradation of the polymer chain for L1, L2 and L3 respectively.
2.5.2. TGA Thermal stability was studied by TGA (TA Instruments − Q50, USA). Thermal decomposition process was applied under N2 atmosphere from 30 to 800 ° C (heating rate was 20 ° C/min). 2.5.3. Magnetic properties Magnetic properties of PANAA/magnetite nanocomposite powders were evaluated by using a Micro-Sense Easy VSM Software Version Easy VSM 20150927-01, in an applied field range of 0–18 kOe. Magnetic particle diameter was calculated by fitting the magnetization curve to the Langevin function of magnetization [27]:
μH ⎞ ⎛ kB T ⎞ M = coth ⎛ −⎜ ⎟, k Ms ⎝ B T ⎠ ⎝ μH ⎠ ⎜
⎟
(1)
where M is the magnetization for a field strength H, Ms is the saturation magnetization, kB is the Boltzmann constant, the true magnetic moment of each particle μ = MsπD3/6 and D is the magnetic particle diameter. Magnetic measurements were conducted in the solid state at room temperature. 2.5.4. XRD The structure of the composites was investigated by a Philips X-ray diffractometer (model X’pert) with monochromatic Cu Kα radiation operated at 40 kV and 25 mA. Powder diffractometers typically used the Bragg Brentano geometry. The diffraction patterns were recorded with 6° per minute in the range 0–80° of 2θ range. Divergence slit (DS) and the receiving slit (RS) were adjusted at 1° and 0.2 mm, respectively. 2.5.5. Morphology study The morphology of the prepared composite surfaces was determined by scanning electron microscopy (SEM; Inspect S, FEI, Holland), operated at an accelerating voltage of 3.0 kV. The samples were coated by platinum under vacuum. 2.5.6. UV–vis-near infrared measurements The spectra measurements of the thin films were recorded in the range 200–900 nm by using SHIMADZU UV-3101 UV–vis–NIR pc spectrophotometer at room temperature. 3. Results and discussion 3.1. FTIR of PANAA/magnetite nanocomposite powders The FT-IR spectra of PANAA/Fe3O4 nanocomposites are presented in Fig. 1. The spectra of L1, L2 and L3 have two major absorption peaks
Fig. 1. FTIR spectra PANAA/magnetite nanocomposite powders (L1, L2 and L3).
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Fig. 2. TGA and Dr. TGA of PANAA/magnetite nanocomposite powders (L1, L2 and L3).
The cell constants (a, b and c), d-spacing (d) and crystallite size (Dc) were calculated by the formulae [42]:
3.3. Magnetic VSM properties of synthesized PANAA/magnetite composite powders Fig. 3 shows the magnetization (M–H) curve of PANAA/magnetite. The magnetization curve of PANAA/magnetite composites showed nonlinear, reversible characteristics without hysteresis, and exhibiting only superparamagnetic behavior [30]. The value of the magnetic saturation based on VSM data, Ms were found to be 278.70 × 10−2, 186.39 × 10−2 and 885.20 × 10−3 emu g−1 for L1, L2 and L3 respectively. With increasing the contents PANAA around magnetite particles, the magnetization of the resulting composites decreased (pure magnetite has 84.5 emu g-1) [31–35]. The average magnetic particle size obtained by fitting the slope of magnetization near zero-field region, dM/DH)H→0 from the M–H curve as shown in Fig. 3. The magnetic domain size, Dm was calculated from magnetization curve with the equation [36–38]:
(3)
2dsinθ = nλ
(4)
Kλ Bcosθ
(5)
⎜
Dc =
⎟
where K is a constant and equals to 0.94, λ is the X-ray wavelength, B full width at half maximum intensity. The values of lattice constants (a, b and c) of nanocomposites powder are shown in Fig. 4. The results show that the formation of monoclinic crystal system with non-centrosymmetric space group of P21 of the crystal and the estimated cell parameters are, a = 8.832 Å, b = 9.178 Å, c = 11.576 Å, γ = α = 90°, β = 104.52°. The Bragg reflection peaks are relatively broad due to the small
1/3
18kB T (dM / dH ) H → 0 ⎞ Dm = ⎜⎛ ⎟ ρMs2 ⎝ π ⎠
1 1 ⎛ h2 k 2sin2B l2 2hlcosB ⎞ l2 = + + 2 − + 2 d2 sin2B ⎝ a2 b2 c ac ⎠ c
(2)
where kB is the Boltzmann constant T is absolute temperature, ρ is the density of the nanocomposite (4.5 g cm−3) and the Ms represents the saturation magnetization value. The values of Dm for the synthesized composites were found to be 10.92, 8.50 and 7.38 nm for L1, L2 and L3 respectively. The values of magnetic moment decreases with decreasing of magnetite percentage. The decrease in the magnetic moment value is due to the reduction in saturation magnetization as the magnetic moment and saturation magnetization are directly related to each other. The saturation magnetization and magnetic moment data are in agreement with each other [38,39]. 3.4. XRD of PANAA/magnetite composite thin films Fig. 4 shows the WXRD patterns of PANAA/magnetite nanocomposites thin film. The thin film particles has several relatively strong well-defined reflection peaks in the 2θ region of 10–80°. Similar results of pure-phase magnetite particles were reported in previous studies [40]. Based on the Joint Committee on Powder Diffraction Standards (JCPDS) No. 19-0629, the resulting peaks confirm the formation of magnetite (Fe3O4) [41].
Fig. 3. Magnetization curve of PANAA/magnetite nanocomposite powders (L1, L2 and L3).
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Fig. 4. X-Ray diffraction patterns of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
3.5. Morphology study of PANAA/magnetite nanocomposite thin films
dimensions of the nanostructure thin films (Eq. (4)), where (n) is a positive integer, (λ) is the wavelength of incident wave and d is the spacing between layers of atoms. The crystallite size (Dc) of the nanocomposites thin films were determined using the Scherer’s equation (Eq. (5)). The average crystallite size of nanostructured thin films are 11.14, 8.75, and 7.59 nm for L1, L2 and L3, respectively. The crystallite domain size of the nanocomposites particles based on the breadth of (111), (220), (311), (400), (422), (511) and (440) reflection was determined by Debye–Scherer formalism of WXRD results. The average crystallite size of PANAA/magnetite thin film decreased with increasing copolymer contents around the magnetite particles from L1 to L3.
Fig. 5 shows FE-SEM images of the nanostructured thin film. The particles within the deposited film have a uniform spherical shape and display highly monodisperse with an average diameter of 40 nm. 3.6. Optical properties of the PANAA/magnetite nanocomposite thin films The UV–vis absorption spectra of PANAA/magnetite nanocomposite thin films are shown in Fig. 6. The absorbance increases with increasing PANAA thickness around the magnetite particles. An absorption band is located at 340 nm, which assigned to π-π* electronic transition of copolymer PANAA thin film [43,44]. Fig. 5. FE-SEM image of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 6. The absorption spectra of the PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
Table 2 Optical properties of PANAA/magnetite nanocomposite thin films (λ = 450 nm). Film
Thickness, nm
%T
Eg(direct)(eV)
Eg(indirect)(eV)
Eu (eV)
nr
ke
L1 L2 L3
205 230 275
93.33 79.43 73.88
3.21 3.11 2.91
3.38 3.44 3.41
2.52 5.97 7.52
1.84 1.81 1.67
5.24 × 10−4 1.56 × 10−3 6.12 × 10−3
Fig. 7. The extinction coefficient (ke) and the refractive index distributions (nr) of PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 8. The allowed direct band gap for PANAA/magnetite nanocomposite thin films (L1, L2 and L3). Fig. 10. The variation of ln (α) versus hν for PANAA/magnetite nanocomposite thin films (L1, L2 and L3).
The extinction coefficient (ke) was calculated using the relation: (6)
ke = αλ /4π
R was calculated using the relation [46]:
where α is the absorption coefficient, defined as the absorbance (A) divided by the film thickness. The values of measured film thickness were 205, 230, and 275 nm for L1, L2 and L3 respectively. The percentages of transmittance (%T) at λ = 450 nm are given in Table 2. The data show that the%T of the PANAA/magnetite nanocomposite films decreases with increasing PANAA coated layer thickness. Fig. 7 displays the plots of (ke) versus the wavelength (λ) and the refractive index (nr) versus the wavelength (λ). The refractive index (nr) was calculated by using the reflectance (R) and the extinction coefficient (ke) of the considered films [45]:
nr = [(1 + R)/(1 − R)] +
⎡ 4R ⎤ − k 2 e 2 ⎢ ⎣ (1 − R) ⎥ ⎦
R=1−
(Texp (A)
(8)
The values of nr at λ = 450 nm are listed in Table 2. The nr value increases with increasing of PANAA layer thickness. The band gap (Eg) values of the produced films were calculated from the optical absorption spectra based on the equation [47]:
αh ν = Ao (h ν − Eg )m
(9)
where hν is the photon energy, m is assumed values of 1/2 and 2 for allowed direct and allowed indirect transitions, respectively [48,49]. Aois an energy independent constant having values between 1 × 105 and 1 × 106 (cm eV)−1 [50,51]. The values of the allowed direct Eg(direct) and the allowed indirect Eg(indirect) optical band gaps were
(7)
Fig. 9. The allowed indirect band gap for PANAA/ magnetite nanocomposite thin films (L1, L2 and L3).
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Fig. 11. The real and imaginary parts of the dielectric constant of PANAA/magnetite thin films (L1, L2 and L3).
Fig. 12. Spectral dependence of the real and imaginary parts of optical conductivity of the PANAA/ magnetite nanocomposite thin films (L1, L2 and L3).
calculated by extrapolating the linear portion of the plots of (αhν)2 versus hν and that of square root (αhν) versus hν to (αhν)2 = 0 and square root (αhν) = 0, respectively. Figs. 8 and 9 show the plots of allowed direct and indirect band gap for the PANAA/magnetite nanocomposite films. The linear dependence of both (αhν)2 and (αhν)1/2 on (hν) at higher photon energies indicates to both the direct and indirect optical transitions are possible for the films. The straight-line portion of the curves is extrapolated to zeros to give the optical band gap, Eg(direct) and Eg(indirect), and the resulting values are listed in Table 2. Both Eg(direct) and Eg(indirect) decreased with
increasing the amount of PANAA copolymer, and accordingly the conductivity increases with increasing of PANAA amount around magnetite particles. Urbach energy (EU) refers to the width of the exponential absorption edge. The EU is calculated using the relation [52]:
α = αo exp[(h ν − EI )/ EU ]
(10)
where EI and αo are constants. Fig. 10 shows the variation of ln(α) versus hν for PANAA/magnetite thin films. The EU values were calculated from the slopes of Fig. 10 using the relationship: 41
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EU = (d(ln α)/dhν)−1
(11)
PANAA around magnetite particles leads to increasing the conductivity and decreasing the percentage of transmittance (%T) and Both Eg(direct) and Eg(indirect). The real part of the optical dielectric constants ε1 (ω) was found to be 59 times of the imaginary part of dielectric constants ε2 (ω) . The loss factor ranged from 5.05 × 10−3 to 34.37 × 10−3 indicating low power dissipation of the PANAA/magnetite nanocomposite. The imaginary part of the optical conductivity of the PANAA/magnetite nanocomposite films was found to be 63 times of the real part.
and the obtained EU values are listed in Table 2. EU values of the PANAA/magnetite thin films increased with increasing of the PANAA layer thickness. The increase of EU value leads to a rearrangement of states from band to tail, and thus allows for a large number of possible bands to tail and tail-to-tail transitions [53]. 3.7. Dielectric properties and optical conductivity The dielectric constant is an essential inherent characteristic of photovoltaic material. The real part of the dielectric constant ε1 (ω) gives an indication to how considerable it will sluggish the speed of light in the material and the imaginary part ε2 (ω) gives an indication to how a dielectric absorbs energy from an electric field due to dipole motion. The knowledge of the values of real and imaginary parts of the dielectric constant make it possible to estimate the loss factor which is the ratio ε2 (ω) and is a measure of the loss of energy in a dielectric material
Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.synthmet.2017.06.021. References [1] R.G. Gordon, Criteria for choosing transparent conductors, MRS bulletin 25 (2000) 52–57. [2] Y. Wang, X. Jing, Transparent conductive thin films based on polyaniline nanofibers, Mater. Sci. Eng.: B 138 (2007) 95–100. [3] T. Mäkelä, S. Pienimaa, T. Taka, S. Jussila, H.H. Isotalo, Thin polyaniline films in EMI shielding, Synth. Met. 85 (1–3) (1997) 1335–1336. [4] S. Kuwabata, S. Masui, H. Yoneyama, Charge–discharge properties of composites of LiMn2O4 and polypyrrole as positive electrode materials for 4 V class of rechargeable Li batteries, Electrochim. Acta 44 (1999) 4593–4600. [5] N. Ahmad, A.G. MacDiarmid, Inhibition of corrosion of steels with the exploitation of conducting polymers, Synth. Met. 78 (1996) 103–110. [6] J.M.G. Laranjeira, W.M. De Azevedo, M.C. Ugulino de Araújo, A conductimetric system based on polyaniline for determination of ammonia in fertilizers, Anal. Lett. 30 (1997) 2189–2209. [7] M.R. Anderson, B.R. Mattes, H. Reiss, R.B. Kaner, Gas separation membranes: a novel application for conducting polymers, Synth. Met. 41 (1991) 1151–1154. [8] B.R. Mattes, M.R. Anderson, J.A. Conklin, H. Reiss, R.B. Kaner, Morphological modification of polyaniline films for the separation of gases, Synth. Met. 57 (1993) 3655–3660. [9] T.L. Rose, S. D'Antonio, M.H. Jillson, A.B. Kon, Rajendran Suresh, F. Wang, A microwave shutter using conductive polymers, Synth. Met. 85 (1997) 1439–1440. [10] A.P.L. Pacheco, E.S. Araujo, W.M. de Azevedo, Polyaniline/poly acid acrylic thin film composites: a new gamma radiation detector, Mater. Charact. 50 (2003) 245–248. [11] A.H. Parente, E.T.A. Marques, W.M. Azevedo, F.B. Diniz, E.H.M. Melo, J.L. Lima Filho, Glucose biosensor using glucose oxidase immobilized in polyaniline, Appl. Biochem. Biotechnol. 37 (1992) 267–273. [12] F.B. Diniz, K.C. de Freitas, W.M. de Azevedo, Salinity measurements with polyaniline matrix coated wire electrodes, Electrochem. Commun. 1 (1999) 271–273. [13] J.M.G. Laranjeira, H.J. Khoury, W.M. de Azevedo, E.F. da Silva Jr., E.A. de Vasconcelos, Conducting polymer/silicon heterojunction diode for gamma radiation detection, Radiat. Prot. Dosim. 101 (2002) 85–88. [14] J.M.G. Laranjeira, H.J. Khoury, W.M. de Azevedo, E.F. da Silva Jr, E.A. de Vasconcelos, Fabrication of high quality silicon–polyaniline heterojunctions, Appl. Surf. Sci. 190 (2002) 390–394. [15] T. Olinga, A. Pron, J. Travers, Use of sulphonic and phosphonic acids as dopants of conductive polyaniline films and conductive composite material based on polyaniline, U.S. Patent 7,014,794, issued March 21, 2006. [16] M.G. Han, Y.J. Lee, S.W. Byun, S.S. Im, Physical properties and thermal transition of polyaniline film, Synth. Met. 124 (2001) 337–343. [17] M.M. Ayad, E.A. Zaki, Doping of polyaniline films with organic sulfonic acids in aqueous media and the effect of water on these doped films, Eur. Polym. J. 44 (2008) 3741–3747. [18] M. Sniechowski, D. Djurado, B. Dufour, P. Rannou, A. Pron, Direct analysis of lamellar structure in polyaniline protonated with plasticizing dopants, Synth. Met. 143 (2004) 163–169. [19] N.M. Hosny, N. Nowesser, A.S. Al Hussaini, M. Sh Zoromba, Solid state synthesis of hematite nanoparticles from doped poly o-aminophenol (POAP), J. Inorg. Organomet. Polym. Mater. 26 (2016) 41–47. [20] M. Sh. Zoromba, N.M. Hosny, Synthesis of Fe2O3, Co3O4 and NiO nanoparticles by thermal decomposition of doped polyaniline precursors, J. Therm. Anal. Calorim. 119 (2015) 605–611. [21] M. Sh Zoromba, A.A.M. Belal, A.E.M. Ali, F.M. Helaly, A.A. Abd El-Hakim, A.S. Badran, Preparation and characterization of some NR and SBR formulations containing different modified kaolinite, Polym.-Plast. Technol. Eng. 46 (2007) 529–535. [22] N.M. Hosny, N. Nowesser, A.S. Al-Hussaini, M. Sh. Zoromba, Doped copolymer of polyanthranilic acid and o-aminophenol (AA-co-OAP): synthesis, spectral characterization and the use of the doped copolymer as precursor of α-Fe2O3 nanoparticles, J. Mol. Struct. 1106 (2016) 479–484. [23] J. Deng, C. He, Y. Peng, J. Wang, X. Long, P. Li, A.S.C. Chan, Magnetic and conductive Fe3O4–polyaniline nanoparticles with core–shell structure, Synth. Met. 13 (2003) 295–301.
ε1 (ω)
through conduction. The real and imaginary dielectric constants ε1 (ω) and ε2 (ω) are related to the refractive index nr (ω) and the extinction coefficient ke (ω) by the equations [54]:
ε1 (ω) = nr2 (ω) − ke2 (ω)
(12)
and
ε2 (ω) = 2nr (ω) ke (ω)
(13)
Fig. 11 shows the variation of both ε1 (ω) and ε2 (ω) values for the PANAA/magnetite thin films as a function of photon energy. The spectrum of ε2 (ω) is characterized by the presence of one peak at 0.015, 0.043 and 0.055 for L1, L2 and L3 films respectively at a photon energy 3.65 eV. The values of ε1 (ω) were 2.97, 2.12 and 1.60 for L1, L2 and L3 films respectively at the same photon energy values. The ε2 (ω) values of the PANAA/magnetite composite thin films increased with increasing the PANAA contents. On contrary, the ε1 (ω) values decreased with increasing the PANAA contents. Fig. 12 displays the dependence of the real and imaginary parts of the optical conductivity on the incident photon energy. The optical conductivity gives an indication to the optical response of the material is defined by the equation: σ (ω) = σ1 (ω) + i σ2 (ω) (14) The data show that at a photon energy 3.65 eV, the relationship between the real optical conductivity σ1 (ω) with photon energy (hν) is characterized by existing one peak at 3.73, 20.99 and 26.98 Ω−1 cm−1 for L1, L2 and L3 film respectively. While, σ2 (ω) the imaginary part of the optical conductivity decreases with increasing PANAA layer thickness. The values of σ2 (ω) are 1458.75, 1037.87 and 784.09 Ω−1 cm−1 for L1, L2 and L3 films, respectively, at a photon energy 3.65 eV. The optical conductivity increases with increasing PANAA thickness at all values of photon energy. The increase in optical conductivity may be attributed to the high absorbance coefficient associated with increasing film thickness as shown in Fig. 10. The optical conductivity is directly proportional to the absorption coefficient and are related by the equation [55]: αn C σ = 4πr (15)where C is speed of light,α is the absorption coefficient, and nr is the refractive index. The optical and electrical properties of the prepared PANAA/magnetite nanocomposite films allow the material for promising photovoltaic applications, solar cells and optoelectronic devices. 4. Conclusions PANAA/magnetite nanocomposites were successfully fabricated by using surface initiated polymerization method (SIP). Thermal stability of PANAA was remarkably enhanced in the presence of magnetite nanoparticles in the range of 300–800 ° C. Increasing the amount of 42
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M.S. Zoromba et al.
hybridization to DNA-functionalized surfaces, Langmuir 21 (2005) 3096–3103. [41] B.Y. Yu, S. Kwak, Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structure, J. Mater. Chem. 20 (2010) 8320–8328. [42] M.J. Iqbal, M.N. Ashiq, I.H. Gul, Physical, electrical and dielectric properties of Casubstituted strontium hexaferrite (SrFe12O19) nanoparticles synthesized by co-precipitation method, J. Magn. Magn. Mater. 322 (2010) 1720–1726. [43] A. Ibrahim, A.F. Al-Hossainy, Thickness dependence of structural and optical properties of novel 2- ((1,1-bis(diphenylphosphino)-2-phenylpropan-2-yl)-chromiumtetracarbonyl-amino)-3-phenyl-propanoic acid copper (II) (DPP-Cr-Palan-Cu) nanocrystalline thin film, Synth. Met. 209 (2015) 389–398. [44] H. B-Senturk, J. Choi, E. Oral, J.H. Kung, C.E. Macias, G. Braithwaite, O.K. Muratoglu, The effect of polyethylene glycol on the stability of pores in polyvinyl alcohol hydrogels during annealing, Biomaterials 29 (2008) 141–149. [45] A.M. Badr, A.A. EL-Amin, A.F. Al-Hossainy, Synthesis and optical properties for crystals of a novel organic semiconductor [Ni(Cl)2{(Ph2P)2CHC(R1R2)NHNH2}], Eur. Phys. J. B – Condens. Matter Complex Syst. 53 (2006) 439–448. [46] A.M. Badr, A.A. El-Amin, A.F. Al-Hossainy, Elucidation of charge transport and optical parameters in the newly 1CR-dppm organic crystalline semiconductors, J. Phys. Chem. C 112 (2008) 14188–14195. [47] A.F. Al-Hossainy, Synthesis, spectral, thermal, optical dispersion and dielectric properties of nanocrystalline dimer complex (PEPyr–diCd) thin films as novel organic semiconductor, Bull. Mater. Sci. 39 (2016) 209–222. [48] W.E. Mahmoud, A.A. Al-Ghamdi, S. Al-Heniti, S. Al-Ameer, The influence of temperature on the structure of Cd-doped ZnO nanopowders, J. Alloys Compd. 491 (2010) 742–746. [49] R. Wen, L. Wang, X. Wang, G.H. Yue, Y. Chen, D.L. Peng, Influence of substrate temperature on mechanical, optical and electrical properties of ZnO:Al films, J. Alloys Compd. 508 (2010) 370–374. [50] M. Dutta, S. Mridha, D. Basak, Effect of sol concentration on the properties of ZnO thin films prepared by sol–gel technique, Appl. Surf. Sci. 254 (2008) 2743–2747. [51] E.F. Keskenler, G. Turgut, S. Dogan, Investigation of structural and optical properties of ZnO films co-doped with fluorine and indium, Superlatt Microstruct. 52 (2012) 107–115. [52] I. Studenyak, M. Kranjčec, M. Kurik, Urbach rule in solid state physics, Int. J. Opt. Appl. 4 (2014) 76–83. [53] A.E. Kandjani, M.F. Tabriz, O.M. Moradi, H.R. Mehr, S.A. Kandjan, M.R. Vaezi, An investigation on linear optical properties of dilute Cr doped ZnO thin films synthesized via sol–gel process, J. Alloys Compd. 509 (2011) 7854–7860. [54] A.F. Al-Hossainy, A. Ibrahim, Structural, optical dispersion and dielectric properties of novel chromium nickel organic crystalline semiconductors, Mater. Sci. Semicond. Process. 38 (2015) 13–23. [55] P. Sharma, S.C. Katyal, Determination of optical parameters of a-(As2Se3) 90Ge10 thin film, J. Phys. D: Appl. Phys. 40 (7) (2007) 2115–2120.
[24] M. Sh Zoromba, S. Alghool, S.M.S. Abdel-Hamid, M. Bassyouni, M.H. Abdel-Aziz, Polymerization of aniline derivatives by K2Cr2O7 and production of Cr2O3 nanoparticles, Polym. Adv. Technol. 28 (2017) 842–848. [25] Z. Zhang, M. Wan, Nanostructures of polyaniline composites containingnanomagnet, Synth. Met. 132 (2003) 205–212. [26] M. Sh. Zoromba, M.I.M. Ismail, M. Bassyouni, M.H. Abdel-Aziz, N. Salah, A. Alshahrie, A. Memic, Fabrication and characterization of poly (aniline-co-o-anthranilic acid)/magnetite nanocomposites and their application in wastewater treatment Colloids and Surfaces A: Physicochem, Eng. Aspects 520 (2017) 121–130. [27] B.D. Cullity, C.D. Graham, Ferromagnetism, Introduction to magnetic materials, 2nd ed., John Wiley, Hoboken, NJ, 2009. [28] M. Wan, W. Zhou, J. Li, Composite of polyaniline containing iron oxides with nanometer size, Synth. Met. 78 (1996) 27–31. [29] M. Sh Zoromba, M.H. Abdel-Aziz, Ecofriendly method to synthesize poly (ο-aminophenol) based on solid state polymerization and fabrication of nanostructured semiconductor thin film, Polymer 120 (2017) 20–29. [30] T. Challier, R.C. Slade, Nanocomposite materials: polyaniline-intercalated layered double hydroxides, J. Mater. Chem. 4 (1994) 367–371. [31] S. Wan, J. Huang, H. Yan, K. Liu, Size-controlled preparation of magnetite nanoparticles in the presence of graft copolymers, J. Mater. Chem. 16 (2006) 298–303. [32] B.Y. Yu, S.-Y. Kwak, Assembly of magnetite nanocrystals into spherical mesoporous aggregates with a 3-D wormhole-like pore structure, J. Mater. Chem. 20 (2010) 8320–8328. [33] Y. Hou, H. Kondoh, M. Shimojo, E.O. Sako, N. Ozaki, T. Kogure, T. Ohta, Inorganic nanocrystal self-assembly via the inclusion interaction of β-cyclodextrins: toward 3D spherical magnetite, J. Phys. Chem. B 109 (2005) 4845–4852. [34] D. Yu, X. Sun, J. Zou, Z. Wang, F. Wang, K. Tang, Oriented assembly of Fe3O4 nanoparticles into monodisperse hollow single-crystal microspheres, J. Phys. Chem. B 110 (2006) 21667–21671. [35] C. Cheng, Y. Wen, X. Xu, H. Gu, Tunable synthesis of carboxyl-functionalized magnetite nanocrystal clusters with uniform size, J. Mater. Chem. 19 (2009) 8782–8788. [36] R. Massart, Preparation of aqueous magnetic liquids in alkaline and acidic media, IEEE Trans. Magn. 17 (1981) 1247–1248. [37] T. Ozkaya, M.S. Toprak, A. Baykal, H. Kavas, Y. Köseoğlu, B. Aktaş, Synthesis of Fe3O4 nanoparticles at 100C and its magnetic characterization, J. Alloys Compd. 472 (2009) 18–23. [38] D.K. Kim, Y. Zhang, J. Kehr, T. Klason, B. Bjelke, M. Muhammed, Characterization and MRI study of surfactant-coated superparamagnetic nanoparticles administered into the rat brain, J. Magn. Magn. Mater. 225 (2001) 256–261. [39] Y. Cha, M. Kim, Y. Choa, J. Kim, B. Nam, J. Lee, D.H. Kim, K.H. Kim, Synthesis and characterizations of surface-coated superparamagentic magnetite nanoparticles, IEEE Trans. Magn. 46 (2010) 443–446. [40] D.B. Robinson, H.H.J. Persson, H. Zeng, G. Li, N. Pourmand, S. Sun, S.X. Wang, DNA-functionalized MFe2O4 (M = Fe, Co, or Mn) nanoparticles and their
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