Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines
The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pres...
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Інститут хімії поверхні ім. О.О. Чуйка НАН України
2002
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| Цитувати: | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines / Yu. Gromovoy, E.V. Basiuk, V.A. Pokrovskiy, A.A. Chuiko // Поверхность. — 2002. — Вип. 7-8. — С. 215-220. — Бібліогр.: 10 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859821750858022912 |
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| author | Gromovoy, Yu. Basiuk, E.V. Pokrovskiy, V.A. Chuiko, A.A. |
| author_facet | Gromovoy, Yu. Basiuk, E.V. Pokrovskiy, V.A. Chuiko, A.A. |
| citation_txt | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines / Yu. Gromovoy, E.V. Basiuk, V.A. Pokrovskiy, A.A. Chuiko // Поверхность. — 2002. — Вип. 7-8. — С. 215-220. — Бібліогр.: 10 назв. — англ. |
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| description | The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pressure and temperature of 160-170ºC. Applicability of temperature-programmed desorption mass spectrometry for chemical characterization of the derivatized SWNTs was analyzed. Heating of the amine-treated SWNTs at temperature >200ºC causes cleavage of alkenes from the amine residues: nonene and pentene are formed in the case of nonylamine and dipentylamine, respectively.
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| first_indexed | 2025-12-07T15:26:00Z |
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215
MASS-SPECTROMETRIC STUDY OF SINGLE-WALLED
CARBON NANOTUBES MODIFIED BY ALIPHATIC AMINES
T.Yu. Gromovoy1, E.V. Basiuk2, V.A. Pokrovskiy1, and A.A. Chuiko1
1Institute of Surface Chemistry, National Academy of Sciences
Gen.Naumov Str. 17, 03680 Kyiv-164, UKRAINE
2Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México
Apdo. Postal 70-543, México, D.F. 04510, MEXICO
Abstract
The gas-phase derivatization procedure was employed for direct (i.e., without
chemical activation of terminal carboxylic groups) amidization of oxidized single-walled
carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment
of SWNTs with amine vapors under reduced pressure and temperature of 160-170ºC.
Applicability of temperature-programmed desorption mass spectrometry for chemical
characterization of the derivatized SWNTs was analyzed. Heating of the amine-treated
SWNTs at temperature >200ºC causes cleavage of alkenes from the amine residues: nonene
and pentene are formed in the case of nonylamine and dipentylamine, respectively.
Introduction
In the studies of interaction of carbon nanotubes (NTs) with organic compounds,
amines gained a special attention [1-3]. In turn, the most extensively explored is the formation
of amide derivatives between carboxylic groups on oxidized NT tips and long-chain
amines [1-3]. The reaction is currently performed through a chemical activation of the
carboxylic groups with thionyl chloride or carbodiimides in an organic solvent medium [1-3].
A decade ago we performed systematic studies on the use of the gas-phase chemical
derivatization for the synthesis of chemically modified silicas, mainly for liquid
chromatography applications [4-6]. However, decreasing the pressure to a moderate vacuum
and, on the other hand, increasing the temperature >150ºC provided efficient formation of the
chemically bonded surface derivatives. In particular, the reaction between silica-bonded
aminoalkyl groups and vaporous carboxylic acids to form surface amides proceeds smoothly
under 150-180ºC without chemical activation of the carboxylic groups.
With the above advantages of the gas-phase derivatization in mind, in the present
study we have attempted to apply this procedure to oxidized SWNTs containing carboxylic
groups on their tips, in other words, to verify whether the amide derivatives can be
synthesized directly according to the following general scheme:
SWNT—COOH + HNR1R2 → SWNT—CO—NR1R2 , (1)
where HNR1R2 is an aliphatic amine. Nonylamine, dipentylamine, ethylenediamine and
propylenediamine (Aldrich), SWNTs from MERC were used.
Experimental
Temperature-programmed desorption mass spectrometry (TPD MS) measurements
were performed using a custom-made system. The system was based on a MX-7304A mass
spectrometer (Sumy, Ukraine) with a mass range of 1-400 Da and sensitivity of 10-8 g.
216
Results and Discussion
Looking for spectroscopic methods which could be more informative for chemical
characterization of SWNTs—amine systems, we tested temperature-programmed desorption
mass spectrometry, which is widely used to study organic groups and molecules on inorganic
adsorbent surfaces [7-9] including carbon materials [10]. The first feature found in the
mass-spectra of SWNTs gas-phase treated with nonylamine is the series of hydrocarbon peaks
appearing starting with temperatures of ca. 200ºC (Fig. 1, a) at m/z 27 (C2H3), 29 (C2H5),
41 (C3H5), 42 (C3H6), 43 (C3H7), 55 (C4H7), 56 (C4H8), 57 (C4H9), 67 (C5H7), 69 (C5H9),
70 (C5H10), 71 (C5H11), 79 (C6H7), 81 (C6H9), 83 (C6H11), 84 (C6H12), 85 (C6H13), 97 (C7H13),
98 (C7H14), and 99 (C7H15). Thermograms (i.e. plots of peak intensities vs. temperature) for all
of these peaks have a similar shape; they pass through a maximum at ca. 325ºC (for example,
Fig. 1, b shows thermograms for selected peaks at m/z 42, 43, 55, 57, and 69), and total
disappearance of the hydrocarbon fragments is observed at ca. 400ºC. No hydrocarbon peaks
were found in TPD mass-spectra of SWNTs without amine treatment, recorded for
comparison under the same conditions, in the same temperature interval. Taking into account
consistence in their behavior, one can conclude on a common origin of the hydrocarbon
fragments. Moreover, by searching for similar mass-spectra we found that both the mass
numbers and peak intensity distribution correspond to nonene. The formation of nonene can
be easily explained by pyrolysis of nonylamide terminal groups in SWNTs according to the
following scheme:
NT—CO—NH—(CH2)8—CH3 → NT—CO—NH2 + H2C=CH— (CH2)6—CH3 (2)
Fig. 1. (a) - TPD mass-spectrum of volatile products evolved at 325ºC from SWNTs
gas-phase treated with nonylamine; (b) - experimental thermograms for selected
hydrocarbon peaks at m/z 42, 43, 55, 57, and 69.
217
Apparently, nonylamine molecules firmly adsorbed by SWNTs decompose in a
similar way, forming nonene and ammonia. The presence of two forms of nonylamine can be
confirmed by the following results. For a detailed analysis of thermal evolution of the
hydrocarbon fragments we selected the peak at m/z 43, as one of the most abundant and
illustrative peaks. According to the analytical procedure described in [9], for this peak we
plotted logarithm of desorption rate k as a function of inverse temperature t=(KT)-1, supposing
first, second and third reaction order (Fig. 2). The dependence appears to be linear for
first-order reaction. The calculated values of activation energy and pre-exponential factor
(E=79.6 kJ mol-1 and k0=105 s-1, respectively) are very low, suggesting existence of activation
energy distribution for the process of destruction of the nonylamine species. An attempt to fit
the dependence observed by rectangular distribution on activation energies [8] gave
unsatisfactory results.
Fig. 2. Logarithm of desorption rate k for three values of reaction order (□ - first order,
à - second order, ○ - third order) as a function of inverse temperature t=(KT)-1,
calculated from Eqns (6), in [9]. Temperature dependence is linear for first-order
reaction; values of activation energy E and pre-exponential factor k0:
E=79.6 kJ mol-1, k0=105 s-1.
The reason becomes clear if to consider shape of the thermodesorption curve (for
m/z 43 as well as for other hydrocarbon peaks): it is noticeably asymmetric. A good
agreement with the experimental curve was obtained for two activation energies, that is
admitting the existence of two types of nonylamine species in SWNTs, with E1=81 and
E2=93.5 kJ mol-1 (Fig. 3). Nonylamine physically adsorbed on SWNTs due to strong
hydrophobic interactions (second thermodesorption maximum at ca. 320ºC and higher
abundance of hydrocarbon decomposition products). TPD—MS method was able to provide a
useful information of interaction of gaseous diphenylamine with oxidized SWNTs. In some
respect, its behavior is similar to that of the nonylamine sample. The mass-spectra (Fig. 4, a;
252ºC as an example) contain a series of peaks due to hydrocarbon fragments, however the
highest mass number detected was equeal to 70. This peak, as well as the peaks at lower m/z,
corresponds to pentene (molecular weight of 70): this identification was done by searching in
the Wiley 138K Mass Spectral Library [11]. The formation of pentene can be explained by
218
thermal decomposition of the dipentylamide groups on the SWNT tips, by analogy with the
previous case (reaction 2):
NT—CO—N[(CH2)4CH3]2 → NT—CO—NH2 + 2H2C=CH—(CH2)2—CH3 (3)
Fig. 3. Experimental thermogram (solid line) for the peak at m/z 43 for SWNTs gas-phase
treated with nonylamine as a superposition of two first-order effects: (a) - E1=81 and
(b) - E2=93.5, k0=105.8 s-1.
Fig. 4. (a) – TPD mass-spectrum of volatile products evolved at 252ºC from SWNTs
gas-phase treated with dipentylamine; (b) - experimental thermograms for
selected hydrocarbon peaks at m/z 42, 55, 56, 57, and 70.
219
Thermodesorption curves (Fig. 4, b) for different hydrocarbon peaks have similar
profiles. However, a big difference between two samples is that the curves are symmetric for
the dipentylamide derivative. Their maxima were found at ca. 250ºC: this approximately
coincides with the first maximum for the nonylamine sample. Evolution of the hydrocarbon
species ceased at <400ºC. Estimation of peak intensities in the mass-spectra (sample size and
detector sensitivity were kept the same in all the experiments) shows that organic contents in
the present cases are lower by 0.5-1 order of magnitude as compared to the nonylamine
sample. This fact agrees well with our supposition on the presence of a large fraction of
physically adsorbed nonylamine in the first sample. Dipentylamine adsorption in a similar
way cannot be completely denied; however fraction of the physisorbed species is
incomparably lower.
Rather surprising was the absence of any hydrocarbon fragments in TPD mass-spectra
of the SWNT samples treated with vaporous ethylenediamine and propylenediamine under the
same (and even more harsh, up to 220ºC) temperature conditions. Chemical inertness of
aliphatic amino groups in these compounds is deemed totally impossible. The only remaining
explanation is that the terminal amide species formed undergo further in situ chemical
transformations and cleave off the SWNT tips. An argument on its favor is the formation of a
colorless sticky (apparently polymeric) substance on the upper, cold wall of the reactor. This
finding is of special interest for us, and will be studied in more detail in the future.
Conclusions
Temperature-programmed desorption mass spectrometry can provide an additional
information on chemical state of amines in SWNTs. Heating of the amine-treated SWNTs at
temperature >200ºC causes cleavage of alkenes from the amine residues: nonene and pentene
form in the case of nonylamine and dipentylamine, respectively. For the short-chain amine
(dipentylamine), only one chemical form was detected, whereas two forms (amide and
physically adsorbed ones) can be distinguished for the SWNTs treated with nonylamine. The
contents of physically adsorbed nonylamine is about one order of magnitude higher than the
amide contents.
References
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7. Gunko V.M. and Pokrovskiy V.A. Temperature-programmed desorption mass
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MASS-SPECTROMETRIC STUDY OF SINGLEWALLED CARBON NANOTUBES MODIFIED BY ALIPHATIC AMINES
Abstract
Introduction
Experimental
Results and Discussion
Conclusions
Temperature-programmed desorption mass spectrometry can provide an additional information on chemical state of amines in SWNTs. Heating of the amine-treated SWNTs at temperature >200ºC causes cleavage of alkenes from the amine residues: nonene and pentene form in the case of nonylamine and dipentylamine, respectively. For the short-chain amine (dipentylamine), only one chemical form was detected, whereas two forms (amide and physically adsorbed ones) can be distinguished for the SWNTs treated with nonylamine. The contents of physically adsorbed nonylamine is about one order of magnitude higher than the amide contents.
References
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| id | nasplib_isofts_kiev_ua-123456789-126367 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | XXXX-0106 |
| language | English |
| last_indexed | 2025-12-07T15:26:00Z |
| publishDate | 2002 |
| publisher | Інститут хімії поверхні ім. О.О. Чуйка НАН України |
| record_format | dspace |
| spelling | Gromovoy, Yu. Basiuk, E.V. Pokrovskiy, V.A. Chuiko, A.A. 2017-11-20T18:56:24Z 2017-11-20T18:56:24Z 2002 Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines / Yu. Gromovoy, E.V. Basiuk, V.A. Pokrovskiy, A.A. Chuiko // Поверхность. — 2002. — Вип. 7-8. — С. 215-220. — Бібліогр.: 10 назв. — англ. XXXX-0106 https://nasplib.isofts.kiev.ua/handle/123456789/126367 The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pressure and temperature of 160-170ºC. Applicability of temperature-programmed desorption mass spectrometry for chemical characterization of the derivatized SWNTs was analyzed. Heating of the amine-treated SWNTs at temperature >200ºC causes cleavage of alkenes from the amine residues: nonene and pentene are formed in the case of nonylamine and dipentylamine, respectively. en Інститут хімії поверхні ім. О.О. Чуйка НАН України Поверхность Surface properties of inorganic materials Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines Article published earlier |
| spellingShingle | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines Gromovoy, Yu. Basiuk, E.V. Pokrovskiy, V.A. Chuiko, A.A. Surface properties of inorganic materials |
| title | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| title_full | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| title_fullStr | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| title_full_unstemmed | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| title_short | Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| title_sort | mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines |
| topic | Surface properties of inorganic materials |
| topic_facet | Surface properties of inorganic materials |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/126367 |
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