Lutetium and yttrium oxides are promising scintillating materials suitable for use in medical planar X-ray imaging and mammography. In this paper the procedure for preparation of europium doped mixed ...lutetium–yttrium oxide nanopowders using polymer complex solution synthesis method is presented. Detailed information on nanopowder phase, morphology and crystallinity are obtained using X-ray powder diffraction, SEM and TEM while optical properties are investigated by photoluminescence and radioluminescence measurements. Constituting nanoparticles are 20–40
nm in size, and have excellent structural ordering in cubic bixbyite-type. Unit cell parameter, ionic coordinates, crystal coherence size and microstrain are determined from Rietveld analysis. All powders show strong Eu
3+-characteristic red emission, with an average
5D
0 emission lifetime of 1.5
ms. Radioluminescence efficiency is about 15% of the commercial micron-sized Gd
2O
2S:Eu
3+ powder while negligible level of afterglow is found.
In this work we explored the possibility of obtaining nanocrystalline (Y
0.5Lu
0.5)
2O
3 powders, doped with europium and co-doped with praseodium, employing polymer complex solution synthesis. ...Polyethylene glycol, with average molecular weight 200, served both as a fuel and dispersing medium for nanocrystals formation. We investigated structure, morphology, luminescence emission and decay characteristics of obtained powders and how different concentrations of Pr co-dopant affect theirs optical characteristics.
Whitening‐dependent changes of fluorescence of extracted human teeth Pereira Sanchez, Natalie; Aleksic, Aleksandar; Dramicanin, Miroslav ...
Journal of esthetic and restorative dentistry,
September/October 2017, 2017-Sep, 2017-09-00, 20170901, Letnik:
29, Številka:
5
Journal Article
Recenzirano
Objective
To evaluate in vitro the fluorescence properties of extracted human teeth whitened with 40% hydrogen peroxide.
Materials and Methods
A total of 28 extracted human teeth were pumiced for 1 ...minute using a low‐speed dental handpiece and a disposable rubber cup. Pre‐whitening fluorescence measurements (T0), maximum excitation (Exmax), maximum emission (Emmax), and maximum intensity (Imax108), were performed using a spectrofluorometer. After T0 measurements, the teeth were whitened using the in‐office method with 40% hydrogen peroxide, three times for 20 minutes. The fluorescence parameters were measured under the same conditions 7 and 14 days after bleaching (T1 and T2, respectively).
Results
Exmax exhibited a broader range 7 days after whitening and decreased after 14 days. The Emmax and Imax108 displayed a narrower range after whitening. The mean Exmax differed significantly between the time points (F = 20.09. P < .001). The corresponding analysis for the mean Emmax differed significantly between the time points (F = 16.69, P < .001). The same was true for the mean Imax108 (F = 9.69, P < .001).
Conclusions
Within the limitations of this study, whitening provoked statistically significant changes in fluorescence of the intact teeth in vitro.
Clinical significance
The appearance of human teeth and dental materials and their changes upon aging and exposure to different agents (staining, whitening) is a topic of great relevance to esthetic dentistry. While some appearance parameters, such as color, translucency, and gloss, have been thoroughly studied, fluorescence and its influence on overall tooth appearance is still not well understood, yet it has influenced the development of fluorescence emitting restorative materials.
Single wall carbon nanotubes (SWCNTs) represent an important group of nanomaterials with attractive electrical, chemical, and mechanical properties. In this work we have investigated the structural, ...optical and electrical properties of single wall carbon nanotube films deposited on copper substrate and then transferred to polymethyl methacrylate (PMMA). The properties of deposited films were varied by changing different parameters: substrate temperature, deposition time and electric field strength. Atomic force microscopy (AFM) has been used to study the deposition process of SWCNT films on copper substrate. AFM analysis has shown that sodium dodecyl sulfate (SDS) micellas were deposited on copper substrate before carbon nanotubes because of their higher mobility. Raman spectroscopy revealed that SWCNTs deposited at elevated temperatures are oxidized. FTIR results showed that COOH groups and Cu2O were generated during electrophoretic process. The SWCNT films were transferred to PMMA substrate and they achieved a sheet resistance of 360 Ω/sq with 79% transparency at 550 nm wavelength and a strong adhesion to the substrate. The main reasons for higher values of sheet resistances of SWCNT thin films compared to those of other authors are oxidation of carbon nanotubes during electrophoresis and the presence of used surfactans in carbon matrix of deposited films.
The results of synthesis and characterization of single wall carbon nanotubes functionalized by hydroxyethyl cellulose have been presented. The properties of pristine and modified single wall carbon ...nanotubes have been compared by different techniques: thermo-gravimetric analysis, Raman spectroscopy, Fourier transform infrared and UV-Vis-NIR spectroscopy. Raman analysis reveals that smaller amount of hydroxyethyl cellulose is required for functionalization of metallic single wall carbon nanotubes compared to semiconducting ones. FTIR analysis has shown the presence of hydroxyethyl groups which is strong evidence for nanotube modification.
PDF
