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Träfflista för sökning "WFRF:(Akhtar A.) srt2:(2005-2009)"

Sökning: WFRF:(Akhtar A.) > (2005-2009)

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1.
  • Teleki, A., et al. (författare)
  • The quality of SiO(2)-coatings on flame-made TiO(2)-based nanoparticles
  • 2008
  • Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 18:30, s. 3547-3555
  • Tidskriftsartikel (refereegranskat)abstract
    • Silica-coated titania nanoparticles are important in sunscreens, UV filters and optical nanocomposites. The surface characteristics (extent of coverage, texture and thickness) of in situ SiO(2)-coated, mostly rutile titania nanoparticles made in one step by flame spray pyrolysis (FSP) were compared to FSP-made mixed (co-oxidized) SiO(2)/TiO(2) ones by transmission electron microscopy (TEM), Raman, FT-IR spectroscopy, electrophoretic mobility and isopropanol chemisorption followed by mass spectroscopy. Increasing the silica content shifted the isoelectric point (IEP) toward that of pure silica for externally mixed SiO(2) and TiO(2), co-oxidized SiO(2)/TiO(2) and low SiO(2) content (< 10 wt%) silicacoated TiO(2) nanoparticles. At higher SiO(2) contents, SiO(2)-coated titania exhibited negative z potentials at all pH values (and thus no IEP) indicating hermetic or complete coverage of the TiO(2) surface by SiO(2) as was confirmed by isopropanol chemisorption. Co-oxidized particles containing segregated TiO(2) and SiO(2) domains exhibited Si-O-Ti and Si-O-Si bonds of higher IR intensity than hermetically-coated TiO(2). The latter exhibited a peak at 1225 cm(-1) attributed to Si-O-Si asymmetric vibrations in contrast to the former.
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2.
  • Widenkvist, Erika, et al. (författare)
  • Intercalation and Ultrasonic Treatment of Graphite : a New Synthetic Route to Graphene
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • We will demonstrate that ultrasonic treatment of a graphite crystal in water can lead to the formation of small graphene-like flakes in solution. The delamination of the graphite can be increased dramatically by intercalation of bromine from a Br2-saturated water solution. After ultrasonic treatment, large amounts of graphene-like flakes with varying thickness are observed in SEM and TEM. They can be adsorbed onto a surface of a suitable substrate by a simple dipping technique. The effect of polar and non-polar solvents as well as adsorption of the graphene on hydrophobic and hydrophilic substrates will be demonstrated and compared. DFT calculations of the intercalation process have been carried out using the SIESTA package and the effect of bromine intercalation on cohesive energy and electronic structure will be discussed and compared with experimental data. Finally, the general approach of using ultrasonic treatment and intercalation as a facile route to graphene synthesis compared to other methods will be discussed.
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