Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

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1 Spectrochimic Act Prt A 78 (2011) Contents lists ville t ScienceDirect Spectrochimic Act Prt A: Moleculr nd Biomoleculr Spectroscopy journl homepge: FTIR studies of plsticized poly(vinyl lcohol) chitosn lend doped with NH 4 N 3 polymer electrolyte memrne M.F.Z. Kdir, Z. Aspnut, S.R. Mjid, A.K. Arof Centre for Ionics, Physics Deprtment, University of Mly, Kul Lumpur, Mlysi rticle info strct Article history: Received 19 My 2010 Received in revised form 1 Decemer 2010 Accepted 14 Decemer 2010 Keywords: FTIR Poly(vinyl lcohol) chitosn Ethylene cronte Proton conductor Ammonium nitrte Fourier trnsform infrred (FTIR) spectroscopy studies of poly(vinyl lcohol) (PVA), nd chitosn polymer lend doped with mmonium nitrte (NH 4 N 3 ) slt nd plsticized with ethylene cronte () hve een performed with emphsis on the shift of the croxmide, mine nd hydroxyl nds. 1% cetic cid solution ws used s the solvent. It is oserved from the chitosn film spectrum tht evidence of polymer solvent interction cn e oserved from the shifting of the croxmide nd t 1660 cm 1 nd the mine nd t 1591 cm 1 to 1650 nd 1557 cm 1 respectively nd the shift of the hydroxyl nd from 3377 to 3354 cm 1. The hydroxyl nd in the spectrum of PVA powder is oserved t 3354 cm 1 nd is oserved t 3343 cm 1 in the spectrum of the PVA film. n ddition of NH 4 N 3 up to 30 wt.%, the croxmide, mine nd hydroxyl nds shifted from 1650, 1557 nd 3354 cm 1 to 1642, 1541 nd 3348 cm 1 indicting tht the chitosn hs complexed with the slt. In the PVA NH 4 N 3 spectrum, the hydroxyl nd hs shifted from 3343 to 3272 cm 1 on ddition of slt from 10 to 30 wt.%. cts s plsticizing gent since there is no shift in the nds s oserved in the spectrum of PVA chitosn films. The mechnism of ion migrtion is proposed for the plsticized nd unplsticized PVA chitosn NH 4 N 3 systems. In the spectrum of PVA chitosn NH 4 N 3 complex, the doulet C stretching in is oserved in the vicinity 1800 nd This indictes tht there is some interction etween the slt nd Elsevier B.V. All rights reserved. 1. Introduction Polymer lends hs ttrcted the ttention of mny reserchers. This is due to the possiility of developing new mterils from polymer lends. The properties of the lend re different nd etter thn the properties of the single polymer [1 3]. For exmple, the conductivity of polymer electrolyte cn e improved if the host is lend of two polymers [4 6]. Polymer lending cn gurntee structurl stility [7]. Poly(methylmethcrylte) (PMMA) nd poly(vinylidene fluoride) (PVdF) [8], PMMA nd poly(vinyl lcohol) (PVA) [4], poly(vinyl chloride) (PVC) nd PVdF [9], chitosn nd poly(ethylene oxide) (PE) [10] re mong polymeric lends tht hve een previously studied. Chitosn is nturl polymer nd its chemicl structure (1 4)-2-mino-2- deoxy- -d-glucn, contins N-decetylted derivtives of chitin, (1 4)-2-cetmido-2-deoxy- -d-glucn [11 13]. Chitosn hs een used in mny pplictions for exmple s seprtors in medicine nd iotechnology [14], for the removl of hevy metls nd rdioisotopes to prevent wter pollution [15] s food pckging mterils [16] nd dietry fier nd potentil medicine Corresponding uthor. Tel.: E-mil ddress: krof@um.edu.my (A.K. Arof). ginst hypertension [17]. In our lortory, polymer electrolyte sed on chitosn hs een studied [18 22] for potentil ppliction in electrochemicl devices such s tteries [23 25]. Donoso et l. [26] hve shown tht the nitrogen toms in chitosn serve s complextion sites for ction coordintion. Chitosn is iocomptile nd iodegrdle [27]. Chitosn lso lends with other polymer [3] nd is expected to e used in the development of composite mterils since it hs mny functionl groups [28 29]. Chitosn lend sed polymer electrolytes [30 32] hve een used in electrochemicl devices such s solr cells [33 34] nd super cpcitors [35]. In previous work, we hve prepred polymer electrolyte sed on PVA chitosn lends nd pplied the electrolyte in primry nd secondry ttery [36]. In the iomedicl field it hs een reported tht the memrne formed from chitosn nd PVA lend is more fvorle for cell culture compred to pure PVA memrne [37]. PVA is semi crystlline polymer with cron chin ckone nd hydroxyl groups ttched to the methne crons [4]. PVA is highly hydrophilic, non toxic nd low cost polymer with good mechnicl strength, therml stility, chemicl stility nd excellent film forming properties [38]. PVA is iocomptile, non toxic nd exhiits miniml cell dhesion nd protein sorption. PVA memrne hs formed ppliction in the iomedicl field [39]. Polymer electrolyte sed on PVA hs een reported to exhiit good conductivity [40 42] nd the polymer /$ see front mtter 2010 Elsevier B.V. All rights reserved. doi: /j.s

2 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) electrolyte sed on PVA is potentilly employed in the ppliction of electrochemicl devices such s lithium [43] nd zinc ir tteries [44], fuel cells [45] nd electric doule lyer cpcitors [46]. Hem et l. [47] hve shown tht in PVA sed polymers, the conduction tkes plce when protons from the slt hops vi ech coordinting site (oxygen) of the polymer host. From our previous work [36], conductivity of the polymer NH 4 N 3 electrolyte with 40 wt.% NH 4 N 3 ws Scm 1 nd when plsticized with 70 wt.%, the conductivity incresed to Scm 1. X-ry diffrction nd scnning electron microscopy studies hve shown tht concentrtion of NH 4 N 3 slt influences the conductivity since the diffrctogrm of the smple with crystlline structures protruding its surfce shows peks tht cn e ttriuted to the slt. With more slt crystllizing out of the smple surfce the numer of moile ions tht cn contriute to conductivity decreses. To further discuss the phenomen such s slt polymer complextion, ion ggregtion formtion nd interction etween the slt nd plsticizer in the smple, FTIR ws employed. This pper reports some detils of interctions etween polymer polymer, polymer slt, polymer plsticizer, polymer slt plsticizer nd slt plsticizer with emphsis t the croxmide, mine nd hydroxyl groups present in the polymers Experimentl 2.1. Smple preprtion To study the FTIR in the present work, 7 systems were prepred Chitosn PVA, Chitosn NH 4 N 3, PVA NH 4 N 3, Fig. 1. () FTIR spectr of pure chitosn powder, pure chitosn film nd PVA chitosn lend with the rtio of 3:2 in the region of croxmide nd mine nds. () FTIR spectr of pure PVA, PVA film, pure chitosn powder, pure chitosn film nd PVA chitosn lend with the rtio of 3:2 in the region of hydroxyl nd c (vi) Fig. 2. () FTIR spectr of pure chitosn film nd pure chitosn film with 10 wt.% NH 4N 3, 30 wt.% NH 4N 3, 50 wt.% NH 4N 3 nd pure NH 4N 3 slt in the cm 1 spectr region. () FTIR spectr of pure chitosn film nd pure chitosn film with 20 wt.% NH 4N 3, 30 wt.% NH 4N 3, 40 wt.% NH 4N 3 nd 50 wt.% NH 4N 3 in the cm 1 spectr region. (c) FTIR spectr of pure chitosn film nd pure chitosn film with 20 wt.% NH 4N 3, 30 wt.% NH 4N 3, 40 wt.% NH 4N 3, 50 wt.% NH 4N 3 nd (vi) pure NH 4N 3 slt in the symmetric (N 3 ) virtion mode spectr region.

3 1070 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) wt.% 50 wt.% 30 wt.% 50 wt.% (vi) Fig. 4. () FTIR spectr of pure PVA chitosn lend nd PVA chitosn lend with 50 wt.% in the cm 1 spectr region. () FTIR spectr of pure PVA chitosn lend film with 30 wt.% nd 50 wt.% in the cm 1 spectr region Fig. 3. () FTIR spectr of pure PVA film nd PVA with 10 wt.% NH 4N 3, 20 wt.% NH 4N 3, 30 wt.% NH 4N 3, 50 wt.% NH 4N 3 nd (vi) pure NH 4N 3 slt in the cm 1 spectr region. () FTIR spectr of pure PVA film nd PVA with 10 wt.% NH 4N 3, 40 wt.% NH 4N 3 nd pure NH 4N 3 slt in the symmetric (N 3 ) virtion mode spectr region. PVA chitosn, PVA chitosn NH 4 N 3, PVA chitosn NH 4 N 3, NH 4 N PVA with moleculr weight 10,000 g mol 1, highly viscous chitosn powder nd were procured from Aldrich Chemicl Co. Glcil cetic cid ws procured from AJAX Chemicls. 1% cetic cid solution ws used s the solvent nd ll films were prepred using the solution cst technique Smple chrcteriztion Fourier trnsform infrred (FTIR) spectroscopy Thermo Scientific/Nicolet is10 FTIR spectrometer ws used to record the FTIR spectr with 1 cm 1 resolution in the trnsmission mode from wve numers cm 1. Confirmtion of complextion nd proposition of the conduction mechnism of Wve numer (cm -1 ) 1735 Fig. 5. () FTIR spectr of pure, mixed with 0.5 wt.% of NH 4N 3 nd mixed with 1.1 wt.% of NH 4N 3 in the region C ending nd. () FTIR spectr of pure, mixed with 0.5 wt.% of NH 4N 3 nd mixed with 1.1 wt.% of NH 4N 3 in the region of C stretching nd.

4 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) c (vi) Fig. 6. () FTIR spectr for pure PVA chitosn lend film nd pure PVA chitosn lend film with 10 wt.% NH 4N 3, 20 wt.% NH 4N 3, 40 wt.% NH 4N 3 nd 50 wt.% NH 4N 3 in the cm 1 spectr region. () FTIR spectr for pure PVA chitosn lend film nd pure PVA chitosn lend film with 10 wt.% NH 4N 3, 20 wt.% NH 4N 3, 40 wt.% NH 4N 3, 50 wt.% NH 4N 3 nd pure NH 4N 3 slt in the cm 1 spectr region. (c) FTIR spectr of pure PVA chitosn lend film nd pure PVA chitosn lend film with 20 wt.% NH 4N 3, 30 wt.% NH 4N 3, 40 wt.% NH 4N 3, 50 wt.% NH 4N 3 nd (vi) pure NH 4N 3 slt in the symmetric (N 3 ) virtion mode spectr region. the chrge crriers were the ojectives of performing FTIR spectroscopy. 3. Results nd discussion 3.1. FTIR spectr of PVA chitosn lend The croxmide C NHR nd in the spectrum of pure chitosn powder peks t 1660 cm 1 nd the mine (NH 2 ) nd t 1591 cm 1, Fig. 1. In Fig. 1, the croxmide nd hs shifted to 1650 cm 1 nd the mine nd to 1557 cm 1 in the pure chitosn film. The position of the croxmide nd for the pure chitosn film in the present work is the sme s tht reported y smn nd Arof [48]. Mjid nd Arof [49] reported tht the mine nd in the spectrum of the pure chitosn film is situted t 1553 cm 1 nd their results re lso comprle with the present work. The shift in these nds s depicted in the spectrum of the chitosn film is ttriuted to some interctions etween the cetic cid solvent nd the nitrogen donors of chitosn polymer [48]. The hydroxyl nd in the spectrum of pure PVA powder is shown in Fig. 1 t 3354 cm 1. The hydroxyl nd in the spectrum of PVA film shown in Fig. 1 hs shifted to 3343 cm 1 indicting tht interction etween PVA nd the solvent. The hydroxyl nd is locted t 3337 cm 1 in the spectrum of PVA chitosn lend film, Fig. 1. Zhng et l. [50] suggested tht hydrogen onds occurred etween hydroxyl groups in PVA nd hydroxyl groups in chitosn since the hydroxyl nd for the PVA chitosn lend film shifted to lower wve numers Interctions etween chitosn NH 4 N 3 Fig. 2 shows the spectr of chitosn NH 4 N 3 complexes in the region of hydroxyl nd. From the literture [50], the hydroxyl nd of chitosn hs een reported to e etween 3200 nd 3500 cm 1. From Fig. 2, it cn e seen tht the hydroxyl nd in chitosn lso experienced some shift on the ddition of NH 4 N 3 slt from 3354 to 3348 cm 1. The v s (NH 4 + ) virtion mode ppers

5 1072 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) (c) () plextion etween chitosn nd NH 4 N 3 hs occurred s reported y Mjid nd Arof [49]. The conducting species in this work is H +. This is sed on the work y Hshmi et l. [52] tht the conducting species in the PE NH 4 Cl 4 complex is the H + ion which origintes from the mmonium ion nd the conduction occurs vi the Grotthus mechnism. Buridh et l. [53] hve inferred tht in the chitosn NH 4 I complex the ction from NH 4 I coordintes with the N tom of the mine group in chitosn. NH 4 + ctions hve tetrhedrl structure. ne of the four hydrogen toms in NH 4 + ions is most wekly ound nd cn dissocite esily under the influence of n electric field. This H + ion cn hop from one site to nother leving vcncy which will e filled y nother H + ion from neighoring site [52 53]. Hence from FTIR spectroscopy, the interction etween chitosn nd NH 4 N 3 hs een confirmed nd the conduction mechnism in the polymer electrolytes is expected to occur vi the Grotthus mechnism. Fig. 2c represents the spectr of the symmetric v s (N 3 ) virtion mode. From the spectrum in Fig. 2c(vi), the v s (N 3 ) mode of pure NH 4 N 3 slt is t cm 1. Liu et l. [54] reported tht symmetric ending nd of N 3 in the spectrum of queous NH 4 N 3 is situted t 830 cm 1 nd the mode is infrred ctive nd their result is comprle with the present work. It cn e oserved tht with incresing mount of NH 4 N 3, the intensity of the v s (N 3 ) mode pek increses nd it did not shift to lower or higher wvenumers, Fig. 2c. Hence it cn e concluded tht N 3 nions did not complex with the polymer host in the present work Interctions etween PVA NH 4 N 3 () In the present work, the stretching virtion of hydroxyl groups (H) in the spectrum of pure PVA film ppers t 3343 cm 1, Fig. 3. n ddition of 30 wt.% of NH 4 N 3 slt, the nd shifts to lower wvenumers t 3272 cm 1, Fig. 3. With further ddition of 50 wt.% slt, new pek ttriutle to v s (NH 4 + ) nd v s (NH 4 + ) modes of NH 4 N 3 slt pper t 3253 nd 3086 cm 1, Fig. 3 implying tht interction occurs etween the NH 4 + nd PVA. From Fig. 3(), it cn e oserved tht with incresing mount of NH 4 N 3, the intensity of the v s (N 3 ) mode pek increses nd did not shift inferring tht N 3 nions did not complex with the PVA in the present work. Hem nd co-workers hve reported tht conduction occurs vi the H group following the Grotthus mechnism in PVA NH 4 Br [47] nd PVA NH 4 I systems [55] Fig. 7. FTIR spectr for PVA chitosn 40 wt.% NH 4N 3 film with () 0 wt.%, () 70 wt.% nd (c) 80 wt.% in the region of C ending nd. t cm 1 with the ddition of 50 wt.% NH 4 N 3 slt to the polymer, Fig. 2. In ddition, pek ttriuted to v s (NH 4 + ) ppers t 3096 cm 1 in the spectrum for the smple with 50 wt.% slt, Fig. 2. From Chintplli et l. [51] in the spectrum of PE NH 4 CF 3 S 3 the v s (NH 4 + ) nd v s (NH 4 + ) modes pper t 3222 nd 3097 cm 1 respectively. According to the uthors, the symmetry of NH 4 + is lowered which in turn reflects interction etween NH 4 + nd the polymer in their system. Their result is comprle with the present work, thus it is lso concluded tht chitosn hve intercted with NH 4 N 3 t the hydroxyl nd. In the present work the mine nd of pure chitosn film ppers t 1557 cm 1 nd the croxmide nd t 1650 cm 1 s shown in Fig. 2. n ddition of 20 wt.% NH 4 N 3 slt, Fig. 2 the croxmide nd mine nds hve shifted to 1644 nd 1550 cm 1. The nds shift to even lower wvenumers s more slt is dded nd when 50 wt.% of NH 4 N 3 ws dded to chitosn, Fig. 2, the croxmide nd mine peks shift to 1635 nd 1533 cm 1. This indictes tht com Interction etween PVA chitosn Fig. 4() nd 4 () represents the infrred spectrum of pure PVA chitosn lend nd PVA chitosn lend films with the ddition of in the region etween 2990 nd 3590 cm 1 nd 1505 nd 1685 cm 1 respectively. It cn e concluded tht there is no interction etween PVA chitosn lend nd ethylene cronte since there re no shift of the nds oserved in the spectr Interctions etween NH 4 N 3 Fig. 5 shows the infrred spectrum of pure nd mixed with NH 4 N 3. To study the interctions etween nd NH 4 N 3, ws heted to 38 C until it melts nd ecomes liquid solution. 0.5 nd 1.1 wt.% of NH 4 N 3 ws dded to 50 ml of seprtely nd stirred until complete dissolution. From Fig. 5, it cn e clerly seen tht the C ending nd which ppers in pure t 715 cm 1 (Fig. 5) hs shifted to 717 cm 1 (Fig. 5) fter the ddition of 0.5 wt.% NH 4 N 3 nd to 719 cm 1, Fig. 5 on the ddition of 1.1 wt.% NH 4 N 3. In the work of smn nd Arof [48], the shift of the C ending nd in pure ws reportedly due to the interction etween Li + slt nd C group of the molecule nd their results re in good greement with Chintplli nd Frech [56]. In

6 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) c d e Fig. 8. FTIR spectr for PVA chitosn 40 wt.% NH 4N 3 film with () 0 wt.%, () 40 wt.%, (c) 60 wt.%, (d) 70 wt.% nd (e) 80 wt.% in the region of C nd. stretching the present study it cn e inferred tht the H + from the ction of the slt hs intercted (formed wek ond) with the cronyl C nd of molecule since the C ending nd hs shifted when NH 4 N 3 ws dded. The doulet nds in Fig. 5 represent virtions of C stretching. In pure, the doulet nds re oserved t 1771 nd 1797 cm 1, Fig. 5. With the ddition of 0.5 wt.% NH 4 N 3, the nds shifted to 1772 nd 1802 cm 1, Fig. 5. After the ddition of 1.1 wt.% of slt, the nds hve shifted to 1773 nd 1803 cm 1, Fig. 5. The shifts tht occurred in this doulet nd re in greement with tht reported y smn nd Arof [48] nd inferring interction etween slt nd Interctions etween PVA chitosn NH 4 N 3 In the present work, the mine nd of pure PVA chitosn lend film ppers t the 1558 cm 1 nd the croxmide nd t 1647 cm 1, Fig. 6. n ddition of 10 wt.% NH 4 N 3 slt, Fig. 6. The croxmide nd mine nd hs shifted to 1645 nd 1539 cm 1. n ddition of 50 wt.% NH 4 N 3 the peks for croxmide nd mine nds shifted to 1625 nd 1516 cm 1 respectively, Fig. 6. The hydroxyl nd hs lso shifted from 3337 to 3318 cm 1 with the ddition of 40 wt.% NH 4 N 3, Fig. 6. For NH 4 N 3 concentrtions up to 40 wt.%, N H virtion nd is not ovious. When the concentrtion of slt is greter thn 40 wt.% the N H nd is ovious t 3250 cm 1 compred to cm 1 oserved in the spectrum of pure slt, Fig. 6. It cn thus e inferred tht either the excess slt did not ssocite or the ions recomine to form neutrl ion pirs tht the overll conductivity dropped for slt concentrtions greter thn 40 wt.%. Mson et l. [57] lso reported tht higher ggregtion would result in fewer ville chrge crriers tht will led towrds the decrese of conductivity of their system, poly(n-methyl-propylenimine)-lithium triflte. XRD nd SEM confirm the presence of crystllites [36]. The shifts in the croxmide, mine nd hydroxyl nds indicte tht interction occurred etween the PVA chitosn lend (host) nd NH 4 N 3 (doping slt). N 3 nions clerly did not interct with the PVA chitosn lend polymer electrolyte where it cn e oserved tht the v s (N 3 ) mode did not shift s depicted in Fig. 6c Interctions etween PVA chitosn NH 4 N 3 The infrred spectr of PVA chitosn NH 4 N 3 system re shown in Figs. 7 nd 8, in the region of C ending nd of nd doulet C stretching nd of respectively. From previous work [36], the highest conducting smple for plsticizer free smple hs 40 wt.% NH 4 N 3 concentrtion. Different mounts of hve een dded to enhnce the conductivity. No pek ws oserved for the smple with 0 wt.% in the region of C ending nd, Fig. 7 nd with ddition of wt.% of the pek ppered nd hve shifted to lower wvenumers t 715 cm 1, Fig. 7c. From Fig. 8 no doulet C stretching of ws oserved in the spectrum of the free smple. With ddition of 40 wt.%, C doulet pek ws oserved t 1777 nd 1808 cm 1, Fig. 8. The doulet peks shifted to lower wvenumers on the ddition of 60 wt.%. Further ddition of 70 wt.% hs shifted the doulet peks to even lower wve numers t 1774 nd 1803 cm 1, Fig. 8d. The conductivity vlue for the plsticized system in the previous work ws found to hve mximum vlue t 70 wt.% concentrtion. However, fter the ddition of 80 wt.% of, the doulet pek hs shifted to 1771 nd 1790 cm 1 nd the intensity of oth peks hs lso decresed, Fig. 8e. This pek my indicte the increse in crystllinity of the smple ccompnied y the decrement of conductivity s studied from the previous work [36]. Bsed on these oservtions, the ion conductivity mechnism for PVA chitosn NH 4 N 3 nd PVA chitosn NH 4 N 3 systems is proposed s depicted in Fig. 9.

7 1074 M.F.Z. Kdir et l. / Spectrochimic Act Prt A 78 (2011) H H NH 3 N 3 H H H H H H H H H H H H NH 3 N 3 H H NH 3 N 3 H CH 2 CH 2 CH2 H NH 2 NH 2 H NH 2 H H H H NH 3 N 3 H NH 3 N 3 riginl hopping without plsticizer New pthwys (with plsticizer) Fig. 9. H + conduction mechnism in PVA chitosn NH 4N 3 system. 4. Conclusions From FTIR studies, the PVA chitosn lend films hve croxmide, mine nd hydroxyl nds. The mmonium nitrte slt intercts with the chitosn film s evidenced from the shift of the croxmide, mine nd hydroxyl nds. The hydroxyl nd in PVA film shifts when complextion with NH 4 N 3 slt occurs. NH 4 N 3 slt interction with the PVA chitosn lend is confirmed when the croxmide, mine nd hydroxyl nds hve shifted to lower wve numers. showed no interction with PVA chitosn lend. From the FTIR results, it is clerly explined lthough there is interction etween the two polymers through hydrogen onding, however there is interction etween the slt nd since the C ending nd C stretching nds hve shifted. These shifts re lso oserved in the spectrum of PVA chitosn NH 4 N 3 system. The increse nd decrese in conductivity from our previous work [36] hve een further explined using results oserved from FTIR spectroscopy. Acknowledgements M.F.Z. Kdir would like to thnk the Ministry of Science, Technology nd Innovtion of Mlysi (MSTI) for the PGD scheme scholrship nd University of Mly for the grnt wrded (PS352/2009A). All uthors thnk the University of Mly for the fcilities. References [1] X. Lu, R.A. Weiss, Mcromolecules 24 (1991) n [2] J.L. Acost, E. Morles, Solid Stte Ionics 85 (1996) 85. [3] C. Sndovl, C. Cstro, L. Grgllo, D. Rdic, J. Freire, Polymer 46 (2005) [4] S. Rjendrn,. Mhendrn, Ionics 7 (2001) 463. [5]. Ingnss, Br. Polym. J. 20 (1988) 233. [6] D.W. Kim, J.R. Prk, H.W. 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