Synthesis of graphene oxide-intercalated a-hydroxides by metathesis and their decomposition to graphene/metal oxide composites

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1 CARBON 48 (2010) ville t journl homepge: Synthesis of grphene oxide-interclted -hydroxides y metthesis nd their decomposition to grphene/metl oxide composites C. Nethrvthi, Michel Rjmthi, *, N. Rvishnkr, Lun Bsit c, Cludi Felser c Mterils Reserch Group, Deprtment of Chemistry, St. Joseph s College, 36 Llgh Rod, Bnglore , Indi Mterils Reserch Centre, Indin Institute of Science, Bnglore , Indi c Institute for Inorgnic nd Anlyticl Chemistry, Johnnes Gutenerg University, 599 Minz, Germny ARTICLE INFO ABSTRACT Article history: Received 26 My 2010 Accepted 26 July 2010 Aville online 2 August 2010 Grphene oxide-interclted -metl hydroxides were prepred using lyers from the delminted colloidl dispersions of cetyltrimethylmmonium-interclted grphene oxide nd dodecylsulfte-interclted -hydroxide of nickel/colt s precursors. The rection of the two dispersions leds to de-intercltion of the interlyer ions from oth the lyered solids nd the intercltion of the negtively chrged grphene oxide sheets etween the positively chrged lyers of the -hydroxide. Therml decomposition of the interclted solids yields grphene/nnocrystlline metl oxide composites. Electron microscopy nlysis of the composites indictes tht the nnoprticles re interclted etween grphene lyers. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Lyered composites in which the lyers from two different lyered solids re stcked lterntively re importnt s they would exhiit unique physiochemicl properties such s 2-D mgnetism nd conductivity due to the comined effect of the properties of the structurl unit lyers. Metstle mixed lyered composites hve een prepred through soft chemicl routes. Lyered composites, such s cly/metl hydroxide [1 3], MoS 2 /Ni(OH) 2 or Co(OH) 2 [4], grphite oxide/irnessite [5], hve een prepred y intercltion of M 2+ ions in the interlyer of the host followed y titrting the product with lkli. Birnessite/NiOH 2 [6], irnessite/lial 2 (OH) 6 [7], cly/ LiAl 2 (OH) 6 [8] nd cly/sno 2 [9] hve een prepred y intercltion followed y hydrotherml tretment. Grphite/NiOH 2 hs een prepred through intercltion of Ni 2+ ions in grphite nd sujecting the product to electrochemicl cycling in the presence of lkli [10]. The synthesis pproches to such composites re restricted to few select systems nd re not generl in nture. Delmintion of lyered solids yields solvted monolyers tht could e used s synthons in the preprtion of lyered composites. We hve shown tht interstrtified composites of similrly chrged lyers of lyered solids hving relted structures [11 13] nd of lyered solids hving different structures [14] cn e prepred strting from the monolyer colloidl dispersions of lyered solids. We reported the preprtion of 1-D solid solutions of -hydroxides of Ni nd Co [11], two different lyered doule hydroxides (LDHs), nmely Mg Al nd Co Al LDHs [12], two different ctionic clys diocthedrl cly nd triocthedrl cly [13] nd grphite oxide (GO)/ smectite [14] through the delmintion costcking pproch. It is lso possile to mke lyer-y-lyer composites of two oppositely chrged lyered solids through delmintion [15,16]. We hve recently shown tht positively chrged GO lyers could e introduced into the interlyer of exfolited n- * Corresponding uthor: Tel.: ; fx: E-mil ddress: mikerjmthi@rediffmil.com (M. Rjmthi) /$ - see front mtter Ó 2010 Elsevier Ltd. All rights reserved. doi: /j.cron

2 4344 CARBON 48 (2010) ionic cly y ion-exchnge [17]. In this work, we descrie metthesis route to lyer-y-lyer composites. If we denote the nionic nd ctionic lyered solids s L + A nd L C + where L + nd L re the lyers of the nionic nd ctionic lyered solids nd A nd C + re the interlyer nions nd ctions then we cn visulize rection of the type L þ A þ L C þ! L þ L þ AC if A nd C + re surfctnt ions then the rection my e crried out in n orgnic solvent in which oth the lyered solids would delminte. The product AC eing highly solule in the orgnic solvent, the rection will e driven forwrd to yield L + L, the lyer-y-lyer composite. Grphene (G) sed composites re importnt s they re potent mterils for pplictions in vried fields such s nnoelectronics, sensors, tteries, supercpcitors, hydrogen storge, ctlysts, ctlyst supports, dsorents nd mgnetic mterils [18]. Grphite/polymer [19], grphite/ nnoprticle composites [20], supercpcitor nd ttery electrode mterils [21,22] hve een fricted strting from GO s it is dispersile in wter nd lkline medium [23] nd in orgnic solvents fter modifiction with mines [24 26]. -Hydroxides of nickel nd colt re importnt electrode mterils in lkline secondry tteries [27,28]. In ddition, these solids decompose t reltively low tempertures (<300 C) to give the corresponding oxides. The hydroxides of nickel nd colt crystllize in different polymorphic modifictions, minly the - nd the -form [29,30]. The -form is of the formul M(OH) 2 nd it is n ordered stcking of neutrl lyers of the composition [M(OH) 2 ] with n interlyer spcing of 4.6 Å. The -form is hydroxyl-deficient compound nd consists of stcking of positively chrged lyers of composition ½MðOHÞ 2 x ðh 2 OÞ x Š xþ, which interclte nions such s NO 3,Cl,OAc,SO 2 4, etc. long with wter molecules in the interlyer region to restore chrge neutrlity. Consequently, the -hydroxides hve higher interlyer spcing, which vries with the size of the interlyer nion. On intercltion of surfctnt nions, dodecylsulfte (DS) nd dodecylenzene sulfonte (DBS), these solids delminte to give colloidl dispersion of lyers in orgnic solvents such s 1-utnol [31]. It would e interesting to prepre lyer-y-lyer composites of -hydroxides nd GO. Therml decomposition of these composites would reduce GO to G nd convert hydroxides to oxides resulting in G-metl oxide composites. In this pper, we report the metthesis etween lkylmmonium ion-interclted GO nd DS-interclted -hydroxide of nickel/colt tht yields GO/-hydroxide lyer-y-lyer composites (GO sheets interclted -hydroxides). These composites on heting in different tmospheres yield interesting G/inorgnic mteril composites. 2. Experimentl section 2.1. Synthesis of the precursors DS-interclted -divlent metl hydroxides were prepred y the ddition of 35 ml of solution contining metl cette, M(OAc) 2 Æ4H 2 O [M = Ni, Co] nd the surfctnt, NDS in the mole rtio 1:0.9 into ml of 0.5 M NH 3 solution with constnt stirring [31]. The solid product formed ws immeditely centrifuged, wshed free of nions with wter followed y cetone nd dried in ir t room temperture. Herefter these surfctnt-interclted -hydroxides re referred to s Ni- OH-DS nd Co-OH-DS. The method due to Hummers nd Offemn [32] ws dopted to prepre GO from grphite powder (10 20 lm) supplied y Grphite Indi Limited, Bnglore, Indi. One grm of grphite powder ws dded to 23 ml of cooled (0 C) concentrted H 2 SO 4. Three grms of KMnO 4 ws dded grdully with stirring nd cooling, so tht the temperture of the mixture ws mintined elow 20 C. The mixture ws then stirred t 35 C for 30 min. Forty-six milliliters of distilled wter ws slowly dded to cuse n increse in temperture to 98 C nd the mixture ws mintined t tht temperture for 15 min. The rection ws terminted y dding 140 ml of distilled wter followed y 10 ml of 30% H 2 O 2 solution. The solid product ws seprted y centrifugtion, wshed repetedly with 5% HCl solution until sulfte could not e detected with BCl 2, then wshed 3 4 times with cetone nd dried in n ir oven t 65 C overnight. Cetyltrimethylmmonium (CTA)-interclted GO ws prepred y stirring GO in n queous solution of cetyltrimethyl mmonium romide (5 times the ion-exchnge cpcity of GO) for 3 dys [25,26,33]. The solid thus otined ws wshed with wter till the ph of the wshings turned 7 nd finlly with cetone nd dried t 65 C. This smple is herefter referred to s GO-CTA Delmintion nd colloidl dispersion The delmintion nd monolyer colloidl dispersion of GO- CTA were chieved y sujecting mixture of 100 mg of the smple nd 100 ml of the solvent, 1-utnol, to soniction (35 khz) t room temperture for 30 min. Monolyer colloidl dispersion of Ni-OH-DS/Co-OH-DS ws otined y sujecting mixture of 133/125 mg of the smple nd 400 ml of 1- utnol to soniction (35 khz) t room temperture for 30 min. Composite formtion requires tht the numer of moles of surfctnts (CTA + nd DS ) is equl. From the chrge compenstion clcultions, it ws estimted tht 100 mg of GO-CTA is required to compenste the chrges on 133 mg of Ni-OH-DS/125 mg of Co-OH-DS Metthesis The colloidl dispersions of GO-CTA nd M-OH-DS (M@Ni or Co) were mixed nd sonicted for 30 min. The resulting dispersion ws then stirred t 70 C for 3 dys. The lck precipitte (GO-interclted -hydroxide) otined t the end of 3 dys ws repetedly wshed with cetone to remove the surfctnts nd the solid ws dried in ir t room temperture Therml decomposition of the GO-interclted - hydroxides GO-interclted -hydroxides were sujected to isotherml heting in ir/nitrogen tmosphere. The smples were held t 300 C for 2 h.

3 CARBON 48 (2010) Chrcteriztion 001 c The powder X-ry diffrction (pxrd) ptterns of the smples were recorded using PANlyticl X pert Pro diffrctometer (Cu K rdition, secondry grphite monochromtor, 2 2h/ min). The infrred (IR) spectr of the smples were recorded on Nicolet Impct 400D FTIR spectrometer (KBr pellets, 4cm 1 resolution). The smples were lso chrcterized y trnsmission electron microscopy (TEM) using JEOL 200CX microscope operted t 160 kv. Superconducting quntum interference device (SQUID) mgnetometry ws crried out using Quntum Design MPMS-XL-5 t 300 nd 5 K. The different process involved in the metthetic rection etween the colloidl dispersions of the surfctnt-interclted GO nd metl hydroxide nd the decomposition of GO-interclted -hydroxide to G/metl oxide composites is schemticlly shown in Fig. 1. Reltive Intensity Results nd discussion θ (degrees) Fig. 2 pxrd ptterns of the s-prepred GO-CTA () Co-OH- DS () nd Ni-OH-DS (c). Fig. 2, nd c re the pxrd ptterns of GO-CTA, Co-OH-DS nd Ni-OH-DS with sl spcings of 30, 26 nd 31 Å, respectively. While GO-CTA (Fig. 2) shows only the 00l reflections, the -hydroxides (Fig. 2 nd c) show, in ddition to the 00l reflections, the chrcteristic sw-tooth-shped rod peks due to the 2-D (10) nd (11) reflections rising out of turostrtic disorder [34,35]. The pxrd ptterns of the GO-interclted -hydroxides otined y metthesis re shown in Fig. 3. In order to understnd the mechnism of formtion of the composite, intermedites collected t different intervls were studied. The sence of sl reflections nd the presence of the swtooth-shped rod reflections (Fig. 3) strting t 33 nd 59 in the cse of the smple otined fter 24 h of rection suggests tht the rectnts still exist in delminted stte. At the end of 48 h (Fig. 3) the lyers hve rected to form the composite with sl spcing of 13.5 Å tht corresponds to the sum of lyer thicknesses of the -hydroxide (4.6 Å) nd GO (6 7 Å). The reduced sl spcing of the composite compred to tht of the precursors (Fig. 2) indicte tht the surfctnt ions re no longer present in the interlyer region of the lyered solids. Possily, negtively chrged GO sheets re present in the interlyer region of the -hydroxides compensting for the positive chrge on the nionic cly lyers. The sence of GO-relted reflections in the composite further indictes this possiility. As the rection is crried on further, the sl spcings of GO-interclted nickel hydroxide (Fig. 3c) nd GO-interclted colt hydroxide (Fig. 3d) decrese to 8.2 nd 7.9 Å, respectively. The sw-tooth-shped rod reflections strting t 33 nd 59 in oth the smples indicte tht the lyer structure of the nionic cly is intct. The reduced sl spcing in the composites otined fter 3 dys is due to the prtil reduction of the interclted GO lyers. In order to scertin the nture of the GO lyers present in the interclted solid, we leched out the inorgnic mtter from the solid in cid. The pxrd pttern of the smple fter cid leching (Fig. 3e) mtches tht of prtilly reduced GO with sl spcing of 4.3 Å. As the metthetic rection ws crried in utnol, reducing solvent, the sl functionl groups of the GO lyers hve een prtilly reduced. Similr reductions hve een reported erlier in other reducing medi [36,37]. Thus the GO lyers in the interclted solids hve smller lyer thickness compred to the pristine GO. This explins the low oserved sl spcing for the GO-interclted -hydroxides t the end of 3 dys. The croxylic cid groups t the edges of the GO lyers re not Fig. 1 Schemtic representtion of the process involved in the formtion of GO-interclted -hydroxide.

4 4346 CARBON 48 (2010) G(002) e Wvenumer (cm -1 ) Reltive Inetnsity d c Trnsmittnce (%) Reltive Intensity Å O-H stretching 3.9 Å C=O C-OH θ (degrees) θ (degrees) Fig. 4 pxrd pttern () nd IR spectrum () of the smple otined on heting GO-CTA t 70 C for 72 h. Fig. 3 pxrd ptterns of the GO-CTA nd Ni-OH-DS rected for 1 () nd 2 () dys; GO-interclted -nickel hydroxide (c) nd GO-interclted -colt hydroxide (d) otined y metthesis t the end of 3 dys; GO otined fter cid leching of GO-interclted -colt hydroxide (e). 55 d expected to get reduced under these conditions nd these groups contriute to the negtive chrge on the GO lyers which counters the positive chrge on the hydroxide lyers. The lyer chrge (the exchngele protons) on the prtilly reduced GO, otined fter leching out the hydroxide lyers, estimted y potentiometric titrtion using NOH, [33 38] ws 3.9 mmol g 1. As the GO-interclted -hydroxide hs 39% y mss of GO the totl negtive chrge from the GO lyers per grm of the composite is 1.6 mmol. The totl positive chrge from the -hydroxide lyers per grm of the composite is 2 mmol. Thus 80% of the positive chrges on the hydroxide lyers re compensted y the croxyl groups of the reduced GO lyers. In order to see if reduction of GO lyers occurs under the rection conditions we heted GO-CTA in 1-utnol t 70 C for 72 h. The pxrd pttern nd the IR spectrum of the product otined re shown in Fig. 4. The pek t 4Å in the pxrd pttern (Fig. 4) due to prtilly reduced GO confirms tht reduction of GO occurs t the conditions of the composite formtion rection. There is smll mount of unreduced GO s indicted y the pek t 7.7 Å. In the IR spectrum (Fig. 4) we oserve wek peks corresponding to croxylic cid groups suggesting tht these groups re not reduced under the conditions of composite formtion. In Fig. 5 the IR spectrum of GO-interclted -nickel hydroxide is compred with the spectr of the precursors GO-CTA nd Ni-OH-DS. In the cse of GO-CTA (Fig. 5), we oserve strong nd rod sorption t 30 cm 1 due to H- onded O H nd N H stretching virtions. The O H/N H Trnsmittnce (%) C-H O-H/N-H stretching C=O C=O N-H ending S=O C-OH C-OH C-H ending wvenumer (cm -1 ) C-N ending Fig. 5 IR spectr of GO-CTA (), Ni-OH-DS (), GOinterclted -nickel hydroxide (c) nd GO-interclted - colt hydroxide (d). ending nd C N ending virtions re oserved t 1600 nd 10 cm 1 respectively. In ddition, the sorptions specific to GO t 1700 cm 1 due to C@O stretching nd t 1376 cm 1 due to CAOH ending re lso oserved. In ddition to the sorption t 1600 cm 1, the lkylmmonium ion is expected to give wek sorption in the rnge of cm 1. We do not oserve this sorption ecuse either it is too wek or it overlps with the C H ending sorption pek centered t 1470 cm 1. The C H stretching virtions of c

5 CARBON 48 (2010) the lkyl chin of the mine re oserved t round cm 1. The presence of the sorptions due to N H nd C H onds is indictive of intercltion of CTA ions in the interlyer of GO. In the cse of Ni-OH-DS (Fig. 5) we oserve strong nd rod sorption t 30 cm 1 due to hydrogen onded hydroxyl groups, nd the S@O stretching virtion of the sulfte group t 1200 cm 1. In oth GO-CTA nd Ni-OH-DS the C H stretching virtions of the methylene groups of the lkyl chins of the surfctnt re oserved t cm 1. The nture of the C H stretching sorption nd (strong peks t cm 1 ) suggests tht the lkyl chins tke up ll trns conformtion [39,40]. If the chins were disordered, the pek t 2920 cm 1 would e rod nd wek. The IR spectrum of GO-interclted -nickel hydroxide (Fig. 5c) shows no fetures relted to the surfctnt nions (CTA + nd DS ) indicting the removl of surfctnt ions. The nds due to C@O stretching nd C OH ending of the GO lyers re oserved t 1700 nd 1376 cm 1 indicting the presence of GO lyers in the smple. There re no sorptions corresponding to ny nion such s cronte. These oservtions suggest tht the negtively chrged GO sheets re interclted in the interlyer region of the hydroxides for chrge compenstion. The IR spectrum of GO-interclted -colt hydroxide (Fig. 5d) is similr to tht of the nickel hydroxide nlog. The right-field TEM imge of the s-prepred GO-interclted -nickel hydroxide shown in Fig. 6, indictes the wrinkled sheet structure of the composite extending severl microns cross. Het tretment of the GO-interclted -hydroxides is expected to reduce GO component of the solid to grphite [41] nd to convert the lyered hydroxide component to nnoprticles of oxides of colt/nickel to give G/metl oxide inorgnic composites. With the ojective of mking these G- sed composites, the GO-interclted -hydroxides were sujected to decomposition t 300 C in different tmospheres. The pxrd ptterns of the het-treted smples re shown in Fig. 7. On decomposition in ir, the GO-interclted Reltive Intensity (G) θ (degrees) Fig. 7 pxrd ptterns of the GO-interclted -colt hydroxide heted t 300 C in ir () nd in nitrogen () nd GO-interclted -nickel hydroxide heted t 300 C in ir (c) c 220 Ni(II)-O stretching of NiO Trnsmittnce (%) Co(II)-O stretching of Co 3 O 4 Co(III)-O Wvenumer (cm -1 ) Fig. 6 Bright-field TEM imge of the s-prepred GOinterclted -nickel hydroxide. Fig. 8 IR spectr of GO-interclted -colt hydroxide () nd GO-interclted -nickel hydroxide () heted t 300 C in ir.

6 4348 CARBON 48 (2010) Fig. 9 Bright-field imges of the GO-interclted -colt hydroxide decomposed t 300 C in ir () nd the corresponding SAED pttern otined from the prticles (). The imge from the smple heted in nitrogen tmosphere (c) nd the corresponding SAED pttern otined from the prticles (d). -colt hydroxide shows peks due to Co 3 O 4 (Fig. 7). No pek due to GO or grphite is oserved indicting tht the grphite formed is exfolited. When the composite ws heted in nitrogen, peks due to CoO were oserved (Fig. 7). Similrly when GO-interclted -nickel hydroxide ws heted peks due to NiO were oserved (Fig. 7c). In the ove two cses rod pek due to the 002 reflection of grphite ws oserved t 2h = 25 (d =3.6 Å). The oserved sl spcing is higher thn tht of well-ordered grphite, 3.35 Å. The higher sl spcing my e due to the presence of residul oxygen nd hydrogen, indicting incomplete reduction of GO. The 002 reflection of grphite in these smples is very rod, suggesting tht the grphite component is very poorly ordered long the stcking direction. This is n indiction tht these smples comprise exfolited grphite sheets. The GO-interclted -colt hydroxide on heting t 300 C in ir (Fig. 8) shows strong sorptions t 566 nd 662 cm 1 due to decomposition of the lyered hydroxide to Co 3 O 4. The IR spectrum of the decomposition product of GO-interclted -nickel hydroxide (Fig. 8) shows pek t 532 cm 1 due to Ni O stretching of NiO. The GO relted peks t 1700 nd 1376 cm 1 re sent in oth the cses suggesting the reduction of GO to G. The right field imges of the therml decomposition products of GO-interclted -colt hydroxide re shown in Fig. 9 nd c. In oth the cses we oserve crumpled sheets of grphene. The product otined y heting GO-interclted -colt hydroxide in ir (Fig. 9) shows Co 3 O 4 prticles of dimeter 2 nm uniformly distriuted in the G mtrix. The diffuse rings of the selected re diffrction (SAED) pttern otined from prticle (Fig. 9) could e indexed to the cuic spinel phse (JCPDS PDF: 9 418). The smple otined on heting the composite in nitrogen (Fig. 9c) shows CoO prticles of verge dimeter 2 nm in G mtrix. The hexgonl rry of spots in the SAED pttern (Fig. 9d) indictes the presence of ordered grphitic sheets while the fint rings from the cuic CoO phse (JCPDS PDF: 9-402) re lso seen in the pttern. The right field imge of the therml decomposition product of GO-interclted -nickel hydroxide in Fig. 10 shows 2 nm NiO prticles uniformly distriuted in exfolited G mtrix. The SAED pttern (Fig. 10) could e indexed to the cuic NiO phse (JCPDS PDF: ). The mgnetic properties of the colt oxide sed composites were investigted y temperture dependent mgnetometry. Fig. 11 displys the mgnetiztion curves of G/ Co 3 O 4 otined y heting GO-interclted -colt hydroxide in ir (Fig. 11) nd G/CoO otined y heting the sme in

7 CARBON 48 (2010) Fig. 10 Bright-field imges of the GO-interclted -nickel hydroxide decomposed t 300 C in ir () nd the corresponding SAED pttern otined from the prticles (). 0.1 sheet-interclted -hydroxides. These on decomposition yield grphene/metl oxide composites. The metl oxide prticles in these composites Co 3 O 4, CoO nd NiO re very smll (2 nm) nd these re uniformly distriuted in the grphene mtrix. 0.0 Acknowledgements Mgnetic Moment (μ B ) This work ws funded y DST, New Delhi. C.N. thnks CSIR, New Delhi for the wrd of Senior Reserch Fellowship. C.N. nd M.R. thnk UGC, New Delhi for hving provided IR spectrometer through CPE scheme. REFERENCES nitrogen (Fig. 11) mesured t low temperture (T = 5 K). The G/Co 3 O 4 composite exhiits very wek ferromgnetism. It hs een erlier oserved tht nnoprticulte Co 3 O 4 exhiits wek ferromgnetism due to prtil inversion of the spinel structure nd/or cnted surfce spins [42]. The G/CoO composite exhiits superprmgnetism s expected for nnoprticulte CoO. 4. Conclusions -2 0 Field (koe) Fig. 11 Hystersis curves of G/Co 3 O 4 () nd G/CoO () composites t 5 K. Solution sed metthesis etween mcromoleculr sheets of CTA-interclted GO nd DS-interclted -hydroxide could e crried out in n orgnic solvent. The products were GO [1] Ymnk S, Brindley GW. Hydroxy-nickel interlyering in montmorillonite y titrtion method. Clys Cly Miner 1978;26:21 4. [2] Ohtsuk K, Sud M, Tsunod M, Ono M. Synthesis of metl hydroxide-lyer silicte intercltion compounds (metl = Mg(II), C(II), Mn(II), Fe(II), Co(II), Ni(II), Zn(II), nd Cd(II)). Chem Mter 1990;2: [3] Ymnk S, Send K. Therml evolution of nickel chloritelike phse derived from montmorillonite. Cly Sci 1993;9: [4] Golu AS, Pyen C, Protzenko GA, Novikov YN, Dnot M. Nnocomposite mterils consisting of lternting lyers of molydenum disulfide nd colt or nickel hydroxides: mgnetic chrcteriztion. Solid Stte Commun 1997;102: [5] Yng X, Mkit Y, Liu Z-H, Ooi K. Novel synthesis of lyered grphite oxide irnessite mngnese oxide nnocomposite. Chem Mter 2003;15: [6] Xu Y, Feng Q, Kjiyoshi K, Yngisw K. Hydrotherml intercltion rection of nickel hydroxide into lyered mngnese oxide. Chem Mter 2002;14: [7] Feng Q, Honu C, Yngusw K, Ymski N. Hydrotherml soft chemicl rection for formtion of sndwich lyered mngnese oxide. Chem Mter 1999;11:2444. [8] Feng Q, Honu C, Yngusw K, Ymski N, Komrneni S. Synthesis of LiAl 2 (OH) 6 + interclted montmorillonite y

8 43 CARBON 48 (2010) hydrotherml soft chemicl rection. J Mter Chem 2000;10: [9] Németh J, Dékány I, Süvegh K, Mrek T, Klencsár Z,Vértes A, et l. Preprtion nd structurl properties of tin oxide montmorillonite nnocomposites. Lngmuir 2003;19: [10] Xie J, Zhng Q, Shi P, Liu Q. Electrochemicl properties nd structure of Ni(OH) 2 grphite intercltion compounds. Solid Stte Ionics 1999;121: [11] Nethrvthi C, Rvishnkr N, Shivkumr C, Rjmthi M. Nnocomposites of -hydroxides of nickel nd colt y delmintion nd co-stcking: enhnced stility of -motifs in lkline medium nd electrochemicl ehviour. J Power Sources 2007;172: [12] Venugopl BR, Shivkumr C, Rjmthi M. A composite of lyered doule hydroxides otined through rndom costcking of lyers from Mg Al nd Co Al LDHs y delmintion restcking: therml decomposition nd reconstruction ehviour. Solid Stte Sci 2007;9: [13] Venugopl BR, Rvishnkr N, Rjmthi M. Interstrtifiction of triocthedrl nd diocthedrl smectites through delmintion nd costcking. J Colloid Interfce Sci 2008;324:80 5. [14] Nethrvthi C, Viswnth B, Rvishnkr N, Rjmthi M. The production of smectite cly/grphene composites through delmintion nd co-stcking. Cron 2008;46: [15] Hornok V, Erdohelyi A, Dekny I. Preprtion of ultrthin memrnes y lyer-y-lyer (LBL) deposition of oppositely chrged inorgnic colloids. Colloid Polym Sci 2006;284: [16] Li L, M R, Ein Y, Fukud K, Tkd K, Sski T. Lyer-ylyer ssemly nd spontneous floccultion of oppositely chrged oxide nd hydroxide nnosheets into inorgnic sndwich lyered mterils. J Am Chem Soc 2007;129: [17] Nethrvthi C, Rjmthi JT, Rvishnkr N, Shivkumr C, Rjmthi M. Grphite oxide-interclted nionic cly nd its decomposition to inorgnic mteril nnocomposites. Lngmuir 2008;24: [18] Geim AK, Novoselov KS. The rise of grphene. Nt. Mter 2007;6: [19] Stnkovich S, Dikin DA, Dommett GHB, Kohlhs KM, Zimmey EJ, Stch EA, et l. Grphene-sed composite mterils. Nture 2006;442: [20] Cssgneu T, Fendler JH. Preprtion nd lyer-y-lyer selfssemly of silver nnoprticles cpped y grphite oxide nnosheets. J Phys Chem B 1999;103: [21] Cssgneu T, Fendler JH. High density rechrgele lithiumion tteries self-ssemled from grphite oxide nnopltelets nd polyelectrolytes. Adv Mter 1998;10: [22] Frckowik E, Beguin F. Cron mterils for the electrochemicl storge of energy in cpcitors. Cron 2001;39:937. [23] Croft RC. Lmellr compounds of grphite. Qurt Rev 1960;14(1):11 3. [24] Nethrvthi C, Rjmthi M. Delmintion, colloidl dispersion nd ressemly of lkylmine interclted grphite oxide in lcohols. Cron 2006;44: [25] Dékány I, Krüger-Grsser R, Weiss A. Selective liquid sorption properties of hydrophoized grphite oxide nnostructures. Colloid Polym Sci 1998;276: [26] Mtsuo Y, Niw T, Sugie Y. Preprtion nd chrcteristion of ctionic surfctnt-interclted grphite oxide. Cron 1999;37: [27] Flk SU, Slkind AJ. Alkline storge tteries. New York: Wiley; [28] Oliv P, Leonrdi J, Lurent JF, Delms C, Brconnier JJ, Figlrz M, et l. Review of the structure nd the electrochemistry of nickel hydroxides nd oxyhydroxides. J Power Sources 1982;8: [29] Delms C, Fure C, Gutier L, Demourgues-Guerlou L, Rougier A. The nickel hydroxide electrode from the solid-stte chemistry point of view. Philos Trns R Soc Lond A 1996;354: [30] Kmth PV, Therese GH, Goplkrishnn AJ. On the existence of hydrotlcite-like phses in the sence of trivlent ctions. J Solid Stte Chem 1997;128: [31] Nethrvthi C, Hrichndrn G, Shivkumr C, Rvishnkr N, Rjmthi M. Surfctnt interclted -hydroxides of colt nd nickel nd their delmintion restcking ehviour in orgnic medi. J Colloid Interfce Sci 2005;288: [32] Hummers WS, Offemn RE. Preprtion of grphite oxide. J Am Chem Soc 1958;80:1339. [33] Liu ZH, Wng Z-M, Yng X, Ooi K. Intercltion of orgnic mmonium ions into lyered grphite oxide. Lngmuir 2002;18: [34] Wrren BE, Bodenstein P. The diffrction pttern of fine prticle cron lcks. Act Crystllogr 1965;18: [35] Rjmthi M, Kmth PV, Seshdri R. Polymorphism in nickel hydroxide: role of interstrtifiction. J Mter Chem 2000;10:3 6. [36] Herrer-Alonso M, Adl AA, McAllister MJ, Aksy IA, Prud homme RK. Intercltion nd stitching of grphite oxide with diminolknes. Lngmuir 2007;23: [37] Mtsuo Y, Nishino Y, Fukutsuk T, Sugie Y. Introduction of mino groups into the interlyer spce of grphite oxide using 3-minopropylethoxysilnes. Cron 2007;45: [38] Szo T, Tomcz E, Illes E, Dekny I. Enhnced cidity nd ph-dependent surfce chrge chrcteristion of successively oxidized grphite oxides. Cron 2006;44: [39] Snyder RG, Struss HL, Elliger CA. Cron-hydrogen stretching modes nd the structure of n-lkyl chins 1. Long, disordered chins. J Phys Chem 1982;86:5145. [40] McPhil RA, Struss HL, Snyder RG, Elliger CA. Cronhydrogen stretching modes nd the structure of n-lkyl chins 2. Long, ll-trns chins. J Phys Chem 1984;88: [41] Mtsuo Y, Sugie Y. Preprtion, structure nd electrochemicl property of pyrolytic cron from grphite oxide. Cron 1998;36: [42] Nethrvthi C, Sen S, Rvishnkr N, Rjmthi M, Pietzonk C, Hrrecht B. Ferrimgnetic nnogrnulr Co 3 O 4 through solvotherml decomposition of colloidlly dispersed monolyers of -colt hydroxide. J Phys Chem B 2005;109: