Organoboron nanoparticles: Synthesis, structures, and some physicochemical properties

Abstract

Organoboron nanoparticles synthesized from carborane C2B10H12 by high-temperature pyrolysis of carborane vapor were investigated. The structures, electronic characteristics, and related physicochemical properties were found to depend on the sizes and shapes. The data of quantum chemical calculations performed in the framework of the density functional theory also indicate a relationship between sizes, dimensionalities, and electronic structure of the nanoparticles.

Full text

Russian Chemical Bulletin, International Edition, Vol. 63, No. 8, pp. 1815—1822, August, 2014 1815
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1815—1822, August, 2014.
10665285/14/63081815 © 2014 Springer Science+Business Media, Inc.
Organoboron nanoparticles: synthesis, structures,
and some physicochemical properties*
A. K. Gatin, M. V. Grishin,
N. N. Kolchenko, V. G. Slutskii, V. A. Kharitonov, and B. R. Shub
N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences,
4 ul. Kosygina, 119991 Moscow, Russian Federation.
Fax: +7 (499) 137 7950. Email: grishin@chph.ras.ru
Organoboron nanoparticles synthesized from carborane С
2
В
10
Н
12
by hightemperature pyr
olysis of carborane vapor were investigated. The structures, electronic characteristics, and
related physicochemical properties were found to depend on the sizes and shapes. The data of
quantum chemical calculations performed in the framework of the density functional theory also
indicate a relationship between sizes, dimensionalities, and electronic structure of the nanoparticles.
Key words: carboranes, physical properties, ammonia decomposition.
Increasing interest in organoboron nanoparticles
(OBN) is due to the very wide potential spectrum of their
use. For example, a large cross section of neutron capture
of the B atom provides prospects for applying OBN as
neutron radiation detectors and for conversion of the neu
tron energy to the electrical energy.
1
The sensitivity to
neutron radiation makes it possible to use OBN in anti
cancer therapy.
2
The possibility of the development of
catalysts based on carboranes and OBN is also consid
ered.
3—6
In addition, OBN possess a high energy capacity,
which makes it possible to use them as energyenhancing
additives.
7
The energy capacity and density of the OBN
are similar to the corresponding characteristics of bulky
boron. Similarly to the starting carborane, the OBN are
inert at room temperature and their energy capacity is
independent of the particle size.
At the same time, the OBN are free of several draw
backs of metallic nanoparticles: the energy capacity of the
latter decreases with a decrease in their sizes because of
the oxide present in their composition. The volume frac
tion of the oxide increases with a decrease in the particle
size. The major advantage of the OBN is manifested in the
nanometer range: the energy capacity is independent of
the particle size. The advantage of the OBN over carbo
rane at elevated temperatures is the thermal stability of the
OBN, since they are not evaporated and do not decompose
with the temperature increase up to 1000 K.
The purposes of this work are (1) to describe the con
ditions of OBN synthesis, (2) to study the structures and
electronic characteristics of the synthesized OBN, and (3)
to study the possibility of the OBN (supported on the
graphite surface) to accelerate the ammonia decomposi
tion at elevated temperatures.
Experimental
Synthesis. Organoboron nanoparticles (C
2
B
10
H
4
)
n
were syn
thesized from carborane C
2
B
10
H
12
by the hightemperature
pyrolysis of carborane vapors
7
in a flowtype installation (Fig. 1).
A necessary for the synthesis mixture of carborane vapor with
argon was formed in heated mixer 1. A weighed sample of carbor
ane (400 or 50 mg) was loaded into the mixer. Then air was
pumped out from the mixer, the vessel was filled with argon to
a pressure of 0.2 MPa, and heating was switchedon. Carborane
was completely evaporated on heating to 453 K, and the sub
sequent storage for 2 h provided uniform mixing of carborane
vapor with argon. As a result, a mixture with a total pressure of
0.325 MPa and a volume carborane concentration of 6.35 vol.%
(mixture 1) was formed in the mixer for a sample of 400 mg,
whereas a mixture with a pressure of 0.307 MPa and a carborane
concentration of 0.84 vol.% (mixture 2) was formed in the case
of a weighed sample of 50 mg. Then mixture 1 or 2 was passed
through valve 2 along quartz line 3 through electric furnace 4, in
* Based on the materials of the XXV Conference "Modern
Chemical Physics" (September 20—October 1, 2013, Tuapse).
Fig. 1. Scheme of the flow system for the synthesis of OBN from
carborane vapor: 1, mixer for the formation of a mixture of carb
orane vapor with argon; 2, valve; 3, quartz line; 4, electric
furnace; 5, cooling glass line; 6, filter; 7, tank with filter;
8, rotameter; 9, tank with argon; and 10, valve.
1
2
3
4
5
6
78
9
10
Ar C
2
B
10
H
12

Gatin et al.1816 Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
which pyrolysis of carborane vapor and synthesis of OBN oc
curred. The temperature in the furnace was 1273 or 1373 K for
mixture 1 and 1273 K for mixture 2. The residence time for the
mixtures in the furnace was 0.93 s for 1273 K and 0.08 s for 1373 K.
Under these conditions, the conversion of carborane vapor to
OBN was 90%.
7
After leaving the furnace, a suspension of OBN with argon
and a minor hydrogen admixture was cooled in glass line 5 and
then particles were trapped with filter 6 placed in tank 7. After
passing through the filter and rotameter 8, argon with an admix
ture of the gaseous pyrolysis product was ejected to the atmo
sphere. The synthesis of OBN was carried out under the pressure
almost equal to the atmospheric pressure. Prior to experiments,
all lines were purged with argon from tank 9.
After the completion of each experiment, the synthesized
OBN were collected from the filter and placed in a transmission
electron microscope (TEM). The particle size and mass distri
butions were determined using the ImageJ program.
8,9
Structures and electronic characteristics of the OBN were studied
in a ultrahigh vacuum system (basis pressure in the system
1.5
•10
–12
Pa) with an Omicron scanning tunneling microscope
(STM) (Germany) using the standard topographic and spectro
scopic procedures. Along with the STM, the system includes
Auger and mass spectrometers and facilities for the preparation
of samples and STM tips for experiments.
Tips for STM were prepared from a tungsten wire by electro
chemical etching in 0.1 М KOH. After placing in a ultrahigh
vacuum chamber, the tips were subjected to argon ion bombard
ment (Е = 500—1000 eV, I = 1—1.5 nA) to remove surface
oxide. Further only the tips that make it possible to attain atomic
resolution on highly ordered pyrolytic graphite (HOPG) surface
and reproducible Ulike voltage dependences of the STM nano
contact conductivity, which is typical for tunneling contact of
metals.
For STM studies the OBN nanoparticles were adsorbed on
the HOPG surface from the lyosol. For this purpose OBN (1 mg)
was added to CCl
4
(2 mL), and the suspension was ultrasonicat
ed to decompose agglomerates of the nanoparticles. The lyosol
was supported on the hot HOPG surface (Т = 373 K) using
a micropipette (droplet volume 50
L). This procedure makes it
possible to form a uniform coating consisting mainly of isolated
nanoparticles on the graphite surface.
10
Quantum chemical calculations. Structures of the organo
boron compounds of various stoichiometry were simulated using
the HyperChem program package.
11
The model compounds con
tained the boron—carbon cores C
2
B
10
bound at the dehydro
genated B or C atoms. The maximum number of the boron—carb
on cores in the compound is 21 with the total number of atoms
366. The model of the C
4
B
17
H
18
structure was also constructed
which corresponds to the joining boron—carbon cores of two
molecules using one adjacent plane common for both cores and
formed by three B atoms. It was shown by quantum chemical
methods that these compounds can be stable.
12,13
We calculated
the atomic coordinates and characteristics of the electronic structure
with different numbers and spatial arrangements of the boron—carb
on cores. The calculations were performed using the OpenMX
3.7 program package and resources of the Interdepartmental
Supercomputer Center of the Russian Academy of Sciences
(MBC10P supercomputer).
14
Experiments on ammonia decomposition were carried out at
Т = 300 and 700 K. In both cases, the OBNcoated or non
coated HOPG plate was placed in a rectangular molybdenum
cell with the builtin heater. The total surface area of the cell was
4 cm
2
at the HOPG surface area equal to 0.3 cm
2
. Further the
molybdenum cell with the HOPG plate placed in it will be named
the molybdenum—graphite cell.
Three series of experiments were carried out when working
with ammonia. The first series was carried out at Т = 300 K using
the OBNcontaining molybdenum—graphite cell. In the second
and third series, the temperature of the cell was 700 K. However,
the cell without an OBN coating was used in the second series,
while the third series used the cell after the OBN was support
ed on the HOPG. Ammonia was let in the chamber in the
flow mode to form the pressure Р = 7.5
•10
–9
Pa. The reac
tion products were determined from the data obtained with
a HAL301 mass spectrometer (Great Britain). Mass spectra
were measured after the reaction attained the stationary regime
(in 30 min).
Results and Discussion
Properties of the synthesized nanoparticles. The results
of measurements of sizes of the synthesized nanoparticles
are presented in Table 1. Figure 2, а shows the PEM image
of the OBN synthesized at T = 1273 K and the initial
carborane pressure P
c
= 0.00635 MPa. Figure 2, b shows
the corresponding histogram of the mass particle distribu
tion. The weight average size calculated from the histo
gram for the particles synthesized under the indicated con
ditions was d = 15.3 nm. The weight average sizes of the
OBN synthesized under other experimental conditions
were obtained similarly. It follows from Table 1 that the
synthesized OBN have weight average sizes of 8.3, 10.6,
and 15.3 nm. The weight average particle sizes calculated
by the model
7
for the corresponding experimental condi
tions are also given in Table 1. As can be seen from Table 1,
the experimental values of d exceed the calculated values
by
2.7 times. The processing of the OBN sizes calculated
by the model
7
(corrected to a factor of 2.72) for different
P
c
and T gives
d(nm) = 0.21P
c
(MPa)
0.28
exp[14.6 (kcal)/(RT)]. (1)
The values of d calculated by Eq. (1) for different ex
perimental conditions are also given in Table 1.
Table 1. Experimental and calculated weight average sizes of
OBN (d) synthesized at different temperatures T and pres
sures P
c
T/K P
c
/MPa d/nm
Experi Calculation
7
Calculation
ment by Eq. (1)
1273 0.00635 15.3 5.7 15.5
1273 0.00084 18.3 3.2 18.7
1373 0.00635 10.6 3.7 10.1

Properties of organoboron nanoparticles Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014 1817
As shown earlier,
7
time  necessary for synthesis is
independent of the pressure of carborane vapor and can be
calculated by the formula
(s) = 2.5•10
–15
exp[85.3(kcal)/(RT)].
Structures and electronic characteristics. Figure 3 shows
a nanoparticle and the profile of its surface along the line
indicated in Fig. 3, a. The diameter of a nanoparticle
(10 nm) can be estimated and its balllike shape can be
determined using Fig. 3. The OBN profile has the curve
describing the contour of a nanoparticle with a character
istic size of 10 nm and a height of 7 nm and a pro
nounced fine structure: local maxima 0.5—2 nm in height
remote at a distance of 1.5 nm from each other on the
slopes of the envelope. It is most likely that the fine struc
ture reflects the fact that the OBN contains partially de
hydrogenated carborane molecules with a characteristic
size of
1 nm. Figure 3, с presents the voltampere charac
teristics of the tunneling current in STM obtained by aver
aging of several dependences measured for a nanoparticle
(curve 2) and the region of HOPG without nanoparticles
(curve 1). The curves demonstrate a nearly complete co
incidence in the whole voltage range. The measurements
Fig. 2. TEM image of OBN synthesized at T = 1273 K and initial pressure of carborane P
c
= 0.00635 MPa (frame size 520×520 nm) (a)
and the histogram of the size distribution of OBN (b).
C (wt.%)
40
20
81624d/nm
ab
Fig. 3. Balllike OBN: topographic image (а), surface profile (b), and voltampere dependences of the tunneling current (c); 1, HOPG
and 2, OBN.
19
0
Y/nm
019X/nm
6.0
4.0
2.0
2 4 6 8 10 12 14 X/nm
Z/nm
3
2
1
0
–1
–2
I/nА
–1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 V/V
1
2
a
b
c

Gatin et al.1818 Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
showed that balllike particles explicitly prevail among
the synthesized OBN: their number is 75—80% of the
total number of particles found on the HOPG surface.
The topographic image, surface profile, and voltampere
characteristics for a single OBN and a region of the HOPG
surface are shown in Fig. 4. As can be seen, the nanoparti
cle diameter is
20—22 nm, and the nanoparticle itself has
a lens shape with a height of 14 nm. As in the previous
case, a fine structure is observed on the nanoparticle pro
file (see Fig. 4, b). The voltampere dependences measured
for a nanoparticle (curve 2) and neat graphite surface (curve 1)
are shown in Fig. 4, c. As for a balllike nanoparticle,
these curves almost coincide. The number of OBN of this
type is 15—20% of the total number of nanoparticles. Thus, it
was established that the predominant part of the synthesized
OBN (90—95%) has conductivity of the metallic type.
Nanoparticles of the third type (amorphous) were ob
served on the HOPG surface after OBN supporting. This
nanoparticle is exemplified in Fig. 5. According to the
data of topographic measurements (see Fig. 5, a, b), the
nanoparticle length is
50 nm at a width of 15 nm and
a height of 20 nm. The particles of this type have no earlier
observed fine structure. The voltampere characteristics for
the OBN of this type (see Fig. 5, c, curve 2) and HOPG
(see Fig. 5, c, curve 1) differ substantially: a band gap of
1.6 eV is observed in the first case, while no band gap is
observed in the second case. This indicates the semicon
ductor type of amorphous OBN. The number of these
OBN is <5% of the total number of nanoparticles.
Note that the geometric sizes of the OBN measured by
STM are consistent, on the whole, with the results of
TEM studies of the synthesized OBN.
The published data on the electronic structure of carb
oranes are scarce. The STM voltampere characteristics
previously
15
presented for the C
2
B
10
H
12
carborane films
indicate the metallic type of conductivity. The same
type of conductivity of the carborane films or balllike
and lenslike OBN and the fine structure on the sur
face of these OBN indicate that the most OBN con
sists of mutually linked partially dehydrogenated carborane
molecules retaining the boron—carbon core C
2
B
10
.
It is the structure of OBN which was predicted,
7
indicat
ing that the model proposed
7
for the OBN synthesis
is correct.
The results of measurements of band gaps for boron
carbides of various elemental compositions, from C
4.2
B
10
to C
0.2
B
10
,
16
can be useful for the explanation of the
semiconductor type of amorphous OBN (their number
is <5% of the total number of particles). It was found
that the band gap increased with a decrease in the carbon
content in carbide ranging from 0.77 eV for C
4.2
B
10
to
1.8 eV for C
0.2
B
10
. A band gap of 1.8 eV for carbide
with a small carbon content is close to that measured
in this work (1.6 eV) for amorphous OBN. This in
dicates that amorphous OBN consist of carbonde
pleted products of deep decomposition of carborane
molecules, including the decomposition of their boron—
carbon core.
Fig. 4. Lenslike OBN: topographic image (а), surface profile (b), and voltampere dependences of the tunneling current (c); 1, OBN
and 2, HOPG.
60
0
Y/nm
060X/nm
10
6
2
510152025X/nm
Z/nm
1.5
1.0
0.5
0
–0.5
–1.0
I/nA
–1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 V/V
1
2
a
b
c

Properties of organoboron nanoparticles Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014 1819
The low content of carbon in amorphous OBN means
that the properties of these OBN should be close to those
of bulky boron consisting of icosahedra B
12
connected to
each other. The distinction of the boron icosahedron from
carborane icosahedron C
2
B
10
is that the former has an
unoccupied highest valent orbital, while in the carborane
icosahedron all orbitals are occupied (two C atoms donate
lacking electrons for filling the highest valent level of the
boron icosahedron). Therefore, the band gaps of bulky
boron (
2 eV (see Ref. 17)) and amorphous OBN (1.6 eV)
exceed almost zero band gaps of carboranes and struc
tured (balllike and lenslike) OBN. As a consequence,
the structured OBN demonstrate in experiments the me
tallic type of conductivity, while the amorphous OBN are
semiconductors.
Results of quantum chemical calculations of a С
2
В
10
Н
12
molecule agree with the published data on the interatomic
distances,
18,19
dipole moment, and electronic structure.
20
Similar calculations of the C
4
B
20
H
22
structure, being the
cores of two carborane molecules connected at the B—B,
В—С, and С—С bonds, show a decrease in the difference
in the HOMO and LUMO energies in the considered
nanoparticle by 0.5—0.9 eV compared to the carborane
molecule (paraisomer). The values of the energy gap be
tween the LUMO and HOMO are given in Table 2.
A gap of
5 eV corresponds to the compound of two
molecules with three B—B bonds (C
2
B
10
H
9
)
2
. A similar
addition of carborane molecules to form a linear structure
is accompanied by a gradual decrease in the gap: down to
2.9 eV for the structure containing 20 C
2
B
10
cores.
The electronic structures of quasidimeric and trimer
ic structures built by the attachment of some C
2
B
10
cores
with three or four neighbors to the B—B or B—C bonds,
respectively, were also calculated. The models of the qua
sidimeric and trimeric compounds are shown in Figs 6
and 7, and the values of
E
LUMO—HOMO
calculated for
these models are listed in Table 3.
As a whole, the quantum chemical calculation results
show that an increase in both sizes and dimensionality of
the structures can decrease the energy gap between the
LUMO and HOMO for this class of compounds.
Ammonia decomposition on the OBN films. The topo
graphic image, surface profile, and averaged voltampere
dependences of the tunneling current measured by STM
at various points on the OBN clusters are shown in Fig. 8.
Fig. 5. Amorphous OBN: topographic image (а), surface profile (b), and voltampere dependences of the tunneling current (c);
1, HOPG and 2, OBN.
62
0
Y/nm
062 X/nm
25
20
15
10
5
51015X/nm
Z/nm
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
I/nA
–1.5 –1.0 –0.5 0 0.5 1.0 1.5 V/V
1
2
a
b
c
Table 2. Energy gaps (E
LUMO—HOMO
) for the
carborane monomer and dimer
Isomer E
LUMO—HOMO
/eV
Monomer C
2
B
10
H
12
ortho 6.61
meta 6.78
para 6.89
Dimer (C
2
B
10
H
11
)
2
ortho 6.03
meta 6.24
para 6.35

Gatin et al.1820 Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
It was found that irregular OBN clusters of different sizes
were formed on the HOPG surfaces. Some clusters exist
near structural defects of the graphite support (terrace
boundaries), but the most clusters are located on defect
less regions. The large clusters are multilayer in structure,
and the fine clusters consist of one nanoparticle layer only.
In the limiting case, the cluster contains only one OBN.
The conductivity of the OBN clusters is close to that typi
cal of a single nanoparticle (see Fig. 8, c, curve 1). Howev
er, a band gap is observed for the voltampere dependences
at some points of the surface, which can be explained by
an admixture of boron carbides.
It was found in the first series of experiments (see above)
that at
20 C ammonia did not interact with the OBN.
This is indicated by both the results obtained by mass
spectrometry and topographic and spectroscopic measure
ments in STM. In this series of experiments, the mass
spectra contained only lines of ammonia and water (which
was desorbed from the chamber walls) without any no
ticeable admixtures of molecular nitrogen and hydrogen.
The mass spectra of the reaction products obtained in
experiments with NH
3
on the heating to 700 K of the
molybdenum—graphite cell in the absence (a) and in the
presence of OBN (b) are presented in Fig. 9. As follows
from Fig. 9, a (cell without OBN), the mass spectrum
includes three groups of lines attributed to hydrogen (lines
at m/z = 1, 2), ammonia and water (lines at m/z = 14—19),
and molecular nitrogen (lines at m/z = 26—30 with the
peak at m/z = 28) present in the reaction products. Know
ing the ratio of intensities of the lines at m/z = 17 (ОН)
and m/z = 18 (Н
2
О) for water (23 : 100) and taking into
account the relatively low intensity of the line at m/z = 18,
one can conclude that almost the whole signal at m/z = 17
is due to ammonia. The ratio of signal intensities at m/z = 28
(N
2
+
) and m/z = 17 (NH
3
+
) is 27 : 100. The obtained
mass spectrum shows that ammonia decomposes to hy
drogen and nitrogen on the heated surface of the cell. This
process is catalytic, since molybdenum composing the cell
is known as a catalyst for ammonia decomposition.
21
The mass spectrum of the reaction products in Fig. 9, b
(cell with OBN) exhibits the same three groups of lines as
in Fig. 9, a (cell without OBN). However, the ratio of
intensities of the lines at m/z = 28 and m/z = 17 is already
65 : 100. This means that the decomposition rate of NH
3
molecules increased significantly (by 2.5 times) in the
presence of the OBN. The ability of the OBN (supported
on the graphite surface) to accelerate chemical reactions
exemplified for ammonia decomposition has been estab
lished for the first time.
The voltampere dependences of the tunneling current
measured on the OBN clusters after their interaction with
ammonia at Т = 700 K (see Fig. 8, c, curve 3) did not
experience substantial changes compared to the initial de
pendences (see Fig. 8, c, curve 2), indicating that the elec
tronic structure of the OBN is retained. The STM topo
graphic measurements did not either reveal substantial
changes in the structure and arrangement of the OBN
clusters after their keeping in ammonia at the indicated
temperature.
Fig. 6. Quasidimeric structure containing 16 C
2
B
10
cores.
Note. Figures 6 and 7 are available in full color in the online
version of the journal (http://www.springerlink.com).
Fig. 7. Trimeric structure containing 21 C
2
B
10
cores.
H
B
C
H
B
C
Table 3. Energy gaps (
E
LUMO—HOMO
) for the carb
oranebased structures
Structure E
LUMO—HOMO
/eV
(C
2
B
10
H
9
)
2
4.96
C
4
B
17
H
18
3.31
(C
2
B
10
)
20
H
126
(linear) 2.89
(C
2
B
10
)
16
H
77
(quasidimeric) 3.08
(C
2
B
10
)
21
H
84
(trimeric) 1.38

Properties of organoboron nanoparticles Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014 1821
An analysis of the reaction products of ammonia with
the OBN (supported on the graphite surface) shows that
the route of this reaction differs from that predicted for the
reaction of ammonia with carborane
22
: the interaction of NH
3
and C
2
B
10
H
12
molecules results in the substitution of the
BH group in carborane for the H
–
ion and in the forma
tion of HB(NH
2
)(NH
3
)
+
or (NH
2
)B(NH
2
)(NH
3
)
+
ions
in the bulk, which was not observed in our experiments.
Thus, OBN (C
2
B
10
H
4
)
n
were synthesized by the high
temperature pyrolysis of vapors of carborane C
2
B
10
H
12
.
The structures and electronic characteristics of the OBN
formed by the hightemperature pyrolysis of carborane
С
2
В
10
Н
12
vapor were studied by STM. Three types of OBN
structures were found: balllike (75—80% of the total num
ber), lenslike (15—20%), and amorphous (<5%). The
ball and lenslike OBN are characterized by the metallic
type of conductivity, whereas the amorphous OBN are
semiconducting. The ball and lenslike OBN consist of
partially dehydrogenated carborane molecules, while the
amorphous OBN consist of carbondepleted products of
Fig. 8. OBN coating on the HOPG surface formed for ammonia decomposition: topographic image (а), surface profile (b), and
voltampere dependences of the tunneling current (c) corresponding to a single OBN (1) and OBN cluster before (2) and after keeping
in ammonia (3).
559
0
Y/nm
0 559 X/nm
60
50
40
30
20
100 200 300 400 X/nm
Z/nm
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
I/nA
–1 0 1.0 V/V
a
b
c
1
2
3
Fig. 9. Mass spectra of the gas phase measured in the absence (a) and in the presence of OBN (b).
600000
500000
400000
300000
200000
100000
I (arb. units)
10 20 30 40 50 m/z
a
600000
500000
400000
300000
200000
100000
I (arb. units)
10 20 30 40 50 m/z
b

Gatin et al.1822 Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
carborane decomposition. The coating of the graphite sur
face with the studied OBN results in the acceleration of
ammonia decomposition to hydrogen and nitrogen. The
voltampere dependences of the tunneling current were
measured for single OBN before and after their interaction
with ammonia. The dependences almost coincide, indi
cating that the electronic structure of the OBN is retained.
The quantum chemical calculations were performed
using resources of the Interdepartmental Supercomputer
Center of the Russian Academy of Sciences.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 120300176,
130300391, 140300156, and 140331068).
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Received January 28, 2014;
in revised form February 24, 2014