Ci a ion: Abdel-Mohsen, A.M.;
Abdel-Rahman, R.M.; Kalina, L.;
Vishakha, V.; Kap álko á, L.;
Nˇemeˇcek, P.; Janˇcᡠ, J.; Kelna , I. E ec
o Chi in Nanoc ys al Deace yla ion
on a Na u e-Mimicking In e ace in
Ca bon Fibe Composi es. J. Compos.
Sci. 2024,8, 163. h ps://doi.o g/
10.3390/jcs8050163
Academic Edi o s: Jiadeng Zhu and
F ancesco To nabene
Recei ed: 31 Janua y 2024
Re ised: 15 Ap il 2024
Accep ed: 23 Ap il 2024
Published: 26 Ap il 2024
Copy igh : © 2024 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
A icle
E ec o Chi in Nanoc ys al Deace yla ion on a
Na u e-Mimicking In e ace in Ca bon Fibe Composi es
Abdella i M. Abdel-Mohsen 1, Rasha M. Abdel-Rahman 1, Lukáš Kalina 2, Vishakha Vishakha 3,
Ludmila Kap álko á1, Pa el Nˇemeˇcek 1, Jose Janˇcᡠ2,3 and I an Kelna 1,*
1Ins i u e o Mac omolecula Chemis y, Czech Academy o Sciences, Hey o ského nám. 2,
162 00 P aha, Czech Republic; [email p o ec ed] (A.M.A.-M.); [email p o ec ed] (R.M.A.-R.);
[email p o ec ed] (L.K.); [email p o ec ed] (P.N.)
2Ma e ials Resea ch Cen e , Facul y o Chemis y, B no Uni e si y o Technology, Pu kyˇno a 464/118,
612 00 B no, Czech Republic; [email p o ec ed] (L.K.); [email p o ec ed] (J.J.)
3CEITEC-Cen al Eu opean Ins i u e o Technology, B no Uni e si y o Technology, Pu kyˇno a 656/123,
612 00 B no, Czech Republic; [email p o ec ed]
*Co espondence: [email p o ec ed]
Abs ac : The o ma ion o a igid, ough in e ace based on a nac e-like s uc u e in ca bon ibe
(CF) composi es is a p omising way o elimina e low delamina ion esis ance. An e ec i e me hod
o coa ing CFs is elec opho e ic deposi ion (EPD), which, in he case o dissimila componen s like
g aphene oxide (GO) and polyme ic glue, usually equi es chemical bonding/s ong in e ac ions. In
his wo k, we ocus on chi in nanoc ys als (ChNCs), leading o an excellen mechanical pe o mance
o a i icial nac e, whe e a o able in e ac ions and bonding wi h GO a e con olled by deg ees o
deace yla ion (5, 15, and 30%). We p epa ed coa ings based on GO/ChNC adduc s wi h 95/5, 90/10,
50/50, and 25/75 a ios using op imized EPD condi ions (pH, concen a ion, ol age, and ime). The
p epa ed ma e ials we e cha ac e ized using FTIR, TEM, XPS, SEM, DLS, and XRD. SEM e alua ion
indica es he o ma ion o a homogeneous in e laye , which has a ai po en ial o chemical bonding
wi h he epoxy ma ix. Sho -beam es ing o epoxy ma ix composi es indica es ha he coa ing does
no dec ease s i ness and has a ela i ely low dependence on composi ion. The e o e, all coa ings a e
p omising o a de ailed s udy o delamina ion esis ance using lamina e samples. Mo eo e , acile
EPD om he wa e solu ion/suspension has a ai po en ial o indus ial applica ions.
Keywo ds: g aphene oxide; chi in nanoc ys als; delamina ion esis ance; ough in e ace;
elec opho esis
;
ca bon ibe composi e
1. In oduc ion
I is now well accep ed ha combina ions o ca bon nanopla ele s (CN) wi h small
amoun s o a ious polyme s [
1
–
3
] and polysaccha ides [
4
] may o m na u e-mimicking
ma e ials wi h unique compac s uc u es and imp essi e mechanical pa ame e s, which
can exceed hose o nac e, ha is, he na u al ‘gold s anda d’ o s ong, ough ma e ial [
5
,
6
].
I was ecen ly demons a ed ha analogous ma e ials wi h unique pe o mance (de-
o ma ion mechanism) can be ob ained by combining CN wi h sui able o ganic aniso opic
nanopa icles, mos ly nano ib ils/whiske s. An example is a sys em con aining educed
g aphene oxide (GO) and co alen ly linked cellulose nano ib ils (CNC) [
7
] wi h a ypical
composi ion o nac es (80–97% GO), some o he nanopla ele /CNC combina ions [
7
–
12
]
o he nano ib illa ed cellulose/CN/diblock p o ein sys em [
13
]. O he high-pe o mance
na u e-mimicking ma e ials a e based on di e en silk ib oin/GO combina ions [14,15].
So a , only one s udy has epo ed he applica ion o chi in nanoc ys als (ChNCs) in
a sys em combining silk nano ib il, hyd oxyapa i e nanoc ys als, and ChNCs [
16
]. These
esul s a e consis en wi h he ac ha nac e is a e na y composi e consis ing o a agoni e
J. Compos. Sci. 2024,8, 163. h ps://doi.o g/10.3390/jcs8050163 h ps://www.mdpi.com/jou nal/jcs
J. Compos. Sci. 2024,8, 163 2 o 16
pla ele s, nano ib illa chi in, and p o ein [
5
]. In his espec , conside ing he p ime impo -
ance o in e ac ions/linking be ween componen s [
7
,
10
], we can conside he p omising
po en ial o nanosized pola amino- unc ionalized ChNCs wi h a a o able aspec a io
(AR) o o m GO-based nac e analogs. Fu he mo e, ChNC p epa a ion is easie han
nano ib illa ed cellulose, wi h u he bene i s in using was e ma e ial [17,18].
ChNCs, mos ly p epa ed om chi in, is a igid c ys alline nano ibe wi h Young’s mod-
ulus a 40–80 GPa. I comp ises epea ing uni s o glucosamine and N-ace ylglucosamine
ha con ain eac i e g oups, i.e., amines. Thus, chi in has mo e signi ican po en ial o
chemical modi ica ions han cellulose. Chi in nanoc ys als can be p oduced in a ela-
i ely wide ange o leng hs, diame e s, cha ge densi ies, ypes o cha ge, and c ys allini y
h ough a ious op-down p ocedu es [17–20].
In he a ea o ib ous composi es, di e en nanopa icles, mainly CN and CNT, a e
applied o modi y he in e ace as a single coa ing. This includes elec opho e ic deposi ion
(EPD) [
21
,
22
] and ca bon apo deposi ion [
23
], componen s o sizing [
24
], o e en di ec
linking o CF o o m hie a chical hai y ibe s [25–27].
In he case o cellulose nanoc ys als (CNC) and mic o ib ils [
28
–
30
] o silane-modi ied
CNC [
30
], a ious dip coa ings o glass ibe s and ca bon ibe s (CFs) a e epo ed, while
a amid ibe s we e coa ed wi h a amid mic o ibe s by EPD [
30
,
31
] o by he dip coa ing o
he a amid mic o ibe s/g aphene combina ion [
32
]. This modi ica ion o he ibe su ace
p o ides he bene i o enhanced oughness, inc easing ic ional adhesion componen s, and
highe in e phase modulus. A he same ime, an impo an de iciency o composi es wi h
low esis ance agains impac -delamina ion [
33
] (in e lamina c acking) can be elimina ed
by a ough, usually low-modulus in e ace [
34
] due o an inc ease in impac ene gy elease.
Howe e , his leads o a signi ican educ ion in s i ness [35].
Fai mechanical p ope ies, including inc eased in e lamina shea s eng h (ILSS),
we e ound wi h a mo e igid coa ing by CNC [
28
,
29
]. A he same ime, he solu ion by
a ious me hods ha imp o e he oughness o he ma ix b ings p ocessing limi a ions
and a educ ion in esis ance agains ibe buckling [
36
]. On he basis o he abo e ac s, we
conside he impo an ole o he ough, igid in e aces using na u e-mimicking nac e-like
s uc u es. So a , igid-so s uc u es based on ca bon nano ubes (CNTs) modi ied wi h
he poly(e hylene glycol)me hyle he [
37
] and CNT/polye he imide combina ion [
37
] ha e
been epo ed. Howe e , unlike he compa able e ec on a single coa ing using nea GO
o CNT [
38
] o enhance in e acial p ope ies, he abili y o ubula nanoelemen s o o m
e ec i e complex s uc u es wi h polyme s and excellen mechanical p ope ies is limi ed.
In he case o 2D pla ele s, he po en ial o c ea e e ec i e o de ed nac e-mimicking “b ick
and mo a ” s uc u es and, hus, a igid, ough in e ace is mo e ma ked [5,38].
So a , only some laye -by-laye deposi ion o al e na ing polyme /nanopa icle
(NP) laye s has been epo ed. Examples a e laye s o polydopamine (PDA)/GO [
39
,
40
],
PDA/polyhed al silsesquioxane (POSS) [
41
], o PDA/NiOH pla ele s [
42
]. The g a ing o
nanopa icles o he deposi ed polyme ic laye [43] has also been epo ed.
Recen ly, we p epa ed CF coa ings using nac e-like in e laye s by EPD o PDA-coa ed
GO o some polyme -g a ed GO combina ions, showing an excellen abili y o enhance
ILSS wi hou loss o s i ness [
37
]. To con ol he composi ion o EPD coa ings in he
wo-componen sys em, he g a ing o an amina ed polyme o GO o bo a e-media ed in-
e ac ions/bonding o hyd oxyl-con aining poly( inylalcohol) and ca boxyme hylcellulose
was necessa y. The e o e, his s udy is aimed a highligh ing he po en ial o al e na-
i e nac e-like coa ings o ca bon ibe s based on GO wi h a ached chi in nanoc ys als
(GO/ChNC adduc s) o upg ade epoxy/ ibe composi es oge he wi h a ho ough s udy o
he e ec o ChNCs pa ame e s and adduc composi ion on he elec opho e ic deposi ion
o he mul iscale igid ough hie a chical in e phase.
J. Compos. Sci. 2024,8, 163 3 o 16
2. Expe imen al Pa
2.1. Ma e ials
Epoxy esin LG700 based on diglycidyl e he o bisphenol A (DGEBA) + ha dene
HG737 (GRM Sys ems, s. .o.). Chi in lakes, 1-e hyl-3-(3-dime hylaminop opyl) ca bodi-
imide hyd ochlo ide (EDC), and N-hyd oxysuccinimide (NHS) we e pu chased om Sigma
Ald ich (P aha, Czech Republic); g aphi e lakes we e om (G aphi e Týn, Týn nad, Vl-
a ou, Czech Republic); and he ca bon ibe (CF) o ing ya n ilamen To ayca
T700SC 12 k
was om GRM Sys ems, s. .o. (Olomouc, Czech Republic).
2.2. P epa a ion o G aphene Oxide (GO)
The modi ied Humme ’s me hod [
44
] was used; b ie ly, 95 mL o concen a ed sul u ic
acid and 2 g o NaNO
3
we e added o 4 g o g aphi e lakes in an ice ba h. In o al, 12 g o
KMnO
4
was slowly added, and he mix u e was s o ed a 35
◦
C o 100 min. Then, 184 mL
o wa e was added while he empe a u e inc eased o ~95
◦
C. A e 15 min, 420 mL o
wa e wi h 5 mL o 30% H
2
O
2
was added. The esidue was washed wi h a mix u e o wa e ,
35% HCl, and e hanol by cen i uga ion. The oxygen con en was ~40%, as e alua ed using
elemen al analysis. The inal ~2% wa e suspension was delamina ed using a Bandelin
200 W sonica o wi h 30% ampli ude o 15 min.
2.3. P epa a ion o Chi in Nanoc ys als (ChNCs)
Chi in nanoc ys als (ChNC) wi h di e en deg ees o deace yla ion (DDA) we e p e-
pa ed acco ding o ou p e ious wo ks [
18
,
45
]. B ie ly, chi in nanoc ys als we e syn hesized
by an acid hyd olysis p ocess using HCl (5 M) o 6 h a 90
◦
C, and he solid- o-medium-
solu ion a io was app oxima ely (1/100). The nanoc ys als we e ob ained a e cen i uga-
ion a 7500 pm o 30 min a oom empe a u e. ChNCs we e dialyzed using a cellulose
memb ane cu (12–14 KDa) o one week a oom empe a u e using deionized wa e , which
changed e e y 12 h un il he pH eached 4.5. ChNCs we e s o ed a 4
◦
C in a e ige a o un-
il u he use. The DDA o ChNCs was 5, 15, and 30% DDA om
13
C-CP/MAS NMR [
18
],
espec i ely. The deg ee o deace yla ion was also con i med by FTIR spec oscopy in
combina ion wi h XRD [45]; see Figu e S1a,b.
2.4. GO/ChNC Adduc Syn hesis
A ce ain amoun (0.5%) o GO was dispe sed in deionized wa e . Then, 50/25 mM o
EDC/NHS was added o he GO while s i ing o 2 h a oom empe a u e o ac i a e he
ca boxylic and epoxide g oups o he GO. ChNCs wi h di e en deg ees o deace yla ion (5,
15, 30% DDA) we e added o he GO suspension d op by d op wi h s i ing o 5 h a oom
empe a u e o ob ain he GO/ChNC adduc . The p epa ed ma e ials we e coded acco ding
o DDA (GO/ChNCs
5
, GO/ChNCs
15
, and GO/ChNCs
30
adduc s). The ma e ials ob ained
we e dialyzed o 3 days a using deionized wa e .
2.5. Elec opho e ic Coa ing
Oxidized ca bon ibe s (OCFs), p epa ed wi h ni ic acid a 22
◦
C o 120 h acco ding
o ou p e ious wo k [
46
], we e ixed be ween wo s ainless s eel elec odes wi h a dis ance
o ~10 mm. Elec opho e ic deposi ion (EPD) p oceeded acco ding o he de ails in Table 1,
also showing he composi ion o he espec i e adduc s. The applied ol age was 5, 10, and
20 V, espec i ely, and h ee concen a ions o GO/ChNC adduc s (5, 10, and 15 mg/mL)
we e applied. Mo eo e , coa ing was pe o med a a ious pHs (3.5, 7.5, and 11) and
imes o 10 and 20 min. A e washing and d ying, he composi e ba was p epa ed (see
Sec ion 2.5). Acco ding o he li e a u e, su ace oxida ion o CF has a negligible e ec on
he mechanical pa ame e s o CF [47].
J. Compos. Sci. 2024,8, 163 4 o 16
Table 1. Composi ion o GO/ChNC adduc s used o CF coa ing.
Numbe GO
(% w )
ChNCs
(% w )
DDA o ChNCs *
(%) Abb e ia ion
1 95 5 5 GO/ChNCs5adduc
2 90 10 5 GO/ChNCs5adduc
3 80 20 5 GO/ChNCs5adduc
4 50 50 5 GO/ChNCs5adduc
5 95 5 15 GO/ChNCs15 adduc
6 90 10 15 GO/ChNCs15 adduc
7 80 20 15 GO/ChNCs15 adduc
8 50 50 15 GO/ChNCs15 adduc
9 95 5 30 GO/ChNCs30 adduc
10 90 10 30 GO/ChNCs30 adduc
11 80 20 30 GO/ChNCs30 adduc
12 50 50 30 GO/ChNCs30 adduc
* deg ee o ChNCs deace yla ion.
2.6. Cha ac e iza ion o OCF Coa ed wi h a GO/CHNC Adduc
A enua ed o al e lec ance Fou ie ans o m in a ed spec oscopy (ATR-FTIR) was
ca ied ou using a B uke Ve ex V70 FTIR spec ome e and a B uke Pla inum ATR
accesso y (B uke GmbH, E lingen, Ge many) wi h a single e lec ion diamond c ys al
moun (B uke Op ik GmbH, E lingen, Ge many). Samples we e clamped di ec ly agains
he diamond c ys al using he pla inum ATR sample clamp mechanism, ensu ing consis en
p essu e pe sample. Spec a we e collec ed in he wa enumbe egion 3900–650 cm
−1
.
Fou da a se s pe sample we e eco ded, adding 128 in e e og ams pe se . Spec a
we e measu ed a a esolu ion o 4.0 cm
−1
, and 128 backg ound scans pe sample we e
collec ed. The a e aged spec a pe sample we e gene a ed using he B uke OPUS e sion
7.2 so wa e, whe e all spec a we e co ec ed o ATR.
Sho -beam s eng h (SBS), also called in e lamina shea s eng h (ILSS), i applied
o lamina e samples, was de e mined acco ding o ASTM D2344/D2344M using beam
samples 3
×
6
×
18 mm. These samples we e cu om unidi ec ional composi es p epa ed
by he manual imp egna ion/mixing o a bundle o a weighed amoun o CF (0.52 g) wi h
epoxy in a silicone mold. The dimension o mold was 3
×
6
×
60 mm; he leng h o CF
was ~60 mm. The h ee-poin sho -beam bending es (span leng h 12 mm, span leng h o
hickness a io o 4) was pe o med wi h Ins on 5800 appa a us using 1 mm/min c osshead
speed. The mo phology o na i e GO, ChNC, and GO/ChNC adduc wi h di e en DDA
(%) was isualized by ansmission elec on mic oscopy (TEM). The expe imen was ca ied
ou wi h a Tecnai G2 spi i 12 elec on mic oscope (FEI, B no, Czech Republic). The su ace
o he ibe s and ac u e su aces was obse ed using a scanning elec on mic oscope
(SEM) using a, Maia appa a us(FEI, B no, Czech Republic) a 3 kV.
The heological cha ac e iza ion o wa e suspensions (5 mg/mL) o na i e GO,
ChNCs, and he GO/ChNC adduc was conduc ed a oom empe a u e using he ARES
G2 Rheome e (TA Ins umen s, New Cas le, IN, USA). Pa allel pla es wi h cone/pla e ge-
ome y (cone angle o 2
◦
, diame e o 40 mm) we e used. F equency sweep measu emen s
we e made in he ange om 0.05 o 100 ad/s a a 1% s ain ampli ude.
The X- ay pho oelec on spec oscopy (XPS) o oxidized CF (OCF), nea ChNW, GO,
and coa ed OCF was ca ied ou wi h he K a os Analy ical Axis Ul a DLD sys em (K a os
Analy ical, Manches e UK) using a monoch oma ic Al K
α
(h
ν
= 1486.7 eV) ope a ing a
75 W (5 mA, 15 kV). Spec a we e ob ained using an analysis a ea o ~300
×
700
µ
m. The
K a os cha ge neu alize sys em was used o all analyses. The high- esolu ion spec a
we e measu ed wi h 0.1 eV s ep size and 20 eV pass ene gy. The ins umen base p essu e
was 2
·
10–8 Pa. Spec a we e analyzed using he CasaXPS so wa e ( e sion 2.3.15) by
applying a Gaussian–Law ence line shape o i ing and he ORIGIN 2016 so wa e.
X- ay di ac ion pa e ns we e collec ed using a D-8 Ad ance di ac ome e (B uke
AXS, Ka ls uhe Ge many) wi h a B agg–B en ano (
θ
-
θ
) goniome e ( adius 217.5 mm)
J. Compos. Sci. 2024,8, 163 5 o 16
equipped wi h a seconda y beam cu ed g aphi e monoch oma o and Na (Tl) I scin illa ion
de ec o . The gene a o was ope a ed a 40 kV and 30 mA.
3. Resul s and Discussions
3.1. E ec o DDA on GO/ChNC Adduc Fo ma ion
The deg ee o deace yla ion (%) a ec ed he mo phology o he ChNCs, as is clea om
(Figu e 1a–c), showing he STEM o he ChNCs wi h di e en DDAs. A a lowe DDA %,
ChNCs show high agg ega ion wi h sho c ys al leng h (Figu e 1a, ); when inc easing he
DDA om 15 o 30%, he nanoc ys als a e sligh ly longe compa ed o 5 DDA (Figu e 1b,c, ).
Figu e 1d shows he FTIR o ChNCs wi h di e en DDAs. The peak in ensi y a io be ween
he amino- o-ace amide g oups inc eased wi h an inc ease in he amino g oup con en om
5 o 30 DDA. Figu e 1e shows he XRD o na i e chi in and ChNC wi hin di e en DDAs (5,
15, 30%). F om XRD, all he p is ine chi in and ChNCs wi h di e en DDAs exhibi ed six
di ac ion peaks a 2
θ
= 9.5
◦
, 12.8
◦
, 19.2
◦
, 20.71
◦
, 23.4
◦
and 26.4
◦
, indexed as (020), (021),
(110), (120), (130) and (013), espec i ely (Figu e 1e), sugges ing he c ys alline s uc u e o
he
α
-chi in [
18
,
48
,
49
]. F om Figu e 1e, DDA did no signi ican ly a ec he c ys alliza ion
o he ChNCs.
J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 7 o 19
Figu e 1. Rep esen a i e STEM ((a–c,a’–c’)), FTIR (d), XRD (e), and his- og ams ( ) o ChNCs (see
sub igu es inside (a’–c’) wi h diffe en DDAs (5, 15, 30%). The dashed a eas a e magni ied in (a’–c’).
Ou p elimina y esul s indica e ha diffe en cha ge densi ies and
mobili y/dimensions o bo h GO and ChNCs p ac ically exclude he con ol o
elec opho e ic deposi ion (EPD) o hese wo-componen sys ems, simila o o he
GO/polyme combina ions [46]. The e o e, mu ual bonding be ween componen s, using
hei unc ionali y enabled by EDC/NHS, was applied o p epa e he GO/ChNC adduc .
When op imizing he EDC/GO/ChNCs/NHS a io, amide and es e bonds be ween GO
and ChNCs we e c ea ed (Scheme 1a).
Figu e 1. Rep esen a i e STEM ((a–c,a’–c’)), FTIR (d), XRD (e), and his- og ams ( ) o ChNCs (see
sub igu es inside (a’–c’) wi h di e en DDAs (5, 15, 30%). The dashed a eas a e magni ied in (a’–c’).

J. Compos. Sci. 2024,8, 163 6 o 16
Ou p elimina y esul s indica e ha di e en cha ge densi ies and mobili y/dimensions
o bo h GO and ChNCs p ac ically exclude he con ol o elec opho e ic deposi ion (EPD) o
hese wo-componen sys ems, simila o o he GO/polyme combina ions [
46
]. The e o e,
mu ual bonding be ween componen s, using hei unc ionali y enabled by EDC/NHS, was
applied o p epa e he GO/ChNC adduc . When op imizing he EDC/GO/ChNCs/NHS
a io, amide and es e bonds be ween GO and ChNCs we e c ea ed (Scheme 1a).
J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 6 o 17
Figu e 1. Rep esen a i e STEM ((a)–(c), (a’)–(c’)), FTIR(d), XRD (e), and his- og ams ( ) o ChNCs
(see sub igu es inside (a’)–(c’) wi h diffe en DDAs (5, 15, 30%). The dashed a eas a e magni ied in
(a’)–(c’).
Ou p elimina y esul s indica e ha diffe en cha ge densi ies and mobili y/dimen-
sions o bo h GO and ChNCs p ac ically exclude he con ol o elec opho e ic deposi ion
(EPD) o hese wo-componen sys ems, simila o o he GO/polyme combina ions [46].
The e o e, mu ual bonding be ween componen s, using hei unc ionali y enabled by
EDC/NHS, was applied o p epa e he GO/ChNC adduc . When op imizing he
EDC/GO/ChNCs/NHS a io, amide and es e bonds be ween GO and ChNCs we e c e-
a ed (Scheme 1a).
Scheme 1. P oposed chemical bonding and in e ac ion be ween GO and he ChNC and he coa ing
o OCF using he GO/ChNC adduc . (a) Linking GO wi h ChNCs using EDC/NHS as he c osslinke
and ca alys , espec i ely; (b) he coa ing o OCF using he GO/ChNC adduc (GO/ChNC
adduc @OCF).
F om Figu e 2, i ollows ha he o ma ion o a GO/ChNC polyelec oly e complex
and c osslinking educed abso p ion o he OH and NH/NH2 s e ching ib a ion peaks.
Fu he mo e, a new peak in he 1718 cm–1 egion showed he es e i ica ion eac ion be-
ween he –COOH o g aphene oxide (GO) and –OH o ChNCs. The band in he spec um
o na i e GO a 1729 cm–1 was na u ally b oad due o he p esence o a ious ypes o
“ca bonyls” and was sha pe a e he es e bond o med a e g a ing wi h ChNCs30 (Fig-
u e 2a). The s ong ionic in e ac ion be ween ca boxylic/epoxide GO and amino/hyd oxyl
ChNCs in he p esence o an EDC/NHS c osslinke agen (Figu e 2a) caused he peak in-
ensi y o he ee amino g oups a 1553 cm-1 o weaken.
Scheme 1. P oposed chemical bonding and in e ac ion be ween GO and he ChNC and he
coa ing o OCF using he GO/ChNC adduc . (a) Linking GO wi h ChNCs using EDC/NHS
as he c osslinke and ca alys , espec i ely; (b) he coa ing o OCF using he GO/ChNC
adduc (GO/ChNC adduc @OCF).
F om Figu e 2, i ollows ha he o ma ion o a GO/ChNC polyelec oly e complex
and c osslinking educed abso p ion o he OH and NH/NH
2
s e ching ib a ion peaks.
Fu he mo e, a new peak in he 1718 cm
–1
egion showed he es e i ica ion eac ion be ween
he –COOH o g aphene oxide (GO) and –OH o ChNCs. The band in he spec um o na i e
GO a 1729 cm
–1
was na u ally b oad due o he p esence o a ious ypes o “ca bonyls”
and was sha pe a e he es e bond o med a e g a ing wi h ChNCs
30
(Figu e 2a). The
s ong ionic in e ac ion be ween ca boxylic/epoxide GO and amino/hyd oxyl ChNCs in
he p esence o an EDC/NHS c osslinke agen (Figu e 2a) caused he peak in ensi y o he
ee amino g oups a 1553 cm−1 o weaken.
J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 8 o 18
Figu e 2. FTIR (a), XRD (b), and DLS (c) o na i e componen s and hei adduc s.
Figu e 2b shows he XRD pa e ns o he GO, ChNCs
30
, and GO/ChNC adduc
30
. The
diff ac ion peak o GO appea ed a 2θ = 11.5°, which was associa ed wi h he cha ac e is ic
peak (001 plane) o he in e laye s uc u e o he GO nanoshee s [50,51,52]. The ChNCs
30
diff ac ion peaks exhibi ed six diff ac ion peaks a 2θ = 9.5°, 12.8°, 19.2°, 20.71°, 23.4° and
26.4°, indexed as (020), (021), (110), (120), (130) and (013), espec i ely. GO g a ed wi h
ChNCs
30
showed only b oade diff ac ion peaks a 2θ = 20–30°, a ibu ed o he p esence
o GO and ChNCs. Chi in nanoc ys als a e conside ed o be in e cala ed in he laye ed
GO nanoshee s.
Figu e 2c shows he DLS o he na i e GO, GO/ChNCs
5
adduc , and GO/ChNCs
30
adduc . The size dis ibu ion o he na i e GO was abou 90 nm, whe eas, o he
GO/ChNCs5 adduc , i dec eased o 55 nm. A highe DDAs, he size dis ibu ion o he
adduc was abou 150 nm. This co esponds o he size o he ChNCs inc easing wi h
inc eased DDA om 5 o 30% (Figu e 1).
In e es ingly, he heological cha ac e iza ion o wa e suspensions (Figu e S2a)
indica es subs an ially imp o ed iscosi y o adduc s compa ed o bo h cons i uen s,
wi h he highes alue o adduc s con aining 75% ChNC. This indica es he impo an
effec o he adduc composi ion on i s size, shape, and in e ac ions.
Figu e 3 shows ine ChNCs (Figu e 3a,b) and a e y hin laye o GO wi h a smoo h
su ace (Figu e 3c,d). The GO/ChNC adduc showed a laye ed s uc u e wi h a la ge
hickness agains GO, indica ing adduc o ma ion (Figu e 3e, ).
Figu e 2. FTIR (a), XRD (b), and DLS (c) o na i e componen s and hei adduc s.
J. Compos. Sci. 2024,8, 163 7 o 16
Figu e 2b shows he XRD pa e ns o he GO, ChNCs
30
, and GO/ChNC adduc
30
.
The di ac ion peak o GO appea ed a 2
θ
= 11.5
◦
, which was associa ed wi h he cha -
ac e is ic peak (001 plane) o he in e laye s uc u e o he GO nanoshee s [
50
–
52
]. The
ChNCs30 di ac ion
peaks exhibi ed six di ac ion peaks a 2
θ
= 9.5
◦
, 12.8
◦
, 19.2
◦
, 20.71
◦
,
23.4
◦
and 26.4
◦
, indexed as (020), (021), (110), (120), (130) and (013), espec i ely. GO
g a ed wi h ChNCs
30
showed only b oade di ac ion peaks a 2
θ
= 20–30
◦
, a ibu ed o
he p esence o GO and ChNCs. Chi in nanoc ys als a e conside ed o be in e cala ed in
he laye ed GO nanoshee s.
Figu e 2c shows he DLS o he na i e GO, GO/ChNCs
5
adduc , and GO/ChNCs
30
adduc . The size dis ibu ion o he na i e GO was abou 90 nm, whe eas, o he GO/ChNCs5
adduc , i dec eased o 55 nm. A highe DDAs, he size dis ibu ion o he adduc was abou
150 nm. This co esponds o he size o he ChNCs inc easing wi h inc eased DDA om 5 o
30% (Figu e 1).
In e es ingly, he heological cha ac e iza ion o wa e suspensions (Figu e S2a) indi-
ca es subs an ially imp o ed iscosi y o adduc s compa ed o bo h cons i uen s, wi h he
highes alue o adduc s con aining 75% ChNC. This indica es he impo an e ec o he
adduc composi ion on i s size, shape, and in e ac ions.
Figu e 3shows ine ChNCs (Figu e 3a,b) and a e y hin laye o GO wi h a smoo h
su ace (Figu e 3c,d). The GO/ChNC adduc showed a laye ed s uc u e wi h a la ge
hickness agains GO, indica ing adduc o ma ion (Figu e 3e, ).
J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 8 o 17
Figu e 3. Rep esen a i e SEM images o na i e ChNCs (a), he GO (c) and GO/ChNCs30 (e) adduc
a e eeze-d ying. Dashed a eas a e magni ied in igu es below (b,d, ).
F om he XPS analysis o he adduc composi ion (Figu e 4), i ollows ha only C, O,
and N we e de ec ed om he b oad spec a o oxidized ca bon ibe s (OCF). OCF C 1
showed diffe en binding ene gies o -C=C, -C-C, -C-OH, -C-O, -COO, a 284.26 284.96,
286.03, 286.9 and 288.2. E . F om he C 1s and O 1s da a, we can con i m ha due o he
ni ic acid used o oxidize he ca bon ibe , a pa ial ni a ion eac ion was obse ed in N
1 (Figu e 4). The b oad XPS spec um o na i e ChNCs showed expec ed signals o C, O,
and N. The C 1s o na i e ChNCs showed ha he binding ene gy o 289.33 and 290.62
belongs o he ca bona e egion. The C 1s spec um showed he bonds o ca bon wi h ni-
ogen. The binding ene gies o 289.33 and 290.62 belong o he egion o ca bonyl g oups
coo dina ed wi h wa e molecules. The binding ene gy a 288.18 ela es o amide bonds,
and 286.32 is connec ed o C–N bonds (p ima y amino g oups). The O 1s o na i e ChNCs
we e obse ed only a 532.9 and 531.5 eV in ela ion o he -C-O and -C=O g oups in he
chemical s uc u e. Pa ially deace yla ed ChNCs show wo binding ene gies a 400.01
and 402.14 ha co espond o amide (N-C=O) and posi i ely cha ged ni ogen (Figu e 4).
F om he wide spec um o na i e g aphene oxide, as shown in he igu e abo e, only
O and C a e obse ed. C 1s o GO@OCF show ca bon in he hyb idiza ion s a e sp3 (285
eV) and sp2 (284.5 eV). The peak o ca bon in he sp2 s a e indica es a s ong asymme y,
as expec ed, wi h a high p opo ion o C-O bonds. The diffe en binding ene gies a 284.5,
286.67, 288.24, and 285 eV co espond o C=C, C-O, COOH, and C-C/C-H, espec i ely.
Oxidized ca bon ibe s coa ed wi h na i e g aphene oxide (GO@OCF) a e shown in
Figu e 4. As expec ed om he wide-spec um da a, C, O, and Na peaks we e obse ed.
The p esence o a sodium hyd oxide peak was due o he neu aliza ion o OCF wi h
NaOH a e he oxida ion s ep, which esul ed in a sal o m (-COONa). The C 1s spec um
shows ca bon in wo hyb idiza ion s a es as in he na i e GO spec um. Howe e , he
con ibu ion o C-O bonds dec eases in compa ison o ha o pu e GO. The spec um con-
ains he bonds C=O and es e g oups. A new es e g oup appea ed in he C 1s spec um
o GO@OCF a 288.42 eV, belonging o ca bon in he es e g oups, due o he es e i ica ion
eac ion be ween GO and OCF. The in ensi y o C-O g oups o GO@OCF was dec eased
compa ed o na i e GO due o he in e ac ion be ween OCF and GO.
Na i e ChNCs
Na i e GO GO-g-ChNCs
30
5 μm5 μm5 μm
500 nm 500 nm 500 nm
a
b
c
d
e
Figu e 3. Rep esen a i e SEM images o na i e ChNCs (a), he GO (c) and GO/ChNCs30 (e) adduc
a e eeze-d ying. Dashed a eas a e magni ied in igu es below (b,d, ).
F om he XPS analysis o he adduc composi ion (Figu e 4), i ollows ha only C,
O, and N we e de ec ed om he b oad spec a o oxidized ca bon ibe s (OCF). OCF C
1 showed
di e en binding ene gies o –C=C, –C–C, –C–OH, –C–O, –COO, a 284.26 284.96,
286.03, 286.9 and 288.2. E . F om he C 1s and O 1s da a, we can con i m ha due o he
ni ic acid used o oxidize he ca bon ibe , a pa ial ni a ion eac ion was obse ed in
N
1 (Figu e 4)
. The b oad XPS spec um o na i e ChNCs showed expec ed signals o
J. Compos. Sci. 2024,8, 163 8 o 16
C, O, and N. The C 1s o na i e ChNCs showed ha he binding ene gy o 289.33 and
290.62 belongs
o he ca bona e egion. The C 1s spec um showed he bonds o ca bon
wi h ni ogen. The binding ene gies o 289.33 and 290.62 belong o he egion o ca bonyl
g oups coo dina ed wi h wa e molecules. The binding ene gy a 288.18 ela es o amide
bonds, and 286.32 is connec ed o C–N bonds (p ima y amino g oups). The O 1s o na i e
ChNCs we e obse ed only a 532.9 and 531.5 eV in ela ion o he –C–O and –C=O g oups
in he chemical s uc u e. Pa ially deace yla ed ChNCs show wo binding ene gies a
400.01 and 402.14 ha co espond o amide (N–C=O) and posi i ely cha ged ni ogen
(Figu e 4).
J. Compos. Sci. 2024, 8, x FOR PEER REVIEW 9 o 17
Figu e 4. XPS o OCF, ChNCs, and OCF coa ed by he GO and GO/ChNCs30 adduc The EPD con-
di ions we e as ollows: adduc concen a ion a 5 mg/mL, ime o 10 min, ol age a 5 V, pH 3.5 and
empe a u e a 23 °C.
F om he wide spec um o GO/ChNC adduc @OCF, only C, O, and N peaks ap-
pea ed, and hese peaks we e peaks o Na as well. C 1s o GO/ChNC adduc @OCF show
diffe en binding ene gies a 284.24, 285, 285.6, 286.62, 288.07, 289.41 co esponding o C=C,
C-C/CH, C-OH, C-O-, N-C=O-/COO- and ca bon binding wi h wa e molecules. F om he
C 1s spec um, we could conclude ha an es e ifica ion/amida ion eac ion could occu
be ween he unc ional g oup o he GO/ChNC adduc and g oups o OCF. F om he N 1s
spec um o he GO/ChNC adduc @OCF, only he N-C=O peak appea ed, and no C-N
peak appea ed o ee amino g oups o pa ially deace yla ed ChNCs. F om bo h C 1 and
O 1 o GO/ChNC adduc @OCF, bo h es e ifica ion and amida ion eac ions could occu
be ween he GO/ChNC adduc and OCF (Figu e 4). Un o una ely, he high complexi y o
he whole sys em [46] did no allow o he p ecise calcula ion o he GO/ChNC a io. To conclude,
bo h XPS and FTIR indica ed in e ac ions/bonding be ween componen s in he GO/ChNC
adduc .
1200 1000 800 600 400 200 0
296 294 292 290 288 286 284 282 280
540 538 536 534 532 530 528 526 408 405 402 399 396 393
1200 1000 800 600 400 200 0
in ensi y (a.u.)
Binding ene gy (eV)
C 1s
O KLL
C=C
C–C; C–H
C–OH
C–O–
COO–
Binding ene gy (eV)
Binding ene gy (eV)
O=C
–O–C
Binding ene gy (eV)
N–(C=O)–
–NO
2
–NO
3
i
n ensi y (a.u.)
O KLL
O 1s
N 1s
C 1s
Na i e ChNWs
C 1s
O 1s
N 1s
Binding ene gy (eV)
296 294 292 290 288 286 284 282 280
C–C; C–H
C–O–
N–(C=O)–
CO
32–
CO
32–
C–N–
GO coa ed OCF
GO-g-ChNWs
coa ed OCF
Binding ene gy (eV)
540 538 536 534 532 530 528 526
–O–C
esidual H
2
O
O=C
Binding ene gy (eV)
410 408 406 404 402 400 398 396 394 392
N–(C=O)–
–N–C
Wide spec a
C 1s
O 1s
N 1s
Na i e OCF
Binding ene gy (eV)
1200 1000 800 600 400 200 0
In ensi y (a.u.)
Binding ene gy (eV)
Na KLL
Na 1s
O KLL
O 1s
N 1s
In ensi y (a.u.)
296 294 292 290 288 286 284 282 280
C=C
C–C; C–H
C–O–
C=O
COO–
Binding ene gy (eV)
540 538 536 534 532 530 528 526
–O–C
O=C
Binding ene gy (eV)
410 408 406 404 402 400 398 396 394 392
N–(C=O)–
–NO
2
Binding ene gy (eV)
1200 1000 800 600 400 200 0
Binding ene gy (eV)
C 1s
O 1s
Na KLL
N 1s
O KLL
Na 1s
296 294 292 290 288 286 284 282 280
C=C
C–C; C–H
C–OH
C–O–
N–(C=O)–; COO–
CO
3
2–
Binding ene gy (eV)
540 538 536 534 532 530 528 526
–O–C
oxides
Binding ene gy (eV)
N–(C=O)–
410 408 406 404 402 400 398 396 394 392
Binding ene gy (eV)
Figu e 4. XPS o OCF, ChNCs, and OCF coa ed by he GO and GO/ChNCs
30
adduc The EPD
condi ions we e as ollows: adduc concen a ion a 5 mg/mL, ime o 10 min, ol age a 5 V,
pH 3.5 and empe a u e a 23 ◦C.
F om he wide spec um o na i e g aphene oxide, as shown in he igu e abo e, only
O and C a e obse ed. C 1s o GO@OCF show ca bon in he hyb idiza ion s a e sp3 (
285 eV
)
and sp2 (284.5 eV). The peak o ca bon in he sp2 s a e indica es a s ong asymme y, as
expec ed, wi h a high p opo ion o C–O bonds. The di e en binding ene gies a 284.5,
286.67, 288.24, and 285 eV co espond o C=C, C–O, COOH, and C–C/C–H, espec i ely.
J. Compos. Sci. 2024,8, 163 9 o 16
Oxidized ca bon ibe s coa ed wi h na i e g aphene oxide (GO@OCF) a e shown in
Figu e 4. As expec ed om he wide-spec um da a, C, O, and Na peaks we e obse ed.
The p esence o a sodium hyd oxide peak was due o he neu aliza ion o OCF wi h NaOH
a e he oxida ion s ep, which esul ed in a sal o m (–COONa). The C 1s spec um shows
ca bon in wo hyb idiza ion s a es as in he na i e GO spec um. Howe e , he con ibu ion
o C–O bonds dec eases in compa ison o ha o pu e GO. The spec um con ains he bonds
C=O and es e g oups. A new es e g oup appea ed in he C 1s spec um o GO@OCF a
288.42 eV, belonging o ca bon in he es e g oups, due o he es e i ica ion eac ion be ween
GO and OCF. The in ensi y o C-O g oups o GO@OCF was dec eased compa ed o na i e
GO due o he in e ac ion be ween OCF and GO.
F om he wide spec um o GO/ChNC adduc @OCF, only C, O, and N peaks ap-
pea ed, and hese peaks we e peaks o Na as well. C 1s o GO/ChNC adduc @OCF show
di e en binding ene gies a 284.24, 285, 285.6, 286.62, 288.07, 289.41 co esponding o C=C,
C–C/CH
, C–OH, C–O–, N–C=O–/COO– and ca bon binding wi h wa e molecules. F om
he
C 1s
spec um, we could conclude ha an es e i ica ion/amida ion eac ion could occu
be ween he unc ional g oup o he GO/ChNC adduc and g oups o OCF. F om he N 1s
spec um o he GO/ChNC adduc @OCF, only he N–C=O peak appea ed, and no C–N
peak appea ed o ee amino g oups o pa ially deace yla ed ChNCs. F om bo h C 1 and
O 1 o GO/ChNC adduc @OCF, bo h es e i ica ion and amida ion eac ions could occu
be ween he GO/ChNC adduc and OCF (Figu e 4). Un o una ely, he high complexi y o
he whole sys em [
46
] did no allow o he p ecise calcula ion o he GO/ChNC a io. To
conclude, bo h XPS and FTIR indica ed in e ac ions/bonding be ween componen s in he
GO/ChNC adduc .
3.2. E ec o he GO/ChNC Adduc Composi ion and EPD Va ia ions on he S uc u e o
he Coa ing
The sys ema ic e alua ion o he deg ee o ChNC/GO in e ac ions/bonding on he
OCF coa ing was combined wi h a ia ions in he EPD condi ions o ob ain comple e
in o ma ion abou his p ocess, which, up o now, has no been s udied. Figu es 5, S3
and S4 ollow he ma ked e ec o pH, ol age, and GO/ChNC adduc concen a ion on
he homogenei y and hickness o he coa ing. Figu e 5shows he impo an e ec o pH;
a a lowe pH, he OCF was coa ed wi h compac homogeneous laye s using adduc s o
all DDAs (Figu e 5a–c). A neu al pH, he compac laye o he adduc s showed a small
agg ega ion on he OCF su ace, which was di e en o espec i e DDAs (Figu e 5d– ). A
pH 11, he hickness o he coa ing was small compa ed o pH 3.4, wi h high agg ega ion
on he OCF su ace, mainly o 5 and 30% DDA (Figu e 5g–i).
The mos homogeneous coa ing o he GO/ChNC
15
adduc a all pHs (Figu e 5b,e,h)
con i med he e ec o DDA on he s uc u e o he adduc . This ac was also indi ec ly
indica ed by he heology o he wa e suspensions as well; he di e ences in G’ o he
adduc s wi h di e en DDAs can be obse ed (5, 30%, Figu e S2b).
Due o he ela i ely la ge size o he adduc s and he expec ed high cha ge densi y
oge he wi h he ela ed slowe assembly/o de ing, unlike he GO-g-polyme chain o
polydopamine-coa ed GO, he bes deposi ion occu ed a a lowe ol age [
46
]. As we can
see, he lowe applied ol age (5 V) led o mo e homogeneous and compac laye s o he
GO/ChNC adduc (Figu e S3) compa ed o he highly applied ol age (20 V). Figu e S4
shows he e ec o adduc concen a ion on he homogenei y o he OCF coa ing. As we
can see, a lowe concen a ions, he coa ing had a he e ogeneous dis ibu ion on he ibe
su ace up o (1 mg/mL). A mo e compac and homogeneous laye was ob ained on he
OCF su ace a highe adduc concen a ions.
F om Figu e 6, i ollows ha he e ec o DDA and, hus, he s uc u e, size, and
cha ge densi y o he adduc s ongly in luenced he hickness o he EPD laye ; i s g owing
endency wi h DDA can be obse ed, ma king i s mos conside able hickness o 30%
DDA wi h abou 120–160 nm.
J. Compos. Sci. 2024,8, 163 16 o 16
43.
Wang, J.; Zhou, S.; Huang, J.; Zhao, G.; Liu, Y. In e acial modi ica ion o basal ibe illing composi es wi h g aphene oxide and
polydopamine o enhanced mechanical and ibological p ope ies. RSC Ad . 2018,8, 12222–12231. [C ossRe ]
44.
Ma cano, D.C.; Kosynkin, D.V.; Be lin, J.M.; Sini skii, A.; Sun, Z.; Slesa e , A.; Alemany, L.B.; Lu, W.; Tou , J.M. Imp o ed
Syn hesis o G aphene Oxide. ACS Nano 2010,4, 4806–4814. [C ossRe ]
45.
Kelna , I.; Kap álko á, L.; Nˇemeˇcek, P.; Dybal, J.; Abdel-Rahman, R.M.; Vy oubalo á, M.; Ne o alo á, M.; Abdel-Mohsen, A.M.
The E ec s o he Deace yla ion o Chi in Nanowhiske s on he Pe o mance o PCL/PLA Bio-Nanocomposi es. Polyme s 2023,
15, 3071. [C ossRe ]
46.
Kelna , I.; Kap álko á, L.; Nˇemeˇcek, P.; Jana a, M.; Dybal, J.; S oboda, J.; Pado ec, Z.; Abdel-Mohsen, A. Na u e-mimicking igid
ough in e ace in ib ous composi es: E ec o polyme /GO combina ion. Ma e . Today Commun. 2022,33, 104883. [C ossRe ]
47.
Wu, Q.; Yang, X.; Ye, Z.; Deng, H.; Zhu, J. Dopamine-dependen g aphene oxide modi ica ion and i s e ec s on in e acial
adhesion o ca bon ibe composi es. Su . In e aces 2022,31, 102086. [C ossRe ]
48.
Abdel-Mohsen, A.; Abdel-Rahman, R.; Kubena, I.; Kobe a, L.; Spo z, Z.; Zboncak, M.; P ik yl, R.; B us, J.; Janca , J. Chi osan-glucan
complex hollow ibe s ein o ced collagen wound d essing embedded wi h aloe e a. Pa I: P epa a ion and cha ac e iza ion.
Ca bohyd . Polym. 2020,230, 115708. [C ossRe ]
49.
Aly, A.S.; Abdel-Mohsen, A.M.; H dina, R.; Abou-Okeil, A. P epa a ion and Cha ac e iza ion o Polye hylene Glycol/Dime hyl
Siloxane Adduc and I s U iliza ion as Finishing Agen o Co on Fab ic. J. Na . Fibe s 2011,8, 176–188. [C ossRe ]
50.
Lin, Z.; Ma, Y.; Hu, C.; Zhang, Q. Molecula in e cala ed g aphene oxide wi h inely con ollable in e laye spacing o as dye
sepa a ion, Colloids Su . A: Physicochem. Eng. Asp. 2023,677, 132437. [C ossRe ]
51.
Dong, S.; Wang, B.; Liu, D.; He, M.; Chen, M.; Zhao, J.; Jin, W. Tailo ing he in e laye channel s uc u e o g aphene oxide
memb ane wi h conjuga ed ca ionic dyes o bu anol dehyd a ion. Sep. Pu i . Technol. 2023,325, 124728. [C ossRe ]
52.
Xu, W.L.; Fang, C.; Zhou, F.; Song, Z.; Liu, Q.; Qiao, R.; Yu, M. Sel -Assembly: A Facile Way o Fo ming Ul a hin, High-
Pe o mance G aphene Oxide Memb anes o Wa e Pu i ica ion. Nano Le . 2017,17, 2928–2933. [C ossRe ]
53.
Zheng, N.; Huang, Y.; Liu, H.-Y.; Gao, J.; Mai, Y.-W. Imp o emen o in e lamina ac u e oughness in ca bon ibe /epoxy
composi es wi h ca bon nano ubes/polysul one in e lea es. Compos. Sci. Technol. 2017,140, 8–15. [C ossRe ]
54.
Ricca di, C.C.; Adabbo, H.E.; Williams, R.J.J. Cu ing eac ion o epoxy esins wi h diamines. J. Appl. Polym. Sci. 1984,29,
2481–2492. [C ossRe ]
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