Advanced Materials Research Vol.685 (2013) pp 119-122 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.685.119
Using X-Ray Diffraction and Scanning Electron Microscope to Study Zinc Oxide Nanoparticles prepared by Wet Chemical Method Tahseen H. Mubarak 1, a, Karim H. Hassan 2, b and Zena Mohammed Ali Abbas3, c * 1,3 2
Iraq, University of Diyala, College of Science, Department of physics
Iraq, University of Diyala, College of Science, Department of Chemistry
a
Email:
[email protected], b
[email protected], c
[email protected]
Keywords : Zinc oxide, nanoparticles, X-ray diffraction, scanning electron microscope. Abstract: The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. Materials whose crystallites, particle sizes are smaller than 100 nm are commonly named nanocrystalline, nanostructured, nanosized materials. There are many methods used for the preparation of nanomaterials. We use is a method which is easy if compared to other methods with the chemicals required for these methods are available and cheap. Nano zinc oxide has been prepared by wet chemical method from zinc nitrate and using sodium bicarbonate as precipitation agent. The resulting nanopowders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM).The particle size measurement using XRD Scherer’s formula calculations confirms that the crystallite size of the ZnO nanoparticles range from 41 to 67 nm and depending on calcinations temperature. SEM micrographs reveals less number of pores with smaller lump size in addition to clearly showing the micro structural homogeneity and remarkably dense mode of packing of grains of ZnO nanoparticles with minimum porosity. Introduction Zinc oxide is an important basic material due to its low cost, large band gap (3.37 eV), large exciton binding energy (60 MeV),and luminescent properties [1]. It is widely used in many applications, such as catalyst, gas sensor, filtering materials for ultraviolet light, microbe resistant defence clothing [2] and also as antimicrobial and retanning agent [3]. The interest in nanomaterials has increased in recent years because of their unique physical and chemical properties. The experimental conditions used in the preparation of these materials play an important role in determination of the particle size of the product. For this reason, a great variety of experimental methods have been implemented in the production of nanoparticles, such as the sol– gel [4,5] and sol combustion [6] techniques, one that use liquid ammonia as solvent, spray pyrolysis, thermal decomposition, laser ablation and chemical vapor deposition and others. The characters of metal nanoparticles like optical, electronic, magnetic, and catalytic are depending on their size, shape and chemical surroundings [7,8].Control of the particle shape and size is of interest for nanostructured material synthesis because electrical and optical properties of these materials depend sensitively on them. In nanoparticle preparation it is very important to control the particle size, particle shape and morphology. Currently many interesting ZnO nanostructures, including nanorods, nanobridges and nanonails have been fabricated [9]. These structures are expected to have potential applications in building functional nanoelectronic devices. XRD study is most important tool used in nano materials science and it is one of the primary techniques used by mineralogists and solid state chemists to examine the physico-chemical make-up of unknown materials and it is an important as characterization tools in solid state chemistry and materials science. Also being an easy tool to determine the size and shape of the unit cell for any compound and giving information on translational symmetry - size and shape of the unit cell from peak positions and information on electron density inside the unit cell, namely where the atoms are located from peak Intensities..
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The aim of the present investigation is to prepare and characterize zinc oxide nanoparticles and show the effect of calcination temperature on particle size. Experimental The method of preparation of nano zinc oxide Materials and methods.Zinc nitrate hexahydrate, Zn(NO3)2.6H2O, sodium bicarbonate, NaHCO3 and distilled water are of analytical grade. Apparatus.The X-ray diffraction pattern were recorded using XRD-6000 with CuKα (λ=1.5406A°) that have an accelerating voltage of 220/50HZ which is produced by SHIMADZU company, and the scanning electron microscope used in imaging the nanoparticles was a VEGA//EasyProbe which is a favorable combination of a scanning electron microscope and a fully integrated energy dispersive X- ray microanalyser produced by TESCAN, s.r.o., Libušina trída 21. Preparation method.The zinc oxide nanoparticles were prepared by wet chemical method in which aqueous zinc nitrate (0.1 M) and sodium bicarbonate (0.1 M) solutions were prepared. A 100 ml of bicarbonate solution was added to 100 ml nitrate solution gradually with stirring and the reaction mixture being kept at 45°C and at pH of 6.7 until completion of precipitation was achieved [6]. The slurry basic zinc carbonate in the form of white precipitate obtained was left decanted for 6 hours and then filtered, washed several times with distilled water to be free from excess bicarbonate being left and dried in an oven for four hours at 80 °C. Finally the products was calcinied at 350°C and 450°C for 2 hour to obtain the zinc oxide powder [10]. Results and Discussion ZnO characterization from X–ray diffraction.Figures (1a) and (1b) show the XRD patterns of ZnO samples calcined at 350°C and 450°C respectively It is very clear from the above figures that the major reflections peaks between 30°and 40°(2θ values) indicate more crystalline regions in the zinc oxide sample. Also the less intense peaks at 48°, 57°, 63°and 70°(2θ values) indicate the high crystallinity of ZnO samples. The detailed analysis of the XRD and the assignments of various reflections are given in Table 1, Table 2. Table 1: Strongest three peaks of fig.1 (a) No.
Peak No.
2 Thea (deg)
d(Aº)
FWHM (deg)
Intensity (counts)
1
3
36.2477
2.47628
0.19540
4674
2
1
31.7648
2.81477
0.19800
2683
3
2
34.4213
2.60337
0.19680
1980
Table 2: Strongest three peaks of fig. 1(b) No. 1
Peak No. 3
2 Thea (deg) 36.4078
FWHM (deg) 0.129
2
1
31.9307
0.1209
3
2
34.5833
0.1184
Calculation of particle size of ZnO from X-ray diffraction .The average particle size, D has been estimated using Debye-Scherrer formula [11, 12]. D = 0.9λ / β cos θ where λ is the wavelength of X-ray (0.15406 nm).
(1)
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β is FWHM (full width at half maximum). θ is the diffraction angle. For sample calcined at 350°C : 2θ = 36.2477 , θ = 18.124 , λ = (0.15406 nm), β = 0.19540 calculated from the XRD more intense peak of fig. 1(a). D = 0.9λ/ β cos θ
(2)
= 41.86 nm And for sample calcined at 450°C
2 θ = 36.4078 , θ = 18.204 ,
λ = (0.15406 nm), β = 0.129 calculated from the XRD of the more intense peak of fig.1(b). D = 0.9λ/ β cos θ
(3)
= 66.19 nm
(a)ZnO calcining at 350 °C
(b)ZnO calcining at 450 °C Fig. 1: XRD patterns of ZnO calcined at (a) 350 °C and (b) 450 °C Scanning electron microscope of ZnO powder. The SEM images of prepared ZnO nanoparticles shown in figure (2) indicate that most of the ZnO nanoparicles are in the form of nanospheres [13] with less than 100 nm diameter as was previously obtained [6,9]. Large crystallites were also present, but with low concentration. This small particle size ZnO will open tremendous uses in catalysis and petrochemical industries as adsorbents for gases purification. These micrographs shows clearly that the network formation and agglomeration of the ZnO has taken place. Also SEM micrographs reveals less number of pores with smaller lump size in addition to clearly showing the micro structural homogeneity and remarkably dense mode of packing of
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grains of ZnO nanoparticles with minimum porosity. It was also noticed that increasing the temperature give rise to increase in particle size as was also observed by [6] in sol-gel preparation technique where the temperature raise the aggregation of nanoparticles to larger sizes and the optimum temperature was 500 °C to form ZnO with smaller particle size.
Fig. 2: SEM images of ZnO powders References [1] Zhong J, Kitai AH, Mascher P and Puff W, "The influence of processing conditions on point defects and luminescence centers in ZnO", J. Electrochem. Soc. 140,3644-3649 (1993). [2] V.Parthasarathi, G.Thilagavathi, International Journal of Pharmacy and Pharmaceutical Sciences, 3, 4 , 392-398 (2011). [3] H.R.Hawaz, B.A.Solangi, B.Zehra and U..Nadeem, Canadian Journal on scientific and industrial research, 2, 4, 164-170 (2011). [4] D.G. Lamas, G.E. Lascalea, N.E.Walsoe de Reca, J. European Ceramic. Society. 18,1217, (1998). [5] R.F. Juarez, D.G. Lamas, G.F. Lascalea, N.F.Walsoe de Reca, J. European Ceramic Society, 20, 133, (2000). [6] N.R.Noori, R.S.Mamoory,P.Alizadeh and A.Mehdikhani, J.Ceramic Processing Research, 9, 3, 246-249 (2008). [7] Cao G.; Nanostructures and Nanomaterials, Imperial College Press, (2004). [8] Chang K.; Tiny is Beautiful, Translating“Nano”into Practical, The New York Times (2005). [9] R.Wahab, S.G.Ansari, Y.S.Kim, H.K.Seo, G.S.Kim, G.Khang and H.S.Shin, Materials Research Bulletin, 42, 1640-1648 (2007). [10] Karim.H.Hassan, Zuhair A-A Khammas and Ameel. M. Rahman, Al-Khwarizmi Engineering Journal, 4, 3, 74-84 (2008). [11] Nath S. S., Chakdar D., and Gope G., journal of nanotechnology and its application, 2, 3, ( 2007). [12] B. D. Hall, D. Zanchet and D. Ugarte ; "Estimating nanoparticle size from diffraction measurements , Journal of Applied Crystallography, 33, 6 (2000). [13] S.S.Ashtaputre, A.Deshpande, S.Marathe, M.E.Wankhede, J.Shimanpure, R.Pasricha, JUrban, S.K.Haram,S.W.Gosavi and S.K.Kulkarni, PRAMANA Journal of Physics, 65, 4, 615-620 (2005).
