1
In luence o sil e con en on he ibomechanical beha iou on Ag-
TiCN bioac i e coa ings
J.C. Sánchez-López1, M.D. Abad1, I. Ca alho2, R. Escoba Galindo3, N. Beni o4, S.
Ribei o2, M. Hen iques5, A. Ca alei o6, S.Ca alho2
1Ins i u o de Ciencia de Ma e iales de Se illa (CSIC-US), A da. Ame ico Vespucio 49,
41092 Se illa, Spain
2Uni e sidade do Minho, Dep . Física, Campus de Azu ém, 4800-058 Guima ães,
Po ugal
3 Ins i u o de Ciencia de Ma e iales de Mad id (ICMM-CSIC), Can oblanco, 28049,
Mad id, Spain
4 Depa amen o de Física Aplicada (CXII), Uni e sidad Au ónoma de Mad id,
Can oblanco, 28049, Mad id, Spain
5 IBB-Ins i u e o Bio echnology and Bioenginee ing Cen e o Biological Enginee ing
Uni e sidade do Minho Campus de Gual a , 4700-057, Po ugal
6 SEG-CEMUC Mechanical Enginee ing Depa men , Uni e si y o Coimb a, 3030-
788 Coimb a, Po ugal
Abs ac
Su ace modi ica ion o bulk ma e ials used in biomedical applica ions has become an
impo an p e equisi e o be e biocompa ibili y. In pa icula , o o e come he pa icle
gene a ion, low-wea coa ings based on ca bon (ni ogen) and con aining an imic obial
elemen s such as sil e a e p omising candida es. Thus, he p esen wo k explo es he
po en iali ies o sil e -con aining ca boni ide-based (Ag-TiCN) hin ilms p epa ed by
di ec cu en unbalanced eac i e magne on spu e ing. The sil e con en in he
coa ings was a ied om 0 o 26.7 a .% by changing he a ge s and he ac ion o C2H2
and N2 in he gas mix u e wi h A . The ob ained Ag-TiCN based coa ings we e
cha ac e ized in e ms o composi ion and mic os uc u e. Mechanical and ibological
p ope ies o he ilms we e s udied by nanoinden a ion and ecip oca ing pin-on disk
*Manusc ip changes highligh ed
Click he e o iew linked Re e ences
2
es ing in a e al bo inum se um solu ion, espec i ely. Raman, SEM and ene gy
dispe si e X- ay (EDX) analysis was ca ied ou in he con ac egion a e ibological
es s o ob ain in o ma ion abou he ic ion mechanism. The cy o oxici y o he
coa ings was assessed by in i o es s using ib oblas cells. The coa ings comp ised a
mix u e o TiCxN1-x, Ag and a-C(N)x phases whose ela i e p opo ion a ied depending
on he Ag/Ti a io. The mechanical, ibological and cy o oxici y we e co ela ed wi h
he chemical and phase composi ion. When he Ag/Ti a ios we e below 0.20 (Ag
con en s < 6.3 a .%) he ilms esul ed ha de (18 GPa) wi h highe wea esis ance
(10-6 mm3/Nm), showing simila ic ion coe icien (0.3) and good biocompa ibili y.
Keywo ds: Biocompa ibili y, sil e , nanocomposi e, amo phous ca bon phases,
ibology, e al bo ine se um, wea mechanism, cy o oxici y.
3
1. In oduc ion
Applica ion o hin ilms in he biomedical enginee ing ield ep esen s an a ac i e
challenge due o he mul iple si ua ions whe e hey may imp o e o e en unc ionalize a
ce ain pa o he human body. Al hough he use o hip implan s is con inuously
inc easing, implan ailu e is a huge p oblem o bo h he pa ien and go e nmen al
agencies, once i in ol es epea ed su ge ies and consequen ly conside able economical
esou ces, as well as pa ien s’ dea h. This ailu e can be a ibu ed o excessi e wea and
wea deb is and also o mic obial in ec ion, which p omo es he sho du abili y [1]. Fo
hese easons he in es iga ion o new bioma e ials is equi ed o ob ain good
mechanical, ibological and biological p ope ies ha allow he de elopmen o be e
p os hesis. To o e come he p oblem o pa icle gene a ion, he use o a e y low wea
coa ing ma e ial as diamond-like ca bon (DLC), ansi ion-me al ca bides (MeCx),
ni ides (MeNx), o o he s p o ec i e hin ilms, ha e been p oposed [2-5].
In ecen yea s, he esea ch has been di ec ed owa ds he use o an ibac e ial
ma e ials ha could educe he ailu e o medical de ices p o oked by he in ec ions.
Many o hese s udies ocus on he use o sil e , which is known o be an an imic obial
elemen [5-8]. When sil e is ans o med in ions and en e s he en i onmen , he
mul iplica ion o bac e ia may be s opped because i is belie ed ha Ag+ abso bs he
p o eins o he cell wall [9]. The an ibac e ial ac i i y is dependen on he o al amoun
o Ag+ ions which is esponsible o he des uc ion o he bac e ia. Con e sely, i he
quan i y o sil e eleased om he ilms is oo high i can p oduce cy o oxici y [10].
Ea ly wo ks ha e s udied he combina ion o ha d phases (TiN o TiC), ha p o ide
ha dness, wi h sil e as so me al o play he ole o lub ican , o in es iga e hei
ibological pe o mance [11,12]. Fo he use in a i icial implan s, good
4
biocompa ibili y is also equi ed, in pa icula due o he known oxici y o he sil e o
he human body. In he las ew yea s, he esea ch e o s ha e been di ec ed o assess
he he biocompa ibili y o hese mul iphase nanocomposi e ma e ials wi h op imum
ibological p ope ies [5,6, 13-15]. We ha e in es iga ed p e iously he deposi ion o
TiC(O)N-based coa ings by di ec cu en (DC) magne on spu e ing gaining
knowledge abou he syn hesis condi ions ha yielded a good comp omise be ween
ibological and ha dness p ope ies [16,17]. In he p esen s udy he addi ion o a iable
concen a ions o Ag in o TiCN ilms is explo ed wi h he goal o main aining a good
ibological pe o mance wi hou cy o oxici y e ec s. To achie e his pu pose, he
coa ings a e e alua ed in e ms o s uc u e and composi ion and he ibological
p ope ies a e s udied in lub ica ed condi ions using e al bo inum se um (FBS) o
simula e he biological condi ions. The inal mechanical and ibological pe o mance is
co ela ed wi h he e olu ion o he a io o Ag/Ti inside he coa ings as well as he
e ec o he Ag con en in he cy o oxici y.
2. Expe imen al De ails
Ag-TiCN samples we e deposi ed by eac i e DC magne on spu e ing using an
Alca el SCM650 appa a us on o polished and ul asonically cleaned 316L s eels and
single c ys alline silicon (100) subs a es. Two ypes o a ge s (pu e Ti and mixed
Ti/Ag) o dimensions (200100 mm2) we e used in A +C2H2+N2 mix u es, wi h he
subs a es o a ing a 70 mm o e he a ge a a cons an speed o 7 pm. A gon low
was kep cons an a 60 sccm while he eac i e gases luxes, C2H2 and N2, we e
changed in he anges o 5-11 and 5-12 sccm, espec i ely, in o de no o change
signi ican ly he C and N con en s. This ep esen s a a ia ion o he wo king p essu e
o he deposi ion chambe be ween 0.31 o 0.47 Pa. The ilms we e g own a a cons an
5
empe a u e (300 ºC) and bias ol age (-70 V). Va ying he densi y o cu en applied o
each magne on and he chemical composi ion o he mixed Ti/Ag a ge , a se o
samples was p epa ed wi h Ag con en a ying om 0 o 26.7 a . %. Fu he de ails
abou he syn hesis condi ions can be ound elsewhe e [18].
The a omic composi ion o he deposi ed samples was measu ed by elec on p obe
mic oanalysis (EPMA) using a Cameca SX 50 appa a us. Ball c a e es s we e used o
ob ain he ilm hickness. The s uc u e and phase dis ibu ion o he coa ings we e
de e mined by X- ay di ac ion (XRD) using a con en ional Philips PW 1710
di ac ome e , ope a ing wi h Cu Kα adia ion, in a B agg–B en ano con igu a ion. X-
ay pho oelec on spec oscopy (XPS) was measu ed using a hemisphe ical analyze
(SPECS EA-10 Plus) and Al K adia ion as exci ing sou ce a a cons an powe o 300
W. The pass ene gy was 15 eV gi ing a cons an esolu ion o 0.9 eV. The Ag 3d5/2
line a 367.9 was used o calib a e he binding ene gies. The samples we e spu e -
cleaned in si u using a b oad 3 keV A + beam o 10 minu es.
Ha dness measu emen s we e conduc ed using a Mic oMa e ials Nano es sys em
equipped wi h a Be ko ich inden e applying a maximum load o 10 mN. Co ec ion o
he geome ical de ec s in he ip o he inden e , he mal d i o he equipmen and
unce ain y o he ini ial con ac was done [19]. The esidual s esses, , we e ob ained
by he de lec ion me hod om he S oney’s equa ion, using subs a e cu a u e adii,
bo h be o e and a e coa ing deposi ion [20]. The ibological p ope ies we e e alua ed
by ecip oca ing ic ion es s using alumina-6-mm balls in dilu ed e al bo ine se um
(FBS, 10% solu ion in wa e ) in a CSM ibome e . The es pa ame e s we e se o 0.5
N o applied load; 3 mm/s o linea speed o e a ack leng h o 3 mm and 3000 cycles.
The speci ic ilm wea a e was es ima ed a e di iding he wo n olume by he applied
load and he sliding dis ance. Scanning elec on mic oscopy (SEM) and ene gy

6
dispe si e X- ay analysis (EDX) o he ic ion con ac egion we e eco ded in a FEG
Hi achi S5200 mic oscopes ope a ing a 5 keV. Raman spec a measu emen s (200-
2000 cm-1) we e ca ied ou in a LabRAM Ho iba Jobin Y on spec ome e equipped
wi h a CCD (cha ge-coupled de ice) de ec o and a He-Ne lase (532 nm) a 5 mW.
Cy o oxici y es s we e pe o med using ib oblas s 3T3 (CCL-163) ob ained om
Ame ican Type Cell Collec ion. Coa ed coupons (p e iously s e ilized a 121ºC o 15
min) we e inse ed in six well pla es and 3 ml o Dulbecco modi ied eagle medium
DMEM (Gibco) we e added o each well. The pla es wi h he ma e ials we e hen
incuba ed wi h 5% CO2 a 37ºC o 7 days. Meanwhile, he cells we e g own in DMEM
con aining 10% o FBS (Gibco) and 1% penicillins ep omicin, PS (Gibco). The cells
we e allowed o g ow un il a aining 80% con luence and a e de achmen 500 μL o
cell suspension wi h 1x105 cells/ml we e added o each well o a 24 wells' pla e. A e 7
days o ma e ial con ac wi h he medium, 500 μL we e emo ed om each well and
added o he pla es wi h cells. The pla es we e incuba ed wi h 5% CO2 a 37ºC o 48h.
A e ha ime, all he medium was emo ed and a solu ion con aining 100 μL o MTS
(3-(4,5-dime hyl hiazol-2-yl)-5-(3-ca boxyme hoxyphenyl)-2-(4-sul ophenyl)-2H-
e azolium, inne sal (P omega CellTi e 96® AQueous Non-Radioac i e Cell
P oli e a ion Assay) and 1 ml o DMEM wi hou phenol ed was added o each well.
A e 1 h, he abso bance o he esul ing solu ion was ead a 490 nm. The pe cen age
o ib oblas s dea h was de e mined by he a io o he di e ence be ween cell g ow h in
he absence o Ag-TiCN sample (con ol – 100%) and he g ow h in he p esence o a
sample o e he con ol g ow h. The assays we e pe o med a leas h ee imes and in
iplica e.
3. Resul s and discussion
7
3.1 Coa ing chemis y and mic os uc u e
The chemical composi ion o he deposi ed coa ings ob ained by EPMA is shown in
Table 1 oge he wi h he ilm hicknesses and he esul ob ained a e e alua ion o he
ibo-mechanical p ope ies. The ca bon con en do no a y signi ican ly om 30 a .%.
The N con en dec eases sligh ly om 33.9 o 21.8 a . %, he Ti con en dec eases om
36.9 o 17.9 a . % while he Ag con en inc eases om 0 o 26.7 a %. Oxygen appea s
as con aminan in a ange o 4-8 a .%, usually below 5 a .%. Since i anium and sil e
display an opposi e end, he Ag/Ti a io will be used he ea e o label he samples and
o discuss he changes obse ed in he s uc u e and unc ional p ope ies.
The XRD pa e ns ob ained o he di e en Ag/Ti a ios a e shown in Fig. 1. In he
i s sample (non-con aining Ag) exhibi h ee e lec ions a 36º, 42º and 61º
co esponding o he ypical (111), (200) and (220) peaks o igina ed by a cubic la ice
whose posi ions lie in e media e be ween hose o bulk TiC and TiN phases. By
conside ing ha he inco po a ed sil e canno o m ca bide o ni ide phases and he
comple e mu ual solid solubili y o he TiN-TiC sys em, he o ma ion o a TiCyN1-y
phase is o eseen. A con ibu ion o he peak shi due o he comp essi e esidual s ess
in he coa ings can be also possible. Wi h he inco po a ion o sil e , he TiCyN1-y
di ac ion peaks ge b oade and lose in ensi y concomi an ly wi h he de elopmen o
he cha ac e is ic pa e n o me allic sil e . In pa icula , o Ag/Ti a ios abo e 0.40 he
main iden i ied peaks co espond o cc-Ag. The g ain size o TiCyN1-y and Ag phases
was de e mined by Sche e o mula using he (111) peak. The calcula ed alues a y
om 15 down o 9 nm and om 5 up o 8 nm, o TiCyN1-y and Ag espec i ely, wi h
he inc ease o Ag/Ti. Unde hese p emises, aking in o accoun he a omic
composi ions gi en in Table 1, an excess o C and N is no iced o e he Ti con en and
his di e ence becomes mo e signi ican as he Ag con en inc eases. This can be
8
unde s ood by assuming he o ma ion o amo phous ca bon-based phases (a-C and a-
CNx) whe e C a oms a e connec ed o C o N a oms p e e en ially by sp2 bonds, as
obse ed in p e ious publica ions [21,22].
In o de o ob ain u he in o ma ion abou hese ca bon-con aining phases, XPS
analysis was ca ied ou on he C 1s and N 1s pho oelec on spec a o Ag-TiCN
coa ings. Fig. 2a shows he C1s spec a o samples wi h Ag/Ti a omic a ios o 0, 0.20,
0.40 and 1.49. The spec a can be decon olu ed in o ou componen s a 282.0 (C-Ti),
283.2 (C-TiO), 285.1 (C-C) and 286.9 eV (C-N) bonds. The i s conclusion ha can be
d awn om he analysis is he p edominance o an amo phous ca bon phase o igina ed
by he C2H2 p ecu so al hough a ce ain con ibu ion om ad en i ious ca bon canno
be disca ded. The ela i e con ibu ion o he ca bide componen s (C-Ti and C-TiO)
con inuously dec eases as he sil e con en inc eases, especially o he highes Ag/Ti
a ios (0.40, 1.49), whe e he con ibu ion o he C-C and C-N peaks is signi ican ly
highe . This esul s in ag eemen wi h he conclusions ob ained p e iously a ending o
he changes deno ed in chemical composi ions and XRD da a. In he N1s spec a o Fig.
2b, wo con ibu ions we e ound a 397.0 eV and 399.2 eV asc ibed o N-Ti and N-C
bonds, espec i ely. The in ensi y o he N-C componen becomes signi ican when he
Ag/Ti inc eases up o 0.40 and 1.49 (in ag eemen wi h he esul s o C1s spec a). By
using he da a ob ained om he decon olu ion o he N1s and he elemen al chemical
composi ion measu ed by EPMA i was possible o es ima e he phase composi ion as a
unc ion o he Ag/Ti a io. The ob ained esul s a e plo ed in Fig. 3. The amo phous
CNx is sligh ly inc easing while he main changes a e no iced in he c ys alline phases
whe e he inc emen o Ag co ela es wi h a diminu ion o he TiCyN1-y phase. This
mul iphase s uc u e will ce ainly ha e an in luence on he unc ional p ope ies o he
coa ings ( ibological, mechanical and biological) as we e ise in he nex sec ions.
9
Figu e 4 shows he c oss-sec ional SEM mic og aphs o ac u ed Ag-TiCN samples
wi h Ag/Ti a ios o 0, 0.20, 0.40 and 1.49. The ilm mo phology displays a ypical
columna -like mic os uc u e al hough ine columns and po osi y is obse ed as he
Ag/Ti a omic a io inc eases. This dense mic os uc u e may be a ibu ed o he
seg ega ion o he immiscible Ag and a-C(N) phases leading o enuclea ion si es ha
dis up s he columna mo phology. Simila beha io has been obse ed p e iously in
Ag-C N nanocomposi es [23]. A he highes Ag/Ti a io (Fig. 4d), Ag clus e s a e
seg ega ed o he column bounda ies as obse ed be o e [14] which can be iden i ied as
b igh e spo s on he su ace.
3.2. Mechanical p ope ies: Ha dness and esidual s ess
The ha dness and in e nal s ess alues a e p esen ed in Fig. 5 as a unc ion o he
Ag/Ti a io. The ha dness a ied in a ange om 8 o 18 GPa, much lowe han he
ypical alues epo ed o pu e TiCN coa ings, anging om 30 o 36 GPa [24-26].
These o e all lowe alues should be ce ainly ela ed wi h mic os uc u al and
chemical composi ion aspec s. Thus, low ene ge ic condi ions o he deposi ion (low
nega i e subs a e bias and low deposi ion empe a u e) can lead o columna and open
mo phologies. The phase composi ion o hese nanocomposi es is also a ec ing he
dependence o he mechanical p ope ies as i in luences he balance be ween ha d and
so phases and hei dis ibu ion. Thus, acco ding o he achie ed accu acy inc easing
Ag con en up o 6.3 a .% does no almos a ec he ha dness; howe e , u he inc ease
is accompanied wi h a signi ican ha dness dec ease. A simila beha iou o so me als
has been epo ed in he pas in o he sys ems, such as Z N/Cu [27], Z N/Ni [28], o
o he s including sil e , Ag/TiN [5] and Ag/TiC [29]. Howe e , i is also likely ha ion-
induced de ec s in he ilms du ing he deposi ion o mo e compac ilm mic os uc u e
16
[18] N. K. Manninen, R. Escoba Galindo, N. Beni o, N.M. Figuei edo, A. Ca alei o,
S.Ca alho, “Ag-Ti(C,N)-based coa ings o biomedical applica ions: in luence o sil e
con en on he s uc u al p ope ies”, Jou nal o Physics D: Applied Physics 44 (2011)
375501.
[19] J.M. An unes, A. Ca alei o, L.F. Menezes, M.I. Simões, J.V. Fe nandes, Su .
Coa . Technol. 149 (2002) 27.
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Coa . Technol. 203 (2008) 756.
[22] D. Ma ínez-Ma ínez, C. López-Ca es, A. Jus o, A. Fe nández, J. C. Sánchez-
López, Solid S a e Sciences 11(2009) 660.
[23] C.P. Mulligan, T.A. Blanche , D. Gall,, Su . Coa . Technol. 203 (2008) 584.
[24] S.J. Bull, D.G. Bha , M.H. S aia, Su . Coa . Technol. 163 –164 (2003) 499.
[25] A.P. Se o, C. Comple o, R. Colaço, F. dos San os, C. Loba o da Sil a, J.M.S.
Cab al, H. A aújo, E. Pi es, B. Sa amago, Su . Coa . Technol. 203 (2009) 3701.
[26] E.J. Bienk, H. Rei z, N.J. Mikkelsen, Su . Coa . Technol. 76 - 77 (1995) 475.
[27] J. Musil, Su . Coa . Technol. 125 (2000) 322.
[28] J. Šůna, J. Musil, V. Ondok, J.G. Han, Su . Coa . Technol. 200 (2006) 6293.
[29] J.L. End ino, J.J. Nainapa ampil, E. K zanowki, Sc ip a Ma e . 47 (2002) 613.
[30] E. Sil a, M. Rebelo de Figuei edo, R. F anz, R. Escoba Galindo, C. Palacio, A.
Espinosa, S. Calde on V. , C. Mi e e , S. Ca alho, Su . Coa . Technol. 205 (2010)
2134.
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Solid Films 468 (2004) 125.
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155–159.
[33] J.C. Sánchez-López, A. Fe nández, in: A. E demi , C. Donne (Eds.), T ibology o
Diamond-Like Ca bon Films: Fundamen als and Applica ions, Sp inge , New Yo k,
2008, p. 311.
[34] K. Holmbe g, A. Ma hews, Coa . T ibology, T ibology se ies, 28 Ed. D. Dowson,
Else ie , 1994.

17
[35] J.C. Sánchez-López, D. Ma ínez-Ma ínez, M.D. Abad, A. Fe nández, Su . Coa .
Technol. 204, 947-954 (2009).
[36] J. L. End ino, J.C. Sánchez-López, R. Escoba Galindo, D. Ho wa , A. Ande s,
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18
Figu e Cap ions
Fig. 1. XRD pa e ns o he Ag-TiCN coa ings deposi ed by DC eac i e magne on
spu e ing, wi h di e en Ag/Ti a omic a ios.
Fig. 2. C1s (a) and N 1s (b) pho oelec on spec a o 4 ep esen a i e coa ings wi h
Ag/Ti a ios o 0, 0.20, 0.40 and 1.49.
Fig. 3. Phase composi ion o he samples p epa ed wi h Ag/Ti a ios o 0, 0.20, 0.40 and
1.49.
Fig. 4. C oss-sec ional SEM mic og aphs o samples wi h a omic a ios Ag/Ti: a) 0; b)
0.20; c) 0.40 and d) 1.49.
Fig. 5. Ha dness and esidual s ess alues o Ag-TiCN coa ings s. he Ag/Ti a omic
a io.
Fig. 6. Va ia ion o he ha dness and wea a e p ope ies as a unc ion o he a io o
so (Ag+CNx)/ha d (TiCyN1-y) phases.
Fig. 7. F ic ion coe icien (a) and wea a e (b) alues o Ag-TiCN as a unc ion o he
Ag/Ti a omic a io.
19
Fig. 8. Op ical mic og aph o he alumina ball a e he ic ion es on o he Ag-TiCN
coa ing wi h 10.8 a . % o Ag (a) and co esponding Raman spec a (b) and EDX (c)
analysis.
Fig. 9. Op ical mic og aph o he wea ack a e he ic ion es o he Ag-TiCN
coa ing wi h 10.8 a . % o Ag (a) and co esponding Raman spec a (b).
Fig. 10. The a e o inhibi ion o cellula as a unc ion o he Ag/Ti a omic a io, a e
7days incuba ion.
Table 1. Chemical composi ion and ibomechanical p ope ies o he deposi ed Ag-TiCN coa ings.
Sample
Chemical composi ion
a . %
Thickness
m
H
GPa

GPa

K
mm3/Nm
Ag/Ti
Ag
Ti
C
N
0
0
36.9
29.2
33.9
2.9
17.0
-0.5
0.29
7.1E-06
0.06
2.0
35.1
29.9
33.0
2.0
17.8
-1.0
0.31
1.9E-05
0.15
4.6
31.1
32.4
31.9
2.4
18.2
-1.4
0.25
5.3E-06
0.20
6.3
31.6
30.5
31.6
1.4
18.0
-1.7
0.26
5.2E-06
0.27
8.0
29.2
29.5
33.3
1.5
16.5
-1.8
0.27
2.8E-05
0.40
10.8
26.9
31.2
31.1
3.0
15.0
-2.5
0.27
3.8E-05
0.77
19.8
25.7
30.6
23.9
2.9
10.0
-1.6
0.28
4.8E-05
1.49
26.7
17.9
33.6
21.8
3.2
8.0
-1.3
0.25
8.7E-05
Table 1 R1
Figu e 1
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Figu e 2a
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Figu e 2b
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Figu e 3
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Figu e 4
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