Materials Research, Vol. 10, No. 2, , Sonia Regina Federman a *, Vilma Conceição Costa b,

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1 Mterils Reserh, Vol. 10, No. 2, , Sol-Gel SiO 2 Biofilm with Surfe Engineered for Medil Applition Soni Regin Federmn *, Vilm Coneição Cost, Dniel Cordeiro Leite Vsonelos, Wnder Luiz Vsonelos Instituto Nionl d Propriedde Industril INPI, Av. Amzons 1909, Belo Horizonte - MG, Brzil Fundção Centro Tenológio de Mins Geris, Av. Cândido d Silveir, 2000, Belo Horizonte - MG, Brzil Deprtmento de Engenhri Metlúrgi e Mteriis, UFMG, Ru Espírito Snto, 35, s/206, Centro, Belo Horizonte - MG, Brzil Reeived: Ferury 6, 2007; Revised: My 31, 2007 Sol-gel film in the SiO 2 system ws prepred from TEOS, TEP, lohol nd hydrted lium nitrte in n idi medium. The otings were deposited on stinless steel using the dip-oting tehnique. After deposition, the omposite ws sumitted to het tretment, t different tempertures nd exposure times to investigte the influene of suh prmeters on the surfe morphology of the omposite. The oted surfes were hrterized y AFM, SEM nd FTIR. The present study showed tht the formtion of different textures (n importnt prmeter in implnt fixtion) ould e ontrolled y temperture nd time of het tretment. Keywords: otings, iofilm, sol-gel, surfe 1. Introdution The inrese in the verge lifespn of humn eing, rought out y ontinuous improvements in the qulity of modern life, is diretly ssoited with the progressive deteriortion of the musuloskeletl system. To keep the qulity of life, sientists hve een onstntly serhing for mterils, whih re le to repir defets, orret deformities, nd reple dmged tissues 1-5. A gret numer of mterils re used tody to reple dmged ones nd tissues, inluding metlli mterils due to their exellent mehnil properties, suh s strength nd hrdness. Unfortuntely, these mterils hve two min disdvntges: 1) the tendeny to relese metlli ions when exposed to ody fluids nd 2) the formtion of non-dherent firous psule round implnt Considering these disdvntges, ermi mterils (iotive mterils) hve een suessfully used to ot metlli mterils for dedes. Literture 1,5,6,11,12 shows tht the importne of ermi mterils is due lrgely to their exellent ehvior ginst orrosion nd its pity to spontneously ond to nd integrte with ones in the living tissue. The sol-gel method involves hydrolyzing n lkoxide to produe sol, whih then undergoes poliondenstion to form gel. This proess llows one to engineer multiomponent oxide systems on moleulr level nd mnipulte proess prmeters to hieve desired produts with speifi properties. This proess is hrterized y hydrolysis, ondenstion retions, s well s its potentil to pply uniform oting on omplex shpes using different methods, inluding dip-oting, spin-oting nd spry Beuse of its low proessing temperture, higher purity, nd homogeneous mterils, the sol-gel method hs een intensely studied s n lterntive proess for prepring ermi nd glss mterils for wide vriety of pplitions, suh s in the field of ioermis (iotive glss) 13, The high speifi surfe re is enefiil towrd medil pplitions s it n elerte surfe retions nd promote the growth of living tissue. The lrger the surfe re is, the lrger the retivity of the mteril. It hs een reported on the literture numerous *e-mil: federmn@inpi.gov.r methods used to improve the surfe re, suh s pore ontrol nd the use of mehnil equipment pressed ginst the surfe, whih is oted with thin lyer to form protuernes, whih in turn will t s the sites promoting implnt/tissue intertion. Therefore, the im of this study is to prepre SiO 2 iofilm whose surfe re ould e determined using sol-gel route. The s-prepred solution ws used to ot stinless steel with the intention of exploring its mehnil properties for ioprothesis pplition. In this mnner, the finl omposite ould then e dvntgeously nd suessfully pplied s iomteril implnt. 2. Mterils nd Methods Prior to oting, to improve the dhesion of films on metl surfes, the metl surfe must e prepred. In the present study, the smple, stinless steel AISI 409, ws ut in piees of 2.0 x 2.0 m, polished until 600 mesh to higher surfe finishing, wshed with detergent, deionized wter, nd degresed with etone. Finlly, the smple ws pled in n ultrsoni th with etone nd dried in hot ir. The ternry film SiO 2 preprtion synthesis followed similr proedure to one used y Zhong et l. 23 nd ws s follows: the solution ws prepred y mixing wter, ethnol, nd nitri id, followed y the ddition of TEOS (tetrethyl orthosilite), TEP (triethylphosphte) nd tetr hydrted lium nitrte. Susequently, the solution otined ws vigorously stirred for t lest 50 minutes. The initil ph of the solution ws 2 nd the molr rtio of TEOS: H 2 O: TEP: C = 1: 4: 0.03: After stirring the mixed solution t room temperture the s-prepred solution ws redy to ot. The sustrte ws lowered into the oting solution nd withdrwn t speeds rnging etween 3 nd 5 m/min t room temperture to ensure the elimintion of orgni residues s well s to develop thin film. Following the deposition, smples were trnsferred to n oven for uring, using two heting shedules to set nd solidify the SiO 2 iofilm: ) the temperture ws mintined t 200 C

2 178 Federmn et l. Mterils Reserh nd the time proessing hnged from 15 minutes to 1 hour; ) the time proessing ws mintined t 15 minutes nd the temperture inresed to 400 C. After het tretment, the smples were removed from the oven to ool in open ir, t whih time the oting ws found to e ler nd free of ny visile defets. FTIR spetrosopy ws employed to register the presene of speifi hemil groups on the deposited SiO 2 iofilm. A Vrile Angle Speulr Refletne (VASR) essory ws used nd the ngles of inidene were 75, 45, nd 25. The vrition of the inidene ngle in the infrred spetrosopy llows n investigtion of the film in lyers of depth. The spetr were reorded etween 4000 nd 400 m -1, with 4 m -1 resolution nd 64 sns. The surfe topogrphy of the sol-gel derived thin films on stinless steel ws investigted, t room temperture, with n tomi fore mirosope (Shimdzu Snning Proe Mirosope, SPM-9500-J3). Imges were tken in dynmi tpping mode nd the estlishment of profile of roughness ws done using the online pplition softwre, progrm liensed for SPM-9500 series. Rmn spetr were olleted, t room temperture, in ksttering geometry using Join Yvon/Hori (model LABRAM-HR 800) instrument. An He-Ne lser (20 mw) ws employed s the exiting rdition. Experimentl onditions inluded 10 to 120 seonds for quisition time. Sol-gel ternry film surfe morphology ws nlyzed y snning eletron mirosopy (SEM) (JEOL, JSM-6360LV), using seondry eletron detetor. Prior to SEM nlysis, the surfe smple ws ron oted to redue hrging in the smples. 3. Results nd Disussion Figure 1 shows the infrred spetr of three sol-gel het treted films t 200 C for 15 minutes in the rnge of 1500 to 400 m 1, otined with 75 ngle of inidene. Figure 1 : shows: ) unry film (only SiO 2 ), ) inry film (SiO 2 -CO) nd ) ternry film SiO 2 CO-. The first two ) nd ), otined in the sme mnner nd under the sme onditions s the SiO 2, re illustrted only to point out the differenes etween the unry nd inry films when ompred to the ternry iofilm. Compring the three spetr, it n e seen tht the pek round the 1050 m -1, in the unry film whih is ssoited with the trnsverse optil virtion mode orresponding to the symmetri strething of the intertetrhedrl oxygen toms in the Si-O-Si linkge 24-26, hd in ft shifted towrd lrger wvenumers (~1060 m -1 ) in the ternry film. This shift hs een ssoited to the inorportion of phosphorus into the unry sol-gel film 27,28. In ddition, on the inry film, the ddition of phosphorus lso led to shift in the Si-O-Si nd from 1050 to 1060 m -1, s illustrted in Tle 1. Figure 1 nd, show dditionl wek nds loted round m -1. These nds re ssigned to the presene of the nitrte group on the film struture 29,32. However, these peks re sent in the unry film, s shown in fig. 1. The pek loted round 932 m -1 (unry film), ttriuted to the strething virtions of SiOH or SiO - groups 26,33,34, shifted towrd lrge wvenumer (~938 m -1 ) in the ternry film; its intensity, however, deresed. It is importnt to reognize tht the pek of round 1238 m -1, whih hs een ttriuted to the orresponding longitudinl optil (LO) virtion mode of the Si-O-Si linkge 24,35 in Figure 1, hs the highest intensity, euse of the lrge ngle of inidene used, whih is in ordne with tht reported in prior literture 24. For the ternry films the nds t the m -1 rnge were ttriuted to the Si-O nd P-O strething virtions. Literture shows tht there is superposition of nds loted lose to one nother 34,36. As n e seen in Figure 2, when smll inident ngle (25 ) ws used in the FTIR experiment, the pek loted round 1230 m -1 diminished its intensity, whih supports tht reported in the literture for ll three spetr 23. It is ler tht the nitrte group is lso present on Asorne (u..) Wvenumer (m -1 ) Figure 1. FTIR spetr of ) unry film; ) inry film; ) ternry film t 200 C for 15 minutes t 75 of inidene. Asorne (u..) Wvenumer (m -1 ) Figure 2. FTIR spetr of ) unry film; ) inry film; ) ternry film t 200 C for 15 minutes t 25 of inidene. Tle 1. Shift in the Si-O-Si pek (m -1 ) used y ddition of phosphorous in unry, inry, nd ternry sol-gel films. Sol-Gel film 200 C, 15 minutes 200 C, 1 hour 400 C, 15 minutes 400 C, 1 hour Unry Binry Ternry

3 Vol. 10, No. 2, 2007 Sol-Gel SiO 2 Biofilm with Surfe Engineered for Medil Applition 179 the inner lyer next to the sustrte of SiO 2 nd SiO 2 -CO sol-gel films. Compring Figures 1 nd 2, one n oserve tht the intensity of the peks due to lium nitrte tends to diminish, from the externl surfe (Figure 1) to the inner surfe (Figure 2). Figure 2 lso illustrtes the presene of the nitrte group loted t m -1 in the inner lyer, next to the metlli sustrte. Compring the spetr () in Figures 1 nd 2, we n onsider tht s the intensity of peks loted round m -1 tends to diminish from the externl surfe (75 ) to the inner surfe (25 ), in the se of the ternry film, when using the inidene ngle of 25, it is possile to oserve tendeny of deresing the mount of nitrte groups on the inner lyer of the film. Another importnt feture of the SiO 2 film is tht the intensity of the pek loted t 938 m -1, due to its Si- OH / Si-O-C virtion mode 35, tends to diminish in omprison with unry nd inry sol-gel films. This result suggests tht the hnge in this nd is ttriuted to P ontining speies 33,35. Tle 1 presents the results otined fter the phosphorous speies hve een dded to the unry nd inry sol-gel films. In the se of the ternry film (the im of this work), it is ler tht the ddition of phosphorous on unry or even on inry sol-gel film tends to use shift from peks ner 1050 m -1 towrd higher wvenumers for ny het tretment t ny shedule of temperture nd t ny prt of the lyer (75, 45 or 25 ). Another feture to point out is tht peks ssigned to Si-O-Si symmetri strething (~1050 m -1 ) tend to shift slightly to lesser wvenumer, when moving from the externl surfe to the inner surfe of the ternry film. This n e orrelted with deresing inorgni network density of this ternry film from the externl to the inner surfe. Figure 3 illustrtes the SiO 2 sol-gel film whih ws het treted t 200 C for 1 hour. Peks due to nitrte groups re still present on the externl lyer of the ternry film. However, s shown in Figure 4, for the ternry film (Figure 4) het treted t 400 C for 15 minutes, one n oserve the sene of reltive sorption nds due to the nitrte groups (~ m -1 ). These peks re still present, ut only on the inry film (Figure 4), suggesting tht the het tretment of the films t 400 C for t lest 15 minutes leds to the deomposition of the nitrte residue on the film surfe 24,37,38. When lium nitrte is deomposed y het tretment t 400 C for 15 minutes, lium ions remin present in the sili network, s illustrted in Figure 5. Figure 5 is Rmn spetrum of the SiO 2 -CO- film nd shows pek loted t 1090 m -1 (strething virtion) ssigned to lium ronte 39,40. Figure 5 lso illustrtes the sene of peks round 1046 m -1, ssigned to the symmetri strething of the nitrte groups. The sene of this sorption nd onfirms the totl deomposition of the nitrte 31,39. An dditionl pek, in Rmn spetrum, ppers ner 720 m -1 nd is lso ssigned to ronte groups 41. The results shown up to now re in ordne with Figures 6 to 9. Figure 6 presents AFM imge of smples oted with SiO 2 - CO- iofilm, whih ws het treted t 200 C for The AFM imge shows distint protuernes, whih we suspet to e due to lium nitrte, onsequently rising the surfe re of the sol-gel ternry film. In Figure 7, the AFM imge of the sol-gel ternry film heted t 200 C for 1 hour is shown. From this imge, it n e oserved tht the protuernes on the ternry iofilm surfe deresed nd its pperne hnged. When the temperture of the het tretment ws hnged to 400 C, mintining the time (15 minutes), the density nd size of protuernes on the ternry iofilm drstilly diminished on its surfe, s illustrted in Figure 8. Chnging the time proessing to 1 hour while the temperture of 400 C ws mintined resulted in low roughness surfe. Another importnt SiO 2 iofilm feture to e emphsized from the AFM imges is tht the otined ternry film onforms Asorne (u..) Wvenumer (m -1 ) Figure 3. FTIR spetr of ) unry film; ) inry film; ) ternry film t 200 C for 1 hour t 75 of inidene. Asorne (u..) Wvenumer (m -1 ) Figure 4. FTIR spetr of ) unry film; ) inry film; ) ternry film t 400 C for 15 minutes t 75 of inidene. Intensity (u.) Wvenumer (m -1 ) Cronte Figure 5. Rmn spetrum of ternry sol-gel film het treted t 400 C for

4 180 Federmn et l. Mterils Reserh Figure 6. AFM imge of ternry SiO 2 film heted t 200 C for Figure 9. AFM imge of ternry SiO 2 heted t 400 C for 1 hour Figure 7. AFM imge of ternry SiO 2 film heted t 200 C for 1 hour kv 1,000x 10 m Demet/UFMG Figure 10. SEM mirogrph of otined SiO 2 iofilm oted sustrte t 200 C Figure 8. AFM imge of ternry SiO 2 heted t 400 C for losely to the metlli surfe. In the nlyzed re through AFM, there is no suggestion of the mropores presene, rks or ny peelings from the sustrte. Moreover, Figures 6 to 9 suggest tht just s otined ternry iofilm hs very smll thikness, s n e seen from the prllel grinding lines eneth the SiO 2 iofilm. Figure 10 shows the SEM mirogrph of the otined SiO 2 -CO- iofilm oted sustrte, het-treted t 200 C. This result is in ordne with Figures 6 to 9 where, one gin, the integrity of the ternry film n e seen, through of its strong dherene with the sustrte. 4. Conlusion The present study shows tht it is possile to otin thin, uniform, pore/rk-free ternry iofilm in the SiO 2 system using the sol-gel method. It lso indites tht the iofilm topology n e ltered, in reltion to the presene (or sene) of protuernes, simply y hnging the proessing time nd the temperture with the im of designing its surfe re. Aknowledgments The uthors knowledge Dr. Mri Silvi Sylv Dnts for Rmn mesurement nd finnil support from Mins Geris Foundtion of Reserh (Fpemig) nd CNPq for finnil support on this projet.

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