Synthesis and Photoluminescence of Er 3+ and Yb 3+ Doped ZnS Nanocrystals

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1 Rre Metl Mterils nd Engineering Volume 47, Issue 6, June 2018 Online English edition of the Chinese lnguge journl Cite this rticle s: Rre Metl Mterils nd Engineering, 2018, 47(6): ARTICLE Synthesis nd Photoluminescence of Er 3+ nd Y 3+ Doped ZnS Nnocrystls Li Lihu 1, Zhng Xing 2, Li Xinli 1, Hung Jinling 1, Alex A. Volinsky C 3 1 Henn University of Science nd Technology, Luoyng , Chin; 2 Chin Avition Lithium Bttery Co., Ltd, Luoyng , Chin; 3 University of South Florid, 4202 E. Fowler Ave., ENB118, Tmp FL 33620, USA Astrct: ZnS:Er/Y nnocrystls were synthesized y hydrotherml method using thioglycolic cid s stilizer. The crystlline phses, morphology, chemicl ond sttes nd photoluminescent properties of the nnoprticles were chrcterized y X-ry diffrction, trnsmission electron microscopy, X-ry photoemission spectroscopy nd fluorescence photometer. The results show tht most prepred nnoprticles re sphericl in shpe with n verge size of 5 nm, nd hve cuic zinc lende crystl structure. The emission spectrum of ZnS:Er/Y nnocrystls excited t 270 nm displys three min peks t 470, 530 nd 580 nm, nd the intensity of fluorescence peks is the strongest for nnocrystls prepred t 120 C. When ZnS: Er/Y nnocrystls re excited t 980 nm, the emission peks round 540 nd 650 nm pper, ssocited with the 4 F 3/2 4 I 15/2 nd 4 F 9/2 4 I 15/2 of Er 3+ ions trnsitions, respectively. Key words: ZnS:Er/Y nnocrystls; hydrotherml; photoluminescence Zinc sulfide (ZnS) is n importnt II-VI semiconductor mteril nd its direct nd gp ws reported to e 3.65 ev [1]. Due to its excellent luminescence nd photochemistry properties, ZnS hs een widely pplied in solr cells [2], nucler tteries [3], optoelectronic devices [4], light emitting diodes (LEDs) [5, 6] nd io-proes in sensing nd imging [7-10]. Doping is one of the most intensively used methods to modify the luminescence, electricl nd opticl properties of semiconducting nnomterils y introducing trps nd discrete energy sttes in the nd gp for the excited electrons. In 1994, Bhrgv et l. first demonstrted opticl properties of mngnese-doped ZnS nnocrystls [11], fter which lrge numer of investigtions on trnsition metl doped ZnS nnocrystls hve een reported. Mngnese-doped ZnS exhiits excellent luminescence efficiency nd therml stility, which highlight the prospects of potentil pplictions in therpeutic nd dignostic fields [12-14]. ZnS nnorods doped with 0 mol%~15 mol% of Cu hve een prepred y simple solvotherml process [15]. Z. H. Xu et l. [3] designed, fricted, nd tested et rdioluminescence (RL) nucler ttery sed on the ZnS: Cu phosphor lyers with plne nd V groove structures. Cr-doped ZnS nnoprticles with Cr concentrtions of 0.5 t%, 1 t%, 2 t% nd 3 t% were successfully synthesized y the chemicl co-precipittion method using EDTA s the cpping gent [16]. It is known tht the rre-erth elements s dopnts could e more eneficil in modifying the luminescence properties of ZnS y considering their specil 4f-4f intr-shell trnsitions. M. Pl et l. hve synthesized Eu-doped ZnS nnoprticles y wet chemicl route, nd oserved the red PL emission due to the intr-4f trnsitions of Eu 3+ ions [17-19]. For the T-doped ZnS nnocrystls photoluminescence properties, the four trnsitions from 5 D 4 7 F 6, 5 D 4 7 F 5, 5 D 4 7 F 4 nd 5 D 4 7 F 3 of T 3+ ions hve een reported in literture [20]. In this pper, photoluminescence properties of Er/Y doped ZnS nnocrystls with out 5 nm in dimeter otined y hydrotherml method with thioglycolic cid s stilizer were discussed. Received dte: June 09, 2017 Foundtion item: Ntionl Nturl Science Foundtion of Chin ( ) Corresponding uthor: Hung Jinling, Ph.D., Professor, School of Mterils Science nd Engineering, Henn University of Science nd Technology, Luoyng , P. R. Chin, Tel: , E-mil: hungjl@hust.edu.cn Copyright 2018, Northwest Institute for Nonferrous Metl Reserch. Pulished y Elsevier BV. All rights reserved.

2 Li Lihu et l. / Rre Metl Mterils nd Engineering, 2018, 47(6): Experiment All the regents or solvents were of nlyticl grde nd used without further purifiction. Sodium sulfide (N 2 S 9H 2 O: 98%) nd zinc cette (Zn(Ac) 2 : 99%) were purchsed from Tinjin Kermel Chemistry Regent Co., Ltd. Thioglycolic cid (C 2 H 4 O 2 S: 99.8%) ws purchsed from Tinjin FuYu Chemistry Regent Co., Ltd. Erium nitrte (Er(NO 3 ) 3 5H 2 O: 99.95%) ws purchsed from Shnghi PuZhen Biologicl Technology Co., Ltd. Ytterium nitrte (Y(NO 3 ) 3 5H 2 O: 99.9%) ws purchsed from the Shnghi Purple Regent Fctory. ZnS:Er/Y nnocrystls were prepred y the hydrotherml method. The molr rtio of sodium sulfide to zinc cette ws 1:1. Zinc cette nd doped ions with different molr rtios were dissolved in deionized wter. Susequently, thioglycolic cid (C 2 H 4 O 2 S) ws dded in the ove solution, nd cted s the stilizer with constnt stirring t room temperture for 30 min. Then the solution ws slowly poured into the utoclve, nd synthesized for 8 h t 100, 120, 140 nd 160 C. The products were filtered, wshed severl times with deionized wter nd then with ethnol, nd susequently dried in vcuum t 60 C. The procedure yielded lrge numer of ZnS:Er/Y nnoprticles with prticle size of out 5 nm. The luminescent properties of these prticles were studied. The crystlline phses of ZnS:Er/Y nnocrystls were identified y X-ry diffrction (XRD, DX-1000, Dndong, Chin). The dt ws recorded for 2θ vlues rnging from 20 to 80. The scn rte ws 1 /min. The size nd morphology of the nnocrystls were oserved y high-resolution trnsmission electron microscopy (HRTEM, JEM-2010, Shimdzu, Jpn). The chemicl ond sttes were nlyzed y X-ry photoemission spectroscopy (XPS, Escl 250Xi, USA). The photoluminescence spectr of the nnocrystl smples were mesured using fluorescence spectrophotometer (F-280, Tinjin, Chin) nd grting spectrogrph (Zolix SBP-300, USA). 2 Results nd Discussion 2.1 Structure nlysis X-ry diffrction ptterns of Er,Y doped ZnS nnoprticles which were synthesized t 140 C for 8 h re shown in Fig.1. The XRD ptterns of nnoprticles exhiit cuic structure with some peks for the (311), (220) nd (111) plnes. The verge size (D) of the ZnS nnoprticles cn e clculted ccording to the Scherrer's eqution: D=kλ/βcosθ, where k is constnt (shpe fctor of out 0.89), λ is the X-ry wvelength ( nm), β is the full width t hlf mximum nd θ is the diffrction ngle. The verge crystlline size of the ZnS:Er/Y nnoprticles is estimted to e 5.2, 4.8, 5.4 nd 5.6 nm. Typicl TEM, HRTEM imges nd selected re electron (111) (220) θ/( ) Fig.1 XRD ptterns of ZnS:Er/Y nnoprticles: (-) ZnS:Er(1 mol%), Y(1 mol%), (-) ZnS:Er(1 mol%), Y(2 mol%), (-c) ZnS:Er (1 mol%), Y(3 mol%), nd (-d) ZnS:Er (1 mol%), Y(4 mol%) Fig.2 TEM imge () nd HRTEM imge nd SAED pttern () of ZnS:Er/Y (2%) nnoprticles (311) diffrction (SAED) pttern of ZnS:Er/Y (2%) nnocrystls re shown in Fig.2. As seen from Fig.2, s-prepred nnoprticles re nerly sphericl nd the verge dimeter is out 5 nm, which is in greement with the vlue otined from XRD nlysis. According to the SAED pttern in Fig.2, the fringe spcing is out 0.29 nm, corresponding to the (111) crystl plnes of the zinc lende ZnS. From the smll inset of Fig.2, it is lso seen tht the ZnS nnoprticles re polycrystlline. The (111), (220) nd (311) plne rings of the SAED nlysis clerly d c 20 nm 8 nm

3 1746 Li Lihu et l. / Rre Metl Mterils nd Engineering, 2018, 47(6): confirm the zinc lende structure of ZnS [21]. 2.2 XPS nlysis Fig.3 shows the XPS survey spectr of the product. The inding energy vlues re ev for S 2p nd ev for Zn 2p 3, nd the kinetic energy for Zn LMM is ev. These results re consistent with the vlues reported y Jing et l [22]. The mount of impurities, such s CO 2, H 2 O, nd O 2 dsored on the surfce of the ZnS nnomterils is smll, s cn e seen from the survey spectrum of the smple. Since XPS is surfce-sensitive technique, the XPS spectr cn primrily revel the chemicl sttes of the outermost lyers of the prticles. The detiled scns of the Er 4d nd Y 4d regions re displyed in Fig.4 nd 4. It is found tht most of the Er, Y-doped sites re locted ner the surfce of the prticle. 2.3 Photoluminescence property nlysis Photoluminescence emission spectr of ZnS:Er/Y with doped concentrtion of 2 mol% nnocrystls excited t 270 nm prepred t different tempertures re shown in Fig.5. The ZnS:Er/Y nnocrystls hve three strong emission peks t 470, 530 nd 580 nm. The emissions centered t 470 nd 580 nm from colloidl suspensions of ZnS were ssigned to vcncy nd interstitil defects [23]. The pek t 530 nm is due to the trnsition of Er ions from the energy level 2 H 11/2 4 I 15/2. In ddition, the fluorescence intensity of the ZnS:Er/Y nnocrystls first increses nd then decreses with the rection temperture. The fluorescence pek intensity is the strongest for nnocrystls prepred t 120 C. The enhncing ions therml motion cuses prt of the fluorescence quenching s the rection temperture increses. The fluorescence intensities of ZnS:Er/Y nnocrystls with different Y ions concentrtions prepred t 120 C is shown in Fig.6. The intensity of the emission peks increses nd then decreses with the doping concentrtion. When Er ion concentrtion is 1 mol%, ZnS:Er/Y nnocrystls hve the strongest performnce with Y ions doping mount of 3 mol%. It fcilittes efficient energy trnsfer from the Y 3+ ions to the Er 3+ ions in the condition. Fig.7 indictes the emission spectr of ZnS:Er/Y nnocrystls excited t 980 nm. The peks round 540 nd 650 nm (168.68, ) Er 4d Fig.4 XPS detil scns of Er 4d () nd Y 4d (d) of ZnS nnocrystls 470 nm (190.83, ) Binding Energy/eV 530 nm 580 nm 100 C 140 C 160 C 120 C Y 4d Zn2p 3 Survey Fig.5 Emission spectr of ZnS:Er/Y nnoprticles excited t 270 nm prepred t different tempertures N1s Er4d C1s S2p N1s Y4d Fig.3 XPS wide survey spectrum of the ZnS:Er/Y nnocrystls O1s Binding Energy/eV re ssocited with trnsition 4 F 3/2 4 I 15/2 nd 4 F 9/2 4 I 15/2 of Er 3+ ions, respectively. Trivlent Y possesses n extremely simple energy level scheme with only one excited 4f level of 2 F 5/2. The 2 F 7/2 2 F 5/2 trnsition of Y 3+ is well resonnt with mny f-f trnsitions of typicl uncovering lnthnide ions, such s Er 3+. The electric dipole moment opertor of the rdition results in the strongest interction. Menwhile, the excited Y 3+ ions trnsfer the energy to the Er 3+ ions. The trnsition energy level digrm of the Y 3+ ions nd the Er 3+ ions is shown in Fig.8 [24].

4 Li Lihu et l. / Rre Metl Mterils nd Engineering, 2018, 47(6): Fig.6 Emission spectr of ZnS:Er/Y nnocrystls with different Y Fig.8 ions concentrtions t 120 C Fig.7 Emission spectr of ZnS:Er/Y nnocrystls excited t 980 nm Energy level digrm of Y 3+ ions nd Er 3+ ions 3 Conclusions nm k l j i 540 nm i: 1 mol% Er, 1 mol% Y j: 1 mol% Er, 2 mol% Y k: 1 mol% Er, 3 mol% Y l: 1 mol% Er, 4 mol% Y 650 nm nm 1) ZnS:Er/Y nnocrystls cn e synthesized y the hydrotherml method with thioglycolic cid s stilizer. ZnS:Er/Y nnoprticles hve out 5 nm prticle size with cuic zinc lende crystl structure. 2) The emission spectrum of the ZnS:Er/Y nnocrystls excited t 270 nm shows three min peks t 470, 530 nd 580 nm, nd the intensity of fluorescence peks is the strongest when the nnocrystls re prepred t 120 C. When ZnS: Er/Y nnocrystls re excited t 980 nm, the emission peks round 540 nd 650 nm pper, ssocited with trnsition 4 F 3/2 4 I 15/2 nd 4 F 9/2 4 I 15/2 of Er 3+ ions, respectively. References 1 Zhng Y C, Wng G Y, Hu X Y et l. Mterils Reserch Bulletin[J], 2006, 41(10): Shit A, Chtterjee S, Nndi A K. Physicl Chemistry Chemicl Physics[J], 2014, 16(37): Xu Z H, Tng X B, Hong L et l. Journl of Rdionlyticl nd Nucler Chemistry[J], 2015, 303(3): Ni W S, Lin Y J. Applied Physics A[J], 2015, 119(3): Gupt S, McClure J C, Singh V P. Thin Solid Films[J], 1997, 299(1-2): 33 6 He X X, Wng W J, Li S H et l. ECS Solid Stte Letter[J], 2015, 4(2): 10 7 Geszke M, Muris M, Bln L et l. Act Biomterils[J], 2011, 7(3): Bn R, Li J J, Co J T et l. Anlyticl Methods[J], 2013, 5(21): Augustine M S, Ans A. Spectrochimic Act Prt A: Moleculr nd Biomoleculr Spectroscopy[J], 2015, 136: Zhou W B, Swift J F, Bneyx B F. Chemicl Communictions[J], 2015, 51: Bhrgv R N, Gllgher D, Hong X et l. Physicl Review Letters[J], 1994, 72(3): Wng H F, Wu Y Y, Yn X P. Anlyticl Chemistry[J], 2013, 85(3): Zhng K, Yu T, Liu F et l. Anlyticl Chemistry[J], 2014, 86(23): Tni J B, Meriem G, Helene G D et l. Journl of Nnoprticle Reserch[J], 2015, 17(6): 1 15 Srivstv R K, Pndey N, Mishr S K. Mterils Science Semiconductor Process[J], 2013, 16(6): Reddy D A, Murli G, Vijylkshmi R P et l. Applied Physics A[J], 2011, 105(1): Lotey G S, Jindl Z, Singhi V et l. Mterils Science Semiconductor Process[J], 2013, 16(6): Ashwini K, Pndurngpp Y C. Opticl Mterils[J], 2014, 37: Pl M, Mthews N R, Morles E R. Opticl Mterils[J], 2013, 35(12): Ling Z G, Mu J, Hn L et l. Journl of Nnomterils[J], 21 Mohmmdikish M, Dvr F, Loghmn-Estrki M R. Cermics Interntionl[J], 2013, 39(3): 3173

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