Green synthesis and characterization of nanostructured ZnO thin films using Citrus aurantifolia (lemon) peel extract by spin-coating method

Accepted Manuscript Green synthesis and characterization of nanostructured ZnO thin films using Citrus aurantifolia (lemon) peel extract by spin-coating method Hakan Çolak, Ercan Karaköse PII:

S0925-8388(16)32468-9

DOI:

10.1016/j.jallcom.2016.08.090

Reference:

JALCOM 38592

To appear in:

Journal of Alloys and Compounds

Received Date: 4 July 2016 Revised Date:

10 August 2016

Accepted Date: 11 August 2016

Please cite this article as: H. Çolak, E. Karaköse, Green synthesis and characterization of nanostructured ZnO thin films using Citrus aurantifolia (lemon) peel extract by spin-coating method, Journal of Alloys and Compounds (2016), doi: 10.1016/j.jallcom.2016.08.090. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Green synthesis and characterization of nanostructured ZnO thin films using Citrus aurantifolia (lemon) peel extract by spin-coating method Hakan Çolak1* and Ercan Karaköse2

Cankiri Karatekin University, Faculty of Science, Department of Chemistry, 18100, Cankiri,

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1

Turkey 2

Cankiri Karatekin University, Faculty of Science, Department of Physics, 18100, Cankiri,

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Turkey *Corresponding Author: Hakan Çolak

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E-mail address: [email protected] Telephone: +90 376 218 95 37 / Ext: 8050

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Fax: +90 376 218 95 41

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ACCEPTED MANUSCRIPT ABSTRACT Green synthesis of nanostructured ZnO is becoming increasingly importance as eco-friendly alternative to traditional production process because of its growing industrial application. In this study, we produced two nanostructured ZnO thin films for comparison. The first thin film

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was produced using Zn(Ac)2.2H2O solution in Citrus aurantifolia (lemon) peel extract by spin-coating system. The second thin film was produced using Zn(Ac)2.2H2O solution in distilled water (dH2O). The solutions which prepared in Citrus aurantifolia peel extract and

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dH2O were named as SA, and SB, respectively. The ZnO thin films were named as TF1 and TF2, produced using SA and SB, respectively. TF1 and TF2 were characterized by XRD and

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indexed as wurtzite structure. Average crystallite sizes were calculated to be 35 and 45 nm, for TF1 and TF2, respectively, using Scherrer equation. Morphological properties of the ZnO thin films was determined with FE-SEM and average particle sizes are found to be 50 nm and 1 µm, for TF1 and TF2, respectively. Electrical conductivity measurements of the ZnO thin

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films were carried out via four probe dc system. The electrical conductivity values of the nanostructured ZnO films are between 6.0*10-9 and 2.8*10-4 Ω-1.cm-1, at 30 and 550°C, respectively. Optical spectra of the ZnO thin films were measured and band gap (Eg) was

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found to be 3.36 eV for the both films in Uv/vis range.

Keywords: Green synthesis, biosynthesis, citrus aurantifolia peels, zinc oxide nanostructures.

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ACCEPTED MANUSCRIPT INTRODUCTION Recently, the interest of the nano materials has been increasing due to their significant structural, optical and electrical characteristics which are highly useful in producing nanoscaled optoelectronic and electronic devices with multifunctionality [1]. The chemical

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and physical properties of nanostructured materials are different from the bulk materials [2]. Nanoscaled ZnO has been preferred one of the best metal oxide owing to its superior electrical and optical features. So, nanosized ZnO materials has many applications in

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optoelectronics, solar cells, gas sensors, varistors, etc [3]. ZnO nanoparticles (ZnO-NPs) can be fabricated by different methods such as sol–gel [7], hydrothermal synthesis [9, 10], spray

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pyrolysis [6], chemical precipitation [4, 5], and thermal decomposition [8]. Chemical synthesis tecniques cause to the existence of some toxic materials adsorbed on the surface [11]. Growing interest in green chemistry methods has caused to the improvement of an ecofriendly approach for the producing of metal oxide-NPs [12]. Producing of NPs via eco-

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friendly methods has attracted great interest by the scientists because it is economic, clean, non-toxic, etc. Mostly, green synthesis method has been applied for the producing of

13].

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inorganic NPs using different biological systems such as plant extracts and microorganisms [

Lemon peel is bio-waste material. In this work, the lemon peel waste was evaluated. ZnO-NPs

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were synthesized using lemon peel extract as a reducing agent. To the best of our knowledge, there has been no previous study on the synthesis of ZnO-NPs thin film by using lemon peel extract. The product synthesized in the present technique is comparable to those obtained from conventional reducing agents such as hexamethylenetetramine (HMTA) or cetyltrimethylammonium bromide (CTAB) [14]. Citrus group is a great family of fruits. Citrus fruits has great amount of bioactive compounds such as carotenoids, coumarins, limonoids and flavonoids [15, 16]. Lemon peel is the outer skin of the citrus fruit of the same

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ACCEPTED MANUSCRIPT name, which is technically referred to as the exocarp. Lemon peel contains flavonoids and other functional compounds [17]. In this study, we obtained ZnO-NPs thin films via sol-gel spin coating technique and

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examined as structural, optical and electrical.

2. Experimental Study 2.1 Materials

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Citrus aurantifolia (lemon) was purchased from local market in Çankırı/Turkey. Zn(Ac)2.2H2O was bought from Sigma-Aldrich, Germany. Distilled water (dH2O) was used

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all experiments. As a substrate for ZnO-NPs thin film, microscope slides (35x10x1 mm in size) were used. Before the film coating, the substrates were cleaned with detergent using toothbrush and rinsed under hot tap water, ultrasonicated in ethanol and dH2O, respectively, and dried in a stream of nitrogen gas.

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2.2 Preperation of Lemon Peel Extract

Lemon was grated and the peels were dried at room temperature in air during two days. 2 g of the dried peels was mixed in 100 mL dH2O for one hour at 95°C. The extract was cooled to

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25°C and filtered with filter paper to remove large particles. The colour of the extract was

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light yellow. The extract was saved in refrigerator at 4°C for subsequent experiments.

2.3 Synthesis of ZnO NPs and Coating Thin Films Zn(Ac)2.2H2O was used as a zinc source. 5 g Zn(Ac)2.2H2O was mixed with 50 mL of the peel extract under vigorous stirring at 95°C until the volume of the solution is 10 mL, namely gelation. The final solution was named as SA and used as coating solution. The cleaned substrate was fixed on the disk of spin-coater. 1 mL of the coating solution was injected on the substrate at 3000 rpm for 30 seconds. After the deposition, the film was dried at 150°C for 10 minutes in a oven in order to remove any residuals and obtain a well-crystallized films. 4

ACCEPTED MANUSCRIPT The spin-coating process was carried out at 25°C. The coating and drying process were repeated three times until the optimum thickness was achieved. Finally, the films were heated at 400°C for 15 minutes in air to obtain highly crystalline ZnO-NPs. Also, for comparison, 5 g

each step described above was repeated using SB.

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Zn(Ac)2.2H2O was dissolved in 50 mL dH2O, and this solution was named as SB, and then

We produced two ZnO thin films. One of them obtained using SA solution was named as TF1 (ZnO thin film 1) and the other film obtained using SB solution was named as TF2 (ZnO thin

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film 2).

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2.4 Characterization

The films were characterized as structural, morphological, electrical and optical by X-ray diffraction (XRD, Bruker AXS D8), field emission scanning electron microscope (FE-SEM, Zeiss Ultra Plus Gemini), four probe dc system and Uv/vis spectrophotometer (Rayleigh UV-

3. Results and discussion

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2601).

3.1 XRD and Structural Study

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Based on other works results, the possible mechanism for the formation of ZnO-NPs using lemon peel extract can be shown in Figure1. The carotenoids/limonoids/flavonoids molecules

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can react with Zn2+ to form zinc-carotenoids/limonoids/flavonoids complex molecules. After the complexation reactions, the solution was coated on the substrate, and dried and annealed. During annealing treatment, the complex molecules turn into ZnO-NPs [19]. The XRD pattern of the thin films is shown in Figure 2. The diffraction patterns indicate high crystalline quality with very well defined peaks and intense. The XRD patterns were indexed as hexagonal (wurtzite) structure (PDF Card No: 2300113). No extra peaks are detected, and this indicates formed ZnO hexagonal structure. The lattice spacing d, I/I0 ratio, angle of diffraction

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ACCEPTED MANUSCRIPT 2θ in the phases identified along with the (hkl) planes of the TF1 and TF2 are given in Table 1. The lattice constants of the samples were determined at room temperature experimentally from the XRD results. The a parameters are 3.2465 and 3.2494 Å and c parameters are 5.2030 and 5.2054 Å for the TF1 and TF2, respectively.

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Using the XRD results, the average crystallite sizes of ZnO NPs were estimated by using Scherrer equation that is shown below:    

(1)

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=

Here, D is the average crystallite size; K is the constant and about 0.9, λ is the wavelength of

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X-rays used, CuKα 1.542 Å, β is the line broadening at half the maximum intensity FWHM and θ is the Bragg angle. The average crystallite size of the TF1 and TF2 was calculated as 35 and 45 nm, respectively. Namely, TF1 has smaller size than TF2. We can deduce that smaller sized nanoparticles can be produced using green synthesis method. Also, in our samples, the

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crystallite size decrases when decreasing the lattice constants.

3.2 FE-SEM and Morphological Study

The FE-SEM analysis for the TF1 and TF2 samples is very important factor for determine

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their structural properties in industrial applications. To make comparison between surface of

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the TF1 and TF2 thin films, the FE-SEM micrographs in different magnification are given in Figure 3. As mentioned previous section, also, the Figure 3 illustrates that green synthesis process is display significant influence on the average crystallite size. The TF2 has pyramidlike morphology and also, heterogeneous grain distribution, an agglomeration (in Figure 3 c and d). The average particle sizes are about 1 µm. The TF1 has spotlike nanostructrures, as seen in Figure 3 a and b, and the actual grain size of the of the TF1 is calculated to be as 50 nm. It can be clearly seen that the morphology of the ZnO thin films is distinctly affected by

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ACCEPTED MANUSCRIPT green synthesis method and also using lemon peel extract causes decreases particle size and number. The morphology is very important for optical and electrical properties.

3.3 Electrical Conductivity Study

this aim, equation (1) was used:

 =  

(1)

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where G is the geometric correction constant [20].

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The electrical conductivity of the ZnO thin films were measured by four probe dc system. For

The change of the electrical conductivity of the ZnO thin films is connected with their

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structure. Furthermore, the heating treatments modify the structural characteristics of the ZnO thin films and as a result, their electrical properties [20, 21]. On this basis, the study of the temperature dependence of the electrical characteristic propose beneficial information about the possible changes on the structure of the ZnO thin films [20]. Figure 4 illustrates

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logσ−103/T graphs of the ZnO thin films. As it is shown in the figure, the electrical conductivity increases with increasing temperature. This behaviour indicates semiconducting characteristic for the both ZnO thin films. ZnO is a n-type and non-stoichiometric

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semiconductor material due to the existence of oxygen holes and interstitial Zn atoms [21]. The electrical conductivity of ZnO is controlled by the native defects created at high

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temperatures [22].

It can be seen from figure 4, generally, TF2 has higher electrical conductivity than TF1. The decrease in particle size increases grain boundary scattering, therefore decreasing the electrical conductivity [23]. Also, when the particle size increases then it may improve the contact of surface between particles. Therefore the mobility of electron improved which reduced the resistivity [24].

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ACCEPTED MANUSCRIPT Usually, for a semiconductors, the electrical conductivity increases exponentially with temperature. This conductivity behaviour indicates a thermally activated process. Total electrical conductivity can be shown as

 =  exp(− / )

(2)

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σ is electrical conductivity, Ea is the activation energy which corresponds to the energy gap between the the conduction and donor level, σ0 is electrical conductivity at absolute

following equation

!



+ 

" #

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 = −

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temperature (T), k is Boltzmann factor [25]. The activation energy can be calculated from the

(3)

The gradient of the linear part of the Arrhenius graph of the logσ-103/T is equal to –Ea/k. The activation energy and σ0 can be found from the graph. The values are given in Table 2. This table illustrates that the activation energy in the high temperature region is higher than the

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energy in the low temperature region, because the conduction mechanism of the ZnO thin films change. In high temperature region, the native defects are source of the electrical conductivity and named as native conduction. The high values of activation energy in this

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region may be attributed to the fact that the energy needed to form the defects is much larger

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than the energy required for its drift. That is why the intrinsic defects that is caused by the thermal fluctuations determine the electrical conductivity of the samples at high temperatures [26].

3.4. Optical Study

The optical transmittance spectra of the TF1 and TF2 are shown in Figure 5. This figure illustartes that a region of high transparency is located in the range of 370 and 1000 nm. Both the ZnO thin films have an optical transparency over 75-85 % in between in the range. The high transparency shows the very good optical quality, and related with a good structural 8

ACCEPTED MANUSCRIPT homogeneity and crystallinity of the ZnO thin films [26]. TF2 has higher optical transmittance than TF1. The increase in optical transmittance of the thin films is related to an icrease in particle size of the thin films [27, 28]. The optical band gap (Eg) was derived has assuming a direct transition between the

photon energy hν can be demonstrated by

%(ℎ') = ((ℎ' − ) )

+ *

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conduction and valence bands, for which the variation in the absorption coefficient with the

(4)

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Here, Eg is the optical energy gap between the conduction and the valence band [29]. Figure 6

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shows the plots of (αE)2 versus photon energy (E, eV) for the ZnO thin films. Optical band gaps (Eg) value is associated with the particle size, carrier concentration, and stress state in material. The Eg values were determined from the plots and found to be 3.36 eV for both ZnO thin films. Also, from the spectra, a weak peak is seen at ~ 680 nm and it is considered to

4. Conclusions

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result from surface (or radiative) defects of the ZnO thin films.

Citrus aurantifolia (lemon) peel is bio-waste material, and the waste was evaluated in this

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study. ZnO thin films were prepared from lemon peel extract using spin coating system. The XRD patterns indicate high crystalline quality with very well defined peaks and intense and

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were indexed as hexagonal (wurtzite) structure. From XRD and FE-SEM analysis, it was determined that TF1 has smaller crystallite and particle size than TF2. Namely, it can be produced smaller sized nanoparticles using green synhthesis method. TF2 has higher electrical conductivity and optical transmittance than TF1 because of the particle size.

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ACCEPTED MANUSCRIPT References 1. S. Talam, S. R. Karumuri, N. Gunnam, Synthesis, characterization, and spectroscopic properties of ZnO nanoparticles, ISRN Nanotech., 2012 (2012) 1-6. 2. Y. T. Prabhu, K. V. Rao, V. S. Sai Kumar, B. S. Kumari, Synthesis of ZnO

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nanoparticles by a novel surfactant assisted amine combustion method, Adv. Nanopart. 2 (1) (2013) 45-50.

3. H. Abdul Salam, R. Sivaraj, R. Venckatesh, Green synthesis and characterization of

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Zinc Oxide nanoparticles from Ocimum Basilicum L. var. Purpurascens Benth.Lamiaceae Leaf extract, Mater. Lett., 13 (2014) 16-18.

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4. K. Prabakar, Heeje Kim, Growth control of ZnO nanorod density by sol–gel method, Thin Solid Films, 518 (2010), e136-e138.

5. M. Sima, E. Vasile, M. Sima, Preparation of nanostructured ZnO nanorods in a hydrothermal–electrochemical process, Thin Solid Films, 520 (2012) 4632-4636.

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6. E. Maryanti, D. Damayanti, I. Gustian, S. Yudha S., Synthesis of ZnO nanoparticles by hydrothermal method in aqueous rinds extracts of Sapindus rarak DC, Mater. Lett., 118 (2014) 96-98.

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7. T. Dedova, I. Oja Acik, M. Krunks, V. Mikli, O. Volobujeva, A. Mere, Effect of substrate morphology on the nucleation and growth of ZnO nanorods prepared by

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spray pyrolysis, Thin Solid Films, 520 (14) (2012) 4650-4653.

8. S. S. Kumar, P. Venkateswarlu, V. Ranga Rao, G. Nageswara Rao, Synthesis, characterization and optical properties of zinc oxide nanoparticles, Int. Nano Lett., 3 (30) (2013) 1-6. 9. A. H. Moharram, S. A. Mansour, M. A. Hussein, M. Rashad, Direct precipitation and characterization of ZnO nanoparticles, J. Nanomater., 2014 (2014), 716210 (1-5).

10

ACCEPTED MANUSCRIPT 10. S. Baskoutas, P. Giabouranis, S. N. Yannopoulos, V. Dracopoulos, L. Toth, A. Chrissanthopoulos, N. Bouropoulos, Preparation of ZnO nanoparticles by thermal decomposition of zinc alginate, Thin Solid Films, 515 (2007) 84618464.

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11. G. Sangeetha, S. Rajeshwari, R. Venckatesh, Green synthesis of Zinc Oxide nanoparticles by Aloe Barbadensis Miller leaf extract: structure and optical properties, 46 (12) (2011) 2560-2566.

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12. S. Ambika, M. Sundrarajan, Green biosynthesis of ZnO nanoparticles using Vitex Negundo L. Extract: spectroscopic investigation of interaction between ZnO

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nanoparticles and human serum albumin, 149 (2015) 143-148.

13. S. Azizi, F. Namvar, R. Mohamad, P. Md Tahir, M. Mahdavi, Facile biosynthesis and characterization of Palm Pollen stabilized ZnO nanoparticles, 148 (2015) 106-109. 14. H. A. Rafaie, R. Md Nor, Y. M. Amin, Magnesium doped ZnO nanostructures

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synthesis using Citrus Aurantifolia extracts: structural and field electron emission properties, Mater. Exp., 5 (3) (2015) 226-232. 15. M. R. Loizzo, R. Tundis, M. Bonesi, F. Menichini, D. De Luca, C. Colica, F.

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Menichini, Evaluation of Citrus Aurantifolia Peel and Leaves extracts for their chemical composition, antioxidant and anti-cholinesterase activities, J. Sci. Food

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Agric., 92 (15) (2012) 2960-2966.

16. M. Boshtam, J. Moshtaghian, G. Naderi, S. Asgary, H. Nayeri, Antioxidant effects of Citrus Aurantifolia (Christm) Juice and Peel extract on LDL oxidation, J.Research in Med. Sci., 16 (7) (2011) 951-955. 17. Y. Miyake, M. Hiramitsu, Isolation and extraction of antimicrobial substances Against oral bacteria from Lemon Peel, J. Food Sci. Tech., 48 (5) (2011) 635-639.

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ACCEPTED MANUSCRIPT 18. H. Colak, O. Turkoglu, Effect of doping and high-temperature annealing on the structural and electrical properties of Zn1−XNiXO (0 ≤ x ≤ 0.15) powders, J. Mater. Sci. Tech., 27 (10) (2011) 944-950. 19. B. Kumar, K. Smita, L. Cumbal, A. Debut, Green approach for fabrication and

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applications of Zinc Oxide nanoparticles, bioinorganic chemistry and applications, 2014 (2014) 523869 (1-7).

20. S. Yilmaz, O. Turkoglu, I. Belenli, Measurement and properties of the ionic

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conductivity of β-phase in the binary system of (Bi2O3)1-X(Sm2O3)X, Mater. Chem. Phys., 112 (2008) 472-477.

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21. J. B. Lee, H. J. Le, S. H. Seo, J. S. Park, Characterization of undoped and Cu-doped ZnO films for surface acoustic wave applications, Thin Solid Films, 398-399 (2001) 641-646.

22. A. Sawalha, M. Abu-Abdeen, A. Sedky, Electrical conductivity study in pure and

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doped ZnO ceramic system, Physica B: Condensed. Matter.,404 (2009) 1316-1320. 23. D-J. Kwak, B-W. Park, Y-M. Sung, Bias voltage dependence of the electrical and optical properties of ZnO:Al films deposited on PET substrates, J. Korean Phys. Soc.,

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55 (5) (2009) 1940-1944.

24. M. I. Khan, K. A. Bhatti, R. Qindeel, L. G. Bousiakou, N. Alonizan, F. e-Aleem,

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Investigations of the structural, morphological and electrical properties of multilayer ZnO/TiO2 thin films, deposited by sol–gel technique, Results Phys., 6 (2016) 156-160.

25. H. Colak, O. Turkoglu, Studies on structural and electrical properties of copper-doped Zinc Oxide powders prepared by a solid state method at high temperatures, Mater. High Temp., 29 (4), 344-350, 2012.

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ACCEPTED MANUSCRIPT 26. A. V. Patil, C. G. Dighavkar, S. K. Sonawane, S. J. Patil, R. Y. Borse, Effect of firing temperature on electrical and structural characteristics of screen printed ZnO thick films, J. Optoelectron. Biomed. Mater., 1 (2) (2009) 226-233. 27. L. C. Nehru, M. Umadevi, C. Sanjeeviraja, Studies on structural, optical and electrical

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properties of ZnO thin films prepared by the spray pyrolysis method, Int. J. Mater. Eng., 2 (1) (2012) 12-17.

28. G. A. Kumar, M. V. Ramana Reddy, Narasimha K. Reddy, Structural and optical

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properties of ZnO thin films grown on various substrates by rf magnetron sputtering, IOP Conference Series: Mater. Sci. Eng., 73, (2015) 012133 (1-4).

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29. C. S. Hong, H. H. Park, H. H. Park, H. J. Chang, Optical and electrical properties of ZnO thin film containing nano-sized Ag particles, J. Electroceram., 22 (4) (2008) 353-

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356.

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ACCEPTED MANUSCRIPT Tables and Figures Captions Table 1. 2θ, d and I/I0 values of the TF1 and TF2. Table 2. Activation energy values of the TF1 and TF2. Figure 1. A possible mechanism for the formation of ZnO-NPs [19].

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Figure 2. XRD pattern of the ZnO thin films.

Figure 3. FE-SEM images of the ZnO thin films: (a) and (b) for TF1, (c) and (d) for TF2. Figure 4. Electrical conductivity plots for ZnO thin films; red line (―) and blue line (―) are

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for TF1 and TF2, respectively.

for TF1 and TF2, respectively.

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Figure 5. Optical transmittance spectra of ZnO thin films; red line (―) and blue line (―) are

Figure 6. The plot of the graph of (αE)2 versus photon energy (eV) of ZnO thin films; : for : for TF2.

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TF1, and

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ACCEPTED MANUSCRIPT Table 1. ZnO thin films TF1

TF2

h

k

l

2θ (°)

d [Å]

I/I0

2θ (°)

d [Å]

I/I0

1 2 3 4 5 6 7 8 9 10 11 12 13

1 0 1 1 1 1 2 1 2 0 2 1 2

0 0 0 0 1 0 0 1 0 0 0 0 0

0 2 1 2 0 3 0 2 1 4 2 4 3

31.866 34.527 36.352 47.623 56.674 62.970 66.460 68.035 69.160 72.657 77.080 81.480 89.713

2.8060 2.5956 2.4694 1.9079 1.6228 1.4748 1.4057 1.3769 1.3571 1.3002 1.2362 1.1803 1.0920

56.6 40.2 100 23.6 35.8 32.2 4.5 27.4 13.4 2.0 4.3 2.6 4.7

31.794 34.442 36.269 47.548 56.600 62.882 66.380 67.978 69.118 72.600 76.983 81.402 89.653

2.8122 2.6018 2.4748 1.9107 1.6248 1.4767 1.4072 1.3778 1.3579 1.3011 1.2376 1.1813 1.0926

47.8 27.8 100 19.4 26.2 25.9 3.6 28.1 11.5 1.8 4.8 2.1 8.3

Table 2.

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No

Activation Energy (eV)

TF2

Ea2

between 30-250 (°C)

between 30-350 (°C)

between 300-550 (°C)

between 400-550 (°C)

-

0.078

-

1.662

-

1.516

-

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TF1

Ea1

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Sample Name

0.224

15

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Figure 1.

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12000 10000

TF2

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8000

TF1

6000 4000 2000 0

10

20

30

40

50 2θ (°)

Figure 2. 16

60

70

80

90

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Figure 3. 18

ACCEPTED MANUSCRIPT -3.5 -4.0 -5.0 -5.5 -6.0

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logσ (ohm-1.cm-1)

-4.5

-6.5 -7.0 -7.5 -8.5 1.0

1.2

1.4

1.6

1.8

2.0

2.2

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-8.0 2.4

2.6

2.8

3.0

3.2

3.4

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1 x 103/T (K-1)

90 70 60

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Transmittance (T %)

80

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100

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Figure 4.

50 40 30 20 10 0

300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 Wavelength (nm) Figure 5. 19

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6E-06 5E-06

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(αE)2(m-2 eV2)

7E-06

4E-06 3E-06 2E-06

1E-13 0.5

1.0

1.5

2.0 Energy (eV)

2.5

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0.0

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1E-06

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Figure 6.

20

3.0

3.5

4.0

ACCEPTED MANUSCRIPT Highlights Citrus aurantifolia (Lemon) peel waste was evaluated.

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Nanostructured ZnO thin film was produced by green synthesis method.

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Lattice parameters, crystallite size and morphology of ZnO vary with using extract.

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Electrical and optical properties of ZnO which is produced using extract is better.

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