Study of the conditions of formation of spectral and absorbption multidimensional images of motor fuels and liquid mineral technical oils

Effect of experimental conditions on the possibility of formation of multidimensional images of motor fuels and liquid mineral technical oils used for the classification and identification of these samples by the method of pattern recognition is studied. Transmission spectra are considered as primary images of the studied samples. Multidimensional statistical analysis of the results of spectroscopic measurements is performed by principal component analysis. A noticeable increase in the separation of spectroscopic images on the statistical plane in the optimization of the spectral range of the primary image and the thickness of the absorbing layer is shown.     

On the Possibilities of Multidimensional Equidistant Absorption Spectroscopy in a Wide Frequency Range in Studies of Fractions of Thermal Distillation of Oil

Optics and Spectroscopy - The features and possibilities of absorption molecular spectroscopy of complex mixtures of organic compounds have been studied by the example of fractions of thermal...     

The role of acidity profile in the nanotubular growth of polyaniline

Conditions of polyaniline (PANI) nanotubes preparation were analyzed. Aniline was oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. There are two subsequent oxidation steps and the products were collected after each of them. At pH > 3, neutral aniline molecules are oxidized to non-conducting aniline oligomers. These produce templates for the subsequent growth of PANI nanotubes, which takes place preferably at pH 2–3. At pH < 2, granular morphology of the conducting PANI is obtained. High final acidity of the medium should be avoided in the preparation of nanotubes, e.g., by reducing the amount of sulfuric acid which is a by-product. Reduction of the peroxydisulfate-to-aniline mole ratio was tested for this purpose in the present study. Lowering of the reaction temperature from 20°C to −4°C had a positive effect on the formation of nanotubes.     

The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes

Polyaniline (PANI) nanotubes were prepared by the oxidation of aniline in solutions of acetic or succinic acid, and subsequently carbonized in a nitrogen atmosphere during thermogravimetric analysis running up to 830 °C. The nanotubular morphology of PANI was preserved after carbonization. The molecular structure of the original PANI and of the carbonized products has been analyzed by FTIR and Raman spectroscopies. Carbonized PANI nanotubes contained about 8 wt.% of nitrogen. The molecular structure, thermal stability, and morphology of carbonized PANI nanotubes were compared with the properties of commercial multi-walled carbon nanotubes.     

Study of conditions of the formation of multidimensional spectroscopic fluorescence images of motor fuels and liquid mineral technical oils

Conditions and specific features of the use of fluorescence spectra for the formation of multidimensional spectroscopic images of liquid mineral technical oils and petrols are studied. Possibilities of the identification of corresponding samples by the method of pattern recognition using multifactor statistical processing of multidimensional analytical signals on the basis of principal component analysis are considered. The optimum conditions of the formation of spectroscopic fluorescence images are found.     

Chemical oxidative polymerization of aminodiphenylamines

The course of oxidation of 4-aminodiphenylamine with ammonium peroxydisulfate in an acidic aqueous ethanol solution as well as the properties of the oxidation products were compared with those of 2-aminodiphenylamine. Semiconducting oligomers of 4-aminodiphenylamine and nonconducting oligomers of 2-aminodiphenylamine of weight-average molecular weights 3700 and 1900, respectively, were prepared by using an oxidant to monomer molar ratio of 1.25. When this ratio was changed from 0.5 to 2.5, the highest conductivity of oxidation products of 4-aminodiphenylamine, 2.5 x 10 (-4) S cm (-1), was reached at the molar ratio [oxidant]/[monomer] = 1.5. The mechanism of the oxidative polymerization of aminodiphenylamines has been theoretically studied by the AM1 and MNDO-PM3 semiempirical quantum chemical methods combined with the MM2 molecular mechanics force-field method and conductor-like screening model of solvation. Molecular orbital calculations revealed the prevalence of N prim-C10 coupling reaction of 4-aminodiphenylamine, while N prim-C5 is the main coupling mode between 2-aminodiphenylamine units. FTIR and Raman spectroscopic studies confirm the prevalent formation of linear N prim-C10 coupled oligomers of 4-aminodiphenylamine and suggest branching and formation of phenazine structural units in the oligomers of 2-aminodiphenylamine. The results are discussed with respect to the oxidation of aniline with ammonium peroxydisulfate, leading to polyaniline, in which 4-aminodiphenylamine is the major dimer and 2-aminodiphenylamine is the most important dimeric intermediate byproduct.     

Evolution of polyaniline nanotubes: the oxidation of aniline in water

The course of aniline oxidation with ammonium peroxydisulfate in aqueous solutions has been investigated. The reaction was terminated at various times and the intermediates collected. Besides the precipitates, the films deposited in situ on silicon windows have also been studied. The kinetic course of polymerization is controlled by the acidity level, which changes during the polymerization from pH 8 to a final value close to pH 1. It has two distinct exothermic phases. Gel-permeation chromatography indicates that aniline oligomers are produced at first at high pH, while polyaniline follows after the pH becomes sufficiently low. The growth of polyaniline nanotubes was observed by optical microscopy and confirmed by electron microscopy. The molecular structure of the reaction intermediates was studied in detail by FTIR spectroscopy. Oxidation products are markedly sulfonated, and they contain phenazine units. Aniline oligomers are more soluble in chloroform than the polymer fraction, which contains nanotubes.