G aphene-high ich polycap olac one nano ibe s p epa ed ia
al e na ing cu en elec ospinning as ad anced sus ainable
so ben s o en i onmen al analysis
Pa el Holec
a
, Ma ina H´
ako ´
a
b
, I ona Kolicho ´
a
b
, Jan Vin e
a
, Tom´
aˇ
s Kalous
a
,
Ma k´
e a Huje o ´
a
a
, Dalibo ˇ
Sa ínský
b,*
, Jakub E ben
a,*
a
The Technical Uni e si y o Libe ec, Facul y o Tex ile Enginee ing, Depa men o Nonwo ens and Nano ib ous Ma e ials, S uden sk´
a 1402/2,
Libe ec 46001, Czech Republic
b
Cha les Uni e si y, Facul y o Pha macy in H adec K ´
alo ´
e, Depa men o Analy ical Chemis y, Ak. Hey o sk´
eho 1203, H adec K ´
alo ´
e 50003,
Czech Republic
ARTICLE INFO
Keywo ds:
G aphene
Polycap olac one
Nano ibe s
So ben
On-line solid phase ex ac ion
En i onmen
ABSTRACT
The inc easing demand o en i onmen al quali y con ol demands ad anced analy ical ools o
po en ially ha m ul subs ances moni o ing. The moni o ing ools o ace le el con aminan
analyses ypically ely on ad anced ch oma og aphic me hods coupled wi h sensi i e de ec o s
and sus ainable sample p e- ea men echniques o emo e ballas ma ix componen s. This
s udy p esen s a s aigh o wa d app oach o p epa ing a no el nano ib ous composi e ex ac ion
so ben based on biodeg adable poly-
ε
-cap olac one (PCL) polyme nano ibe s and g aphene
(GR) nanopa icles p epa ed ia al e na ing cu en (AC) elec ospinning o polyme solu ion.
Using AC elec ospinning, i was possible o p epa e mo e oluminous and po ous laye s wi h a
highe GR pa icle con en compa ed o he mo e common di ec cu en (DC) me hod. The new
composi e ma e ial demons a es high ex ac ion e iciency o a ge analy es o chemical
analysis o su ace wa e pollu an s while o e ing. The PCL-GR composi e, wi h GR pa icle
con en up o 45 w %, was sel -suppo ing, lexible, and did no equi e ene gy-in ensi e
ca boniza ion p ocesses as mo e common GR ma e ials. The composi e was success ully es ed
o he e en ion o selec ed pes icides, insec icides, and esidues ypical o indus ial pollu ion
using on-line ex ac ion coupled o ch oma og aphy, demons a ing i s po en ial as solid-phase
ex ac ion (SPE) ma e ial o a common su ace wa e pollu an s.
1. In oduc ion
Disco e ing new me hods and app oaches o simpli ying sample analysis is one o he key di ec ions in which bo h analy ical and
en i onmen al chemis y is heading. Solid-phase ex ac ion (SPE) is a widely used echnique o sample p e ea men , an essen ial s ep
in chemical analysis. I se es o emo e con aminan s om he analyzed sample while concen a ing he analy es. Conside ing he
sou ces o ch oma og aphic e o s, mo e han one- hi d o igina e om sample p epa a ion. Fu he mo e, his s age accoun s o
app oxima ely wo- hi ds o he o al ime equi ed o he analy ical p ocess, making sample p e ea men one o he mos c i ical
* Co esponding au ho s.
E-mail add esses: [email p o ec ed] (D. ˇ
Sa ínský), [email p o ec ed] (J. E ben).
Con en s lis s a ailable a ScienceDi ec
En i onmen al Technology & Inno a ion
jou nal homepage: www.else ie .com/loca e/e i
h ps://doi.o g/10.1016/j.e i.2025.104591
Recei ed 6 Augus 2025; Recei ed in e ised o m 29 Sep embe 2025; Accep ed 26 Oc obe 2025
En i onmen al Technology & Inno a ion 40 (2025) 104591
A ailable online 28 Oc obe 2025
2352-1864/© 2025 The Au ho s. Published by Else ie B.V. This is an open access a icle unde he CC BY license
( h p://c ea i ecommons.o g/licenses/by/4.0/ ).
s eps in he en i e analysis wo k low. This is pa icula ly ue o en i onmen al samples, which o en ha e complex ma ices ha
equi e speci ic p epa a ion (Backe and Field., 2012). Au oma ion o p ocess is one way o imp o e he analy ical me hods. On-line
coupling he SPE s ep and HPLC belongs o he ad anced ends in his ield. I p o ides ep oducible expe imen al condi ions,
wi h minimal demands o he ope a o ’s skills and e ec o ex e nal condi ions (H´
ako ´
a e al., 2020, 2018a).
Among he comme cially used so ben s o SPE, po ous syn he ic polyme s a e common ep esen a i es (To abi e al., 2024;
Fon anals e al., 2019). Thei main ad an age lies in he g ea di e si y o chemical and physicochemical p ope ies o usable polyme s,
which can u he be modi ied o achie e a wide ange o possible in e ac ions be ween he so ben and he analy e (Fon anals e al.,
2020). The mos used polyme s o SPE so ben s include polys y ene (PS) and i s copolyme wi h di inylbenzene (DVB). Due o hei
high hyd ophobici y and low we abili y, such ma e ials a e no sui able o he e en ion o mo e pola analy es om wa e
compa men and can be chemically modi ied wi h mo e pola g oups o comonome s (Huang e al., 2020; Ning e al., 2022; Yin e al.,
2019). Polyme pa icles a e mos commonly used, o ne wo ks o med by hei addi ional c osslinking.
A p omising inno a i e al e na i e o so ben pa icles could be polyme ic nano ibe s (An e al., 2021; Qi e al., 2008; I egwu e al.,
2014), whose speci ic su ace a ea is compa able o ha o commonly used polyme ic so ben pa icles (Fon anals e al., 2020). These
ma e ials a e also compac and mechanically sel -suppo ing, simpli ying hei p ocessing in o ex ac ion so ben s. Simila o
pa icle-based so ben s, ibe -based coun e pa s can also be u he unc ionalized by addi ional ma e ials (nanopa icles, nano ubes,
me al o ganic amewo ks, c own-e he s, and su ace coa ings) can be inco po a ed du ing o a e hei ab ica ion, o he ibe
su ace can be chemically modi ied o u he al e hei inal p ope ies and expand he po olio o hei usabili y o so p ion
pu poses (Chigome e al., 2011).
Al hough nano ibe s can be p epa ed using a ious me hods (Algho aibi and Aloma i, 2018), elec ospinning o polyme solu ions
is one o he mos commonly used me hods o hei p oduc ion. I s ad an ages include he a iabili y o he spinning p ocess, and hus
he esul ing ibe s uc u es, he abili y o spin a wide ange o polyme s, he possibili y o inco po a ing soluble and insoluble
subs ances in o he esul ing ibe s, as well as ela i ely low cos s o equipmen and he p oduc ion p ocess (Xue e al., 2019). By a
he mos equen ly used echnology is di ec cu en (DC) elec ospinning, which ypically esul s in o ma ion o only hin plana
shee s wi h a limi ed deg ee o o e all po osi y. These ac o s g ea ly limi he possibili ies o i s use as an on-line high-p essu e SPE
me hod. When compa ed o DC elec ospinning, a less common me hod is al e na ing cu en (AC) elec ospinning, which o e s
ad an ages o so ben p epa a ion, such as he p epa a ion o ib ous ma e ials wi h highe po osi y and oluminousness (Poko ny
e al., 2014). A he same ime, i enables o inco po a e highe numbe o addi i es in o he elec ospun solu ion han he s anda d DC
me hod. When compa ing he applica ion po en ial o DC and AC nano ib ous laye s o ex ac ion pu pose, AC ma e ials p o ide
supe io pe o mance due o hei highe po osi y and mechanical du abili y, leading o imp o ed ex ac ion e iciency and epea -
abili y o analyses (E ben e al., 2022).
Poly-
ε
-cap olac one (PCL) is one o he widely used polyme s o elec ospinning ab ica ion o nano ibe s (Cipi ia e al., 2011).
PCL is a semic ys alline linea alipha ic polyes e wi h a low glass ansi ion empe a u e (-60 ◦C) and mel ing empe a u e (50–70 ◦C)
(Ainhoa e al., 2023). This polyme is biodeg adable, bu i s deg ada ion is no so apid as o comp omise i s unc ionali y in ex ac ion
applica ions, making biodeg adabili y an addi ional ad an age o his ma e ial. PCL is widely used in medicine and bioenginee ing
(Mochane e al., 2019), as well as a so ben ma e ial o SPE (Topsoy e al., 2022; Tahmasebi, 2018).
The possibili y o inco po a ing modi ying subs ances in o ibe s du ing elec ospinning can be u ilized o he p epa a ion o
composi e ma e ials combining a ca ie polyme and unc ional pa icles, such as g aphene pa icles (To abi e al., 2024). G aphene,
as a plana , nonpola , and igid moie y could a ec he ex ac ion p ope ies o he esul ing ma e ial, ia hyd ophobic e ec and
π
-
π
in e ac ions (Cipi ia e al., 2011). Due o i s elec on- ich, double-sided polya oma ic s uc u e, g aphene exhibi s s ong a ini y o
a oma ic compounds, which is pa icula ly ad an ageous o in e ac ing wi h common wa e pollu an s ha a e ypically a oma ic in
na u e (H´
ako ´
a e al., 2018a). Howe e , using g aphene in on-line ex ac ion low echniques could be e y p oblema ic, due o e y
small pa icle size. This p oblem could be o e come by using nano ibe s as a sca old whe e he g aphene is inco po a ed. Then,
ex ac ion p ope ies o g aphene-based composi e esul s om p ope ies o bo h pa s – polyme and g aphene. In he a ailable
li e a u e, wo basic app oaches o p epa e nano ibe -g aphene composi es a e commonly desc ibed. The i s in ol es elec ospinning
a polyme solu ion wi h he addi ion o g aphene, whe e he esul ing nano ibe s ypically con ain only a ew pe cen o g aphene
(Ma sumo o e al., 2013; Bao e al., 2010; Abolhasani e al., 2017; Wang e al., 2013; Song e al., 2015). Fo ma e ials equi ing highe
g aphene concen a ions, a me hod in ol ing he ca boniza ion o a ca bon-based ma e ial (e.g., nano ibe s) is used, p oducing a
ma e ial ha can con ain o e 90 % g aphene (Kuzmenko e al., 2017; Song e al., 2014). Howe e , his me hod esul s in he loss o
mechanical p ope ies o he p oduc , ende ing i b i le. This d awback is add essed by inco po a ing a ib ous o plana ca ie ,
which, howe e , educes he ela i e g aphene con en in he ma e ial.
We ocused on he p epa a ion o high-con en g aphene-polycap olac one composi e nano ibe s ia AC elec ospinning o polyme
solu ion wi hou he use o a ca boniza ion s ep and hei applica ion as ex ac ion so ben o on-line ex ac ion high pe o mance
liquid ch oma og aphy (SPE-HPLC) applica ion in en i onmen al analysis. Di e en a ion o he g aphene con en in polyme so-
lu ion was es ed du ing ab ica ion p ocess and he e ec on he ex ac ion yield o con aminan s was e alua ed. Model con aminan s
we e selec ed om he g oup o a oma ic compounds wi h a ious subs i uen s (bisphenols, chlo phenols, insec icides) due o he
expec ed in luence o he g aphene con en on enhanced ex ac ion yield. G aphene- ee polycap olac one was also used o compa e
he e ec o na i e polyme on ex ac ion, which in p e ious s udies ep esen ed a e y in e es ing al e na i e o comme cial C18 o
polyme ic MIP/RAM so ben s (Ma ina e al., 2018; Kholo ´
a e al., 2023b, 2023a). Thus, we showed a new me hod o ab ica ion o
ca bon- ich so ben ha exhibi s good a ini y o a oma ic pollu an s, a ibu ed o he p esence o high con en o g aphene.
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
2
2. Expe imen al pa
2.1. Ma e ials
Poly-
ε
-cap olac one pelle s (M
w
80,000 g/mol, CAS: 83259–71–6) we e pu chased om Polysciences, Inc. (Wa ing on, Penn-
syl ania, USA). Fo mic acid (p.a., CAS: 64–18–6), ace ic acid (p.a., CAS: 64–19–7), and ace one (p.a., CAS: 67–64–1) we e ob ained
om Pen a (P ague, Czech Republic). G aphene nanopla ele s (su ace a ea 750 m
2
/g, CAS: 7782–42–5) wi h pa icle size below 2 µm
we e, bisphenol A (≥99 %, CAS: 80–05–7), bisphenol C (≥99 %, 79–97–0), bisphenol S (≥98 %, CAS: 80–09–1), bisphenol Z (≥99 %,
CAS: 843–55–0), bisphenol AF (≥99 %, CAS: 1478–61–1), bisphenol AP (≥99 %, CAS: 1571–75–1), 3-chlo ophenol (98.0 %, CAS:
108–43–0), enoxyca b (99.5 %, CAS: 72490–01–8), hyd oxypy en (98.0 %, CAS: 5315–79–7), del ame h in (99.6 %, CAS:
52918–63–5) and kade h in (90.8 %, CAS: 58769–20–3), ace oni ile (HPLC g ade, CAS: 75–05–08) and me hanol (HPLC g ade, CAS:
67–56–1) we e pu chased om Sigma-Ald ich (Da ms ad , Ge many). Ul a-pu e wa e was p epa ed by a Milli-Q sys em (Millipo e,
S . Luis, Missou i, USA).
2.2. Spinning solu ion
2.2.1. P epa a ion
The PCL solu ion was p epa ed by dissol ing PCL g anules in a mix u e o o mic acid and ace ic acid (w/w 1:1) o achie e a inal
concen a ion o 14.3 %. The dissolu ion p ocess ook 12 h a oom empe a u e using a magne ic s i e . Once he PCL was comple ely
dissol ed, he esul ing solu ion was dilu ed wi h ace one unde cons an s i ing o ob ain a polyme concen a ion o 10 %. This
esul ed in a inal sol en a io o 1:1:1. G aphene was added o he s i ing solu ions in mass a ios ela i e o he polyme (PCL:GR) o
10:0, 10:1, 10:2, 10:3, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, and 10:10. This heo e ical composi ion was also used o label he indi idual
ibe ma e ial samples. P io o elec ospinning, he solu ions we e sonica ed using a p obe sonica o h ee imes o 10 s each o a oid
excessi e hea ing o he solu ion and sedimen a ion o g aphene pa icles.
2.2.2. Cha ac e iza ion
Viscosi y, speci ic elec ical conduc i i y, and su ace ension we e de e mined o each o he p epa ed PCL solu ions. Viscosi y
measu emen s we e pe o med using a Haake Ro o isco (The mo Fishe Scien i ic, P ague, Czech Republic) wi h a cone-pla e ge-
ome y in a con inuous mode. The cone used was C35/1◦Ti L, wi h a gap size o 0.2 mm, and he measu emen was conduc ed o e 30 s
wi h a linea inc ease in shea a e om 100 o 3000 s⁻¹ . Each measu emen was epea ed a leas h ee imes.
Speci ic elec ical conduc i i y was measu ed using an Eu ech Ins umen s CON 510 conduc ome e (Eu ech Ins umen s,
Landsmee , The Ne he lands) wi h an acid- esis an p obe K10/6MM8. Each sample was measu ed i e imes.
Su ace ension o he solu ions was de e mined using he maximum bubble p essu e me hod, u ilizing a Pocke Dyne de ice (K üss,
Hambu g, Ge many), wi h a bubble li e ime o app oxima ely 210 ms. Each solu ion was measu ed wel e imes. All measu emen s
we e ca ied ou a a empe a u e o 22 ◦C.
Fig. 1. Elec ospinning se up (a) wi h a o a ing d um collec o (1), collec ed ib ous ma e ial (2), nano ib ous plume (3), o e low elec ode (4),
and magne ic clu ch (5). C oss-sec ional de ail o he elec ode (b) wi h an o e low disk elec ode (6), sc ew pump (7), powe supply (8), and
ese oi wi h ci cula ing polyme solu ion (9).
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
3
2.3. Elec ospinning se -up
The p epa ed 10 % PCL solu ion and he PCL+GR solu ions we e elec ospun using an o e low elec ode wi h a sc ew pump ia he
AC elec ospinning me hod (Fig. 1). The polyme solu ion was placed in a ese oi , om which i was pumped o he op o he
cha ged elec ode using a sc ew pump. The ad an age o using a sc ew pump wi h closed solu ion ci cula ion was he con inuous
mixing, which p e en ed he agglome a ion o g aphene pa icles. The al e na ing cu en applied on he elec ode was o equency
50 Hz wi h a sinusoidal wa e o m, and he e ec i e ol age 40 kV. Fibe s we e o med om he ip o he elec ode, wi h he esul ing
ibe bundle being ca ied by he elec ic wind on o a g ounded o a ing d um collec o co e ed wi h an is a ic spunbond- ype
nonwo en polyp opylene ab ic (su ace weigh 18 g/m²). The dis ance be ween he collec o and he elec ode was 250 mm, and
he collec o ’s pe iphe al eloci y was 30 m/s. Elec ospinning was conduc ed a oom empe a u e wi h a ela i e humidi y o 45 %.
2.4. Nano ib ous ma e ial cha ac e iza ion
2.4.1. Su ace mo phology
The su ace mo phology o he p epa ed nano ib ous ma e ial samples was analyzed using a scanning elec on mic oscope (SEM)
Tescan Vega3 (Tescan, B no, Czech Republic) a an accele a ion ol age o 10 kV. P io o imaging, he samples we e coa ed wi h a
7 nm laye o gold using a o a y acuum spu e coa e Q150R (Quo um, Lewes, UK). Manual measu emen s o ibe diame e s om
he ob ained images we e conduc ed using he ImageJ so wa e ( e sion 1.54 g, Be hesda, Ma yland, USA), wi h 300 ibe diame e s
measu ed o each sample.
2.4.2. To al po osi y
A g a ime ic me hod was used o de e mine he o al po osi y o he ib ous ma e ial. Fo each sample, a laye o ma e ial wi h a
o al a ea o 100 cm² was aken, and i s hickness was measu ed using a digi al mic ome e 49–63 (Tes ing Machines, Delawa e, USA)
a a p essu e o 400 Pa acco ding o he s anda d es p ocedu e EDANA – NWSP 120.1.R0. The weigh was measu ed on analy ical
scales KERN ADJ 200–4 (KERN, Balingen, Ge many) wi h an accu acy o ou decimal places. The speci ic densi ies o PCL (1.145 g/
cm³ (Rosa e al., 2004)) and GR (2.2 g/cm³ (Hwang e al., 2013)) we e used o calcula ing he o al po osi y.
2.4.3. Wa e con ac angle
The con ac angle was measu ed using a See Sys em goniome e (Ad ex Ins umen s, B no, Czech Republic). A 5 µl wa e d ople
was applied o each nano ibe sample. Each d ople was hen pho og aphed using he See Sys em so wa e ( e sion 6.2, B no, Czech
Republic). The e alua ion was conduc ed using he h ee-poin me hod, whe e h ee poin s we e ma ked on he pic u e (bo h ends
whe e he d ople ouched he nano ibe laye , and he highes poin o he d ople ). The con ac angle was hen au oma ically
calcula ed by he so wa e.
2.4.4. Speci ic su ace a ea
The speci ic su ace a ea was de e mined using he gas adso p ion iso he m me hod based on he B unaue –Emme –Telle (BET)
equa ion, employing an Au oso b iQ de ice (An on Paa , G az, Aus ia) in s anda d mode. Fibe samples (1000 mg) we e placed in
glass cells and degassed o 24 h a 50 ◦C be o e measu emen . K yp on was used o he analysis, and he da a we e p ocessed using
ASiQwin so wa e ( e sion 4.0).
2.4.5. G aphene con en de e mina ion
A he mog a ime ic analysis (TGA) was used o de e mine he amoun o GR in he PCL ibe s. This exploi ed he possibili y o
comple e he mal and The mo oxida i e deg ada ion o PCL and GR in dis inc non-o e lapping empe a u e anges and unde
di e en a mosphe es. The measu emen s we e pe o med on a he mog a ime ic analyze Q500 (TA Ins umen s, Delawa e, USA).
The analysis was conduc ed in he empe a u e ange o 25–800 ◦C. The he modeg ada ion o PCL was ca ied ou in an ine ni ogen
a mosphe e wi hin he empe a u e ange o 25–630 ◦C, a e which he ni ogen was eplaced by eac i e syn he ic oxygen in he
ange o 630–800 ◦C o bu n o he g aphene and he ca bonaceous esidues o PCL. The low a e o bo h gases used was 60 mL/min.
The mass ac ion o GR in he ib ous ma e ial was hen de e mined om he mass loss cu e in he co esponding empe a u e
in e al.
2.4.6. Mechanical p ope ies
To de e mine Young’s modulus, ul ima e ensile s eng h, and elonga ion, a LabTes 2.050 uni e sal es ing machine (Labo ech,
Opa a, Czech Republic) wi h mechanical g ips equipped wi h a load cell o nominal capaci y 100 N was used. The ensile es was
conduc ed in acco dance wi h ISO 13 934–1, u ilizing es specimens wi h wo king dimensions o 50 ×100 mm, subjec ed o a loading
speed o 100 mm/min. Young’s modulus and ensile s eng h alues we e calcula ed using he po osi y alues o each se o samples,
de e mined based on he espec i e densi y ( aking in o accoun he PCL o GR a io), olume, and mass. Fo each se , i e specimens
we e es ed.
2.4.7. Sol en esis ance
Conside ing he in ended inal use o he p epa ed nano ib ous laye s as ex ac ion ma e ials o dynamic liquid en i onmen s, he
ibe s we e es ed o hei esis ance o swelling o dissol ing in s anda d HPLC mobile phases based on o ganic sol en s (ace oni ile
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
4
and me hanol). To de e mine he solubili y in common HPLC sol en s, he nano ib ous laye s wi h PCL:g aphene a ios o 10:0, 10:1,
10:5, and 10:10 we e es ed. These samples we e imme sed in ace oni ile (ACN), me hanol (MeOH) and mix u es o ACN:MeOH, ACN:
H
2
O, and MeOH:H
2
O (1:1 w a ios). Samples o app oxima ely 0.10 g we e placed in glass ials and subme ged in 4 mL o he
espec i e sol en . They we e s i ed o 24 h. A e emo al, he samples we e d ied in a desicca o o 48 h. Weigh loss was sub-
sequen ly calcula ed om he mass be o e and a e es ing. SEM mo phology o he samples a e exposu e o he sol en s was
pe o med ollowing he me hodology desc ibed abo e.
2.5. SPE ex ac ion
2.5.1. P epa a ion o s anda d solu ions and samples
Each s anda d was dissol ed in me hanol a a concen a ion 1 mg/mL o p epa e he s ock solu ion. The mixed s anda d s ock
solu ion was p epa ed by mixing 50 µL o each s anda d and dilu ing wi h wa e o he concen a ion 50 mg/L. All s anda d sock
solu ions we e s o ed a −20 ◦C a da k. Wo king solu ions we e p epa ed a he day o measu emen ia dilu ing wi h dis illed wa e .
Fo es ing he ex ac ing abili ies o he ma e ials, he concen a ion 10 mg/L was used.
2.5.2. P epa a ion o ex ac ion p e-columns
Ex ac ion p e-columns we e manually assembled by packing an app op ia e amoun o nano ib ous laye in o an emp y column
ca idge (5 ×4.6 mm i.d.; see Supplemen a y Ma e ial – S1). Ca idge was connec ed o he on-line SPE HPLC sys em using he gua d
p e-column holde . Ini ially, each p e-column was washed/ac i a ed by 100 % ace oni ile, hen se e al on-line SPE HPLC analysis
cycles we e pe o med wi hou sample injec ion. No - e ained GR and o he impu i ies and ballas s we e washed ou by his p ocedu e.
Column sui abili y o use was e i ied by UV de ec ion (dec easing signal o de ec o ).
2.5.3. The on-line SPE HPLC
An on-line SPE-HPLC sys em Shimadzu Nexe a X2 was used o he simul aneous p e-concen a ion and de e mina ion o model
analy es. SPE was ca ied ou using nano ib ous p e-columns. Me hanol o ace oni ile (0–40 %) was used as o ganic modi ie in
aqueous washing mobile phase a a low a e 1.0 mL⋅min
−1
. Ch oma og aphic sepa a ions we e ca ied ou using a Kine ex® Biphenyl
150 ×4.6 mm, 5 µm pa icle size analy ical column om Phenomenex (To ance, Cali o nia, USA) a a g adien o he mobile phase
consis ing o wa e (sol en A) and me hanol (sol en B) a a low a e o 1.0 mL/min a empe a u e o 20 ◦C.
10 µL o sample was injec ed in he ex ac ion p e-column illed wi h composi e nano ib ous so ben and washing mobile phase p e-
concen a ed he analy es. A he same ime, he analy ical column was equilib a ed o he ini ial condi ions o he g adien (40 % A).
A e 1.0 min he al e was swi ched and he elu ion o he e ained analy es s a ed. The g adien p og am s a ed a e swi ching he
al e (de ailed in o ma ion on he g adien elu ion p og am is p o ided in he Supplemen a y Ma e ial – S2). The de ec ion o analy es
was achie ed using UV de ec ion a 220 nm and 240 nm ( o hyd oxypy ene and bisphenol S). The o al un ime was 12.5 min.
3. Resul s and discussion
3.1. Composi e nano ib ous so ben p epa a ion and cha ac e iza ion
3.1.1. Spinning solu ions p ope ies
The dynamic iscosi y, elec ical conduc i i y, and su ace ension alues o he selec ed PCL spinning solu ions wi h added GR a e
p esen ed in Fig. 2. The addi ion o g aphene nanopa icles esul ed in a g adual educ ion in he dynamic iscosi y o he solu ions (a
a cons an shea a e o 500/s), dec easing om 0.139 ±0.04 Pa⋅s o he PCL solu ion wi hou GR (labelled 10:0) o 0.106 ±0.009 o
he 10:10 solu ion (Fig. 2a). In con as , he elec ical conduc i i y o he solu ions signi ican ly inc eased wi h he addi ion o GR,
ising om an ini ial alue o 12.5 ±2–176 ±14 mN/m. Unlike iscosi y, conduc i i y did no inc ease linea ly; a no able ise
occu ed a e he addi ion o e en a small amoun o GR (10:1 solu ion), ollowed by a nea -exponen ial inc ease, as shown in Fig. 2b.
Fig. 2. Spinning solu ions p ope ies dependence on PCL:GR a ios – dynamic iscosi y a shea a e o 500/s (a), elec ical conduc i i y (b) and
su ace ension (c).
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
5
This can be a ibu ed o g aphene’s inhe en high elec ical conduc i i y, hough possible impu i ies in oduced alongside he GR may
also ha e had an e ec . The su ace ension o he solu ions exhibi ed only mino a ia ions wi h he addi ion o GR, luc ua ing a ound
32 mN/m (see Fig. 2c). The e o e, he p ima y ac o s in luencing he subsequen elec ospinning o he PCL solu ions we e he in-
c ease in elec ical conduc i i y and, o a lesse deg ee, he educ ion in iscosi y. Su ace ension had a minimal e ec .
3.1.2. Fib ous ma e ial
The p ocess o p oducing ibe laye s con aining GR using AC elec ospinning consis en ly esul ed in he o ma ion o a nano ibe
plume wi h a ypical ubula shape de e mined by he geome y o he wo king elec ode. The diame e o his plume inc eased as he
GR con en in he solu ion ose. This was likely due o he inc easing elec ical conduc i i y o he solu ions, which caused g ea e
epulsion be ween he iden ically cha ged ma e ial du ing each hal -wa e o he applied ol age. A isually obse able dec ease in he
olume o ans e ed ma e ial was also no ed wi h he inc easing GR con en , as he ising p opo ion o GR p og essi ely impai ed he
quali y o he elec ospinning p ocess. The ibe plume became less homogeneous as i s diame e inc eased, and a highe GR con-
cen a ions, i also los cohe ence, making i mo e di icul o collec he esul ing ib ous ma e ial on he o a ing collec o . Fig. 3
shows he nano ibe laye s p oduced wi h inc easing GR con en , spun using AC elec ospinning. All GR concen a ions in he solu ions
we e success ully con e ed in o nano ibe laye s wi hou isible mac oscopic de ec s using his me hod. As can be seen, he laye s
da kened wi h inc easing GR con en , indica ing a highe ac ual GR concen a ion wi hin he laye s hemsel es.
The obse ed dec ease in he homogenei y o he ibe plume wi h inc easing GR con en in he elec ospun solu ions also a ec ed
he p oduc i i y o AC elec ospinning (see Fig. 4a). P oduc i i y d opped om he ini ial alue o 10.7 g/h o 1.9 g/h o he solu ion
wi h he highes GR concen a ion. The decline in p oduc i i y be ween he 10:1 and 10:6 a ios was mo e g adual, bu i hen
dec eased sha ply again a e eaching PCL:GR a io o 10:7. The 10:7 a io was he e o e conside ed a c i ical poin , beyond which he
spinning p oduc i i y signi ican ly declined. This dec ease was caused by he educed cohesion o he ibe plume, leading o i s
b eakage du ing collec ion, wi h po ions o he spun ma e ial deposi ing on he collec o ’s edges o en i ely missing he collec o . A
simila end was obse ed in he a eal densi y o he laye s p oduced. While he p oduc i i y o he solu ion wi h he highes GR
concen a ion (10:10) d opped o abou one- i h o ha o he GR- ee solu ion (10:0), he a eal densi y dec eased o app oxima ely
one- wel h ( om 65 o 5.5 g/m²). This e lec ed he a o emen ioned inc ease in he ibe plume diame e wi h ising GR con en ,
along wi h he educ ion in he p oduc i i y o he AC elec ospinning p ocess.
SEM images o he selec ed ib ous laye s a e demons a ed in Fig. 5. The na i e PCL ma e ial om he ini ial solu ion wi hou GR
(10:0) p o ided a mix u e o smoo h su ace nano ibe s. Inc easing he GR con en in he polyme solu ions esul ed in w inkled
s uc u e o he ibe s ha can be a ibu ed mainly o GR pa icles con en . A low GR concen a ions, hese mani es ed as su ace
i egula i ies on he o iginally smoo h ibe s, ollowed by i egula changes in ibe diame e s. A highe GR concen a ion, his
mo phological change o he ibe s, especially w inkling, is mo e p onounced.
Table 1 p esen s he esul ing a e age ibe diame e s along wi h hei s anda d de ia ions. The ibe diame e s p og essi ely
dec eased wi h he inc easing GR con en in he elec ospun solu ions, as did he s anda d de ia ions. The highe ibe diame e s and
hei de ia ions a e ypical o PCL p epa ed by AC elec ospinning and do no ad e sely a ec he ma e ial’s ep oducibili y (Si an
e al., 2022). In he case o he 10:5 sample, ba ch- o-ba ch ep oducibili y was pe o med, which showed ha he RSD be ween in-
di idual ba ches (n=6) o ibe diame e s was 8 % and o g aphene con en was 6 %. Howe e , he s anda d de ia ions we e o en so
high ha di e ences be ween adjacen samples could no be dis inc ly iden i ied. Despi e his, he o e all end o dec easing di-
ame e s was clea . This phenomenon can be explained by wo in e ela ed ac o s – highe elec ical conduc i i y o he elec ospun
solu ions and he dec easing concen a ion o PCL, which ac ed as he binding elemen o GR in he inal p oduc .
The measu ed con ac angle alues o wa e on he esul ing laye s a e p esen ed in Fig. 6a. Due o he hyd ophobic na u e o he
base ma e ial (PCL) and he addi i e (GR), no signi ican change in he con ac angle was obse ed wi h inc easing GR con en , which
emained in he ange o 130–140◦. A simila obse a ion applies o he ela i e olume ic po osi y o he samples, which emained
consis en ly a 90–95 % ega dless o he amoun o GR p esen (see Fig. 6b). Howe e , a signi ican change was obse ed in he
speci ic su ace a ea. This pa ame e inc eased app oxima ely exponen ially wi h he concen a ion o GR in he elec ospun solu ion
(see Fig. 6c). This beha io can likely be a ibu ed o he dec easing diame e s o he p epa ed ibe s and he oughening o hei
su aces due o he p esence o he GR pa icle agg ega es, and he occu ence o nume ous globula GR s uc u es.
Fig. 7 p esen s he TGA cu es o he indi idual ibe ma e ials used o de e mine he ac ual GR con en . The de e mina ion was
based on he use o dis inc and clea ly sepa a ed zones o he mal decomposi ion, ep esen ing he mass ac ions o PCL and GR,
aking ad an age o hei di e en he mal deg ada ion beha iou s. The decomposi ion occu ed a dis inc empe a u e anges (PCL
be ween 240 and 440 ◦C and GR be ween 630 and 720 ◦C), and he analysis was conduc ed unde di e en a mosphe ic condi ions
Fig. 3. The mac oscopic appea ance o he esul ing ibe laye s wi h inc easing PCL:GR a ios (in he co esponding spun solu ion).
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
6
(ine ni ogen o PCL in e al and eac i e syn he ic oxygen o GR in e al). The mass losses obse ed wi h inc easing empe a u e
co espond o he pe cen age weigh ac ions o each componen , along wi h he incombus ible esidue ep esen ing impu i ies om
bo h componen s.
The esul s o he TGA analyses o ibe laye s a e summa ized in Fig. 8 and Table 2, which shows ha he ac ual concen a ions o
GR in he inal p oduc we e always sligh ly lowe han he alues co esponding o he composi ion o he espec i e spinning so-
lu ions. The gap be ween he wo cu es enhanced wi h highe concen a ions o GR in he solu ion and was app oxima ely 10 % o he
heo e ical alue. Thus, he ans e e iciency o GR om he polyme solu ion was a ound 90 %, demons a ing ha he designed
spinning sys em was sui able o he e ec i e p epa a ion o polyme ibe laye s wi h an ul a-high GR con en .
Fig. 4. The p oduc i i y o AC elec ospinning depending on he PCL:GR a io in he solu ion (a), and he su ace densi y o he esul ing laye s a e
one hou o elec ospinning (b).
Fig. 5. SEM images o he elec ospun ma e ial om solu ions 10:0, 10:1, 10:5 and 10:10. The scales shown on he images o he le apply o all
o he images in he co esponding se ies.
Table 1
Fibe diame e s (d) and he co esponding s anda d de ia ion (
σ
d
) as a unc ion o he elec ospun solu ion.
sample 10:0 10:1 10:2 10:3 10:4 10:5 10:6 10:7 10:8 10:9 10:10
d [nm] 1170 1160 960 1070 850 850 800 860 670 650 530
σ
d
[nm] 570 410 280 390 210 270 250 290 200 180 230
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
7
The esul s o he TGA analysis we e u he suppo ed by complemen a y a enua ed o al e lec ance Fou ie - ans o m in a ed
spec oscopy (ATR–FTIR) using a ge manium c ys al, which clea ly e ealed he cha ac e is ic C–O–H bond peak o PCL a
1246 cm⁻¹ (Supplemen a y Ma e ial – S4). The p esence o g aphene, i.e., a speci ic ca bon o m, was e lec ed by an o e all inc ease
in he slope o he spec al cu e compa ed o he con ol sample (10:0). The a io o he dis ances be ween pla eau egions a
930 cm⁻¹ s ongly co ela ed wi h he ac ual g aphene concen a ion de e mined by TGA, sugges ing ha , a e u he calib a ion,
his me hod could se e as a apid and cos -e ec i e quali a i e assessmen o g aphene con en in he ibe s.
Finally, a ou -poin p obe me hod was used o measu e elec ical conduc i i y. Conduc i i y was con i med, pa icula ly in he
10:10 sample, whe e i inc eased wi h comp ession o he laye wi hou loss o ib ous s uc u e, eaching a alue o 8.33 kΩ. This
sugges s he ma e ial’s po en ial applicabili y in elec ochemical sys ems o as a sensing elemen , bene i ing om i s lexibili y and
non-b i le na u e (Supplemen a y Ma e ial – S5).
Fig. 6. Con ac angles (a), ela i e po osi y (b), and speci ic su ace a ea (c) o selec ed ibe laye s.
Fig. 7. The TGA cu es o selec ed ibe samples: The i s signi ican weigh loss co esponded o he he mal deg ada ion o PCL, he second o he
GR. The TGA cu es o all p epa ed ibe samples a e shown in Supplemen a y ma e ial – S3.
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
8
Fig. 8. The cu es o mass concen a ions o GR in he d y ma e o he p epa ed ibe laye s – he heo e ical alue co esponding o he
composi ion o he spinning solu ion (w
heo e ical
) and he alue de e mina ed by TGA analysis (w
eal
).
Table 2
G aphene w . con en o p epa ed PCL:GR ibe ma e ials de e mined by TGA analysis.
sample 10:0 10:1 10:2 10:3 10:4 10:5 10:6 10:7 10:8 10:9 10:10
GR [%] 0.0 7.7 15.1 20.2 26.0 30.7 31.5 38.9 39.2 43.6 45.5
σ
[%] - 0.8 0.7 1.9 1.0 1.9 1.6 0.6 0.2 0.6 0.7
Fig. 9. Resul s o he ensile s eng h es s o selec ed ib ous ma e ials (a) and he co esponding alues o Young’s modulus and maximum
elonga ion (b).
P. Holec e al.
En i onmen al Technology & Inno a ion 40 (2025) 104591
9
