Search results for " SPECT"
showing 10 items of 11464 documents
Nontemplate Synthesis of CH3NH3PbBr3 Perovskite Nanoparticles
2014
To date, there is no example in the literature of free, nanometer-sized, organolead halide CH3NH3PbBr3 perovskites. We report here the preparation of 6 nm-sized nanoparticles of this type by a simple and fast method based on the use of an ammonium bromide with a medium-sized chain that keeps the nanoparticles dispersed in a wide range of organic solvents. These nanoparticles can be maintained stable in the solid state as well as in concentrated solutions for more than three months, without requiring a mesoporous material. This makes it possible to prepare homogeneous thin films of these nanoparticles by spin-coating on a quartz substrate. Both the colloidal solution and the thin film emit l…
Templated growth of smart coatings: Hybrid chemical vapour deposition of vanadyl acetylacetonate with tetraoctyl ammonium bromide
2009
Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised to produce thin films of vanadium dioxide from vanadyl acetylacetonate. Tetraoctyl ammonium bromide (TOAB) was used in the aerosol precursor solution. The films were analysed by X-ray diffraction, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy. Their optical and thermochromic behaviour was also determined. It was found that the use of TOAB had a templating effect that led to a halving in the particle size and that this consequently led to a significant decrease in the thermochromic transition temperature of the films to 34 8C.
Templated growth of smart nanocomposite thin films: Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition of vanadyl acetylacet…
2009
Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised to produce nanocomposite thin films of gold nanoparticles and vanadium dioxide from vanadyl acetylacetonate and auric acid. The addition of tetraoctyl ammonium bromide (TOAB) to the precursor Solution gave control of the size and distribution of gold nanoparticles in the vanadium oxide matrix. These reactions led to vanadium dioxide films with reduced crystallite sizes and enhanced thermochromic properties. The films were analysed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Their optical and thermochromic behaviour was also determined, This h…
Enhanced organic mass fraction and decreased hygroscopicity of cloud condensation nuclei (CCN) during new particle formation events
2010
In a forested near-urban location in central Germany, the CCN efficiency of particles smaller than 100 nm decreases significantly during periods of new particle formation. This results in an increase of average activation diameters, ranging from 5 to 8% at supersaturations of 0.33% and 0.74%, respectively. At the same time, the organic mass fraction in the sub-100-nm size range increases from approximately 2/3 to 3/4. This provides evidence that secondary organic aerosol (SOA) components are involved in the growth of new particles to larger sizes, and that the reduced CCN efficiency of small particles is caused by the low hygroscopicity of the condensing material. The observed dependence of…
Characterization of Thin Passive Film-Electrolyte Junctions. The Amorphous Semiconductor (a-SC) Schottky Barrier Approach.
2017
A detailed study of the electronic properties of thin (< 20 nm) anodic TiO2 potentiostatically grown on titanium in two different solutions is presented. The results show that the nature of the anodizing solution affects the electronic properties of the anodic film and in particular the density of electronic state (DOS) distribution. Different DOS were derived from the experimental data analyzed according to the theory of amorphous semiconductor (a-SC) Schottky barrier. It is shown that the usual non-linear and frequency dependent Mott-Schottky plots are in agreement with expected theoretical behaviour of a-SC Schottky barrier. It is shown the importance of the DOS distribution in determini…
Amorphous Silicon Nanotubes via Galvanic Displacement Deposition
2013
Amorphous silicon nanotubes were grown in a single step into a polycarbonate membrane by a galvanic displacement reaction conducted in aqueous solution. In order to optimize the process, a specifically designed galvanic cell was used. SEM images, after polycarbonate dissolution, showed interconnected nanotube bundles with an average length of 18 μm and wall thickness of 38 nm.The deposited silicon was revealed by EDS analysis, whilst X-ray diffraction and Raman spectroscopy showed that nanotubes have an amorphous structure. Silicon nanotubes were also characterized by photo-electrochemical measurements that showed n-type conductivity and optical gap of ~1.6 eV. Keywords: Silicon nanotubes, …
Short-range order and luminescence in amorphous silicon oxynitride
2000
Abstract Using Si 2p core-level X-ray photoelectron spectroscopy, we found that the short-range order in amorphous silicon oxynitride (a-SiOxNy) can be quantitatively described by a random bonding model. Results also show that the second and even further neighbours of the Si in the network affect the chemical shifts of the X-ray photoelectron spectra. Cathodoluminescence and photoluminescence of a-SiOxNy with different compositions are also measured. A red band with energies of 1.8–1.9 eV, a blue band with an energy of 2.7 eV and ultraviolet bands with energies of 13.1, 3.4–3.6, 4.4–4.7 and 5.4eV were observed. The 1.8–1.9 eV band is attributed to the O and N atoms with an unpaired electron…
Triterpene saponins from the roots ofAmpelozizyphus amazonicus
1992
A new triterpene saponin was isolated from the roots of Ampelozizyphus amazonicus together with the known 3-O-beta-D-glucopyranosyl-20-O-alpha-L-rhamnopyranosyljujubogenin and the known triterpenes melaleucic acid, 3 beta,27 alpha-dihydroxylup-20(29)-en-28 beta-oic acid, betulinic acid, betulin, lupeol. The structure of this saponin was elucidated as 3-O-[beta-D-glucopyranosyl(1----2)alpha-L-arabinopyranosyl]- 20-O-alpha-L-rhamnopyranosyljujubogenin by spectral analysis and chemical transformations.
Carotenoids of two freshwater amphipod species (Gammarus pulex and G. roeseli) and their common acanthocephalan parasite Polymorphus minutus
2004
Carotenoid compositions of two freshwater Gammarus species (Crustacea: Amphipoda) and of their common acanthocephalan parasite Polymorphus minutus were characterized. The effect of carotenoid uptake by the parasite was addressed by comparing the carotenoid content of uninfected and infected female hosts. Using high-pressure liquid chromatography (HPLC), co-chromatography of reference pigments and electron ionization mass spectrometry of collected HPLC fractions (EI-MS), several xanthophylls and non-polar compounds were identified. Seven kinds of carotenoids, mainly xanthophylls, were identified in gammarids. Astaxanthin was predominant, amounting to 40 wt.% of total carotenoid in both uninf…
Perineural Invasion is a Strong Prognostic Moderator in Ampulla of Vater Carcinoma
2018
Objective Ampulla of Vater carcinoma (AVC) has a broad spectrum of different prognoses. As such, new moderators of survival are urgently needed. We aimed at clarifying the prognostic role of perineural invasion in AVC. Methods Using PubMed and SCOPUS databases, we conducted the first systematic review and meta-analysis on this topic. Results Analyzing 29 articles for a total of 2379 patients, we found that the presence of perineural invasion increased the risk of all-cause mortality more than 2 times (relative risk [RR], 2.07; 95% confidence interval [CI], 1.78-2.42 [P < 0.0001]; hazard ratio [HR], 2.72; 95% CI, 1.86-3.97 [P < 0.0001]), of cancer-specific mortality more than 6 times (…