8.64.6
A New Rou e o Tune he Elec ical
P ope ies o G aphene Oxide: A
Simul aneous, One-S ep N-Doping
and Reduc ion as a Tool o I s
S uc u al T ans o ma ion
Andjela S e ano ić, Muhammad Yasi , Ge a d Tobías-Rossell, S e ania Sando al Rojano,
Dušan S edoje ić, Dejan Kepić, Duška Kleu , Wa da Saeed, Miloš Milo ić, Danica Bajuk-Bogdano ić
e al.
Special Issue
G aphene and G aphene-Rela ed Ma e ials o Ene gy and En i onmen : Syn hesis and Applica ion
Edi ed by
D . Sa e io La o a a and D . And ea Basso Pe essu
A icle
h ps://doi.o g/10.3390/molecules30173579
Academic Edi o : Chongjun Zhao
Recei ed: 10 Augus 2025
Re ised: 27 Augus 2025
Accep ed: 29 Augus 2025
Published: 1 Sep embe 2025
Ci a ion: S e ano i´c, A.; Yasi , M.;
Tobías-Rossell, G.; Rojano, S.S.;
S edoje i´c, D.; Kepi´c, D.; Kleu , D.;
Saeed, W.; Milo i´c, M.; Bajuk-
Bogdano i´c, D.; e al. A New Rou e o
Tune he Elec ical P ope ies o
G aphene Oxide: A Simul aneous,
One-S ep N-Doping and Reduc ion
as a Tool o I s S uc u al
T ans o ma ion. Molecules 2025,30,
3579. h ps://doi.o g/10.3390/
molecules30173579
Copy igh : © 2025 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
A New Rou e o Tune he Elec ical P ope ies o G aphene
Oxide: A Simul aneous, One-S ep N-Doping and Reduc ion as a
Tool o I s S uc u al T ans o ma ion
Andjela S e ano i´c 1, Muhammad Yasi 2,* , Ge a d Tobías-Rossell 3, S e ania Sando al Rojano 3,
Dušan S edoje i´c 1, Dejan Kepi´c 1, Duška Kleu 1, Wa da Saeed 2, Miloš Milo i´c 1,
Danica Bajuk-Bogdano i´c 4and S e lana Jo ano i´c 1,*
1Vinˇca Ins i u e o Nuclea Sciences-Na ional Ins i u e o he Republic o Se bia, Uni e si y o Belg ade,
P.O. Box 522, 11000 Belg ade, Se bia
2Ca l on Ossie zky Uni e si ä Oldenbu g, 26129 Oldenbu g, Ge many
3Ins i u de Ciencia de Ma e ials de Ba celona (ICMAB-CSIC), Campus de la UAB,
08193 Bella e a, Ba celona, Spain; ge a [email p o ec ed] (G.T.-R.); [email p o ec ed] (S.S.R.)
4Uni e si y o Belg ade, Facul y o Physical Chemis y, S uden ski g 12-16, 11158 Belg ade, Se bia;
[email p o ec ed]
*Co espondence: [email p o ec ed] (M.Y.); [email p o ec ed] (S.J.)
Abs ac
The p esence o seconda y elec omagne ic wa es (EMWs) esul s in EMW pollu ion and
a la ge need o EMW-shielding ma e ials. The e o e, new, ligh weigh , lexible, chemi-
cally esis an , and du able EMW shielding ma e ials a e demanded, while g aphene and
i s de i a i es mee he abo e-men ioned equi emen s. Among g aphene de i a i es,
N-doped g aphene exhibi s p omising elec ical p ope ies o shielding applica ions, al-
hough achie ing su icien N-inco po a ion in he g aphene shee s emains a challenge.
He ein, we p oduced g aphene oxide using he modi ied Humme s’ me hod (GO) and he
elec ochemical ex olia ion o highly o de ed py oly ic g aphi e. These wo GO samples
we e he mally ea ed a 500
◦
C and 800
◦
C unde a pu e NH
3
gas o 1 h. UV-Vis, in a ed,
and Raman spec oscopies and X- ay di ac ion, elemen al, and he mog a ime ic analy-
ses we e used o in es iga e he s uc u al p ope ies o modi ied GO. One o he highes
le els o N-doping o GO was measu ed (11.25
±
0.08 a %). The modi ica ion unde a
NH
3
a mosphe e leads o simul aneous N-doping and educ ion o g aphene, esul ing in
he o ma ion o elec ically conduc i e and EMW shielding ma e ials. Densi y unc ional
heo y (DFT) e ealed he e ec o he e oa oms on he ene gy band gap o GO. The clus e
co esponding o N-doped GO had a educed bandgap o 0.77 eV.
Keywo ds: g aphene; g aphene oxide; N-doping; elec ochemical ex olia ion; densi y
unc ional heo y; elec o-magne ic shielding
1. In oduc ion
Elec omagne ic wa es (EMWs) ha e become widesp ead owing o he ex ensi e use
o elec onic de ices, such as mobile phones, wi eless communica ion de ices, a i icial
sa elli es, and ada s [1]. As a esul o elec omagne ic wa e pollu ion, a ious elec onic
and measu ing equipmen mal unc ioned, and signi ican conce ns we e aised abou i s
e ec s on public heal h [
2
]. The p ima y s a egy o con olling EMW exposu e is he
use o elec omagne ic in e e ence (EMI) shielding p oduc s, which e icien ly p e en
he p opaga ion o EMWs. D i en by he u gen need o a o dable, du able, minia u e,
Molecules 2025,30, 3579 h ps://doi.o g/10.3390/molecules30173579
Molecules 2025,30, 3579 2 o 17
ligh weigh , and eco- iendly EMI-shielding ba ie s, a ious nanoma e ials ha e been
apidly de eloping [3–5].
Common me al-based EMI shielding ma e ials e ec i ely block EMWs; howe e , chal-
lenges ega ding hei p ocessabili y, co osion, and cos limi hei wide exploi a ion [
6
].
New ma e ials, including conduc i e polyme s, ca bon nano ubes, and MXenes, ha e
been u ilized as ille s in a ious polyme s, exhibi ing excellen shielding e ec i eness
and o he equi ed p ope ies, such as being ligh weigh , chemically s able, lexible, and
p ocessable. These ma e ials each e y high alues o o al shielding e ec i eness a e y
low hicknesses, such as 84.9
µ
m hickness and o al shielding e ec i eness (EMI SE) o
44.56 dB in he X-band o ca bon nano ube (CNT)-Fe
3
O
4
laye (FCFe) and MXene [
7
],
Ti
3
C
2
T
x
MXene embedded in poly inyl alcohol yielding 34.80 dB shielding e iciency a
5
µ
m hickness [
8
], and Fe
3
O
4
-loaded cellulose/polyac yloni ile nano ibe s wi h Ti
3
C
2
T
x
MXene a 640
µ
m hickness eached EMI SE o 33.2 dB [
9
]. Conside ing he ecological
bu den o plas ic ma e ials and he challenges o plas ic composi e ecycling, scien i ic
a en ion has ocused on bio-based ma e ials such as biocha and cellulose sca olds as
po en ial EMI-shielding ma e ials [10–13].
Owing o hei unable elec ical p ope ies, mechanical s eng h, ligh weigh , and
chemical esis ance, g aphene and i s de i a i es ha e been s udied o shielding appli-
ca ions [
14
–
16
]. When he inciden EMWs collide wi h he g aphene su ace, hey a e
abso bed, e lec ed, in e nally e lec ed, o ansmi ed [
16
]. Dielec ic and magne ic losses
achie e abso p ion loss, whe eas conduc ion and pola iza ion losses in luence he dielec ic
loss. Conduc ion loss is associa ed wi h cha ge mig a ion ac oss g aphene shee s and
cha ge hopping om one laye o ano he , which occu s when ma e ials con ain g aphene
shee s in he cons uc ion ha a e high enough o allow he shee s o c ea e a conduc-
i e [
17
]. This occu s in g aphene composi es when he mass a io is abo e he h eshold
concen a ion [
17
]. This ype o wa e a enua ion depends on he elec ical conduc i i y
o he ma e ial. In con as , pola iza ion loss occu s when dipoles in ma e ials unde an
elec ical ield a e pola ized, leading o he a enua ion o disappea ance o he ield [
18
].
When he dipoles e u n o hei ini ial s a e, hea is gene a ed and los . In g aphene-
based ma e ials, dipoles s em om pola unc ional g oups, such as O- o N-con aining
unc ional g oups, owing o he di e ences in elec onega i i y be ween he C a oms in
g aphene and he he e oa oms. These g oups lead o he o ma ion o de ec si es whe e
cha ge ca ie s can be apped [
19
,
20
]. One s a egy o inc ease EMI shielding e ec i eness
and elec ical conduc i i y o g aphene shee s is o inco po a e elec on- ich a oms in he
g aphene s uc u e [
21
,
22
]. In he case o n- ype doping o g aphene, he e oa oms such
as N, I, P, B, o S o m localized egions wi h inc easing elec on densi y in he
π
-cloud o
g aphene shee s, enhancing cha ge ca ie mobili y and ampli ying pola iza ion a de ec
si es. I was epo ed ha dipole pola iza ion es ablished be ween C-N bonds imp o es he
pola iza ion elaxa ion loss o EMWs, yielding an EMI shielding e ec i eness o 45.6 dB in
he X-band [22].
He ein, we explo ed he possibili ies o using he he mal ea men o g aphene
oxides a 2 di e en empe a u es, 500
◦
C and 800
◦
C, in a pu e NH
3
a mosphe e o achie e
N-doping o GO and he e ec s o ea men on he elec ical p ope ies. Fo he i s ime,
wo di e en s a ing ma e ials we e ea ed: GO ob ained using he modi ied Humme s’
me hod, and GO p oduced using elec ochemical ex olia ion o highly o de ed py oly ic
g aphi e. Namely, one highly oxidized and diso de ed Humme s’ GO and he o he wi h
ewe oxygen-con aining unc ional g oups, and mo e domains wi h sp
2
egions we e
s udied. A simila p ocedu e was p e iously employed o achie e N-doping o GO [
23
],
whe e a empe a u es abo e 500
◦
C, g aphene was hyd ophobic, wi h N inco po a ed in
g aphene shee s as py idinic N, py olic-N, and g aphi ic N, in a omic pe cen ages (a %)
Molecules 2025,30, 3579 3 o 17
be ween 7.7 and 12.5. Conside ing ha py idinic and py olic N we e iden i ied as ac o s
a ec ing he pola iza ion elaxa ion loss, and g aphi ic N acili a es elec on mig a ion and
enhances EMW abso p ion [
22
], his p ocedu e aimed o imp o e elec ical conduc i i y
and EMI SE o GO. Using di e en GO as a ma ix o N inco po a ion, we in es iga ed
how he p ecu so a ec s he abili y o N a oms o build N in o g aphene shee s.
2. Resul s
To in es iga e he chemical composi ion and na u e o he chemical bonds in he
annealed GO, EA, SEM-EDS, TGA, Raman, FTIR, and XRD analyses we e conduc ed.
Table 1shows he esul s o he EA, indica ing ha C is dominan ly p esen in each
sample, anging om 81.04 o 90.00 w %. The w % o H was simila in all samples, whe eas
he w % o N was he highes o GO-500. Oxygen was de ec ed be ween 5.69 and 8.58 w %,
while S was iden i ied in GO-500 and HOPG-500 as a esidue. The amoun o N in oduced
o he GO samples was in e sely p opo ional o he ea men empe a u e. In he wo se s
o samples, he N was inco po a ed a a highe w % a 500 ◦C.
Table 1. Elemen al composi ions o samples in w % measu ed using an elemen mic oanalyze .
Sample C ±STD H ±STD N ±STD S ±STD O1
GO-500 81.04 ±0.21 0.69 ±0.03 11.25 ±0.08 0.21 ±0.01 6.81
GO-800 83.63 ±0.19 0.68 ±0.05 7.11 ±0.06 <0.1 8.58
HOPG-500 87.93 ±0.08 0.34 ±0.01 5.85 ±0.03 0.19 ±0.02 5.69
HOPG-800 90 ±0.13 0.41 ±0.01 3.46 ±0.02 <0.1 6.13
1The alues o O w % we e calcula ed by sub ac ing he w % o he measu ed elemen s (C, H, N, and S).
The su ace chemical composi ion and mo phology o he GO samples we e in es i-
ga ed using SEM-EDS analysis. In Figu e 1, SEM images and associa ed EDS maps o he
iden i ied elemen s o GO-500 and HOPG-800 a e p esen ed. The SEM images showed
laye ed mo phology o bo h samples, while he elemen maps indica ed a homogeneous
and equal dis ibu ion o each de ec ed elemen o e he in es iga ed su ace. Table S1
(Suppo ing In o ma ion) lis s he elemen al composi ions ex ac ed om he EDS spec a
o all he samples, in bo h w % and a %. Compa ed o alues in Table 1, EDS analysis
showed simila bu di e en w % alues o each elemen om he elemen al analysis.
EDS analysis was used o in es iga e he su ace chemical composi ions, and he dep h
o he analyzed specimen depends on he elec on beam ene gy and a omic masses o he
cons i uen elemen s p esen in he specimen [
24
,
25
]. EA s udies he bulk sample ha is
combus ed and analyzed, esul ing in alues ep esen a i e o he o e all specimen. Thus,
simila alues a e in ag eemen , conside ing he di e ence in he p inciples o he wo
analyses and he con i med esul s ob ained.
Figu e 2p esen s he TGA o GO, GO-500, GO-800 (a), and HOPG, HOPG-500, and
HOPG-800 (b). The TGA cu e o GO shows an ini ial weigh loss a ibu ed o physically
bonded wa e molecules (5.83 w %) up o a empe a u e o ca. 150
◦
C (Figu e 2a, black
con inuous line). This indica es he hyd ophilici y o he sample. A ca. 250
◦
C, a la ge
weigh loss was obse ed (28.58 w %), which was associa ed wi h elimina ing oxygen-
con aining unc ional g oups. The comple e combus ion o GO occu ed a 552
◦
C. Fo
GO-500, only 1.82 w % was los a 150
◦
C, while o GO-800, he weigh loss was 0.01.
These esul s indica e ha he pola i ies o GO-500 and GO-800 we e signi ican ly changed,
and ha bo h we e hyd ophobic. A ca. 250
◦
C, weigh loss was no obse ed, while
comple e combus ion occu ed a 608 and 586
◦
C, GO-500 and GO-800 ( ed and blue cu es
in Figu e 2a), espec i ely.
Molecules 2025,30, 3579 4 o 17
Figu e 1. SEM images and EDS maps o GO-500 (a) and HOPG-800 (b).
HOPG, HOPG-500, and HOPG-800 samples exhibi ed simila TGA cu es as GO sam-
ples (Figu e 2b), wi h empe a u es o o al combus ion o 415, 479, and 481
◦
C, espec i ely.
The absence o a weigh loss below 200
◦
C in TG cu es sugges s ha he e is no
p esence o physiso bed wa e in he samples ea ed unde pu e NH
3
gas a 500 and 800
◦
C,
which is associa ed wi h a less hyd ophilic cha ac e compa ed wi h he s a ing GO. Being
a known educing agen , NH
3
no only ac s as a N sou ce, bu also induce he elimina ion
o O-bea ing unc ionali ies om he samples, as con i med by he disappea ance o he
weigh loss associa ed wi h hese species and he inc ease in he he mal s abili y o he
ma e ial, The he mal s abili y o he samples closely depends on he concen a ion o N-
con aining g oups wi hin he conjuga ed la ice. In ag eemen wi h p e ious epo s [
23
,
26
],
Molecules 2025,30, 3579 5 o 17
he highe he N con en in N-doped GOs is (500
◦
C ea men s inco po a ed he la ge
concen a ion o N-based g oups compa ed wi h ea men s pe o med a 800
◦
C), he
highe he he mal s abili y agains oxida ion in ai was obse ed.
Figu e 2. TGA cu es o GO, GO-500, and GO-800 (a); HOPG, HOPG-500, and HOPG-800 (b).
Figu e 3shows Raman (a) and FTIR (b–d) spec a o GO samples annealed unde
pu e NH
3
gas. All Raman spec a showed he p esence o bands a 1355 cm
−1
, assigned o
he diso de ed o as-indica ed D-band, a a ound 1600 cm
−1
, he g aphi ic o G-band was
obse ed, a 2700 cm
−1
, he so-called 2D band, and he band indica ed as D+G (2950 cm
−1
)
was also iden i ied [
27
–
29
]. In he case o HOPG-500 and HOPG-800, G bands a e spli ,
due o changes in he bond leng hs and angles o g aphene shee s as a esul o s ain [
30
].
Namely, ex e nal pe u ba ions o he hexagonal symme y o g aphene occu ed due o
he in oduc ion o N- unc ional g oups in he g aphene shee s. In all spec a, he D band’s
in ensi y is highe han he G bands, indica ing high diso de in he g aphi ic s uc u e o
he samples. The calcula ed alues o he in ensi y a ios be ween D and G bands a e lis ed
in Table 2.
Figu e 3. Raman (a) and FTIR spec a (b) o GO-500, and GO-800; (c) HOPG-500, and HOPG-800.
Table 2shows ha he highes s uc u al o de was calcula ed o GO, while he mos
diso de ed sample is HOPG-800, acco ding o I
D
/I
G
alues. Addi ionally, he posi ion o
he G band is associa ed wi h he g aphi ic egions in g aphene-based ma e ials [
30
]. Using
he Knigh and Whi e equa ion [
31
], he in-plane c ys alli e size (La) was es ima ed and
lis ed in Table 2. The alues we e calcula ed using he ela ion La = 4.4 (I
D
/I
G
)
−1
, and
Molecules 2025,30, 3579 6 o 17
indica e he lowes c ys alline size o sample HOPG-800. Compa ed o o he N-doped
g aphene, whe e La was 16.5 nm [
32
], ou samples showed signi ican ly lowe in-plane
c ys alli e size, while I
D
/I
G
alues a e simila . Fu he mo e, he posi ions o 2D (2699 cm
−1
)
in HOPG-500 and HOPG-800 (2702 cm
−1
) a e simila o he p e iously epo ed N-doped
GO [32].
Table 2. Posi ion o G bands, ID/IG a ios, and La alues.
Sample G Band (cm−1) ID/IGLa
GO 1596 1.11 4.35
GO-500 1603 1.15 3.82
GO-800 1602 1.20 3.70
HOPG-500 1587 1.25 3.55
HOPG-800 1589 1.33 3.34
FTIR spec a we e used o in es iga e he binding na u e o he elemen s iden i ied
using SEM-EDS and EA. In case o GO, ib a ions associa ed wi h H-O (
ν
~3200–3400 cm
−1
)
om physically abso bed wa e o OH g oups, C=O (
ν
~1700 cm
−1
) om ca boxyl, C=C
(
ν
~1590 cm
−1
) om a oma ic domains, O–H (
β
(OH)) (
ν
~1372 cm
−1
), C=O (
ν
~1223 cm
−1
),
C–O in C-O-C (
ν
~1042 cm
−1
), and C-O in epoxy (
ν
~ 952 cm
−1
) we e obse ed [
33
,
34
].
In FTIR spec a o GO-500 and GO-800, he band a 3400 cm
−1
signi ican ly inc eased.
Mo eo e , wo new bands a 2922 and 2853 cm
−1
om CH/CH
2
we e de ec ed. The
band a 1700 cm
−1
anished in he GO-500 spec um, while in he case o GO-800, a
lowe in ensi y and shi ing up o 1739 cm
−1,
owing o he comple e o pa ial emo al
o ca boxyl g oups, occu s. Finally, he 1590 cm
−1
band shi ed o 1552 cm
−1
in GO-500
and GO-800 FTIR spec a. Bo h spec a show bands a 1160 cm
−1
, which we e associa ed
wi h C-N ib a ions [
35
,
36
], while bands a 1042 and 952 cm
−1
almos comple ely anished,
indica ing he emo al o epoxy g oups.
In he case o HOPG, HOPG-500 and HOPG-800 samples showed s ong bands
a ibu ed o C-N (
ν
~1161 cm
−1
), C=C (
ν
~1551 cm
−1
) om a oma ic domains, C=O
(ν~1737 cm−1),
and CH/CH
2
(2922 and 2853 cm
−1
) ib a ions. A s ong band a 3400 cm
−1
was de ec ed in he HOPG-500 sample, while o he HOPG-800 sample, his band was
no de ec ed. The eason o his change is associa ed wi h an al e a ion in he pola i y o
HOPG-800 and an inc ease in i s hyd ophobici y, esul ing in a lowe ing o he endency o
he ma e ial o abso b a mosphe ic wa e physically.
All samples showed e iden changes in FTIR spec a a e he mal ea men unde
pu e ammonia gas. A high empe a u e, ammonolysis led o signi ican changes in
unc ional g oups ancho ed o he g aphene oxide. The new bands assigned o C-N bonds
and de ec ed in all he mally modi ied samples co espond o N inco po a ed in o he
g aphi ic la ice. Mo eo e , he simul aneous elimina ion o he O-con aining moie ies
om he GO was con i med by he disappea ance o he bands co esponding o hyd oxyl
(1042 cm−1) and epoxy g oups (952 cm−1).
The c ys al s uc u e o he samples was analyzed by X- ay di ac ion (Figu e 4). The
XRD p o ile o he ini ial GO has he (001) e lec ion a 2
θ
= 11.4
◦
, co esponding o an
in e plana dis ance o app oxima ely 7.8 Å [
37
,
38
]. On he o he hand, p is ine HOPG
shows wo b oad peaks, a 2
θ≈
24.4
◦
and 2
θ
= 12.4
◦
, which co espond o he (002) and
(001) e lec ions, espec i ely [
39
]. The de ia ion om he li e a u e alue o he (002)
e lec ion o ex olia ed g aphene (2
θ
= 26
◦
) and i s b oadness migh be he consequence o
he co uga ed g aphene’s s uc u e and he inc eased in e laye spacing [
40
]. The mally
ea ed GO samples showed an eme gence o a new ea u e (002) a 2
θ≈
25
◦
and a
simul aneous disappea ance o he (001) e lec ion. The (002) ea u e o GO and HOPG
Molecules 2025,30, 3579 7 o 17
samples he mally ea ed a 800
◦
C was shi ed owa ds a highe angle han samples
ea ed a 500
◦
C. This implies a sligh change in he in e plana dis ances owa d lowe
alues o he samples ea ed a he highe empe a u e, owing o he elimina ion o
hyd oxyl and epoxy g oups om g aphene’s su ace unde hea ing, as obse ed p e iously
in FTIR spec a (Figu e 3b,c).
Figu e 4. XR di ac og ams o GO and HOPG, and he mally ea ed GO and HOPG samples.
The UV-Vis abso p ion spec a o he mally ea ed GO and HOPG we e eco ded
in oluene and p esen ed in Figu e 5. All spec a show an abso p ion peak a 224 nm,
co esponding o he
π
-
π
* ansi ions o a oma ic C-C bonds [
41
,
42
]. The peak was no
shi ed in posi ion a e he annealing a 800
◦
C. In e es ingly, he spec um o GO showed
an addi ional ea u e a 255 nm. This new band could be associa ed wi h N- unc ional
g oups [43].
Figu e 5. UV-VIS spec a o GO-500, GO-800, HOPG-500, and HOPG-800.
Molecules 2025,30, 3579 8 o 17
Fu he in es iga ions o he op ical and elec ical p ope ies o GO, HOPG, and N-
doped samples we e ca ied ou by eco ding e lec ion spec a. The Tauc equa ion was
used o calcula e he op ical band gap. Figu e S1 shows he co esponding Tauc plo s,
(
α
h
ν
)
2
as a unc ion o h
ν
, whe e
α
is he abso p ion coe icien , his he Planck cons an ,
and
ν
is he equency [
44
,
45
]. The alue o he op ical ene gy band gap (Eg) was es ima ed
as he x-in e cep o an ex apola ed Tauc plo , and he ob ained alues a e lis ed in Table 3.
I was obse ed ha he Eg was dec eased signi ican ly a e he mal ea men , om
4.88 eV o 1.88 eV. In he case o N-doping o GO p oduced by elec ochemical ex olia ion o
HOPG, Eg was lowe , and a small dec ease was measu ed a e he mal ea men a 500
◦
C
and 800
◦
C, wi h he lowes alue calcula ed o he HOPG de i a i es co esponding o
he sample ea ed a 500
◦
C. The lowe ing in he alues o Eg was p e iously epo ed o
chemically educed GO [
45
,
46
] o GO educed by speci ic d ying condi ions [
47
]. A dec ease
in he Eg alues leads o ex ended abso p ion in he isible pa o he elec omagne ic
spec um [
41
], imp o ed semiconduc o p ope ies [
46
,
48
], and is associa ed wi h he
es o ing
π
-domains in g aphene shee s. These esul s a e in ag eemen wi h XRD and
FTIR analyses, whe e emo al o O- unc ional g oups and imp o emen o sp
2
domains
we e epo ed.
Table 3. Op ical band gap o GO and HOPG powde s.
Sample Eg(eV)
GO 4.88
GO-500 1.88
GO-800 1.85
HOPG 1.95
HOPG-500 1.82
HOPG-800 1.83
We used DFT calcula ions o in es iga e he elec onic s uc u e o N-doped GO and
compa e i o ha o GO. Ab ini io me hods can p o ide an a omis ic model o a iously
unc ionalized and N-doped GO, e ealing hei op ical and elec onic p ope ies. We
employed hese echniques o calcula e he o al and pa ial densi y o s a es (TDOS/PDOS)
diag ams o GO and N-doped GO. These esul s p o ided in o ma ion abou he ene gy
s uc u e changes mainly occu ing a ound he Fe mi le el when ni ogen a oms a e embed-
ded in o he g aphene co e. Figu e 6shows he op imized s uc u es o [C
40
H
16
O
2
(OH)
2
]
and [C
35
H
14
O
2
N
6
] clus e s wi h he co esponding densi y o s a es (TDOS/PDOS) di-
ag ams. The [C
40
H
16
O
2
(OH)
2
] clus e , wi h wo basal epoxy and hyd oxyl g oups, is
cons uc ed o mimic GO, while he [C
35
H
14
O
2
N
6
] clus e ep esen s N-doped GO. The
[C
35
H
14
O
2
N
6
] clus e has one g aphi ic, wo py olic, and h ee py idinic ni ogen a oms
embedded in o he g aphene la ice. The densi y o s a es diag am o he clus e ep esen -
ing GO indica es ha he bandgap is 2.16 eV, which ca ego izes i as a semiconduc ing
ma e ial (Figu e 6b). This alue is close o he expe imen ally de e mined bandgap o
educed GO. The ene gy s a es o wo ypes o oxygen a oms ( om epoxy and hyd oxyl
g oups) a e almos o e lapping in he alence egion and do no ake pa in he s a es
nea he Fe mi le el. On he o he hand, he clus e co esponding o N-doped GO has a
educed bandgap o 0.77 eV, indica ing inc eased elec ical conduc i i y compa ed o GO,
as demons a ed expe imen ally (Figu e 6b). The PDOS diag am shows ha he elec onic
le els o py idinic ni ogen a oms a e nea he Fe mi le el, while he py olic and g aphi ic
ni ogen le els a e loca ed deep in he alence band. The elec onic s a es o ca bonyl
oxygen a oms also appea as pa o he on ie molecula o bi als and ex end ac oss he
en i e alence egion.
Molecules 2025,30, 3579 15 o 17
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