Lase -Induced MXene-Func ionalized
G aphene Nanoa chi ec onics-Based
Mic osupe capaci o o Heal h Moni o ing
Applica ion
Suji Deshmukh, Kalyan Ghosh, Ma in Pykal, Michal O yepka, and Ma in Pume a*
Ci e This: ACS Nano 2023, 17, 20537−20550
Read Online
ACCESS Me ics & Mo e A icle Recommenda ions *
sı Suppo ing In o ma ion
ABSTRACT: Mic osupe capaci o s (mic o-SCs) wi h mechanical lexibili y
ha e he po en ial o complemen o e en eplace mic oba e ies in he
po able elec onics sec o , pa icula ly o po able biomoni o ing de ices. The
eal- ime biomoni o ing o he human body’s physical s a us using ligh weigh ,
lexible, and wea able mic o-SCs is impo an o conside , bu he main
limi a ion is, howe e , he low ene gy densi y o mic o-SCs as compa ed o
mic oba e ies. He e using a empo ally and spa ially con olled picosecond
pulsed lase , we de eloped high-ene gy-densi y mic o-SCs in eg a ed wi h a
o ce sensing de ice o moni o a human body’s adial a e y pulses. The
pho ochemically syn hesized sphe ical lase -induced MXene (Ti3C2Tx)-de i ed
oxide nanopa icles uni o mly a ached o lase -induced g aphene (LIG) ac as
ac i e elec ode ma e ials o mic o-SCs. The molecula dynamics simula ions
and de ailed spec oscopic analysis e eal he syne gis ic in e acial in e ac ion
mechanism o Ti−O−C co alen bonding be ween MXene and LIG. The
inco po a ion o MXene nanoshee s imp o es he g aphene shee alignmen and ion anspo while minimizing sel -
es acking. Fu he mo e, he mic o-SCs based on a nano-MXene-LIG hyb id demons a e high mechanical lexibili y,
du abili y, ul ahigh ene gy densi y (21.16 ×10−3mWh cm−2), and excellen capaci ance (∼100 mF cm−2@ 10 mV s−1) wi h
long cycle li e (91% e en ion a e 10 000 cycles). Such a single-s ep oll- o- oll highly ep oducible manu ac u ing echnique
using a picosecond pulsed lase o induce MXene-de i ed sphe ical oxide nanopa icles (size o quan um do s) a ached
uni o mly o lase -induced g aphene o biomedical de ice ab ica ion is expec ed o ind a wide ange o applica ions.
KEYWORDS: Lase -induced MXene, lase -induced g aphene, co alen bonding, mic osupe capaci o , biomoni o ing de ice
The booming o minia u ized po able and wea able
elec onics such as s e chable displays,
1
o ce-sensi i e
de ec o s (FSDs),
2
a i icial elec onics skin,
3
and
wea able mic osenso s
4,5
ha e aised he demand o powe
sou ces (ba e ies and supe capaci o s) ha a e capable o
wo king in lexible de o ma ion o o in eg a e wi h a a ie y o
elec onics de ices. A key b anch o such mode n elec onic
sec o s deals wi h heal h moni o ing senso s ha can collec
eal- ime physiological and elec ophysiological da a om he
human body.
6
Howe e , mic oba e ies a e s ill he de ices o
choice o his ype o applica ion despi e hei slow cha ge/
discha ge p ocesses and limi ed li e cycle.
7
Mic osupe capaci-
o s (mic o-SCs), especially wi h plana in e digi a ed s uc-
u es, a e p omising al e na i es o mic oba e ies due o hei
high powe densi ies, longe li e imes, and much as e cha ge/
discha ge a es.
8,9
The main challenge in using mic o-SC de ices
in mode n elec onics sec o s is o inc ease he ene gy densi y o
a le el compa able o o e en exceeding hose o mic oba e ies
wi hou comp omising he elec ochemical p ope ies.
A gene al s a egy o imp o e he ene gy densi y o SCs is o
c ea e po ous conduc i e elec ode ma e ials wi h an adequa e
high packing densi y o maximize he u iliza ion o he small size
o mic o-SCs. In his con ex , g aphene shee s a e ideal
candida es because o hei ul ahigh su ace a ea (2630
m2g−1), excellen elec ical conduc i i y, and ich su ace
chemis y.
10−12
To comme cialize g aphene, me hodologies
Recei ed: Augus 6, 2023
Accep ed: Sep embe 26, 2023
Published: Oc obe 4, 2023
A icle
www.acsnano.o g
© 2023 The Au ho s. Published by
Ame ican Chemical Socie y 20537
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
This a icle is licensed unde CC-BY 4.0
Downloaded ia TECHL UNIV OF OSTRAVA on Ma ch 22, 2024 a 06:02:57 (UTC).
See h ps://pubs.acs.o g/sha ingguidelines o op ions on how o legi ima ely sha e published a icles.
ha e been de eloped o p oducing g aphene on a la ge scale and
oll- o- oll compa ible hin ilms wi hou comp omising he
undamen al p ope ies o g aphene shee s.
13,14
Lase -induced
pho o he mal con e sion o a nonconduc i e ca bon sou ce in o
a conduc i e g aphene s uc u e has ecen ly eme ged as a oll-
o- oll compa ible echnique o p oducing lase -induced
g aphene (LIG).
15
This app oach allows g aphene o assemble
in o many in iguing s uc u es such as one-dimensional
ibe s
16,17
and h ee-dimensional oams
18
as well as he
p oduc ion o desi ed pa e ns o geome ies by adjus ing lase
se ings.
19,20
Al hough LIG-based mic o-SCs ha e la ge
g a ime ic capaci ances, hey a e cons ained by a poo
olume ic pe o mance. A p obable explana ion o his
beha io is he s ong in e shee π−πin e ac ion, which,
al hough boos ing he packing densi y, does no allow o high
ion accessibili y. The pionee ing concep o lase p ocessing
g aphene by El-Kady e al. o mic o-SCs has deli e ed
ou s anding powe ou pu bu ails o achie e he high a eal
capaci ance (<5 mF cm−2) due o he s acking p oblem.
21
Because pu e elec ical double laye s o g aphene ha e limi ed
capaci ance, he s acking p oblem is s a egically mi iga ed by
combining LIG wi h highly elec oac i e ma e ials and
pseudocapaci i e ma e ials ha ha e la ge capaci ance.
22,23
A new class o g aphene-analogous ma e ials, 2D ansi ion-
me al ca bides, and ni ides (known as MXene) ha e gained
huge in e es om esea che s due o hei 2D s uc u e and
cus omizable su ace chemis y, which p o ide MXene wi h a
ple ho a o exci ing ea u es such as ul ahigh me allic
conduc i i y (15 100 S cm−1), s ong hyd ophilici y, and
no able mechanical capabili ies.
24,25
As a esul , MXene has
shown eno mous p omise in ene gy s o age applica ions, such as
SCs as well as li hium- and sodium-ion ba e ies.
26−29
Since he
i s disco e y o 2D MXene (Ti3C2Tx) in 2011 by Gogo si and
colleagues, i has been he mos used ansi ion-me al ca bide
(TMC) o ene gy s o age applica ions.
30
Howe e , like o he
2D ma e ials, he ine i able agglome a ion and laye -by-laye
es acking due o he high an de Waals o ce se e ely educe
he elec ochemically ac i e si es and limi he pe meabili y o
elec oly e ions.
31
As a esul , he dense MXene shee s su e
om low speci ic capaci ance (100−300 F g−1) and poo cyclic
s abili y, which need o imp o e u he .
28,32
Thus, he
in e cala ion o MXene nanoshee s be ween he 3D ne wo k
Figu e 1. Scheme o he syn hesis o he O-LIM-LIG hyb id using picosecond pulsed lase and mo phological cha ac e iza ion. (a) S acked
Ti3C2TxMXene and delamina ed Ti3C2TxMXene wi h inc eased in e laye spacing. Schema ic model o Ti3C2TxMXene laye s composed o Ti,
C, and Txa oms. (b) Scheme o he mic o ab ica ion s eps o he O-LIM-LIG hyb id. (c) The mal oxida ion o delamina ed MXene due o
app eciable IR ene gy abso p ion esul s in sphe ical LIM pa icles a ached o LIG, as demons a ed by a de ocused lasing mechanism. SEM
op iew o (d) s acked Ti3C2TxMXene, (e) delamina ed Ti3C2TxMXene, ( ) LIG, (g) LIM-LIG, and (h) he O-LIM-LIG hyb id showing he
uni o m dis ibu ion o sphe ical LIM ac oss he LIG su ace. (i) Elemen al mapping images o he O-LIM-LIG e ealing he p esence o Ti, O,
and C. Scale ba 0.5 μm.
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20538
o LIG would be a e y e ec i e app oach o inhibi ing he sel -
es acking o bo h g aphene and MXene lakes. Howe e , he
p ocess o ab ica e MXenes in he o m o ul a hin lakes/
pa icles wi h a ew-nanome e hickness/diame e ha can
in e cala e be ween he g aphene ne wo k is a key challenge o
o e come. Beyond he p oduc ion o nanosized MXene, he ease
wi h which hey may be in eg a ed in o de ices ep esen s
ano he key challenge in achie ing he po en ial o MXene o
applica ions.
He ein we epo ed a e sa ile p ocess o ab ica e nano-
MXene (Ti3C2Tx) unc ionalized and c oss-linked wi h
g aphene pla ele s h ough Ti−O−C co alen bonding. The
app oach in ol es a single-s ep lasing p ocess on an MXene-
coa ed polyimide (PI) shee by a diode-pumped Nd:YAG solid
pulsed lase beam. When abla ed by an Nd:YAG solid pulsed
lase , he delamina ed MXene shee abso bs he IR ene gy and
gene a es high empe a u e (o e 2000 K) on he PI shee wi hin
a apid up ake ime (submillisecond ime scale) which causes he
sel -assembly and o de ing o he C−C bond o o m an MXene-
deco a ed 3D g aphene nanos uc u e.
33
I is known ha
Ti3C2Tx, o example, deg ades a oughly 200 °C owing o
su ace g oup collapse, whe eas Ti3C2is p ojec ed o endu e up
o 1000 °C.
33,34
Hence, lase i adia ion i s c ea es Ti−O−C
bonding and π−πb idging a he MXene g aphene in e ace, and
hen, i decays he Ti3C2Txshee s in o Ti- ich oxide nano-
pa icles by he mal oxida ion ha a e deco a ed o e he 3D
ne wo k o LIG. Howe e , he MXene- unc ionalized LIG was
hyd ophobic in na u e; he e o e, we used a oom- empe a u e
oxygen plasma ea men o modi y he unde lying su ace
we abili y o MXene- unc ionalized LIG, allowing be e
elec ode−elec oly e in e ac ion. E en he lase -p ocessed
MXene has now eme ged as a p omising ma e ial o
op oelec onics, senso s, o mic osupe capaci o s.
35−37
The
p oposed app oach is easily scalable, and de ices a e p epa ed
on a wide scale while main aining lexibili y. All o he de ices
de eloped demons a ed ene gy densi ies equi alen o mic o-
ba e ies while e aining good a e pe o mance, cycle s abili y,
and mechanical lexibili y. Di ec pa e ning o lase -induced
nano-MXene in e cala ed g aphene would enable oll- o- oll
manu ac u ing o ac i e elec ode ma e ial o a hos o
applica ions om ene gy s o age de ices o biomoni o ing.
RESULTS AND DISCUSSION
Syn hesis and Cha ac e iza ion o MXene-De i ed
Oxide-Pa icle-Func ionalized G aphene Shee s. The
schema ic diag am o p epa e he MXene-deco a ed LIG is
shown in Figu e 1a,b. Fi s , he delamina ed MXene (Ti3C2Tx)
was spin-coa ed (500 pm; 60 s) on he lexible PI shee ollowed
by pulsed lase (Nd:YAG) w i ing on he MXene-coa ed PI
shee . No e ha we ha e used he e he de ocused me hod
(Figu e 1c), esul ing in mul iple lases in a single un o he
pulsed lase . This me hod allows us o simply adjus he lase ’s
spo size while main aining consis en do densi y. Lowe ing he
subs a e by ∼3 mm below he ocal poin inc eases he spo size
esul ing in mul iple lasing on a gi en spo while main aining he
densi y o he lase spo cons an . Because each spo may lase
many imes in a single lase pass, his de ocused app oach
enhances p ocessing speed. The shee esis ance o de ocused
LIG (∼20 Ωsq−1) is also lowe as compa ed o LIG p epa ed a
he ocal leng h. In his p ocess, an in si u deco a ion/bonding o
he lase -induced MXene de i e Ti- ich oxide nanopa icles
(LIM) inside he 3D po ous ne wo k o g aphene was achie ed.
The lase p ocess mechanism is u he elabo a ed in he
ollowing discussion.
When exposed o an IR lase pulse (Figu e 1c), he MXene-
coa ed PI shee abso bs he IR ene gy and de elops a high local
empe a u e (o e 2000 K) wi hin a apid up ake ime
(submillisecond).
33
This apid ini ial up ake leads o he
Figu e 2. Con ocal lase scanning mic oscope op ical image and co esponding 2D and 3D alse colo p o ile o (a−c) LIG, (d− ) LIM-LIG, and
(g−i) O-LIM-LIG. Scale ba ∼50 μm.
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20539
o ma ion o ca bonized s eam (O2, CO, CO2, CH4, N2) om
he PI shee esul ing in a 3D po ous in e connec ed s uc u e o
LIG (Figu e 1 ). On he o he hand, he ca bon sou ce om he
MXene explosi ely apo izes, and me al ion oxida ion akes
place when he delamina ed MXene nanoshee s wi h abundan
oxygen-con aining unc ional g oups abso b he IR ene gy.
33
This ins an aneous high- empe a u e he mal oxida ion he e-
o e deg ades he Ti3C2Txshee s in o sphe ical Ti- ich oxide
nanopa icles. Howe e , be o e being employed as an SC
elec ode, i was ac i a ed u he by u ilizing oxygen (O2)
plasma ea men . A compa a i e analysis o su ace mo phol-
ogies o he p is ine MXene, delamina ed MXene, LIG, and
lase -p ocessed MXene-g aphene samples a e discussed nex .
The success ul delamina ion o Ti3C2TxMXene and LIM-
deco a ed g aphene elec odes was con i med by scanning
elec on mic oscopy (SEM). The su ace mo phology o he
p is ine Ti3C2TxMXene is displayed in Figu e 1d, con i ming
he mul ilaye s ack o Ti3C2Txwi h an acco dion-like s uc u e.
A e delamina ion wi h a s ong oxidizing agen ( iz. DMSO),
he su ace oxida ion o Ti3C2leads he su ace o become
oughe (Figu e 1e). Figu e 1g illus a es he uni o m
dis ibu ion o sphe ical LIM on he LIG ne wo k (called:
LIM-LIG), whe e he LIM pa icle size anges om 1 μm o he
subnanome e ange. The su ace mo phology o O2plasma-
ea ed LIM-LIG (called: O-LIM-LIG) is simila o ha o LIM-
LIG (Figu e 1h). The he e os uc u e wi h his so o
dis ibu ion o LIM o e g aphene no only is help ul o
imp o ed space u iliza ion bu also e icien ly p e en s g aphene
shee s om sel - es acking. Subsequen ly, in o de o co obo-
a e he uni o m dis ibu ion o i anium- ich sphe ical pa icles
ac oss he LIG ne wo k, an addi ional elemen al mapping
analysis is ca ied ou .
Elemen al mapping images o he O-LIM-LIG (Figu e 1i) and
MXene (Supplemen a y Figu e 1) we e acqui ed by ene gy-
dispe si e X- ay spec oscopy (EDX) o see he su ace elemen
and o e i y he su ace deco a ion o LIM o e he LIG
ne wo k. These e eal he p esence o C, O, and Ti in he O-
LIM-LIG hyb id, which is u he e i ied by Raman, XRD, and
XPS analysis. The c oss-sec ional SEM images (Supplemen a y
Figu e 2) e eal ha he O-LIM-LIG has a hickness o ∼107
μm, which was aken in o accoun o compu e he olume ic
capaci ance o he mic o-SC de ices.
Figu e 2 displays he op ical images o LIG, LIM-LIG, and O-
LIM-LIG cap u ed by a con ocal lase scanning mic oscope
(CLSM). The opog aphy (Figu e 2a,d,g) is ep esen ed
oge he wi h equi alen 2D (Figu e 2b,e,h) and 3D (Figu e
Figu e 3. Physical cha ac e iza ions. (a) Raman spec a o delamina ed Ti3C2TxMXene, LIG, LIM-LIG, and O-LIM-LIG ilms. Fi ed Raman
spec a we e wi hin he ange o 1000−3000 cm−1. (b) XRD spec a o Ti3C2TxMXene, delamina ed Ti3C2TxMXene, LIG, O-LIM-LIG, and
LIM ilms. (c) Ti 2p, C 1s, and O 1s high- esolu ion XPS spec a o delamina ed Ti3C2TxMXene and O-LIM-LIG.
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20540
2c, ,i) alse colo image maps whe e dis inc colo s co espond
o he a ious heigh p o iles o he samples. The heigh p o iling
was used o es ima e he a e age su ace oughness (Rq) o he
samples. The Rq alues o LIG, LIM-LIG, and O-LIM-LIG we e
calcula ed as 7.7, 8.6, and 8.9 μm, espec i ely. The O-LIM-LIG
su ace becomes oughe wi h LIM inse ion in o he LIG
su ace and subsequen ea men wi h he O2plasma ea men .
No e ha he su ace we abili y is highly ulne able o su ace
oughness,
38
and inc easing su ace oughness leads o inc eased
ion-accessible su ace a ea, which is one o he undamen al
ac o s o imp o ing elec ochemical SC pe o mance.
Raman measu emen s we e pe o med o de e mine he so s
o de ec s and g owing diso de s in he g aphene ne wo k caused
by he inco po a ion o MXene and he O2plasma ea men . As
displayed in Figu e 3a, he delamina ed MXene exhibi s bands
a ound ∼258, ∼420, and ∼608 cm−1co esponding o he in-
plane Ti−C ib a ion (Egsymme y o Ti3C2), in-plane
ib a ion o O a oms (Egsymme y) o hyd ogen- e mina ed
MXene Ti3C2(OH)2, and mixed con ibu ion o ou -o -plane
Ti−C ib a ion (A1g symme y o Ti3C2) and ib a ion o H
a oms o Ti3C2(OH)2.
39,40
The band a ∼151 cm−1is he Eg
ib a ional mode o ana ase TiO2 o med due o he
spon aneous oxida ion o Ti a oms.
41
In he case o LIG’s
Raman signal, h ee p ominen peaks a e isible (D ∼1340 cm−1,
G∼1574 cm−1, and 2D ∼2673 cm−1), which is consis en wi h
he p e ious epo .
9
In e es ing o no e ha a e he lase
p ocess and oxidiza ion by plasma ea men , he O-LIM-LIG
exhibi s h ee peaks a ∼151, ∼389, and ∼607 cm−1in addi ion
o D, G, and 2D peaks. These a e he cha ac e is ic Raman ac i e
modes o ana ase TiO2pa icles wi h symme ies Eg(1), B1g(1),
A1g, and Eg(3). The Raman esul s con i med he o ma ion o
ana ase TiO2phase om on he Ti3C2Txsu ace du ing he
lasing p ocess.
To u he cla i y he ypes o de ec s due o he o ma ion o
ana ase Ti- ich oxide pa icles inside he LIG ne wo k, Raman
spec a o LIG, LIM-LIG, and O-LIM-LIG a e u he i ed wi h
he Lo en zian unc ion (Figu e 3a), and he ex ac ed i ed
pa ame e s a e lis ed in he Ma e ials and Me hods sec ion. The
single Lo en zian peak i ing o LIG’s 2D band wi h a ull wid h
a hal -maximum o 86 cm−1con i ms he p esence o a ew
laye s o g aphene s acked along he caxis. No e ha h ee
signi ican changes a e isible when compa ing he Raman
spec a o LIG wi h LIM-LIG and O-LIM-LIG; 2D band
blueshi o ∼3 cm−1, inc emen o he ID/IG a io, and he
p esence o an asymme ic G peak o appea ance o an
addi ional D′peak a ∼1605 cm−1. The 2D band blueshi is
caused by bond angle diso de and comp essi e s ess a he
LIG/MXene-de i ed oxide in e aces.
9
The ID/IG a io is
maximum o O-LIM-LIG, indica ing he MXene-de i ed
ana ase TiO2and oxygen unc ional g oups ha e a s ong
impac on he in-plane sp2domain o LIG. Finally, he ID/ID′
a io (ID/ID′LIM‑LIG ∼5.5, ID/ID′O‑LIM‑LIG ∼3.8) indica es he
de ec s linked wi h acancies (Supplemen a y Table 1).
42
X- ay di ac ion (XRD) s udies we e pe o med (Figu e 3b)
o u he alida e he lase -induced ansi ion o Ti3C2Tx o
MXene-de i ed ana ase TiO2pa icles. The iden i ied XRD
peaks o delamina ed Ti3C2TxMXene and LIG a e consis en
wi h he p e ious published epo s.
9,43
Howe e , he cha ac e -
is ic XRD peaks o MXene a e no isible in he spec al analysis
o O-LIM-LIG. Conside ha delamina ed MXene shee s
unde go signi ican s a i ica ion and agmen a ion by abso b-
ing he lase ene gy, esul ing in losing hei 2D plana (002)
s uck o ma and con e ing o Ti- ich oxide nanopa icles (as
can be seen in Figu e 1). Howe e , i is wo h no ing ha he
ans o ma ion o Ti3C2Tx o ana ase MXene-de i ed TiO2
appea s o be ambiguous based on hese XRD esul s. To
cla i y his ambigui y, we conduc ed a con olled expe imen in
which a glass slide was coa ed wi h delamina ed MXene and
ea ed wi h a lase he ea e . I is in e es ing o no e ha he
esidual p esence o Ti3C2Txs ill exis ed in LIM bu shi ed
owa d a high angle (∼8.9°). Meanwhile, a couple o addi ional
XRD peaks eme ged co esponding o he (101) and (004)
planes o ana ase TiO2. Hence, he dual p esence o bo h MXene
and MXene-de i ed ana ase TiO2nanopa icles is con i med in
he LIM samples.
As e idenced om XRD and Raman, he su ace composi ion
o he O-LIM-LIG has al e ed signi ican ly a e he lase w i ing
and oxida ion due o plasma ea men . To u he con i m he
su ace chemical s a e/composi ion, X- ay pho oelec on spec-
oscopy (XPS) cha ac e iza ion was ca ied ou . The su ey
spec a epo (Supplemen a y Figu e 3) indica es he p esence
o Ti, C, and O in he h ee samples. An addi ional F peak is
e iden in he p is ine MXene ilm due o esidual F−ions o he
hyd o luo ic solu ion used o e ch he MAX phase. The a omic
a io o ca bon o oxygen (C/O) is compu ed om he su ey
spec a, and we ound ha he C/O alue is conside ably
educed o 3.6 o he O-LIM-LIG compa ed o he LIG (C/O =
9.15). This implies ha a signi ican numbe o oxygen
unc ional g oups we e bound andomly ei he wi h plana sp2
hyb idized benzene ings o wi h Ti a oms, which led o he
highe shee esis ance o O-LIM-LIG as compa ed o o he
samples (see Supplemen a y Figu e 8). The decon olu ion o C
1s, O 1s, and Ti 2p cla i ies i u he (Figu e 3C, Supplemen a y
Figu es 4 and 5). The binding ene gy alues o he i ed peaks
a e lis ed in Supplemen a y Table 2. As illus a ed in Figu e 3C,
se e al peaks a e iden i ied in he Ti 2p XPS spec um o
delamina ed MXene, which is consis en wi h he p e ious
indings.
43,44
Fo LIM-LIG and O-LIM-LIG ilms, only TiO2
binding ene gy peaks a e e iden , whe eas he Ti−C binding
ene gy peak is absen . The C 1s XPS spec um o MXene
consis s o ou ob ious peaks designa ed as C−C, C−OH, C−
O�C, and C−Ti−Tx espec i ely. A e lase ea men , he
peak a ibu ed o C−Ti−Txdisappea ed o LIM-LIG and O-
LIM-LIG. Fu he mo e, as shown in he O 1s spec um, he
in ensi y o he C−Ti−Oxpeak is dec eased o O-LIM-LIG
han he Ti3C2Tx, while a p onounced TiO2peak is no ed.
To ein o ce his a gumen , we conduc ed a compa ison o he
Ti 2p XPS spec a (Supplemen a y Figu e 6) o MXene,
delamina ed MXene, and LIM powde . In he case o MXene,
dis inc peaks co esponding o Ti−C (∼455 eV) and TiO2
(∼459 eV) we e obse ed. Con e sely, in he XPS spec um o
delamina ed MXene, he e was a dec ease in he in ensi y o he
Ti−C peak and an inc ease in he in ensi y o he TiO2peak.
This sugges s ha he oxida ion le el o he Ti a oms has
inc eased du ing he solu ion-based delamina ion p ocess.
In iguingly, he LIM sample did no exhibi a Ti−C peak;
only peaks co esponding o he binding ene gy o TiO2we e
e iden . These esul s con i m he con e sion o he Ti3C2Tx
su ace in o MXene-de i ed TiO2nanopa icles, which is in
ag eemen wi h he Raman measu emen s.
The con e sion o Ti3C2Txin o Ti- ich oxide nanopa icles
and he induced oxygena ed g oups ia plasma ea men ha e a
signi ican in luence on he unde lying we abili y o he O-LIM-
LIG hyb id. Supplemen a y Figu e 7 displays he wa e con ac
angle (WCA) alues o LIG (WCALIG ∼110°) and LIM-LIG
(WCALIM‑LIG ∼94°), indica ing ha bo h a e hyd ophobic in
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20541

na u e, while he O-LIM-LIG elec ode becomes supe -
hyd ophilic (WCAO‑LIM‑LIG ∼0°). I could be co ela ed wi h
he inc eased p opo ion o pola bonds C−O, C�O, and o he
oxygena ed g oups,
17
which make he g aphene edges mo e
a o able o in e ac wi h wa e molecules, and e en ually, he
d ople sinks in o he po ous ne wo k o O-LIM-LIG. Inc eased
hyd ophilici y leads o inc eased ion-accessible su ace a ea,
which is c i ical o mic o-SC de ice pe o mance. Howe e , he
Figu e 4. In e acial in e ac ion mechanism be ween MXene and LIG. (a) Ini ial and inal snapsho s aken om molecula dynamics simula ion
execu ed wi h eac i e o ce ield (ReaxFF) showing he o ma ion o an MXene-de i ed nanopa icle co alen ly bound o he g aphene su ace
( he co alen bonds a e highligh ed by yellow ci cles) a he high empe a u e (2000 K) induced by he lase pulse. (b) Snapsho s aken om
a ious MD simula ions wi h di e en ini ial s uc u es using ReaxFF a 2000 K showing he o ma ion o co alen ly bonded nanopa icles on
pe iodic g aphene su aces. The inse shows a de ail o he in e laced ca bon ne wo k o polya oma ic hyd oca bon-like s uc u es wi h
alipha ic side chains (Ti and O a oms a e omi ed o cla i y). A oma ic cycles a e colo ed in yellow. G aphs showing he numbe o di ec
co alen bonds be ween he MXene nanopa icle and he g aphene su ace ( he a e age alue is calcula ed om he las 50 ps). Colo s: C
(o ange), Ti (g ay), and O ( ed).
Figu e 5. Elec ochemical pe o mances o indi idual elec odes in 1 M H2SO4aqueous elec oly e. (a) CV p o iles o he O-LIM-LIG a
di e en scan a es and he co esponding (b) a eal and olume ic capaci ance as a unc ion o scan a e. A quasi ec angula CV shape indica es
e icien double-laye o ma ion. (c) GCD p o ile compa ison be ween LIG, LIM-LIG, and O-LIM-LIG a he cu en densi y o 2.6 mA cm−2.
(d) GCD o O-LIM-LIG wi h a ying cu en densi y. (e) E olu ion o he a eal and olume ic speci ic capaci ance o O-LIM-LIG as a unc ion
o cu en densi y. ( ) EIS plo s o LIG, LIM-LIG, and O-LIM-LIG wi h a magni ied EIS plo o O-LIM-LIG p o ided in he inse .
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20542
shee esis ance is comp omised o he O-LIM-LIG (see
Supplemen a y Figu e 8) as compa ed o o he elec odes due o
he p esence o oxygena ed g oups.
Molecula Dynamics Simula ion. The o ma ion o
MXene-o igina ed nanopa icles on LIG was s udied by
molecula dynamics (MD) simula ions wi h a eac i e o ce
ield ReaxFF (see Ma e ials and Me hods o de ails).
45
We
adop ed he de eloped ReaxFF o ce ield pa ame e s, which
we e success ully used o in es iga e he dynamics and s uc u al
changes o he e os uc u es in ol ing Ti3C2MXenes.
46
We
Figu e 6. Elec ochemical pe o mance o indi idual mic o-SCs in PVA-H2SO4gelled elec oly e. (a) Schema ic ab ica ion p ocess o he
mic o-SC de ice. Mic o-SC de ice ab ica ed h ough lase w i ing on a delamina ed Ti3C2Tx-coa ed PI shee ollowed by solid-s a e gel
elec oly e coa ing. (b) Compa a i e CV cu es o LIG, LIM-LIG, and O-LIM-LIG ilm a a scan a e o 10 mV s−1. (c) CV p o iles o he
co esponding a eal and olume ic capaci ances as a unc ion o scan a e. (d) Compa a i e GCD p o iles o he LIG, LIM-LIG, and he
co esponding O-LIM-LIG a a cu en densi y o 0.125 mA cm−2. ( ) GCD p o iles o O-LIM-LIG a di e en cu en densi ies and (g)
co esponding a eal and olume ic capaci ance as a unc ion o cu en densi ies. (h) Cyclic s abili y o O-LIM-LIG. The de ice e ains ∼91%
o i s ini ial capaci ance a e 10 000 cha ge/discha ge cycles. (i) CV p o iles o O-LIM-LIG unde di e en bending condi ions. The
elec ochemical pe o mances a e una ec ed by mechanical de o ma ion. (j) Cyclic s abili y o O-LIM-LIG unde he 180°bending condi ion.
The ben de ice e ains >85% o i s ini ial capaci ance a e 8000 cha ge/discha ge cycles.
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20543
ocused on o ma ion, mo phological changes, and in e ac ion o
MXene nanopa icles wi h he g aphene su ace wi h a iable
lexibili y ( ixed/a i icially w inkled g aphene) a ele a ed
empe a u es (2000 K) induced by he lase pulse. Rega dless
o he inpu s uc u e, sphe ical o al-shaped pa icles we e
o med, some CO molecules we e eleased, and ca bon a oms
cons i u ed s uc u es esembling unc ionalized polya oma ic
hyd oca bons. The nanopa icles composed o Ti and O a oms,
which we e in e laced wi h polycyclic a oma ic (hyd o)ca bon-
like molecules wi h alipha ic ca bon side chains (inse o Figu e
4b, Ti and O a oms a e omi ed o cla i y). The o med
nanopa icles conjuga ed ia co alen bonds wi h he g aphene,
which displayed a endency o w ap he nanopa icle enla ging
he con ac su ace (Figu e 4 and Supplemen a y Figu e 9) o
bo h sys ems. The esul s o MD simula ions suppo he
expe imen al obse a ions indica ing he endency o MXene o
o m Ti/O- ich nanopa icles co alen ly bound o g aphene.
Flexible Ene gy S o age De ices. The in oduc ion o
nano-MXene in o he 3D ne wo k o LIG esul s in a
subs an ially enhanced po osi y and oughness in he LIM-
LIG ilm as compa ed o LIG (Figu es 1 and 2). Fu he O2
plasma ea men made LIM-LIG ilm supe hyd ophilic, which
is bene icial o elec oly e ion accessibili y inside he po ous
s uc u e. Due o he dis inc i e and uni o m deco a ion o
nano-MXene/MXene-de i ed oxide (MDO) ac oss he po ous
LIG, wi h he added bene i o supe hyd ophilici y, O-LIM-LIG
was expec ed o se e as an inno a i e class o elec ode ma e ial
o SC applica ion.
The elec ochemical pe o mance was i s e alua ed in a
h ee-elec ode sys em. Supplemen a y Figu e 10 ep esen s he
cyclic ol amme y (CV) p o ile o LIG, LIM-LIG, and O-LIM-
LIG a a scan a e o 20 mV s−1. The CV cu es exhibi a ypical
quasi ec angula shape wi hou any dis inc peaks wi hin he
ol age ange om −0.2 o 0.8 V, indica ing elec ical double-
laye ype cha ge s o age. No ably, he O-LIM-LIG ilm shows a
highe CV in eg a ion a ea as compa ed o he MXene and LIM-
LIG ilm. The CV cu es o O-LIM-LIG SC a a ious scanning
a es (1−100 mV s−1) eme ged as almos quasi ec angula
shapes (Figu e 5a and Supplemen a y Figu e 11). No e ha he
O-LIM-LIG mic o-SC deli e ed excep ional a eal (CA∼291 mF
cm−2a 5 mV s−1) and olume ic capaci ance (CV∼27 F cm−3
a 5 mV s−1), bo h o which a e highe han he mos epo ed
LIG and MXene-based mic o-SCs. The scan a e a ia ion o CA
and CVis shown in Figu e 5b wi h a capaci ance e en ion o
a ound 35% om 20 o 100 mV s−1.Figu e 5c shows he
cons an cu en gal anos a ic cha ge−discha ge (GCD) cu es
o he LIG, LIM-LIG, and O-LIM-LIG a a cu en densi y o 2.6
mA cm−2. The longes discha ge GCD p o ile e eals he
supe io i y o he O-LIM-LIG o e he LIG and LIM-LIG. The
iangula GCD shape a di e en cu en densi ies (Figu e 5d
and Supplemen a y Figu e 12) wi h a Coulombic e iciency o
∼97% e eals he excellen e e sibili y o he O-LIM-LIG SC
wi hou any no iceable ol age d op a he beginning o he
discha ge cu e. Figu e 5e illus a es he CV∼35 F cm−3and
co esponding CA∼372 mF cm−2a ∼2 mA cm−2ou -
pe o ming p e iously epo ed LIG and MXene-based mic o-
SCs.
To u he in es iga e he kine ics o ion anspo o he LIM-
LIG ilms and pu e LIG ilm, elec ochemical impedance
spec oscopy (EIS) measu emen s we e pe o med a open
ci cui ol age (OCV). As shown in Figu e 5 , i is clea o
obse e ha he Nyquis plo s o LIG and LIM-LIG deli e
simila ypes o g aphs con aining a s eady p opo ional inc ease
in he imagina y and eal impedance, indica ing a sluggish ion
di usion o hese elec odes, whe eas he O-LIM-LIG showed a
s eepe slope in he low- equency egion ela i e o he LIG and
LIM-LIG ilms, which is consis en wi h he imp o ed ion
accessibili y and anspo due o he addi ional ac i a ion o he
O2plasma ea men . Fu he mo e, he in e acial cha ge
ans e esis ance (Rc ) o O-LIM-LIG (∼40 Ω) is e iden ly
less han LIG (∼70 Ω) and LIM-LIG ilm (∼65 Ω),
demons a ing he ionic conduc i i y o he O-LIM-LIG was
imp o ed ollowing O2plasma ea men , which is consis en
wi h he esul o CV and GCD es ing.
Nex , o p epa e a solid-s a e lexible mic o-SC de ice,
poly( inyl alcohol) (PVA)-H2SO4polyme gel elec oly e was
cas ed on he in e digi a ed elec ode (IDE) su ace wi hou any
binde , sepa a o , o any packaging ma e ial (see Figu e 6a). All
de ices’ CV cu es ha e a quasi ec angula shape (Figu e 6b),
sugges ing s ong elec ical double-laye (EDL) cha ac e is ics.
The O-LIM-LIG exhibi ed he highes I−Vloop a ea among he
h ee CV p o iles, highligh ing he supe io i y o e pu e LIG and
LIM-LIG in e ms o a eal and olume ic capaci ance alue.
The CV cu es o he O-LIM-LIG mic o-SC ha e an almos
quasi ec angula shape a a lowe scan a e (1 o 10 mV s−1),
indica ing he capaci i e beha io o he elec odes (Figu e 6c).
Howe e , he na u e o he CV cu e became esis i e wi h
inc easing scan a e (Supplemen a y Figu e 13), demons a ing
he inc eased e ec o he in e nal esis ance o he elec ode a a
high cu en densi y. This is u he suppo ed by he la ge
in e cep (∼260 Ω) on he axis in he Nyquis plo
(Supplemen a y Figu e 15). None heless, i s gal anos a ic
cha ge−discha ge cu es (Figu e 6e, ) ha e a iangula shape
wi h a Coulombic e iciency o ∼97%, indica i e o he
o ma ion o e icien EDL wi h excellen e e sibili y and
good cha ge p opaga ion be ween he in e digi a ed elec odes.
The longes discha ge pe iod in he iangula GCD p o ile a a
cu en densi y o 0.125 mA cm−2(Figu e 6e) u he con i med
he supe io i y o he O-LIM-LIG o e he LIG and LIM-LIG.
We measu ed he speci ic capaci ance o e a wide ange o GCD
cu en densi y and CV scan a e, espec i ely. No ably, he O-
LIM-LIG mic o-SC de ice deli e ed excep ional CA∼130 mF
cm−2and CV∼12 F cm−3a a scan a e o 5 mV s−1(Figu e 6d).
Figu e 6g illus a es ha he olume ic capaci ance o he
mic o-SC (Ccell/ no malized o he whole de ice olume) is
∼6.6 F cm−3a 0.5 mA cm−2, co esponding o he a eal
capaci ance (Ccell/A) o ∼70 mF cm−2ou pe o ming mos
epo ed LIG and MXene-based mic o-SCs (Supplemen a y
Table 3). Figu e 6h shows ha mic o-SC e ains ∼91% o i s
ini ial capaci ance e en a e 10 000 cha ge−discha ge cycles
demons a ing i s excellen elec ochemical s abili y wi h long
cycle li e.
The O-LIM-LIG mic o-SC was u he subjec ed o a
mechanical bending es o see i s adap abili y o lexible and
wea able elec onics. Figu e 6i shows ha he mic o-SC e ains
∼100% capaci ance compa ed o i s la s a e when se e ely
ben . Fu he mo e, he lexibili y endu ance es o he mic o-SC
de ice was ca ied ou by 8000 GCD cycles by keeping he
de ice ben a 180°. Ou s anding cyclic s abili y was eco ded
(Figu e 6j) wi h capaci ance e en ion o 85% a e 8000 GCD
cycles. The high mechanical lexibili y o he O-LIM-LIG mic o-
SC makes i a iable candida e o lexible mic oelec onics.
Meanwhile, EIS u he explains he excellen capaci i e
pe o mance o he O-LIM-LIG mic o-SC (Supplemen a y
Figu e 15). EIS measu emen shows ha in he high- equency
egion, O-LIM-LIG (∼260 Ω) has he smalles equi alen se ies
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20544
esis ance as compa ed o LIM-LIG (>400 Ω) and LIG (>800
Ω) and displayed a la ge slope in he low- equency egion.
MXene inclusion minimizes he g aphene laye s acking,
esul ing in a wide su ace a ea wi h well-de ined mesopo osi y
o e ec i e elec oly e pene a ion and ion adso p ion.
Meanwhile, he p esence o oxygen unc ional g oups imp o es
he pola in e ac ion wi h he elec oly e solu ion.
7
The Ragone plo (Figu e 7) u he showcases he po en ial o
he O-LIM-LIG in e digi a ed elec odes o high ene gy/powe
densi y mic o-SCs. Ou mic o-SCs ha e an a eal ene gy densi y
o ∼21.2 μWh cm−2and a powe densi y o 0.075 mW cm−2a a
cu en densi y o 0.125 mA cm−2. By inc easing he cu en
densi y o 10- old (1.25 mA cm−2), almos 45% o he ene gy
densi y has been e ained (∼9μWh cm−2), while he powe
densi y inc eases o 0.75 mW cm−2. The ene gy and powe
Figu e 7. Ragone plo o he O-LIM-LIG mic o-SC whe e ene gy and powe densi ies a e compa ed wi h he s a e-o - he-a LIG and MXene-
based ene gy s o age sys ems and comme cially a ailable supe capaci o s. Volume ic ene gy and powe densi ies o O-LIM-LIG mic o-SC
compa ed wi h comme cial supe capaci o s and a 4 V/500 μAh Li ilm ba e y.
7,21,54
Da a o he Li ba e y a e ep oduced om e 3. Da a o
he 2.75 V/44 mV ac i a ed ca bon supe capaci o , 5.5 V/100 mF comme cial supe capaci o , and 3 V/300 μF Al elec oly ic capaci o a e
ep oduced om e s 21 and 49.
Figu e 8. Applica ion o mic o-SC de ices connec ed in se ies and pa allel condi ions. CV cu es a 5 mV s−1and GCD p o iles a 0.5 mA cm−2o
O-LIM-LIG mic o-SC de ices connec ed in (a,c) se ies and (b,d) pa allel. (e) Schema ic o he se ies and pa allel combina ions o h ee mic o-
SC elec odes. ( ) Pho og aphs o comme cial ed, yellow, and g een LEDs powe ed by mic o-SC de ices connec ed in se ies. (g) Schema ic o
powe ing he FSD o moni o he human body adial a e y pulses using wea able mic o-SC de ices. (h) Fo ce-dependen ol age esponse o
FSD powe ed by se ially connec ed mic o-SC (mic o-SC/FSD) and an ex e nal 5 V powe supply (con ol). (i) Reco ded li e adial pulses o a
human body a ound ∼80 BPM.
ACS Nano www.acsnano.o g A icle
h ps://doi.o g/10.1021/acsnano.3c07319
ACS Nano 2023, 17, 20537−20550
20545