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X-RAY PHOTOELECTRON INVESTIGATION OF CARBON CLUSTER SYSTEMS OBTAINED BY LOW-ENERGETIC SYNTHESIS
L.G. MAKAROVA, I.N. SHABANOVA, V.I. KODOLOV, A.P. KUZNETSOV, R. SZARGAN*, K.H. HALLMEIER*
The Udmurt State University, Udniurt Scientific Center, Ural Branch of RAS, Russia, Izhevsk
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, Leipzig University, Germany, Leipzig
ABSTRACT. The results of investigations of carbon cluster systems obtained by the method of low-energetic synthesis from polycyclic aromatic hydrocarbons in active media are presented. The investigations were carried out by the method of X-ray photoelectron spectroscopy. The dependence of C-C bonds forming from the content of initial mixture components, in particular anthracene and metal chloride was investigated by X-ray photoelectron spectra. We chose elements of third period: Mn, Co and Ni as the metal.
INTRODUCTION
The cluster systems became the subject of the intensive studies because of their unique physical properties at the last time. Metal-carbon tubules investigations are of great interest for some ten years. It's know that tubules can be obtained by methods of carbon electrodes destruction in an electric arc in presence of fine metal particles or by the destruction of carbon electrodes by the electrolysis of salt melts [1-3]. The possible mechanisms of tubules formation from aromatic hydrocarbons were proposed in [4].
In this paper X-ray photoelectron spectra of inner levels of systems obtained from anthracene - NaCl - A1C13 - MeCh mixtures were studied. In the early investigations we observed X-ray photoelectron spectra of tubules obtained with the different contents of 3d-metal chlorides. Therefore the dependence of C-C bonds forming from initial components in mixture in particular anthracene and metal chloride was analyzed.
EXPERIMENTAL
The investigations were carried out on X-ray photoelectron magnetic spectrometer with the resolution of 0,1 eV with AlKa-radiation [5-6]. To avoid the influence of charge effects [7] the aluminum foil was set on the X-ray radiation way. By the X-ray radiation of foil the additional electrons were emitted which neutralize the surface positive charge. The absence of the charging effects was controlled by Cls, Ols lines. The spectra shift was not observed.
In this paper we investigated the metal-carbon tubules obtained by the method of low-energetic synthesis from polycyclic aromatic hydrocarbons in active media of lamellar
XMMMHECKAfl <t>H3HKA M ME30CK0riMR Tom 3, N9 1
structure, which was the melts of salts under the influence of temperature. The time of synthesis was three hours [8]. Anthracene was used as a polyaromatic compound. Eutectic melts of aluminum and sodium chlorides with chlorides of manganese, cobalt and nickel were used as active media. The choice of these metal chlorides was limited for their stimulating function in reaction of dehydropolycondensation, in results which the metal-carbon tubules were formed as seen in the paper [4].
RESULTS AND THEIR DISCUSSION
The XPS Cls spectra of tubules, obtained at anthracene and nickel chloride combination with different contents of the initial substances are given on Fig.l. In dependence on nickel chloride contents the percentage composition of C-C and hydrocarbon bonds changes (Table 1). Comparing the spectra on Fig.l one can note that at the increase of nickel chloride contents in mixture from 1 to 2 mole increase the number of C-C bonds from 49,1 % to 72,3% and the number of hydrocarbon bonds decreases up to 15,4%. The carbide bonds forming are observed (4,6%). The further increase of nickel chloride (Fig.lc) does not lead to the increase of C-C bonds. At 3 mole contents of NiCb the number of C-C bonds is 59,8%, C-H bonds are 12,2%, because of a great number nickel ions the number of carbide bonds increases (-21,9%). This fact correlates with the size decrease of the obtained tubules [9].
The XPS Cls spectra of metal-carbon tubules obtained by the mixing of anthracene, cobalt chloride and fine particles of nickel (the correlation of anthracene and cobalt chloride is 1:1) (Fig.2a), and tubules obtained from the mixture of anthracene and cobalt chloride (1:3) (Fig.2c). Cls spectrum consist of four compounds at the binding energies 283, 284, 285 and 286 eV corresponding to Me-C-C, C-C, C-H and C-0 bonds [10]. Their percentage contents is given in Table 1. The Me-C-C bonds forming is possible due to nickel atoms presence in mixture. One can notice that at the increase of C0CI2 contents three times the number increase of the graphite-like bonds from 28% to 76,7% occurs.
The XPS Cls spectra of tubulenes, obtained by the mixture of anthracene and MnCl2, the correlation of which is 1:1 (a), 1:2 (b) and 1:3 (c) are given in Fig.3. The spectra have a complex shape and consist of some compounds, corresponding to C-C, C-H and C-0 bonds. Besides them there is a compound, corresponding to Me-C-C bond in spectrum (b). The data on their percentage contents also are given in Table 1.
The qualitative dependence of the relation of C-C and C-H bonds on chloride contents of 3d-metal is given on Fig.4. Curve 1 corresponds to the dependence for nickel chloride, curve 2 - for cobalt chloride, curve 3 - for manganese chloride. Apparently, such a behavior of the curves one can explain by the ability of 3d-metals atoms to form stable chemical bonds with chlorine. As the localization of the electron density near by the atoms of 3d-metals decreases in Ni-Co-Mn row, and the interaction energy of metal-chlorine increases, then the dependence in Fig.4 behaves differently. In the case of nickel chloride the saturation is
XMMH4ECKAH OM3MKA M ME30CK0I1MR Tom 3, № 1
31
L.G. MAKAROVA, I.N. SHABANOVA, V.I. KODOLOV, A.P. KUZNETSOV, R. SZARGAN,
K.H. HALLMEIER
282 284 286 Binding energy (eV)
Fig.l. The XPS spectra of tubules Cls-line, obtained by the mixture of anthracene and NiCh with different containing of the initial substances: a) 1:1; b) 1:2; c) 1:3
32
XMMMMECKAfl OM3MKA H ME30CK0riMfl. Tom 3, Ns 1
I-1—r
1 I I i r
278 280 282 284 286 288 Binding energy (eV)
290 292
Fig.2. The XPS spectra of tubules Cls-line, obtained by the mixture of anthracene and CoCl2 with different containing of the initial substances: a) 1:1; b) 1:2; c) 1:3
XHMMHECKAfl OM3MKA M ME30CK0nMH. Tom 3, № 1
33
L.G. MAKAROVA, I.N. SHABANOVA, V.l. KODOLOV, A.P. KUZNETSOV, R. SZARGAN,
K.H. HALLMEIER
278 280 282 284 286 288 290 Binding energy (eV)
Fig.3. The XPS spectra of tubules Cls-line, obtained by the mixture of anthracene and MnCh with different containing of the initial substances: a) 1:1; b) 1:2; c) 1:3
observed at 2 mole, in the case of cobalt chloride a great increase of C-C bonds number is observed, but the curve does not reach the saturation, and in the case of manganese chloride a slow increase of lc_cjlc_„ ratio is observed. Different position of the initial points (Fig.4) is connected with different abilities of oxidation ions of the studied 3d-metals. The obtained regularities contribute to the new directions development in tubules synthesis with the unique properties.
34
xmmmmeckafl &m3hka m me30ck0nhr tom 3, № 1
7 l<-</l(-ll 6 —
0 12 3
MeCl2. моль
Fig.4. Forming dependence of C-C bonds on metal-chloride containing: 1 - NiCl2; 2 - CoCl2; 3 - MnCl2
CONCLUSION
A quantitative dependence of the number of C-C bonds on MeCl2 - containing in the samples with different contents of metal-chloride is present. The transitional metals of the third period: manganese, cobalt, nickel were chosen as metals. The following conclusion was made, based on the presented results:
1. The containing increase of the initial substances (MeCl2) leads to the increase of C-C bonds;
2. In dependence on the filling degree of 3d-electron shell of the transitional metals atoms the saturation in C-C bond forming takes place at different metal-chloride containing in the mixture. The less 3d-shell of metal filling is in Ni-Co-Mn row, the more number of metal-chloride is necessary to put into mixture for metal-carbon-containing tubules forming.
ХИМИЧЕСКАЯ ФИЗИКА И МЕЗОСКОПИЯ. Том 3, № 1
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