Quartz from pegmatite mining wastes in North Karelia (Russia) were studied using atomic emission spectroscopy with inductively coupled plasma, IR spectroscopy, and optical and scanning electron microscopy to reveal the main technological characteristics of quartz that determine the possibility of utilizing it as a promising raw material for high-purity quartz concentrate production. It was shown that mineral inclusions in quartz were mainly represented by feldspars, muscovite, calcite, iron oxides, and borosilicate, which was confirmed by the trace element composition of quartz dominated by Al, Ca, K, and Na. Quartz contains OH-complexes associated with structural impurities of Al, Li and B along with molecular water, which was a part of gas-liquid inclusions. A quartz concentrate with a total impurity content of 160 ppm was obtained by unsorted quartz processing that included electromagnetic separation, microwave exposure, and acid pickling. Production of high-purity quartz concentrate with a total impurity content of <50 ppm in quartz grit with a fineness of 0.5-0.1 mm turned out to be difficult because of micron-sized mineral inclusions, gas-liquid inclusions, and structural impurities that were hard to remove during enrichment.

A model of the structure of thermally modified shungite carbon is proposed, which can be used as a container for the production and long-term retention of nanosized particles. Such nanoparticles are characterized by their inherent photoluminescence activity. Since nanosized carbon particles do not enter into chemical interaction with the shungite matrix under normal conditions, their luminescent properties are maintained for a long time. The description of the multilevel structure of shungite carbon by the model of randomly oriented agglomerations of turbostratic stacks of graphene sheets is confirmed by X-ray studies.

The Finback–Warren method is used to determine the quantitative characteristics of the short-range order of thermally modified shungite carbon. The results of spectroscopic studies in the visible spectral region of “shungite carbon–optically active silicon or carbon nanoparticles” compositions are presented. It is shown that shungite samples with nanoparticles encapsulated in pores have photoluminescence activity in the visible region of the spectrum. Stable passivation of the surface of nanoparticles in the shungite matrix pores is observed.

Results of an IR spectroscopic study of the contents of water and hydrogen defects in hydrothermal and pegmatite quartz from quartz-vein deposits in Karelia (northwest Russia) that are considered promising sources of high-purity quartz raw materials are presented. The main amount of water in the analyzed quartz is shown to be in molecular form. OH groups associated with aluminum, lithium, and boron trace elements in the quartz lattice are also identified. Granulated quartz with the lowest contents of molecular water and OH groups is most preferred for use as high-purity quartz raw material.

The dependence of photoluminescent of lithium niobate crystals of different composition and genesis in the near IR- region on stoichiometry, Zn concentration, doping method was observed. It was found that increasing in stoichiometry leaded to decreasing in the photoluminescence. At Zn = 6.5 mol. % in the LiNbO3 crystal an intense emission was observed at 1.45 eV with simultaneous quenching of the NbLi emission. Homogeneous doping method of LiNbO3:Mg,Zn crystal allowed to enhance the luminescence in the region of 1.3–1.5 eV relative to the crystals obtained by direct doping method of the melt.

Фотолюминесценции с поверхности конгруэнтных и близких к стехиометрическому составу кристаллов ниобата лития, полученных по разным технологиям слабо зависит от стехиометрии и технологии выращивания кристаллов и её максимум находится при ~2.8 эВ. Природа центров свечения при 2.776-2.801 и 2.913-2.954 эВ, в основном, связана с излучательной рекомбинацией между двумя электронно-дырочными парами Nb-O’ и Nb-O’’ в кислородно-октаэдрическом кластере NbO6. Слабая люминесценция дефектов с участием NbLi наблюдается в низкоэнергетической области спектра (E<2.5 эВ).

The concentration changes in the photoluminescence spectra of LiNbO3 : Zn crystals (0.004 ÷ 6.5 mol.% ZnO) were studied. It was found that with the increase of zinc concentration from 0.004 to 1.42 mol.% ZnO, the intensity decrease of luminescence bands caused by VLI, NbNb, and NbNb−NbLi defects was observed. As the crystal composition approached the second concentration threshold (≈ 7.0 mol.% ZnO), the luminescent halo shifted by ≈ 0.41 eV to the high-energy region of the spectrum and the intensity of the luminescence centers increased at 2.66 and 2.26 eV. It was caused by the appearance of ZnLi point defects. It was shown that in the LiNbO3 : Zn(4.69 mol.% ZnO) crystal obtained by homogeneous doping technology, there is a greater number of luminescence centers of different origin than in congruent and zinc-doped crystals obtained by direct melt doping technology. In the LiNbO3 : Zn crystal (4.52 mol.% ZnO), the luminescence of the main defects (VLi, NbNb, ZnLi) was quenched by increasing the fraction of nonradiative transitions relative to other LiNbO3 : Zn crystals in the concentration range [ZnO] = 4.46 ÷ 6.50 mol.%.

The results of X-ray studies of samples of purified and thermally modified shungite carbon are presented. The quantitative characteristics of short-range order are determined, and 3D models of regions of short-range ordering are presented. It is found that the structure of these regions can be described by turbostratic models, which are sets of five distorted graphene sheets, disoriented relative to each other, with sizes of 26 × 27 Å. The cluster thickness is 15 Å. The average distance between the sheets is 3.5 Å. As a result of the heat treatment of shungite carbon samples, graphene sheets are exfoliated. The thickness of the clusters forming the structure of regions of short-range ordering decreases to 7 Å.

The concentration changes in the photoluminescence spectra of LiNbO3:Zn crystals (0.004–6.5 mol % ZnO) are investigated. It is observed that, as the zinc concentration increases from 0.004 to 1.42 mol % ZnO, the intensities of the luminescence bands caused by VLi, NbNb, and NbNb–NbLi defects decrease. As the composition of the crystal approaches the second concentration threshold (≈7.0 mol % ZnO), the luminescence halo shifts by ≈0.41 eV towards the high energy range of the spectrum and the intensities of luminescence centers with maxima at 2.66 and 2.26 eV, which are caused by the possible appearance of ZnLi point defects, increase. It is shown that a LiNbO3:Zn crystal (4.69 mol % ZnO) obtained by the t-echnology of homogeneous doping contains a greater number of luminescence centers of different natures than the congruent crystal and zinc-doped crystals obtained by the technology of direct doping of the melt. A Li-NbO3:Zn crystal (4.52 mol % ZnO) exhibits the quenching of main defects (VLi, NbNb, ZnLi) due to an increase in the number of nonradiative transitions as compared to other LiNbO3:Zn crystals in the concentration range [ZnO] = 4.46–6.50 mol %.

The main contribution to the luminescence of LiNbO3 : Zn (0,04 ÷ 2,01 mol. %) at 420 and 440 nm was established to be due to two electro-hole pairs of Nb4+–O-in niobium octahedron. Moreover, the luminescence weakly depends on Li / Nb ratio and Zn concentration. The increase of Zn concentration to 2,01 mol. % ZnO leads to monotonically increasing intensity in long-wave region of the photoluminescent spectra. This fact indicates that there are shallow energy levels near bottom of the conductivity band. Also the features of hydrogen bonds in LiNbO3structure effects on the location of the shallow energy levels as the complex defects caused by OH-group in the structure can contribute to the photoluminescence.

The results of X-ray studies of the structure of components of composite materials based on milled microcrystalline cellulose are presented. The 3D model of the atomic arrangement in the short-range order of amorphous carbon can be described by a mechanical mixture of two types of clusters in the ratio of 1 : 2. One type of clusters is formed by two planar graphene single layers shifted relative to each other and containing vacancies, and the other type is presented by six graphene grids. The cellulose matrix with silicon nanoparticles has a low photoluminescence-signal degradation rate. The introduction of fullerenes into nanomaterial as a third nanofraction, as well as the action of ozone, leads to anomalous luminescence kinetics under UV (ultraviolet) photoexcitation, which can be associated with competing processes of hydrogen and oxygen adsorption on the surface of silicon nanoparticles. A change in the ionic conductivity of the porous cellulose matrix upon exposure to ozone can be used to develop effective ozone detectors. Such a filler as amorphous-crystalline carbon causes not only ionic but also electronic conductivity in the sample; however, the processes of space-charge redistribution remain dependent only on the ion-current component. An increase in the total current passing through the pressed sample eliminates the need for a further increase in the signal in the design of ozone sensors.

A composite has been developed on the basis of nanocrystalline cellulose and silicon nanoparticles, which exhibited more intense photoluminescence in the visible range of the spectrum than did nanoporous silicon. This may be related to the spatial separation of silicon nanoparticles and migration of excitation from their vicinity. The effect of temperature and gas-phase oxidation on the luminescent properties of the material indicates a high stability of the luminescent properties of the composite. Investigation of the charging effect of the nanocomposite allows silicon nanoparticles to be considered as centers of accumulation of the bulk electricity charge.

We have characterized the structure and luminescence properties for two-component material composed of nanocrystalline cellulose and nanocrystalline (less to 100 nm) silicon powder. An efficient and stable photoluminescence of nanocomposite, resistant to the influence of gas-phase oxidants, has been found. The obtained material has electret-like properties and demonstrates the possibility of multiple-recharging in an electric field near 5·103 V/cm at temperatures ranging from −70°C to 100°C. The presence of the electric field, as well as ozone or low-temperature plasma treatment, does not change the luminescence spectrum due to quantum size properties of silicon nanoparticles. We believe that these particles may appear in two states: both embedded in a cellulose matrix and in the form of mechanical mixture.

In this paper, we present a method for growing copper-based nanowires. The method is based on the unusual modification of a halogenated copper surface by exposure to a helium plasma. The nanowires have diameters ranging between 50 and 150 nm and lengths up to 50 microm. They are polycrystalline, and large parts of the wires have a pronounced core-shell structure with a dense shell and less material inside. The wires are grown in a plasma environment at room temperature, and large amounts can be grown in a matter of minutes. The critical process parameters for the growth process are the gas flow and pressure settings, and the impact thereof will be discussed in detail. In order to gain insight in a possible growth mechanism, our observations are compared with literature on the growth of silver whiskers from halogenated silver crystallites. Finally, photoluminescence spectra of the wires are discussed in view of the analytical data about the stoichiometry and structure of the nanowires.

Abstract Luminescence activity and structure of halogen plasma-treated Cu films on Si substrate have been investigated. Peculiar photoluminescence signals in the range of 1.6 – 2.0 eV were detected both at low (from 77 to 15 K), and at room temperature. The observed luminescence peaks are not present for stoichiometric CuCl. The exposure of CuCl- and CuBr-containing layers to helium plasma, with UV-illumination, result in the formation of knots of twisted nanowires on the surface of these layers. These wires don't have luminescent activity. The accelerated degradation of luminescence of these samples in air in the presence of light illumination and ozone treatment was studied.

We have studied in vitro an efficiency of the promising photosensitizer for photodynamic therapy (PDT) on the base of porous silicon (PSi) impregnated with fullerene C-60. It is shown that a low concentration addition of fullerene boosts sharply a cancer cell killing in comparison with the pristine PSi. A dark toxicity of the proposed composite drug for PDT does not exceed that for the pristine PSi as it was revealed for observation period of five days. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim