Toward the synthesis, fluorination and application of N-graphyne

Article abstract of DOI:10.1039/d0ra08143d

The discovery of properties and applications of unknown materials is one of the hottest research areas in materials science. In this work, we navigate a route towards these goals by the development of a new type of graphyne nanostructure. It is synthesise

Full text of DOI:10.1039/d0ra08143d

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Toward the synthesis, fluorination and application
of N–graphyne†
Cite this: RSC Adv., 2020, 10, 40019
a
b
c
a
Gisya Abdi,
Marcin Strawski,
Grzegorz Cichowicz, Piotr J. Leszczynski,
Anna Filip, ‡ Michał Krajewski, ‡ Krzysztof Kazimierczuk,
c
a
c
d
Paweł Szarek,
Bartosz Hamankiewicz,
Zoran Mazej,
e
a
a
Karol J. Fijałkowski
´
a
and Andrzej Szczurek
*
The discovery of properties and applications of unknown materials is one of the hottest research areas in
materials science. In this work, we navigate a route towards these goals by the development of a new
type of graphyne nanostructure. It is synthesised by a Sonogashira cross-coupling reaction of 1,3,5-
triethynylbenzene with cyanuric chloride resulting in an extended carbon-based material called TCC.
2
Also, we modify the obtained TCC via fluorination using XeF at various concentrations to investigate the
effect of fluorination on the triple bonds and the conjugated structure of graphyne. In this study, we put
special emphasis on the determination of the impact of the fluorine content and the type of CF
functionalities on the morphology, chemical and electronic structure, biocompatibility, electrical
conductivity and possible applicability as anode materials for Li-ion batteries. The obtained results
indicate that the character of C–F bonds influences the final properties of fluorinated materials. The
Received 23rd September 2020
Accepted 26th October 2020
2
polar C–F bonds are preferable for cell proliferation while CF groups are most suitable for battery
DOI: 10.1039/d0ra08143d
devices, however, the appearance of PTFE-like units may have a negative impact on battery specific
rsc.li/rsc-advances
capacitance as well as on cell viability.
Thanks to the exible synthesis procedure and large number of
aromatic compounds which could potentially be used as building
Introduction
Graphyne-like nanostructures (GYs) belong to new two- blocks of new nanomaterials, GYs are considered as versatile
2
3
dimensional carbon allotropes composed of sp- and sp -hybri- materials with strong application potential.
1
dised carbon atoms, reported by Baughman et al. The graphyne
Numerous papers have been published discussing theoretical
structure can be viewed as a modication of graphene's structure properties of GY-based materials and their applications. However,
where one-third of the carbon–carbon bonds are replaced by reported papers concerning synthesis and application of graphyne
2
4–6
acetylenic bridges. Due to the unique sp–sp hybridisation of structures are handful and remains elusive practically.
carbon atoms, uniform pores, and highly p-conjugated structure,
Introduction of heteroatoms is an efficient and essential
method to adjust band gaps and electronic structures of carbon
2
2
D graphyne at sheets are of interest to many research groups.
7–9
materials. Even though GYs themselves are interesting and
promising materials, the presence of triple carbon–carbon
bonds in their structure gives an opportunity for additional
modications through doping or functionalisation. These
modications results in deep changes in the structure and
physicochemical properties of such modied materials.
a
˙
Centre of New Technologies, University of Warsaw, Zwirki i Wigury 93, 02-097
Warsaw, Poland. E-mail: a.szczurek@cent.uw.edu.pl
b
Laboratory of Molecular Medical Biochemistry, Nencki Institute of Experimental
Biology, PAS, 3 Pasteur Street, 02-093 Warsaw, Poland
c
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
d
Among numerous possible modication methods, uorina-
tion, due to exceptional reactivity and electronegativity of uo-
The Czochralski Laboratory of Advanced Crystal Engineering, Faculty of Chemistry, rine, appears to be one of the most impressive and effective
Department of Inorganic Chemistry and Technology, Jozef Stefan Institute, Jamova
cesta 39, SI 1000 Ljubljana, Slovenia
e
University of Warsaw, Z˙ wirki i Wigury 101, 02 089 Warsaw, Poland
procedure allowing to receive completely new materials in
†
Electronic supplementary information (ESI) available: Synthesis, uorination
relation to their precursors. Until now, uorination process has
been realised through various chemical routes with different
and measurements protocols, single crystal XRD data, TEM micrographs, XPS
13
spectra deconvolution data, plots of Raman spectroscopy,
photoluminescence,. DFT computation data, plots electric permittivity and
dielectric loss. Pictures of HEK cell cultures and E. coli growth. CCDC 2025547. tronic, optic and conductive nature of uorinated materials.
C NMR,

uorinating agents and resulted in distinct changes of elec-
10–17
For ESI and crystallographic data in CIF or other electronic format see DOI:
Fluorination has been widely used for various carbonaceous
materials starting from amorphous activated carbons,
1
0.1039/d0ra08143d
10
‡
These authors contributed equally to this work.
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1
1,12
13
through carbon nanotubes
and fullerenes, ending on product with a thin layer of a clear solution on top of it, which
14
15
graphite and most recognisable graphene and graphene was continuously washed by 5% HCl solution, Milli-Q water,
16,17
oxide.
However, to our best knowledge, there are few reports ethanol, and acetone until the black product received. Further,
focusing on direct uorination of GYs. The recent papers deal, TCC samples were uorinated using XeF2 under ambient
e.g. with graphdiyne-like structure made from triuorobenzene conditions, in a weight ratio of 1.5, 6.7 and 10 resulting in three
18
precursor and graphdiyne-like structures uorinated using uorinated TCCs with increasing uorine content: TCCF1,
19
XeF
2
focused on their photoluminescence properties.
TCCF2 and TCCF3 respectively.
In the present work, a new type of N–graphyne material built
on 1,3,5-triethynylbenzene and triazine units was synthesised
and subjected to uorination reaction carried out with XeF2.
Xenon diuoride was chosen as uorination agent due to its
high reactivity and selectivity towards organic compounds bearing
Morphology
The set of TEM images taken for TCCF2 sample are shown in
Fig. 1A–F. The low magnication image (Fig. 1A) revealed that
TCCF2 sample forms a cluster of micrometric irregular frag-
ments with average dimensions of 1–15 mm. Closer observations
showed that they are built from randomly arranged stacks of
thinner layers. Furthermore, TCCs show porous and rather
disordered structure conrmed by the SAED pattern presented
in an inset of Fig. 2B. The rough chemical composition of the
samples as well as the surface mapping was evaluated by EDX
technique shown in Fig. 2C–F. Obtained elemental maps
showed mostly homogeneous distribution of uorine atoms
20
double or triple bonds. Reaction of progressive uorination of
triple bonds, understood as transformation of acetylene units into
double bounded CF]CF and single bonded, PTFE-like, CF
units, was proceeded at room temperature. Reaction progress was
controlled by varying concentration of XeF . The impact of uorine
2 2
–CF
2
concentration as well as nature of C–F bonds on morphology,
chemical and electronic structure, biological activity, conductivity
and their applicability as Li-ion battery anodes was in-depth
examined and the results of investigations are presented in the
following sections in detail.
(especially for TCCF1, Fig. S4†) on the whole surface, however,
some agglomerations of uorine atoms, presumably around
inorganic impurities, can be seen for samples prepared using
higher excess of XeF
presence of oxygen and chlorine on the surface of the samples
2
. TEM observations also revealed the
Results and discussion
The N–graphyne, called for our purpose TCC (triethynylbenzene (Fig. 1E and F). The presence of chlorine could result from not
coupling with cyanuric chloride), was synthesised upon sol- fully reacted cyanuric chloride or residual chlorine from the
vothermal route in an equimolar cross-coupling reaction of catalyst used during the synthesis of TCCs (Table 1).
1,3,5-triethynylbenzene (1,3,5-TEB) and cyanuric chloride,
depicted in Scheme 1. Obtained in Step 1 triethynylbenzene was
ꢀ
recrystallized from melt carried out in tubular furnace at 400 C
and under nitrogen atmosphere. Obtained white needle crystals
were investigated by single-crystal XRD to evaluate the structure
of obtained 1,3,5-TEB and results are collected in ESI le
(Fig. S1, S2 and Table S1†). Redetermined crystal data were
deposited in CSD with CCDC number: 2025547 and are of better
21
quality compared to the previously reported. That prepared
substrate was subjected to Step 3 which resulted in a black jelly
Fig. 1 Set of TEM micrographs of fluorinated N–graphynes TCCF2
samples, (A) at low magnification; (B) at high magnification with inset
showing SAED pattern. Low magnification images of EDX elemental
Scheme 1 Detailed synthetic route towards TCC (top) and depiction distribution showing content of: carbon (C), nitrogen (D), oxygen (E),
of product formation in Step 3 (bottom). and fluorine (F).
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Fig. 2 Survey XPS spectra of: (A) pristine and fluorinated N–graphynes. Magnification and deconvolution various bands of XPS spectra: C 1s (B)
and N 1s (C) of pristine TCC; C 1s of TCCF1 (D), TCCF2 (E), TCCF3 (F); and F 1s of: TCCF1 (G), TCCF2 (H), TCCF3 (I).
Structural properties
samples of increasing uorine concentration of 6.38%, 10.16%
and 19.48% for TCCF1, TCCF2 and TCCF3, respectively.
Fig. 2B shows N 1s XPS spectrum of TCC sample having one
broad band which can be convoluted to two overlapping peaks
at 398.28 eV and 400.15 eV characteristic for pyridinic and
pyridonic nitrogen, whereas the latter peak could be a result of
The effects of uorination on TCC can be seen already at rst
glance, as the reaction leads to a change in the samples' colour
with increasing uorine content from dark brown/black (TCC)
through deep brown (TCCF1), pale brown (TCCF2) to yellow
(TCCF3) (Fig. S3†). The structural changes as well as presence of
22
a partial hydrolysation or degradation of triazine rings.
new CF functionalities caused by uorination can be observed
1
3
19
In contrary to rather uniform C 1s band found for TCC
using XPS, FTIR and solid state C and F NMR techniques.
Detailed investigation of elemental composition and func-
tionalities of pristine TCC and its uorinated derivatives was
performed by XPS (Fig. 2A). Four core level peaks C 1s (285
eV), N 1s (399 eV), O 1s (530 eV) and Cl 2p (200 eV) are common
for all TCCs and TCCFs, whereas uorine built in the structure
of the latter was conrmed by sharp F 1s peak around 686 eV
and Auger F KLL peak at 830 eV. The elemental composition was
determined by integration of above-mentioned core level peaks.
It shows that successful uorination was achieved to receive
(Fig. 2C), the C 1s bands recorded for uorinated samples show
separated (TCCF2, TCCF3) or partly separated (TCCF1) broad
peaks. First of these peaks lying in a range of 284–287.6 eV is
common for TCCFs, pristine TCC and other known carbona-
ceous materials presenting mixed hybridisation and armed in
23,24
various functional groups.
revealed that they are composed of several peaks found at 284.3
Deconvolution of C 1s bands
ꢁ
0.2 eV, 284.9 ꢁ 0.1 eV, 286.1 ꢁ 0.2 eV and 287.1 ꢁ 0.5 eV
assignable to C]C, C^C, C–N/C–O and C]O/C]N compo-
nents, respectively. It turns out that, the intensity of bands at
284.9 eV has decreased from 33% (TCC) to 2.9% (TCCF3) as

uorine content increased indicating that uorination took
Table 1 Elemental content of pristine and fluorinated N–graphynes
place predominantly on triple bonds of N–graphynes. The
second broad band, so called CF region, appearing in a range of
Composition TCC (at%) TCCF1 (at%) TCCF2 (at%) TCCF3 (at%)
2

88–292 eV can be attributed to carbon atoms directly linked to
uorine atoms, especially since their increasing intensity
Fig. 2D–F) follow the trend of increasing uorine content in the
C
N
O
F
74.8
9.2
12.6
—
67.6
5.0
15.6
6.4
69.4
2.2
14.9
10.2
3.3
59.2
4.6
9.5
19.5
7.2
(
sequence of TCCF1, TCCF2 and TCCF3. Again, deconvolution of
C 1s bands helped to distinguish several peaks included in the
Cl
2.7
5.3
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CF region and appearing at ca. 288.3 ꢁ 0.2 eV, 289 ꢁ 0.3 eV,
2
91.3 ꢁ 0.5 eV. The band near to 288.3 ꢁ 0.2 eV is typically
2
assigned to uorine covalently bonded to sp carbon atoms. It
could be noticed that the intensity of these units as well as CF
3
functional groups bearing uorine atoms attached to sp
2
carbon units (289.5 eV) and the covalent CF functional groups
appeared at ca. 291.1 ꢁ 0.5 eV has been increasing progressively
with increasing uorine concentration. Finally, the small peaks
2
5
seen at 292.4 ꢁ 0.1 eV can be ascribed to CF
2 2
–CF units.
Deconvolution of F 1s XPS spectra showed that they are built
typically from three or four additional lines corresponding to
different CF bonds present in the uorinated samples. Isolated,
e.g. surrounded by bare C atoms, semi-ionic C–F bonds (1) are
seen in a range 684.6–685.2 eV, semi-ionic –CF]CF– units (2)
present in range 686.5–686.9 eV, covalent –CF
CH
2
–CHF– or –CF
2
–
2
– units (3) can be found in a range 688.1–688.8 eV; while the
lines at ꢂ689.2 eV are assignable to PTFE-like covalent –CF
2
–
25
CF – units. The evolution of the nature of CF bonds with
2
increasing uorine content is clearly visible in the reduction of
group (1) with a simultaneous increase in the share of groups (3)
and (4). It should, however, be noted that bonds (2) remain the
main core of C–F bonds occurring in uorinated N–graphynes,
regardless of the uorine content. The distribution and amount
of particular functional groups occurring on the TCC and
TCCFs surface are collected in Tables S2 and S3† included in EIS

le.
FTIR spectra of pristine TCC and TCCFs are shown in Fig. 3A.
Fig. 3 FTIR spectra of pristine and fluorinated N–graphynes (A);
Raman Spectra (B) and XRD pattern (C) measured for of pristine N–
Taking into account FTIR spectra measured and reported for graphyne (TCC).

uorinated materials, the most signicant and characteristic
ꢃ1 15,26
bands are those appearing in a range 1070–1250 cm
.
respectively, but also from the oxygen containing functional
These bands can also be observed for uorinated N–graphynes: groups, overlapping those covalent C–F bonds.
TCCF1, TCCF2 and TCCF3. Increasing absorbance observed
Because of complete optical transparency of TCCFs to the green
along with increasing uorine concentration allow us to believe light (514 nm), it was impossible to receive signicantly intensive
that these bands are predominantly correlated with different Raman bands (Fig. S5†) for those samples as the energies of the
types of CF bonds present in the structure of TCCFs. In the case lasers used were lower than the band gap of investigated
ꢃ1
ꢃ1
28
of TCCF1, wide shoulders at 1070 cm and 1120 cm and samples. On the other hand, the Raman spectrum of pristine
ꢃ1
broad band 1170–1230 cm
(line 3) were distinguished. TCC is shown in Fig. 3B. It consists of three bands characteristic
Adapting the concepts made for other uorinated carbonaceous for carbonaceous materials. The shoulder at 1380 cm is known
materials [ref. 27 and wherein], we could assign the band at as D band originating from a breathing mode of k-point photons of
070 cm (line 1) to bulk CF groups surrounded by two or three
bare C atoms, while the band at 1100 cm (line 2) to two band, is formed due to disorder scattering of E2g phonons by sp
ꢃ1
ꢃ1
ꢃ1
1
A
1g symmetry. The most signicant band at 1580 cm , called G
ꢃ1
2
neighbouring CF groups surrounded by two bare C atoms. carbon atoms; the broad 2D band found in a range 2600–
ꢃ1
Moreover, the reaction of atomic uorine with carbons of 2900 cm is treated as an overtone of D band and exhibits
acetylenic units was conrmed by presence of vinylene groups a strong frequency dependence on the excitation laser energy. The
ꢃ1
ꢃ1
–
CF]CH– or –CF]CF– at 1690 cm (line 4) as well as by last small band at 2145 cm is a common band for graphyne and
ꢃ1
signicant decrease of absorbance at 2150 cm (line 5) charac- graphdiyne-like structures coming from –C^C– units. Deconvo-
teristic for –C^C– bonds. The effect of uorination became much lution of D and G bands helped to evaluate the areas ratio known
more visible when high concentrations of XeF
they resulted in reduction of a large number of isolated CF groups, carbonaceous nanostructures. In the case of N–graphyne, the I
2 D G
were applied as as I /I , which brings an information about the ordering rate of
29
D
/
which can be observed as decrease of the intensity of shoulders at IG ratio was equal to 2.86 suggesting mostly disordered structure,
ꢃ1
1
070 cm followed by a creation of chain-like uorination pattern later conrmed by powder XRD shown in Fig. 3C. The XRD pattern
ꢃ1
ꢀ
represented by maximum absorbance at 1120 cm . Furthermore, contains one broad and noisy signal at 2q ¼ 24.44 , referring to 002
30
2 2
partial transformation of –CF]C(F)– to –CF –CF – units was reection in graphite structure. The broadness of the signal as
ꢃ1
conrmed by strong reduction of absorbance at 1690 cm . It well as the absence of h0l and hkl reections in the pattern of N–
should be mentioned that the lines occurring in the range 1170– graphyne indicates the lack of graphitic ordering and rather
ꢃ1
1
250 cm should be treated with caution, as they may be derived amorphous nature of N–graphynes.
2
from symmetrical and asymmetrical vibrations of CF groups,
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1
3
C NMR spectra of uorinated N–graphynes are presented for our purposes further named as Car. These bands, however,
in Fig. 4B and C. It could be noticed that all recorded spectra do comprise several shoulders at chemical shis of 104–108 ppm (Car–
not differ strongly from each other. What is more, they were very CH]CF–C ) and 112–113 ppm (C –CF –CF –C ). Signals at
ar
ar
2
2
ar
similar to the spectrum of pristine TCC shown on Fig. 4A, where 133 ppm can be assigned to Car linked directly to –CF]CF– unit,
the inset picture presents a fragment of the investigated whereas those at 140 ppm to Car bonded to –CF –CF – linkers. The
molecular structure with numbered bonds (C1–C5) visible at peaks with chemical shi at 169 ppm belong to Car of triazine ring
2
2
13
NMR spectrum: 152 ppm (C1), 76–90 ppm (C2 and C3) and 118– linked to one of aforementioned CF units. Deconvoluted C NMR
27 ppm (C4 and C5). The spectra of uorinated samples spectra for TCCF3 is depicted in ESI le (Fig. S6†). All possible
comprised broad asymmetric peaks with several shoulders. Due uorinated places have been depicted in Fig. 4E.
1
1
3
to broad and jagged spectra presenting numerous overlapping
C NMR spectra prepared for TCCFs show signicant
lines causing difficulties and uncertainties upon interpretation, differences between these materials and e.g. uorographene.
31
Voight line shape deconvolution have been conducted using Ori- For the latter, usually, two distinct chemical shis can be
3
ginPro 2020 soware in order to determine the chemical structure of distinguished, rst at 82–86 ppm characteristic for C sp –F
the tested materials. Obtained results revealed that spectra are built groups and the second one at 132 ppm assignable to the
2
from several signals of different chemical shis representing interactions between sp carbon and uorine atom from the
32
different types of C–C and C–F bonding. The carbons included in neighbouring CF groups.
acetylenic units –C^C– give a chemical shi in a range of 78– The formation of carbon–uorine bonds aer uorination
1 ppm (discussed C atoms are bold); this line however can overlap conducted with various concentration of XeF was conrmed by
9
2
3
19
with C sp carbons directly bonded to uorine recorded at chemical solid state F NMR and the normalised spectra are shown in
shi of 86 ppm. The chemical shis in a range of 34–40 ppm can be Fig. 4d. For all the samples, three main signals at chemical
assigned to carbons in –CH
2
–CF
2
– units. The main peak at 118– shis of ꢃ122 ppm (CF ), ꢃ127 ppm (–CF]CH–) and
2
2
120 ppm was assigned to aromatic carbons with hybridisation sp , ꢃ150 ppm (–CF]CF–) are observed with the intensity of each
type of a signal clearly depended on uorine content. In the case
of TCCF1, the bands at ꢃ150 ppm are dominant whereas the
increasing uorine concentration leads to a decrease of its
intensity with simultaneous strengthening intensities of signals
at ꢃ122 ppm noticed for samples TCCF2 and TCCF3.
Based on this nding, it can be concluded that CF]CF systems
are created in the rst place, while higher amounts of available
2 2
uorine can further uorinate them to CF –CF systems. The
signals at chemical shi of ꢃ127 ppm, found for TCCF1 and
TCCF2, completely disappeared in the case TCCF3 likely due to the
2 2 2
transformation of –CF]CH– bonds to CF –CHF and/or CF –CF
units. Obtained results well support the ndings of XPS and FTIR.
Electronic structure
The Tauc plots shown in Fig. 5 were prepared in order to
determine the optical gap of investigated materials. The expo-
nent r in (ahv)1/r formula xed at 1 turned out to be the most
2
1
3
Fig. 4
(
C solid state NMR of pristine TCC (A), TCCF1 (B) and TCCF2
, 2
is CF]CH, 3 is CF]CF and asterisks are rotational sidebands of 3 (D); Fig. 5 Tauc plots prepared for pristine (TCC) and fluorinated N–
1
9
C); F solid state NMR of fluorinated N–graphynes, wherein 1 is CF
2
the map of CF bonds made up during fluorination (E).
graphynes (TCCF1, TCCF2 and TCCF3).
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suitable for all the investigated samples suggesting allowed
direct transitions occurring in all these materials regardless the

uorination rate. The optical gap of pristine TCC is estimated to be
.86 eV what nicely corresponds with the values of optical gap
found for other reported nanostructures containing conjugated
1
33
triazine and benzene rings as well as triazine–graphdiyne nano-
structures. As expected, uorination of TCC leads to signicant
34
widening of the optical gap, resulting in the values of 2.93 eV,
3.03 eV and 3.17 eV observed for TCCF1, TCCF2 and TCCF3,
respectively. The reason of such feature lies in increasingly
stronger covalent nature of CF bonds associated with the
augmentation of uorine concentration as well as the occurrence
of electron–hole and electron–electron interactions resulting from Fig. 6 Valence band XPS spectra of fluorinated N–graphynes. Addi-
the impact of UV light on the uorinated samples.
tional lines are drawn to visualise the bands described in the text.
HOMO–LUMO (shortly HL) gaps of uorinated TCCs, were
determined computationally using DFT method using Gaussian
Fig. 6 shows Valence Band XPS (VB XPS) spectra, measured for
uorinated N–graphynes, with six characteristic lines in a range
35
36
37
16 by hybrid functional B3LYP with Def2SVP basis set. The

HL gap has been determined from the eigenvalues of HOMO
and LUMO Kohn–Sham orbitals. The structure considered in
these experiments are shown in Scheme 1S.† Briey, a model
structure of TCC consisting of 10 benzene rings and 3 triazine
rings connected by single acetylene linkers was employed and
the whole structure formed a monolayer of combined three
macrocycles. That prepared model structure served as a starting
point for new structures with attached uorine atoms in the
number from 2 to 48 arranged in different bond congurations
3
.8–32 eV observed for all investigated samples.
Given the high convergence of the results obtained in this
work with previously reported ones for various types of uori-
nated materials,
27,41,42
the p states of aromatic regions can be
ascribed to a shoulder at ca. 3.8 eV (S), a band at 5.5 eV (P1)
represents interactions of uorine orbitals being nearly parallel to
the sheets with TCC s system, a band at 9.6 eV (P2) manifests non-
bonding uorine states, and a band at 13.6 eV (P3) is assigned to
C–F bonding. The bands at 17.6 eV (P4) and 32 eV (F 2s) result from
the C 2s and F 2s states, respectively. For all the samples, the peaks'
positions are nearly the same, however, show moderate variations
in intensity (Table 2). The valence band energy taken as offset of
the VB XPS are in a range 1.60–1.87 eV showing a moderate shi to
higher values with increasing uorine concentration. The values of
conductive band minimum energy estimated as a sum of valence
band maximum energy and the appropriated optical band gap are
collected in Table 2.
(
–CF]CF– and –CF –CF –). Additionally, the calculations of HL
2 2
band gap of a structure with erased triazine rings and con-
taining 12 uorine atoms were also conducted. All considered
structures with a full set of results are presented in ESI le.† The
HL gap calculated for the model structure was equal to 3.43 eV,
whereas the HL gaps calculated for uorinated derivatives lied
in a range of 3.12–3.34 eV and were related to uorine
concentration, CF bond nature as well as aromatic nature of

uorinated sample. Our ndings meet well with band-gap
energy (3.13 eV) found for recently reported 2D halogen-
substituted graphdiyne. Although calculations revealed that
38
Electric properties
band gap can be modulated by the uorine concentration and Conductivity of the samples was investigated by electrochemical
CF bond nature, the change in a band gap is rather moderate impedance spectroscopy (EIS) using IMPED CELL, an in-house
and does not exceed 0.4 eV. It turns out that the most signicant designed and patented device made of hardened stainless steel,
change in the band gap (0.8 eV) was noticed when triazine ring providing simultaneous control of pressure up to 2000 MPa,
ꢀ
43,44
was erased from N–graphyne structure. In this case, HL gap and temperature in the rage of 0–80 C.
Fig. 7A and B shows
increased to 3.78 eV making it very close to experimental values an exemplary Nyquist plot registered for TCCF1 along with
39
16
found for uorographene or uorinated graphene oxide.
equivalent circuit used. Fig. 7b shows Nyquist plots of TCCF2
Unfortunately, discrepancy between theory and experiment
could be seen in overall trends of gap modication. In contrary
to the experimentally estimated optical gap, the theoretical
considerations disclosed that HL gap decreased with decreasing
Table 2 Peak positions extracted from valence band XPS data
TCCF1
[eV]
TCCF2
[eV]
TCCF3
[eV]
VB XPS

uorine concentration. The explanation of such behaviour may
be attributed to defects and corrugations occurring in real
samples. Furthermore, the DFT calculations did not consider
Shoulder (S)
Peak 1 (P1)
3.8
5.5
3.7
5.5
3.8
5.7
photon-assisted electron–hole and electron–electron interac- Peak 2 (P2)
9.6
9.5
9.5
tions. The agreement between theory and experiment could Peak 3 (P3)
13.5
17.1
32.2
1.6
13.7
17.7
32.5
1.8
13.8
17.6
32.0
1.9
Peak 4 (P4)
likely be improved in the future by applying other calculation
model such as the GW–Bethe–Salpeter Equation (GW–BSE)
F 2s
VB
CB
allowing to apply rectication of the gap by comprising elec-
4.5
4.8
5.1
40
tron–electron and electron–hole interactions.
40024 | RSC Adv., 2020, 10, 40019–40029
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ꢀ
ꢀ
ꢀ
measured in three different temperature: 20 C, 30 C and 40 C. on electron–hole transport way between carbon and uorine.
For each sample, a single semicircle or deformed semicircle was Furthermore, the increase of temperature results in higher
observed. However, for some uorinated samples semicircles mobility of polar molecules, in consequence leading to an
ꢀ
were followed by a Warburg impedance (line tilted at 45 ) at increase of the dielectric constant shown in Fig. S8.†
lower frequencies related to the charge accumulation at block-
ing electrodes, suggesting some ionic conductivity of these Electrochemistry
samples. The arc is identied as a bulk property from the fact
Fig. 8A and B show the results of galvanostatic charge (A) and
0
00
that it passes through the Z –Z origin, and from the associated
capacitance. The deformed semicircle may occur due to differ-
ence in time constants e.g. grain interior, grain boundaries
conductivity and reactions with electrode material in the low
frequency range as well. EIS measurements showed that both
pristine and uorinated TCCs exhibit very high resistivity in the
discharge (B) cycling for TCCFs. All compounds delivered high
discharge capacity during preliminary discharge, reaching
ꢃ1
ꢃ1
1
1
175.5 ꢁ 38.3 mA h g , 1394.3 ꢁ 42.8 mA h g and 1109.5 ꢁ
ꢃ1
6.6 mA h g for TCCF1, TCCF2 and TCCF3, respectively. Aer
the initial discharge, the capacities dropped drastically to 285.0
ꢃ1
ꢃ1
ꢁ
8.2/325.8 ꢁ 8.5 mA h g , 402.7 ꢁ 15.4/454.3 ꢁ 27.5 mA h g
2
range of MU m which translate into very low electrical
ꢃ1
and 280.0 ꢁ 34.6/372.4 ꢁ 46.1 mA h g during 1st charge/
discharge cycle for TCCF1, TCCF2 and TCCF3, respectively.
The irreversible capacity during preliminary discharge, as
a result of Solid Electrolyte Interphase (SEI) layer formation on
the surface of the electrodes, can be attributed to Li reaction
with electrochemically active CF groups. In consequence,
conductivity. Fig. 7C presents relationship between electrical
conductivity and uorine concentration in the samples.
The electrical conductivity of pristine TCC was equal to 2.31
ꢃ9
ꢃ1
ꢄ 10 S m and addition of 6.38 at% of uorine yielded in
enhancement of the electrical conductivity by almost 1.5 times.
Further increase of uorine concentration resulted in further
enhancement of conductivity reaching the level higher by about
+
45
received capacities are signicantly lower than those found for
F-substituted graphdiyne or triazine–graphdiyne mate-
1–2 orders of magnitude than conductivity of TCC sample.
21,34,46
rials.
Aer ve additional cycles the electrochemical
Obtained results tted with the low power function can be
performance of the cells stabilised and aer 20th cycle the
powders delivered specic capacities of 253.1 ꢁ 15.2/260.7 ꢁ
b
expressed by equation: y ¼ a ꢄ x , where scaling exponent, b, is
ꢃ8
5
.78 and initial growth index, a, is equal to 7.0 ꢄ 10
.
ꢃ1
ꢃ1
1
3
6.2 mA h g , 322.2 ꢁ 60.1/332.1 ꢁ 62.4 mA h g and 272.7 ꢁ
Temperature resolved EIS measurements (293–318 K)
ꢃ1
4.0/284.8 ꢁ 36.8 mA h g for TCCF1, TCCF2 and TCCF3,
showed a dependence of electrical conductivity on temperature.
Fig. 7D shows temperature-dependent conductivity of TCCF2
exhibiting a linear behaviour in an Arrhenius plot, which
enables determination of activation energy of conductivity of
TCCF2 to be 0.46 eV. The energy activation level as well as
a shape of semicircles indicate that electric transport, in this
range of temperature, appears to be realised on electronic route.
The enhancement of electrical properties of TCCFs seems to be
directly caused by increasing uorine content, linked with
carbon mostly via semi-ionic –CF]CF– units. In such case,
2
respectively. From all the examined samples, TCCF showed the
highest specic capacities. This might be the result of CF
2
+
groups formation, leading to increased vacancies for Li
47
storage. It turns out that type of CF bonding could inuence
2

uorine being an electron acceptor acts as a p-dopant for
investigated materials and the electrical conductivity is realised
Fig. 7 Electric properties of N–graphyne and its fluorinated deriva-
tives: (A) Nyquist plot with Warburg impedance measured for TCCF1; Fig. 8 Cyclability of TCCFs during charge (A) and discharge (B)
B) dependence of electrical conductivity on fluorine content of processes and charge/discharge curves for TCCF powders: initial
TCCFs; (C) Nyquist plot measured for TCCF2 in different temperatures; discharge (C), 1st (solid line) and 20th (dashed line) cycle charge/
D) Arrhenius plot derived for TCCF2. discharge curves of TCCF1 (D), TCCF2 (E) and TCCF3 (F).
(
(
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ꢃ1
the nal electrochemical properties of uorinated materials as maximum for cell cultures treated with 100 mg ml of investi-
we noticed that higher number of CF –CF units in the structure gated materials, whereas further increasing material concen-
2
2
of TCCF3 resulted in drop of its specic capacity. Cyclability of tration yielded in the drop of living cells.
all the examined samples had similar values, within the margin
The results discussed above were received in an experiment
of error, reaching 88.8 ꢁ 3.6/80.0 ꢁ 3.6%, 79.6 ꢁ 12.4/72.5 ꢁ conducted on conuent cell cultures, thus, we could speculate
9
.8% and 97.4 ꢁ 3.6/76.5 ꢁ 3.8% of capacity retained aer 20 that treated cells continue the process of proliferation or does
cycles, for TCCF1, TCCF2 and TCCF3, respectively.
Fig. 8C–F show charge/discharge proles of TCCF samples. The control cells.
charge/discharge proles have similar courses as described In order to investigate the impact of TCCF materials on cell
The discharge curves show a steady proliferation, the cells cultures with 30%, 50% and 80% of cell
not undergo the process leading to decrease of living cells as in
45–48
previously in the literature.
decline in electrode potential during reduction for every examined conuences were employed. The results presented in Fig. 9A
+
sample. One can see a short plateau emerging below 1.00 V (vs. Li / show the diverse inuence of the tested materials on cell
0
Li ), which quickly fades into another decline up to ca. 0.50 V (vs. proliferation. Considering cell cultures with 50% and 80% of
+
0
Li /Li ). This process is a result of SEI formation and reactions with conuence, the number of living cells was on the same level as
+
0
+
CF groups present in TCCs. Below 0.5 V (vs. Li /Li ), insertion of Li
those presented in Fig. 9A, what suggests that samples may assist
ions into the uorinated N–graphyne interlayers starts to take in the proliferation, but only to a limited extent. The most signif-
place. During charge processes, for every examined sample, there icant impact of investigated materials on cell growth was observed
is almost steady increase of electrode potential in the entire range for cell cultures at 30% conuence level seen as six-fold (TCCF1)
+
0
of 0.01–3.00 V (vs. Li /Li ), with no distinct plateaus, which is and four-fold (TCC) increase in cell densities. The biological
consistent with previous reports on alkali ion storage in graphene- importance of uorinated carbonaceous materials lies in highly
4
5,47
like structures.
polar C–F bonds being expected to induce biological responses.
The introduction of CF groups reduces surface energy of the
modied materials leading to a change in wetting features which
results in better cell adhesion and proliferation. The reason of
low cell proliferation grown on TCCF2 may be related to decrease
Biocompatibility
49
Biological tests, cell viability and antibacterial activity, were
conducted in order to determine the biocompatibility of pris-
tine TCC and TCCFs. Using Escherichia coli strain, no antibac-
terial properties of the materials have been found (Fig. S10†),
however, it seems that cell viability is signicantly affected
during 24 h treatment. Fig. 9 presents the results of human
embryonic kidney (HEK) cell viability tests. The obtained results
prove that all investigated materials did not show cell toxicity
within considered concentration range. On the contrary, the
treated cells exhibited higher number of living cells in a range
of overall number of CF bonds and appearance of –CF –CF– and
2
–
CF –CF – units on the surface.
2 2
The CF bonds are characterised by a smaller dipole moment
2
than C–F bonds, thus, smaller value of the total electric eld
acting on the surface. Weak electrostatic interactions and
a lower polarity of CF groups lead to poorer cell adhesion and,
2
consequently, much weaker cell proliferation comparing to
highly polar CF bonds. In the case of pristine TCC samples the
high cell proliferation may result from electrostatic interactions
between oxygenated functional groups of TCC and fetal bovine
1
03–133% for the most of the samples compared to the data
from control untreated HEK cell culture. It turns out that
sample concentration had some effect on cell viability, e.g. the
cell viability has been progressively increasing reaching
serum used in a cell cultures as proteins contained in the serum
49,50
directly affect cell adhesion and their morphology.
Fig. 9C
shows micrographs of cell cultures treated with investigated
materials. In comparison to round shaped control cells, those
grown on uorinated samples are elongated. The latter feature
is directly related to electrostatic interactions occurring at the
50
interface of cell and uorinated N–graphynes.
Experimental
TCC synthesis
N–graphyne was produced in 3-step reaction shown in Scheme
. In rst step ZnCl@trimethylsilylacetylene complex was syn-
thesised and coupled with tribromobenzene in presence of
Pd(PPh as a catalyst. Obtained tris[(trimethylsilyl)ethynyl]
1
3 4
)
benzene was deprotected using 1 M TBAF, vacuum dried and
ꢀ
recrystallised in tubular furnace at 400 C under nitrogen
atmosphere. Received white needle-shaped crystals of 1,3,5-TEB
were nally used in cross-coupling reaction with cyanuric
chloride. The received product was washed with 5% HCl, Milli-
Q water, ethanol, and acetone.
Fig. 9 Cell viability investigated on: (A) confluent cells; (B) cells with
30%, 50% and 80% of confluence; (C) photos of growing cells taken for
0% of confluence.
3
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TCC uorination
Electrode preparation
Three batches of solid TCC equal in mass (150 mg) were TCCF samples were rstly ground with Vulcan XC72R (Cabot)
uorinated by adding of XeF onto TCC/CH Cl (dichloro- conductive carbon in an agate mortar for 20 minutes. Then, the

2
2
2
methane) frozen mixture in a weight ratio varying from 1.5 up solid mixture was transferred to a conical ask, 5 wt% poly-
to 10. Reaction mixtures were slowly warmed to ambient vinilidene uoride (PVDF, Alfa Aesar) solution in N-methyl-
temperature resulting in three uorinated TCCs with pyrrolidone (Sigma-Aldrich) was added dropwise and the
increasing uorine content: TCCF1 (ratio 1.5), TCCF
2
(ratio received suspension was stirred on a magnetic stirrer for the
6
.7), and TCCF3 (ratio 10). Direct reaction between the TCC next 4 hours. So prepared slurry was then cast onto a copper foil
ꢀ
and XeF without the presence of CH Cl should be avoided!! by a doctor blade technique, preliminarily dried at 55 C in air,
such attempt resulted in the violent explosion inside the dry- and vacuum dried at 120 C overnight. Round, 9 mm in diam-
2
2
2
ꢀ
box. Detailed description of these experiments is available in eter, electrodes where then cut, pressed on the hydraulic press
ꢀ
ESI le.†
at 6 t for 1 minute, weighted, dried under vacuum at 120 C
overnight and transferred to argon lled glove-box (MBraun) for
the cell assembly. The obtained electrode composition was
8
: 1 : 1 (wt.) TCCF : Vulcan : PVDF.
Physicochemical characterisation
The crystals of 1,3,5-TEB were investigated by single crystal
XRD at 130(2) K on a Bruker D8 Venture Photon II diffrac-
Electrochemical measurements
tometer equipped with a TRIUMPH monochromator and Prepared electrodes were assembled into three-electrode
Swagelok® system, with working electrode made of TCCF,
ꢀ
a MoK
a
ne focus sealed tube (l ¼ 0.71073 A). A total of 1608
frames were collected with Bruker APEX3 program [S1]. The both counter and reference electrodes made of metallic lithium
frames were integrated with the Bruker SAINT soware (Sigma-Aldrich) and Celgard® 2325 separator soaked in elec-
package [S2] using a narrow-frame algorithm. Morphology of trolyte solution of 1 M LiPF in ethylene carbonate/dimethyl
6
pristine and uorinated N–graphyne samples were investi- carbonate (1 : 1, v/v). Galvanostatic charge/discharge cycling
gated by transmission electron microscopy (TEM), energy- was performed on multichannel battery tester ATLAS 1741
+
0
dispersive X-ray spectroscopy (EDX) and selected area elec- (Sollich) between 0.01 and 3.00 V (vs. Li /Li ) at room temper-
tron diffraction (SAED) using Thermo Scientic TALOS F200X ature. The cells were preliminarily discharged at current rate of
ꢃ1
microscope, working with electron excitation energy of 200 400 mA g and then charged/discharged for 20 consecutive
keV. Prior the tests, powdered samples were ultrasonically cycles at the same current rate.
dispersed in acetone and transferred onto a 200-mesh
carbon-coated copper grid (Electron Microscopy Science, Biological test
USA). Elemental composition and functionalities of the dis-
The cell viability was performed on HEK293 cells (human
cussed materials were investigated by X-ray photoelectron
embryonic kidney) using the CellTiter Blue Reagent (CTB,
spectroscopy (XPS) recorded on Kratos Axis Supra spectrom-
Promega, Poland) and antibacterial activity tests were carried
eter, equipped with a monochromatic Al Ka radiation source
out on Escherichia coli microorganisms using agar disk-
(
1486.7 eV) operating at 150 W. The instrument work func-
diffusion method.
tion was calibrated to give a BE of 84.0 ꢁ 0.1 eV for the 4f7/2
line of metallic gold and the spectrometer dispersion was
adjusted to give a BE of 932.62 eV for the Cu 2p3/2 line of
Computations
metallic copper. Fourier transform infrared spectroscopy (FT- DFT calculations of electronic structure were conducted with
IR) characterisation was performed with Bruker Vertex 80 the Gaussian 16 soware and using the hybrid B3LYP func-
1
3
spectrophotometer using a KBr pellets. Solid-state C and tional calculations and Def2SVP basis set.
1
9
F NMR spectra were collected with Agilent 700 MHz spec-
Further details regarding material's synthesis and applied
trometer at room temperature using 3.2 mm HXY triple- measurements methodology is included in ESI le.†
channel probe under MAS rate of 20 kHz. Raman spectra
were measured on a Horiba T64000 spectrometer using a 20ꢄ
Conclusions
objective lens and a laser excitation at 514.5 nm. XRD
patterns were recorded by Panalytical X'Pert Pro diffractom- The present work focuses on synthesis, modication and
ꢀ
ꢀ
eter with a 2q range of 5–90 with 0.1 step. UV-vis absorption investigation of new N–graphyne material prepared via sol-
spectra of ethanol dispersions of investigated materials were vothermal reaction of 1,3,5-triethynylbenzene with cyanuric
recorded on a Shimadzu UV-1800 spectrophotometer at room chloride. The received N–graphyne was further modied by
temperature. Electrical impedance spectroscopy (EIS) uorination carried out at ambient conditions using xenon
measurements were carried out using a Solartron 1260A diuoride as uorinating agent. Detailed spectral analysis
Frequency Response Analyser equipped with 1296A dielectric showed the evolution of CF bonds nature when different
interface and coupled with IMPED CELL sample holder. EIS amounts of XeF were used upon uorination, starting from
2
7
spectra were collected within the frequency range of 10 to isolated CF groups through CF]CF or –CF]CH– units and
ꢃ2
1
0
Hz and AC amplitude of 10–1000 mV.
CF
2
–CF, –CF
2
–CH
2
– ending on PTFE-like linkers. Despite the
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evolution of CF bonds, the semi-ionic –CF]CF– units remained
dominant for all investigated uorinated samples.
The diversity of CF bonds has a direct impact on physico-
chemical, electronic or electrical properties. The presence of
9 M. Kurban, Optik, 2018, 172, 295.
10 X. Wang, H. R. Harris, K. Bouldin, H. Temkin,
S. Gangopadhyay, M. D. Strathman and M. West, J. Appl.
Phys., 2000, 87, 621.
semi-ion bonds translates directly into the electrical properties 11 M. Adamska and U. Narkiewicz, J. Fluorine Chem., 2017, 200,
of the materials tested. Fluorinated N–graphyne can stimulate 179.
cells to grow. Interestingly, it seems that the type of CF groups 12 W. Zhang, P. Bonnet, M. Dubois, C. P. Ewels, K. Guerin,
have an inuence on electrochemical properties. In our case,
the increase in the share of CF –CF groups have contributed to
2
E. Petit, J. Y. Mevellec, L. Vidal, D. A. Ivanov and
A. Hamwi, Chem. Mater., 2012, 24, 1744.
2
2
a decrease in the capacity of Li-ion batteries.
13 J. Szala-Bilnik, M. F. Costa Gomes and A. A. H. Padua, J. Phys.
Chem. C, 2016, 120, 19396.
Concluding, results presented in this study proved that

uorination of N–graphynes is an effective way to receive 14 I. P. Asanov, L. G. Bulusheva, M. Dubois, N. F. Yudanov,
versatile materials with desired properties potentially appli-
cable in many eld of science and industry.
A. V. Alexeev, T. L. Makarova and A. V. Okotrub, Carbon,
2013, 59, 518.
15 D. D. Chronopoulos, A. Bakandritsos, M. Pykal, R. Zboril and
M. Otyepka, Appl. Mater. Today, 2017, 9, 60.
Conflicts of interest
16 F.-G. Zhao, G. Zhao, X.-H. Liu, C.-W. Ge, J.-T. Wang, B.-L. Li,
Q.-G. Wang, W.-S. Li and Q.-Y. Chen, J. Mater. Chem. A, 2014,
There are no conicts to declare.
2
, 8782.
7 W. Feng, P. Long, Y. Feng and Y. Li, Adv. Sci., 2016, 3,
500413.
1
Acknowledgements
1
This research has been nanced from the Sonata Bis project 18 X. Shen, J. He, K. Wang, X. Li, X. Wang, Z. Yang, N. Wang,
(
(
2016/22/E/ST5/00529) operated by the National Science Centre
NCN). A. Filip would like to thank the National Science Centre 19 W. Xiao, H. Kang, Y. Lin, M. Liang, J. Li, F. Huang, Q. Feng,
Y. Zheng and Z. Huang, RSC Adv., 2019, 9, 18377.
0696). K. J. Fijałkowski acknowledges The National Centre 20 G. Liu, Fluorination of Alkenes and Alkynes for Preparing
Y. Zhang and C. Huang, ChemSusChem, 2019, 12, 1342.
for nancial support within Sonata project (2017/26/D/NZ4/
0
for Research and Development (TANGO2/340584/NCBR/2017)
for nancial support M. K. and B. H. acknowledge The
Alkyl Fluorides, in Fluorination. Synthetic Organouorine
Chemistry, ed. J. Hu and T. Umemoto, Springer, Singapore,
2018.
National
Centre
for
Research
and
Development
(
TECHMATSTRATEG1/347431/14/NCBR/2018) for nancial 21 H.-C. Weiss, D. Bl ¨a ser, R. Boese, B. M. Doughan and
support. Zoran Mazej acknowledges the Slovenian Research M. M. Haley, ChemComm, 1997, 18, 1703.
Agency for nancial support within Research Program P1-0045 22 Z. H. Hei, G. L. Song, C.-Y. Zhao, W. Fan and Mu-H. Huang,
Inorganic Chemistry and Technology. Spectral measurements RSC Adv., 2016, 6, 92443.
were conducted on Center for Preclinical Research and Tech- 23 L. Wachowski, J. W. Sobczak and M. Hofman, Appl. Surf. Sci.,
nology (CePT) infrastructure nanced by the European Union—
2007, 253, 4456.
the European Regional Development Fund within Operational 24 M. Seredych, A. Szczurek, V. Fierro, A. Celzard and
Program “Innovative Economy” for 2007–2013 POIG.02.02.00- T. J. Bandosz, ACS Catal., 2016, 6, 5618.
4-024/08-00. DFT calculations were performed at the Wro- 25 G. Nanse, E. Papirer, P. Fioux, F. Moguet and A. Tressaud,
1
claw Centre for Networking and Supercomputing. We thank
Carbon, 1997, 35, 175.
prof. M. Mazur (CNBCh UW) for enabling photoluminescence 26 X. Wang, Y. Dai, J. Gao, J. Huang, B. Li, C. Fan, J. Yang and
measurements.
X. Liu, ACS Appl. Mater. Interfaces, 2013, 5, 8294.
27 I. P. Asanov, L. G. Bulusheva, M. Dubois, N. F. Yudanov,
A. V. Alexeev, T. L. Makarova and A. V. Okotrub, Carbon,
Notes and references
2013, 59, 518.
1
R. Baughman, H. Eckhardt and M. Kertesz, J. Chem. Phys., 28 R. R. Nair, W. Ren, R. Jalil, I. Riaz, V. G. Kravets, L. Britnell,
1
987, 87, 6687.
P. Blake, F. Schedin, A. S. Mayorov, S. Yuan, M. I. Katsnelson,
H.-M. Cheng, W. Strupinski, L. G. Bulusheva, A. V. Okotrub,
I. V. Grigorieva, A. N. Grigorenko, K. S. Novoselov and
A. K. Geim, Small, 2010, 6, 2877.
2
3
M. Inagaki and F. Y. Kang, J. Mater. Chem. A, 2014, 2, 13193.
C. Xie, N. Wang, X. Li, G. Xu and C. Huang, Chem.–Eur. J.,
2020, 26, 569.
4
5
6
Y. Song, X. Li, Z. Yang, J. Wang, C. Liu, C. Xie, H. Wang and 29 A. Ferrari and D. M. Basko, Nat. Nanotechnol., 2013, 8, 235.
C. Huang, Chem. Commun., 2019, 55, 6571.
30 J. D. Bernal, Proc. R. Soc. Edinburgh, 1924, 106, 749.
T. Chen, W. Q. Li, X. J. Chen, Y. Z. Guo, W. B. Hu, W. J. Hu, 31 V. Caldas, F. G. Morin and G. R. Brown, Magn. Reson. Chem.,
Y. A. Liu, H. Yang and K. Wen, Chem.–Eur. J., 2020, 26, 2269. 1994, 32, 72.
C. Yang, Y. Li, Y. Chen, Q. Li, L. Wu and X. Cui, Small, 2019, 32 J. Giraudet, M. Dubois, K. Guerin, J. P. Pinheiro, A. Hamwi,
1
5, 1804710.
W. E. E. Stone, P. Pirotte and F. Masin, J. Solid State Chem.,
2005, 178, 1262.
7
8
I. Muz and M. Kurban, J. Alloys Compd., 2020, 842, 155983.
I. Muz and M. Kurban, J. Alloys Compd., 2019, 802, 25.
40028 | RSC Adv., 2020, 10, 40019–40029
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3
3 D. Schwarz, Y. Noda, J. Klouda, K. Schwarzov ´a -Peckov ´a , 42 Y. V. Fedoseeva, L. G. Bulusheva, A. V. Okotrub, D. V. Vyalikh
J. Tar ´a bek, J. Ryb ´a cek, J. Janou ˇs ek, F. Simon,
and A. Fonseca, J. Chem. Phys., 2010, 111, 224706.
M. V. Opanasenko, J. Cejka, A. Acharjya, J. Schmidt, 43 K. J. Fijalkowski, R. Jurczakowski, W. Ko ˙z mi n´ ski and
S. Selve, V. Reiter-Scherer, N. Severin, J. P. Rabe, W. Grochala, Phys. Chem. Chem. Phys., 2012, 14, 5778–5784.
P. Ecorchard, J. He, M. Polozij, P. Nachtigall and 44 K. J. Fijalkowski, R. Jurczakowski, PL Pat., 221643, 2016; EU
M. J. Bojdys, Adv. Mater., 2017, 29, 1703399.
Pat., 2788745, 2016; US Pat., 9651595, 2017; JP Pat., 6219831,
34 Z. Yang, N. Wang, J. He, K. Wang, X. Li, X. Shen, X. Wang,
2017.
Q. Lv, M. Zhang, T. Jiu, Z. Hou and Ch. Huang, Carbon, 45 H. An, Y. Li, Y. Feng, Y. Cao, C. Cao, P. Long, S. Li and
2018, 137, 442.
W. Feng, ChemComm, 2018, 54, 2727.
3
3
3
5 https://gaussian.com/citation/.
6 A. D. Becke, J. Chem. Phys., 1993, 98, 5648.
7 F. Weigend and R. Ahlrichs, Phys. Chem. Chem. Phys., 2005,
46 Z. Yang, X. Shen, N. Wang, J. He, X. Li, X. Wang, Z. Hou,
K. Wang, J. Gao, T. Jiu and C. Huang, ACS Appl. Mater.
Interfaces, 2019, 11, 2608.
7
, 3297.
47 Z. Xing, Z. Ju, Y. Zhao, J. Wan, Y. Zhu, Y. Qiang and Y. Qian,
Sci. Rep., 2016, 6, 1.
48 S. Zhang, J. He, J. Zheng, C. Huang, Q. Lv, K. Wang, N. Wang
and Z. Lan, J. Mater. Chem. A, 2017, 5, 2045.
3
3
8 Z. Feng, Y. Li, Y. Tang, W. Chen, R. Li, Y. Ma and X. Dai, J.
Mater. Sci., 2020, 55, 8220.
9 K.-J. Jeon, Z. Lee, E. Pollak, L. Moreschini, § A. Bostwick,
C.-M. Park, R. Mendelsberg, V. Radmilovic, R. Kostecki, 49 W. C. Lee, C. H. Y. X. Lim, H. Shi, L. A. L. Tang, Y. Wang,
T. J. Richardson and E. Rotenberg, ACS Nano, 2011, 5, 1042. C. T. Lim and K. P. Loh, ACS Nano, 2011, 5, 7334.
0 D. K. Samarakoon, Z. Chen, C. Nicolas and X.-Q. Wang, 50 Y. Wang, W. C. Lee, K. K. Manga, P. K. Ang, J. Lu, Y. P. Liu,
4
4
Small, 2010, 6, 2885.
C. T. Lim and K. P. Loh, Adv. Mater., 2012, 24, 4285.
1 L. G. Bulusheva, A. V. Okotrub and O. V. Boltalina, J. Phys.
Chem. A, 1999, 103, 9921.
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