Color and Luminescence stability of selected dental materials in vitro

To study luminescence, reflectance, and color stability of dental composites and ceramics. Materials and Methods: IPS e.max, IPS Classic, Gradia, and Sinfony materials were tested, both unpolished (as-cast) and polished specimens. Coffee, tea, red wine, and distilled water (control) were used as staining drinks. Disk-shaped specimens were soaked in the staining drinks for up to 5 days. Color was measured by a colorimeter. Fluorescence was recorded using a spectrofluorometer, in the front-face geometry. Time-resolved fluorescence spectra were recorded using a laser nanosecond spectrofluorometer. Results: The exposure of the examined dental materials to staining drinks caused changes in color of the composites and ceramics, with the polished specimens exhibiting significantly lower color changes as compared to unpolished specimens. Composites exhibited lower color stability as compared to ceramic materials. Water also caused perceptible color changes in most materials. The materials tested demonstrated significantly different initial luminescence intensities. Upon exposure to staining drinks, luminescence became weaker by up to 40%, dependent on the drink and the material. Time-resolved luminescence spectra exhibited some red shift of the emission band at longer times, with the lifetimes in the range of tens of nanoseconds. Conclusions: Unpolished specimens with a more developed surface have lower color stability. Specimens stored in water develop some changes in their visual appearance. The presently proposed methods are effective in evaluating the luminescence of dental materials. Luminescence needs to be tested in addition to color, as the two characteristics are uncorrelated. It is important to further improve the color and luminescence stability of dental materials

TiO2 thin film synthesis from complex precursors by CVD, its physical and photocatalytic properties

Photocatalytic TiO2 films on glass and quartz plates were obtained by the chemical vapour deposition using Ti(dpm)(2)(Opr(i))(2) complex compound (CC-CVD method) in a standard vacuum apparatus at 1.2-2.0 x 10(-4) mbar. The substrate temperature was stabilised in the range of 450-600 degreesC. The growth rate varied from several nanometres to several dozen of nanometres per minute. Structural information on TiO2 thin films was obtained from synchrotron radiation experiments. High-resolution grazing incidence X-ray diffraction (GIXRD) experiments were performed at the high-resolution powder diffractometer at the DESY/HASYLAB beamline B2 (Hamburg, Germany). Thin films deposited on either single-crystal Si wafers or on amorphous quartz substrates were analysed. The photocatalytic activity of the TiO2 thin films was studied using a photocatalytic reactor. The fungicide Fenarimol was chosen as chemical indicator and its degradation kinetics was followed by High-Performance Liquid Chromatography (HPLC)

Temperature dependence of the spin relaxation time of Fe3O4 and hemozoin superparamagnetic nanocrystals

We report experimental temperature and concentration dependences of the natural spin relaxation time of superparamagnetic Fe3O4 and hemozoin nanocrystals. We recorded the H-1 NMR spectrum of 0.5% benzene dissolved in CS2 in function of superparamagnetic particle concentration and temperature, interpreting the 7.261 +/- 0.002 ppm beniene line broadening. Our model for the line broadening includes natural, hyperfine magnetic dipole-dipole, and contact hyperfine contributions. The latter arises due to excharige interaction between benzene molecules and suspended nanoparticles. Estimated frequency of fluctuation in the 1 cm(3) sample volume is in the 10(7) Hz scale. Estimated natural electron spin-lattice relaxation frequencies of the superparamagnetic nanocrystals using frequency of fluctuations, and developed theoretical model applied to analysis of experimental data are in good agreement between each other. Thus the presently developed approach may be used to study fluctuations and natural spin-lattice relaxation frequencies in different media. Published by Elsevier B.V.NASA EPSCoR grant PR NASA EPSCoR (NASA) [NNX13AB22A]info:eu-repo/semantics/publishedVersio