Synthesis and structural analysis of cobalt doped zinc nanoparticles

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1 IOSR Journl of Applied Physics (IOSR-JAP) e-issn: Volume 9, Issue 5 Ver. III (Sep. - Oct. 17), PP Synthesis nd structurl nlysis of coblt doped zinc nnoprticles *S. Amrit Kur 1, G.S. Rndhw 1, nd Rndhir Singh. 1 Deprtment of Physics, Khls College, Amritsr Deprtment of Chemistry, Khls College, Amritsr Corresponding Author: *S. Amrit Kur Abstrct: Nno science nd nnotechnology involves studying nd working with mtter on n ultr smll scle from sub nnometer to severl hundred nnometers. The synthesis of nno prticles hs been considered s preferred field in the nnotechnology sector due to size dependent properties of the mterils. The wide bnd gp semiconductors like ZnO (3.3 ev) hs gined lot of ttention mong semiconductor mterils due to their potentil pplictions in optoelectronic devices in the visible nd UV regions. In this pper, the structurl prmeters of pure nd coblt substituted ZnO nnoprticles sintered t 45 C hve been nlysed to utilize them in the technologicl bsed pplictions using X-ry diffrction (XRD) technique. Keywords: Structrl prmeters, ZnO, Coblt, Nnoprticles, XRD Dte of Submission: Dte of cceptnce: I. Introduction In recent yers, nno-crystlline ZnO hs gined specil interest, becuse of possibilities for modifiction nd control of vrious ZnO-bsed nnostructures. Moreover, it hs wide bnd gp, lrge exciton binding energy, bundnt in nture, environment friendly nd inexpensive bioluminescent mteril nd ultrviolet(uv) lsing [1,]. Also the queous precursor derived ZnO mteril is relible option for orgnic semiconductors nd morphous silicon mterils to be pplicble in trnsprent thin film trnsistors t low tempertures [3], light-emitting diodes [4], diode lsers [5], drug delivery [6], photo detectors [7] opticl modultor wve guides [8], photovoltic cells [9], phosphor [1], vristors, biosensors [11] nd dt storge & bioimging [1], photodiode [13] piezoelectric trnsducers [14] nd other usges such s doped- cermic compounds [15]. Nno structured ZnO, nnorods or nnowires in prticulr, hve ttrcted reserch, primrily due to their lrge surfce re for pplictions in sensors nd detectors, their light confinement in nno-lsers, nd their freedom in lterl prmeters for more sensitive piezoelectric devices. For ll such purposes, the growth of ZnO nno scle mteril by chemicl route is to be followed. Most of the present methods rely strongly on ZnO grin mnipultion techniques while drying nd sintering the hydrted zinc oxide precipittes. Also, the defect structure in the evolution process of nno mterils hs to be given mjor ttention s there is strong evidence tht defects ply vitl role in ferromgnetic order in such mterils nd the ferromgnetic coupling cn be medited by crriers. II. Experimentl Detils.1 Synthesis of ZnO Nnoprticles: The glss wres hve been first clened nd rinsed with distilled wter nd then dried. All the mterils nd solvents hve been weighed with help of electronic weighing blnce nd mixed in clened round bottom flsk. In order to synthesize pure ZnO nnoprticles nd coblt doped ZnO nnoprticles by co-precipittion method. Zinc cette nd coblt cette hve been used s precursors. Double distilled wter hs been used s solvent nd different concentrtions of dopnts hve been incorported. To strt with, zinc cette nd coblt cette in proposed rtios re mixed well in 5 ml of double distilled wter nd the obtined solution hs been stirred well using mgnetic stirrer for bout 1 hour to get n lmost cler solution. After complete dissolution, mmoni solution is dded drop by drop to get the precipittes of zinc oxide nnoprticles. The precipittes re filtered nd then dried in oven t 1 C temperture for bout n hour nd nneled t 45 C temperture for two hours in furnce nd llowed to cool to room temperture yielding coblt doped ZnO nnoprticles. During drying, Zn(OH) is completely converted in to ZnO. With similr technique ZnO nnoprticles hve been prepred without doping. The prepred ZnO nnoprticles hve lso been chrcterized for their nno structurl properties. DOI: 1.979/ Pge

2 TABLE 1: Synthesis of ZnO Nnopowder in Bsic Medium Smple 1- ZnO Bse: Zinc cette gm Ammoni solution Doping of Coblt (Co) Smple - ZnO: 5% Co : Zinc cette gm Coblt cette gm Ammoni solution ml Smple 3- ZnO: 1% Co : Zinc cette gm Coblt cette.5.67 gm Ammoni solution ml Smple 4- ZnO: 15%Co: Zinc cette gm Coblt cette gm Ammoni solution ml. Chrcteriztion techniques: X-ry diffrction (XRD): X-ry diffrction pttern for the ZnO nnoprticles hs been recorded using n X-ry diffrct meter using Cu K α rdition of wvelength λ =.1541nm. X-ry diffrction is one of the primry techniques used by minerlogists nd solid stte chemists to exmine the physiochemicl mkeup of unknown solids nd helps to determine the crystl structures nd lttice prmeters. This method is exploited for qulittive nd quntittive phse digrm determintions of unknown substnces longwith determintion of the nture of polycrystlline ggregtes like prticle size, perfection etc. III. Result And Discussion 3.1 Structurl Anlysis The structurl prmeters of pure nd coblt substituted (different concentrtion) ZnO nnoprticles sintered t 45 C hve been determined using X-ry diffrction (XRD) Fig.1 shows XRD ptterns of pure nd coblt substituted (-15%) ZnO nnoprticles. The diffrction peks correspond to the plnes (1), (), (11), (1), (11), (13), (), (11), (1), () nd (4) [16]. It hs been observed from the obtined pttern tht ll the sintered smples hve hexgonl (wurtzite) crystl structure. These plnes re in good greement with the stndrd XRD peks of crystlline bulk ZnO hving hexgonl wurtzite structure. In ll XRD ptterns, the (11) pek is dominnt nd its intensity is higher thn those of the other peks which indictes tht growth of this prticulr orienttion is preferred. The positions of diffrction peks of Co-doped ZnO grdully chnge with doping thus reveling the interesting chnges in d vlues, lttice prmeters (, & c) nd lttice volume V. It lso hs been observed tht XRD peks get brodened with rise in coblt content. Not ny extr pek of coblt oxide or ny other impurity phse hs been observed. It indictes the single phse presence in the smples with bsence of secondry phse. There is slight shift in reflection peks of the diffrction pttern of coblt substituted ZnO nnoprticles to lower ngle thn those of pure zinc oxide nnoprticles. It shows the Co + ions incorportion into Zn + sites. However, n insight nlysis of the position of the XRD peks (s shown in Fig. ), indictes shifting of peks towrds lower ngle with rise in coblt content. The chnge in the position of peks (1) () nd (11) clerly shows tht coblt ions occupy the zinc sites in the zinc oxide mtrix [14]. DOI: 1.979/ Pge

3 Intensity [.u] Intensity [.u] Intensity [.u] Intensity [.u] Intensity [.u] Synthesis nd structurl nlysis of coblt doped zinc nnoprticles (c) (b) ZnO-1 ZnO [Degree] [Degree] ZnO-15 8 ZnO [Degree] (d) [Degree] () Figure 1: XRD ptterns of pure nd Coblt substituted ZnO nnoprticles. 6 ZnO 3 ZnO-15 ZnO-1 ZnO [Degree] Fig.: Shifting of [1], [], [11] peks with the Zn 1-x Co x O smples 3. Lttice Prmeters It is well known fct tht the lttice prmeters show remrkble chnge with ddition of different dopnts. In doping, ionic rdii plys n importnt role. If the ionic rdii of dopnts re higher or lower thn the host lttice, then lttice prmeters of host increse or decrese to ccommodte it. In this study, the lttice prmeters go on incresing with rise in coblt content in Zn 1-x Co x O nnoprticles due to lesser ionic rdius of Co + ions thn those of Zn + ions. However, the lttice prmeters increse up to 15% coblt ddition. But decrese in lttice constnt hs been reported by Abrishmi et.l [17] with metl ion doping in ZnO nnometer sized crystls in contrst to the observed increse in present study. This is ttributed to the different ionic rdius (.58 Å) of Co + in tetrhedrl configurtion to tht of Zn + (.6 Å) [18]. The vlues of lttice prmeters re listed in tble nd hve shown in Fig.3. DOI: 1.979/ Pge

4 Lttice Prmeter, [A ] Lttice Prmeter, c [A ] Synthesis nd structurl nlysis of coblt doped zinc nnoprticles C Coblt Concentrtion Fig.3 Lttice prmeters versus coblt concentrtion of the prepred smples Smple Code TABLE : Lttice prmeters of ZnO: Co (5%, 1%, 15%) Lttice prmeters Volume [Å] 3 APF (%) (Å) c(å) c/ ZnO ZnO ZnO ZnO Volume of Unit Cell The volume of unit cell hs been clculted using the eqution V 3 where & c re lttice prmeters. It hs been found tht the volume of unit cell increses with rise in coblt content which my be ttributed to n increse in the lttice prmeters nd c nd the vlues of unit cell volume re given in Tble. It indictes tht coblt ions hve moved to zinc sites vilble in the structure. 3.4 Atomic Pcking Frction (APF) Atomic pcking frction (APF) hs been clculted using formul nd hs been listed in tble APF DOI: 1.979/ Pge c Where nd c re lttice prmeters [19]. It is found tht the APF first decreses with incresing coblt content which my due to the reduction of voids of smples. The APF of bulk hexgonl ZnO mterils is bout 74% but in this study the APF of Zn 1-x CoO x nnoprticles is more thn 75% which depicts tht APF in nnocrystls is slightly greter thn tht of bulk mterils. This is ttributed to the size effect in the nnocrystlline smples. The APF increses with incresing coblt content in Zn 1-x CoO x nnoprticles which indictes homogenous substitution of coblt ions in the zinc sites of ZnO structure. 3.5 Averge Crystllite Size (D) XRD pek profile nlysis is simple nd powerful method to evlute the pek brodening with crystllite size nd lttice strin cused by disloction. The verge crystllite size hs been estimted using Scherrer s formul []. 3 3c K D cos hkl Where D is the verge crystllite size in nnometers, K is constnt or shpe fctor equl to.9, λ is the wvelength of the rdition ( Å with Cu K α rdition), β hkl represents the pek width t hlf mximum

5 intensity nd θ is the pek position. The verge crystllite size is in the rnge of 8-4 nm which decreses with incresing coblt content in Zn 1-x Co x O nnoprticles. It my be due to the smll grin growth of coblt doped zinc oxide nnoprticles which is not present in pure ZnO nnoprticles. The vlues of verge crystllite size re listed in Tble Bond Length The Zn O bond length (L) is given by L 3 1 u c where u is the positionl prmeter in the wurtzite structure nd mesures the mount which ech tom gets displced with respect to the next [1-] nd u is given by u.5 3 c It hs been observed tht the vlue u increses in such wy tht the four tetrhedrl distnces lmost remin nerly constnt by distorting tetrhedrl ngles. The Zn O bond length clculted ccording to this study is Å to Å; wheres the reported Zn O bond length in the unit cell of ZnO nd neighboring toms is A []. There is good greement of the clculted & ctul bond length which supports the results of present study. The vlue of bond length is given in Tble 3. TABLE 3: Prticle size nd bond length of ZnO:Co Smple [ hkl ] θ (Degree) FWHM d XRD d jcpds (Å) Observed (Degree) Observed Observed (Å) Prticle size (nm) Bond length (Å) ZnO [] [] [11] ZnO:5%Co [1] [] [11] ZnO:1%Co [1] [] [11] ZnO:15% Co [1] [] [11] Strin The strin-induced brodening in powders, cused by crystl imperfection nd distortion hs been clculted using the formul, hkl 4Tn XRD pttern of the prepred smples (shown in Fig.). It depict tht FWHM of the reflection peks chnges fter ddition of dopnt ctions s mentioned in Tble 3. This indictes the growth of the crystllites or chnges in the crystl strins. There is lso slight shift in pek positions, nd their FWHM in the smples hving different coblt content s compred to the un-doped ZnO nnoprticles. This shift corresponds to the strin of the compound nd replcement of some zinc ctions with coblt. It hs been reported in the literture tht with ddition of foreign prticle in the crystl lttice, strin nd defect(s) re produced in the lttice which my result in reduction of crystl qulity. DOI: 1.979/ Pge

6 TABLE 4: Strin, disloction density nd specific surfce re of ZnO:Co Specific Surfce Are Smple [hkl] Strin Disloction Density 1-3 (nm) - ZnO [1] [] [11] ZnO: 5%Co [1] [] [11] ZnO: 1%Co [1] [] [11] ZnO: 15%Co [1] [] [11] Disloction density Disloction is crystllogrphic defect or irregulrity within crystl structure nd the disloction density is mesure of the disloctions which re present in specific quntity of mteril. It is defined s the length of disloction lines per unit volume of the crystl nd is clculted using. Where D is the crystllite size. It hs been shown tht the disloction density increses while crystllite size decreses with incresing strin nd ultimtely rech sturtion vlues. The disloction density of the prepred smples hs been given in Tble Specific surfce re It is property of solids defined s the totl surfce re of mteril per unit of mss nd cn be used to determine the type nd properties of mteril. The vlues obtined for specific re depend on the method of mesurement. The specific surfce re cn be clculted from prticle size given by S = / D ρ The specific surfce re increses with coblt incorported s shown in Tble 4. 1 D IV. Conclusion Nnoprticles of ZnO undoped nd doped with coblt with different concentrtion hve been successfully prepred by chemicl precipittion method. The XRD ptterns obtined confirmed the formtion of wurtzite hexgonl ZnO nnostructures without ny impurities. The clculted vlue of lttice constnts re =b=.35 nm nd c=.5 nm nerly equl to stndrd vlue nd reltive d- spcing for lttice plnes (1), () nd (11) re nerly equl. The sizes of ZnO prticles re in the rnge of 8-4 nm which hve been determined using Debye Scherrer formul. The Co doped ZnO nnoprticles decrese with increse in concentrtion of coblt. The Zn-O bond length clculted is chnged from to Å with Coblt concentrtion (5-15%). The volume, density nd specific surfce re lso chnge with incorportion of coblt. Acknowledgments The uthor is highly obliged to deprtment of physics, G.N.D.U., Amritsr, for providing me XRD fcilities nd lso grteful to Dr. Gurinder Pl Singh nd Dr. Pvinder Kur, Deprtment of Physics, Khls College, Amritsr for providing me the vluble suggestions. References [1]. Y. Ju-Nm, et l. Mnufctured nnoprticles: An overview of their chemistry, interctions nd potentil environmentl implictions []. Sci. Totl Environ., 4 (1-3), 8, [3]. Y.L.Wu, C.S. Lim, S.Fu, X.T. Zeng,Surfce modifiction of ZnO quntum dots for bioimging, Nnotechnology 18 (1), 7, [4]. K.Mtsubr, P.Fons, K.I.Wt, A.Ymd, K. Skuri, H. Tmpo, S. Niki. Thin Solid Films: Proceedings of Symposium B, Thin Film Chlcogenide Photovoltic Mterils, E-MRS Spring Meeting, Strsbourg, Frnce,431 43,3, [5]. N.Sito, H. Hned, T. Sekiguchi, N. Ohshi, I. Skguchi nd K. Koumoto. Low-Temperture Fbriction of Light-Emitting Zinc Oxide Microptterns Using Self-Assembled Monolyers Adv. Mter. 14,, 418. DOI: 1.979/ Pge

7 [6]. Y. Wng, L.Chen. Quntum dots, lighting up the reserch nd development of nnomedicine Nnotechnology, Biology, nd Medicine, 7, 11, [7]. M. H. Koch, P. Y. Timbrell nd R. N. Lmb. The influence of film crystllinity on the coupling efficiency of ZnO opticl modultor wveguides, Semicond. Sci. Tech. 1, 1995, 153. [8]. K.Keis, E.Mgnusson, H.Lindstorm, S.E.Lindquist nd A.Hgfelt. Nnowire-bsed dye-sensitized solr cellssol. Energ. Mter. Sol. Cells, 73,, 51. [9]. S. J. Perton, D. P. Norton, K. Ip. Y. W. Heo nd T. Steiner. Synthesis of ZnO nno rods by dip coting method, Superltt. Microstr. 34, 3, 3. [1]. Y. C. Kong, D. P. Yu, B. Zhng, W. Fng, nd S. Q. Feng. Ultr violet- emitting nnowires synthesized by physicl vporiztion, Appl. Phys. Lett. 78, 1, 4. [11]. Z. Zho, X. Lei. Zhng, B. Wng, nd H. Jing, ZnO bsed Amperometric enzyme biosensor, Sensors 1, 1, [1]. K. Senthilkumr, O. Senthilkumr, Kzuki Ymuchi,Sto Moriyuki, Morito Shigekzu, Ohb Tkuy, Nkmur Morihiko, Fujit Ysuhis. Preprtion of ZnO nnoprticles for bio-imging pplictions, Phys.Sttus Solidi. B, 46, 9, [13]. S. Ling, H. Sheng, Y. Liu, Z. Hio, Y. Lu nd H. Shen. Synthesis nd chrcteriztion of ZnO/ZnS core/shell, J. Cryst. Grow. 5, 1, 11. [14]. D.C. Oertel, M. G.Bwendi, A.Arngo, C.V. Bulovic. Guging structurl spects of ZnO nno crystl growth, Appl. Phys. Lett. 87, 5, [15]. D.R. Clrke, Vristor cermics, J. Am.Cerm. Soc. 8, 1999, [16]. P. Bindu, Sbu.Thoms. Estimtion of lttice strin in ZnO nnoprticles: X-ry pek profile nlysis, J. Theor. Appl. Phys. 8, 14, [17]. M.E. Abrishni, S.M. Hosseini, E.A. Kkhki, A.Kompny. Structurl nd opticl properties of zinc oxide nnopowders doped with Mn, Phys. Sttus. C, 7, 1, [18]. V. D. Mote, J. S. Drgd, B. N. Dole. Effect of doping on structurl, physicl, morphologicl nd opticl properties of Zn 1 x Mn x O nno-prticles, Nnoscience nd Nnoengineering. 1(), 13, [19]. U.Seetwn, S.Jugsujind, T.Seetwn, A.Rtchsin, C.Euvnnont, C.Junin, C.Thnchynont, P.Chinronk. Effect of clcintions temperture on crystllogrphy nd Nnoprticles in ZnO Disk, Mters. Sci. Appls., 11, []. M.Sleem, L. Fng, H.B. Run, F. Wu, Q.L. Hung, C.L. Xu, C.Y. Kong. Effect of Zinc cette concentrtion on structurl nd opticl properties I of ZnO thin films deposited by Sol-Gel method,int.. J. Phy. Sci. 7(3), 1, [1]. C.S.Brret, T.B.Msslski. Structure of metls : crystllogrphic methods, principles nd dt, (Pergmon Press, Oxford, 198). []. F.C.M. Vndepol. Thin-film ZnO - properties nd pplictions, Am. Cer. Soc. 69(1), 199, IOSR Journl of Applied Physics (IOSR-JAP) is UGC pproved Journl with Sl. No. 51, Journl no S.Amrit Kur. Synthesis nd structurl nlysis of coblt doped zinc nnoprticles. IOSR Journl of Applied Physics (IOSR-JAP), vol. 9, no. 5, 17, pp DOI: 1.979/ Pge

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