Poly(vinyl alcohol) (PVA)-phosphotungstic acid (PTA) nanocomposite films were prepared from aqueous solutions with added ethylene glycol (EG), which is a plasticizer for PVA and contains OH groups, capable of being electron donors in the photoreduction of PTA. Spectroscopic studies have shown that the addition of EG significantly enhances the photochromic properties of the resultant nanocomposites due to photoinduced electron transfer from the organic matrix of the nanocomposite to PTA molecules.

A detailed analysis of the previously discovered effect of the concentration of phosphotungstic acid (PTA) on its reduction within nanocomposite films with poly(vinyl alcohol) (PVA) induced by gamma radiation indicated that the molar absorption coefficient of the maximum of the PTA band due to intervalence charge transfer in reduced PTA heteropolyanions at low PTA concentrations is eight times higher than at high concentrations. Only 20

производится при отсутствии каких-либо объектов в зоне анализа, что позволяет определять диапазон достоверно определяемых

Subject of Research. The paper deals with theoretical justification of moving from an organoleptic analysis of milk quality in accordance with the requirements of the national standard to objective control based on quantitative assessment by an instrumental method. We propose a theoretical model for changes in color of milk reductase sample depending on its bacterial ontamination. Methods. The proposed model was based on the known patterns of the chemical process of resazurin, resofurin and hydroresofurin mutual transformation, as well as the impact of the concentration of coloring matters on the resulting solution color for homogeneous and inhomogeneous media. Real transmission spectra of the mentioned substances were measured for model development. For theoretical model verification, experimental studies of quality changes during the storage of a milk sample, which was delivered to a shop, were carried out by reductase method. The experiment duration was 3 days, until the souring of milk. The milk was stored between the measurements at the temperature of +4 °C. A theoretical dependence of color changes for the reductase sample of milk was built during the experiment taking into account real ransmission spectrum of milk. Real transmission spectra of the reductase sample were measured. The hromaticity coordinates (x, y) of the sample were calculated from the transmission spectra obtained through the modeling and measurement. To visualize the color change of the sample, the color coordinates in the sRGB color space were calculated for the case of a D65 light source, which is equivalent to daylight. Main Results. The simulation results are completely consistent with the results of experimental studies. The discrepancy between the results of theoretical modeling and experimental data does not exceed, on the average, 0.01 for the chromaticity coordinates x and y. The proposed model gives the possibility to calculate the concentration of enzymes for reductase sample with resazurin at any time, and, as a result, determine its color coordinates and color in accordance with the standards of the International Commission on Illumination for transparent and translucent media. Practical Relevance. The obtained temporal dependence of the chromaticity coordinates and the color of the reductase sample with resazurin can be used to control milk quality by spectrophotometric method and the method of technical vision.

Flexible SERS substrates were obtained by the photo-activated synthesis of silver nanoparticles in a thin (10–170 nm) layer of poly(acrylic acid) chemically grafted to the surface of a polypropylene fi lm. The plasmonic absorption and the SERS activity of the substrates were studied as a function of the thickness of the grafted layer for a fixed time of nanoparticle synthesis. The results indicate dense three-dimensional packing of plasmonic nanoparticles in the grafted polymer layer. The substrates have a storage-stable and surface-uniform SERS activity.

Fluorescent silver nanoclusters immobilized on a plastic substrate are obtained by photoinduced template synthesis using polyacrylic acid chemically grafted to the substrate surface as a template. The electronic absorption and fluorescence spectra of nanoclusters are studied depending on the polyacrylic acid grafting density. It is found that the optical absorption and fluorescence intensities of nanoclusters monotonically increase with increasing grafting density. The position and shape of the absorption and emission spectra almost do not change. The higher the polymer template grafting density, the higher the fluorescence stability of samples during storage at room temperature.

AbstractFluorescent silver nanoclusters immobilized on a plastic substrate are obtained by photoinduced template synthesis using polyacrylic acid chemically grafted to the substrate surface as a template. The electronic absorption and fluorescence spectra of nanoclusters are studied depending on the polyacrylic acid grafting density. It is found that the optical absorption and fluorescence intensities of nanoclusters monotonically increase with increasing grafting density. The position and shape of the absorption and emission spectra almost do not change. The higher the polymer template grafting density, the higher the fluorescence stability of samples during storage at room temperature.

A microfiber carboxylic cationite is prepared via the photoinduced polymerization of acrylic acid on the surface of nonwoven polypropylene material. Changes in the amount of the graft polymer (grafting density) and in the strength of hydrogen bonds between its carboxyl groups, depending on the polymerization time, are investigated by attenuated total internal reflectance FTIR spectroscopy. The sorption properties of the obtained ionite in the acidic (COOH) and salt (COONa) forms with respect to Zn2+ ions at various grafting densities are studied. The sorption capacity of the investigated cationite in its salt form is higher than that in the acidic form, and this difference increases quickly with the grafting density. The data of IR spectroscopy showed that this behavior is caused by the formation of stronger hydrogen bonds between COOH groups of the grafted polyacrylic acid, complicating their ionization and, thus, preventing the ion exchange.

Балтийский государственный технический университет "Военмех

Physics, Chemistry and Application of Nanostructures, pp. 327-330 (2017) No AccessFLUORESCENT SILVER NANOCLUSTERS IRREVERSIBLY BOUND TO PLASTIC SUBSTRATESA. A. Gorbachev, T. M. Sheypak, P. P. Pershukevich, and O. N. TretinnikovA. A. GorbachevB. I. Stepanov Institute of Physics NASB, Nezavisimosti Ave. 68, Minsk 220072, Belarus, T. M. SheypakB. I. Stepanov Institute of Physics NASB, Nezavisimosti Ave. 68, Minsk 220072, Belarus, P. P. PershukevichB. I. Stepanov Institute of Physics NASB, Nezavisimosti Ave. 68, Minsk 220072, Belarus, and O. N. TretinnikovB. I. Stepanov Institute of Physics NASB, Nezavisimosti Ave. 68, Minsk 220072, Belarushttps://doi.org/10.1142/9789813224537_0076Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: A method for the preparation of fluorescent Ag nanoclusters (NCs) irreversibly bound to the surface of a plastic substrate is described. It consists in surface functionalization of the plastic substrate with chemically end-grafted poly(acrylic acid) (PAA) followed by photo-activated template synthesis of Ag NCs in the grafted polymer. The surfaceimmobilized Ag NCs show bright visible fluorescence with intensity and wavelength dependent on the surface density of PAA template and on the time of NCs synthesis. FiguresReferencesRelatedDetails Physics, Chemistry and Application of NanostructuresMetrics History PDF download

Subject of Research.The paper deals with the study of a self-regulating radial gas-dynamic bearing. Methodology for its calculation and design is presented. We have developed the modeling methods for the bearing surface rotational segments stable in angle of rotation, load and rotor speed. We have also developed a numerical method for the segment position determining when the zero moments are acting on it and the method of the segment stability analyzing in this position. Main Results. A technique for determining the stable equilibrium position of a segment was described. For different values of the lubricating layer average thickness and the speed of the shaft, the values and direction of the torque on the segment and the resultant forces acting on the segment were determined. The pressure plots in the lubricating layer of the segment were obtained. Parametric dependences of the design characteristics of the bearing on the load on the segment and on the rotational speed of the shaft were defined. Practical Relevance. The developed calculation technique can be used in the design of hybrid air bearings during the selection of the segment rotation axis position. The rotation of the segments enables to extend the range of self-regulation of air bearings and, within certain limits, to parry the overloads that occur on the shaft.

A method for irreversible immobilization of fluorescent silver nanoclusters on a plastic substrate using template synthesis of them in a polymer matrix is proposed and demonstrated. The matrix was produced by surface graftpolymerization, due to which it was covalently bonded to the substrate.

This paper studies terahertz transmission spectra of silicon and erbium silicides which can be used to create uncooled bolometers for terahertz frequency domain.

The photoinduced grafting polymerization of acrylic acid onto the surface of a polypropylene film under the action of radiation with a wavelength of 365 nm and an intensity of 8–193 mW/cm2 emitted by high-power UV light-emitting diodes is studied. Grafting is performed from a thin layer of the aqueous solution of the monomer onto the surface containing a photoinitiator (benzophenone) deposited from a solution in a volatile solvent. The amount of graft polymer is determined with the use of ATR FTIR spectroscopy. At an intensity of UV radiation of 193 mW/cm2, the time of attainment of grafting-polymerization saturation is decreased by a factor of 6 relative to this time at an intensity of 8 mW/cm2, typical for emitters based on mercury lamps. The rate of grafting polymerization in the studied UV-radiation-intensity range grows in proportion to the square root of intensity.

Photoinduced graft-polymerization of acrylic acid on the surface of polyethylene and polypropylene films containing a photoinitiator pre-adsorbed from a thin layer of non-de-aerated aqueous monomer solution was investigated. Data about the monomer conversion and grafting depth as functions of the UV irradiation time and polymer nature were obtained using IR-ATR spectroscopy.

This paper discusses the fundamental structural features of ranging optoelectronic systems with a conjugate matrix analysis field that is invariant to unrecorded rotations of the elements and units. (C) 2007 Optical Society of America.