A method for the direct identification of organic inclusions in graphite on the basis of field desorption mass spectrometry is proposed, based on the possibility of using a fractured graphite sample as a field emitter. Under such circumstances, the organic inclusions adsorbed on the surface of the microcrystallites of modified graphites may be directly field desorbed and identified by their mass spectra without any pretreatment of the sample. Two differently modified types of graphite were analysed by this method and the nature of the admixtures was established: one sample appeared to contain a mixture of polymethylsiloxanes and the other and blend of dyes. For the latter sample, temperature fractionation of admixed substances was performed and the presence of three individual dyes was established. Such features of field desorption as the production of abundant molecular ions with negligible fragmentation and the possibility of obtaining of mass thermograms greatly facilitate the identification of individual components of mixture inclusions. I N T R O D U C T I O NIn our recent studies' it was shown that on the surface of a broken graphite rod sharp microcrystallites are uncovered, the radius of curvature of which is sufficient for the generation of high electric fields with the strengths ( 109-10'0 Vm-') required for field desorption (FD) or field ionization (FI) of an analyte by the tunneling mechanism* under the conditions of mass spectrometry. Such fractured graphite rods were tried as emitters in conventional FI/FD ion sources and a good-quality FI and F D mass spectra were obtained for a series of organic substances.' Several types of graphite were tested as emitter materials and an interesting peculiarity was observed for some of them, namely the presence of the 'background' spectra characteristic of the graphite sample. The identification of these spectra showed that they pertain to certain organic substances, which may be incorporated into graphite in the course of its manufact ure.On the basis of these observations, a method for the direct identification of organic inclusions in graphite by means of F D mass spectrometry is proposed. EXPERIMENTAL Materials and emitter preparation and structureTwo types of graphite were used, which were manufactured to serve as pencil leads: (I) a rod 0.5 mm in diameter (produced by the Stationery Plant, Kharkov, Ukraine) and (11) a rod 2 mm in diameter from a socalled chemical pencil, to which dyes are added in the course of its fabrication (Sakko and Vanzetti Plant, Leningrad, Russia).The working surface of the FI/FD emitter was prepared by transverse fracture of a graphite rod,' the regular sharp finely dispersed microcrystallites being exposed on the cross-section. A piece of such a graphite rod of appropriate length (4-5 mm) was mechanically fixed in a metal holder and set into the position of a conventional FI/FD emitter in the dedicated ion source.A study of the surface structure of the emitter was performed with the help of scanning electron microscopy with a Tes...
Luminescence and Raman scattering spectroscopy are used to study nonpolymerized and photopolymerized (with 45% and 85% polymerization) fullerene films (0.5μm thick on a Si substrate) at 5 and 297K. The films were polymerized while they were being deposited and irradiated with UV light. The wide-band emission observed at room temperature from a nonpolymerized fullerene film becomes structured at 5K. A short-wavelength band peaking at 695nm appears in the emission. The intensity of this band decreases with polymerization. Analysis of the low-temperature luminescence spectra of fullerene shows that polymerization is accompanied by a shift of the luminescence bands into the red region. Low-temperature investigations revealed lines in the Raman scattering spectrum of an 85% polymerized film which peak at the frequencies 1466 and 1461cm−1. These lines are due to the vibrations of fullerene dimers and a polymerized chain, respectively. Dimers predominate in a film with 45% polymerization in the polymerized phase, while the fraction of dimers in an 85% polymerized film decreases and chain formations predominate.
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