Vol 11, No 1-2 (2016)

We studied the size effects in homogeneous Au_n nanoclusters (n = 11–21, 31–37) and a heterogeneous “planar” Au_nH_m nanocluster (n = 13, 31, m = 1–12, 1–6) by computer simulation in the electron density functional approximation. The correlation between the features of size effects on the physicochemical properties of heterogeneous Au_nH_m nanoclusters and a sequence of electronic magic numbers demonstrates a delocalized nature of occupied electronic states with near-Fermi energy.

Much attention is paid to studies of the processes occurring in heterogeneous catalysis with the use of nanomaterials, in particular, photocatalysis. Titanium dioxide and zinc oxide are among the most widespread photocatalysts due to their high chemical stability, suitable band gap, and rather high lifetime of nonequilibrium electron–hole pairs. In order to increase the photocatalytic activity (PCA) of these materials, including the case of a visible light action, various approaches are applied, in particular, the development of a composition material with a metal–semiconductor or semiconductor–semiconductor contact. We have chosen semiconductors of n-type (WO₃) and p-type (CuO) as components of such composites because of their potential positive influence on the PCA of titanium dioxide at the expense of spatial separation of nonequilibrium charge carriers and, respectively, increase in their lifetime. In order for the obtained composites to be commercially valuable, we have chosen a method of synthesis by modifying the ready TiO₂ preparations, including those that are commercially available (Degussa P25). It has been shown that the modification with CuO lowers PCA of titanium dioxide, while the modification with WO₃ enhances it by 25%. It has been demonstrated that WO₃/TiO₂ composite manifests PCA under visible light illumination.

Nanocomposites TiO₂/SiO₂ with photocatalytic and adsorptive properties were prepared by codispersing of η-modification and anatase (commercial Hombifine N) and SiO₂ (opal, granules, ultrafine) in ethanol (or ethanol–water mixture in the presence of chlorophylls or porphyrins) with ultrasonic treatments of the mixture (method 1) and an aqueous solution of KOH with a microwave treatment (method 2), as well as the introduction of SiO₂ in the reaction mixture during the synthesis of TiO₂ by brief hydrolysis of sulfate titanyl (method 3). It was found that the state of titania in the sample (X-ray amorphous or nanocrystalline) and its deposition on SiO₂ nanocomposites depend on the method and the conditions of obtaining. It was established that the photocatalytic activity of nanocomposite TiO₂/SiO₂ (granules) (method 1) photosensitized by coproporphyrin I in the visible range and the photocatalytic activity of nanocomposite TiO₂/SiO₂ (opal) (method 3) in the near UV range exceed activity of the commercial sample of TiSiO₄ by more than 20-fold and ~7-fold, respectively. It was shown that the nanocomposite TiO₂/SiO₂ (opal) significantly reduces the concentration of cations (in particular, Be, Ni, Bi) in the model water systems.

Key results concerning large-scale application of nanomaterials in nuclear engineering are reviewed. The data on redox reactions of uranium and actinides in solutions and solid-phase transformations for the development of modern technologies for fuel reprocessing and handling of alkaline radioactive waste are discussed. The information concerning various methods for treatment of liquid radioactive waste with nanostructured sorption materials (carbon materials included) is also presented.

Hybrid nanosystems (conjugates)—CdS quantum dots with an average diameter of 2.4 nm containing two types of ligands in the organic shell: coordinating (covering) benzyl mercaptan ligand and photoisomerizable styrylquinoline (SQ) ligand, viz., 2-(4-[9-mercaptononoxy]styryl)quinolone—were synthesized in one step by microwave irradiation. The average number of SQ molecules in the hybrid nanosystem shell was found to depend nonlinearly on the relative concentration of this ligand in the starting reaction mixture, the disproportion and cooperative effects being observed upon synthesis. It was shown that, owing to the photoactivity of SQ ligand, the resulting hybrid nanosystems can act as photon switches.

This paper is devoted to a consideration of the possibility to predict the color characteristics of a luminescent video display based on fluorescent polyolefin films containing CdSe/CdS/ZnS quantum dots. It is shown that the use of new colloid semiconductor materials based on CdSe/CdS/ZnS opens up wide prospects for the development of a new generation of luminescent video displays. New methods are developed and existing ones are adapted for the calculation and prediction of the color gamut of luminescent and liquid-crystal (LC)monitors.

This study was carried out in a factory producing multiwalled carbon nanotubes (MWCNTs) by the catalytic chemical vapor deposition method in a pyrolysis reactor. Air samples of the personal breathing areas were collected simultaneously on mixed cellulose ester filters, for analysis by transmission electron s (TEM), and on high-purity quartz filters for thermal-optical analysis of elemental carbon (EC). It is found that the production of MWCNTs is accompanied by the release of the MWCNT structures in the air of different working zones. The concentration of respirable aerosol in the personal breathing areas, averaged over an 8-hour period, ranges from 0.54 to 6.11 μg/m³ based on EC. Airborne MWCNTs were found in the form of agglomerates that range in size from about 1 to 10 μm. These data are consistent with measurements in different plants by two other international groups (from the United States and Sweden) using similar methodology (TEM in combination with EC analysis). In the absence of convincing data on the potential health risks of MWCNTs, and following the principle of reasonable precautions, preventive measures should be taken to minimize exposure to these materials.