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Achieving accurate FTIR measurements on high performance bandpass filters
The sources of ordinate error in FTIR spectrometers are reviewed with reference to measuring small out-of-band features in the spectra of bandpass filters. Procedures for identifying instrumental artefacts are described. It is shown that features well below 0.01%T can be measured reliably
Electron beam excitation of plasmonic modes in gold dimers
We report on the first realization of hyperspectral imaging for visualization and excitation of plasmon modes in dimers of 100 nm gold decahedra by a scanning electron beam
Structure and vacancy distribution in copper telluride nanoparticles influence plasmonic activity in the near-infrared
Copper chalcogenides find applications in different domains including photonics, photothermal therapy and photovoltaics. CuTe nanocrystals have been proposed as an alternative to noble metal particles for plasmonics. Although it is known that deviations from stoichiometry are a prerequisite for plasmonic activity in the near-infrared, an accurate description of the material and its (optical) properties is hindered by an insufficient understanding of the atomic structure and the influence of defects, especially for materials in their nanocrystalline form. We demonstrate that the structure of Cu1.5±xTe nanocrystals can be determined using electron diffraction tomography. Real-space high-resolution electron tomography directly reveals the three-dimensional distribution of vacancies in the structure. Through first-principles density functional theory, we furthermore demonstrate that the influence of these vacancies on the optical properties of the nanocrystals is determined. Since our methodology is applicable to a variety of crystalline nanostructured materials, it is expected to provide unique insights concerning structureâproperty correlations
Role of Temperature in the Growth of Silver Nanoparticles Through a Synergetic Reduction Approach
This study presents the role of reaction temperature in the formation and growth of silver nanoparticles through a synergetic reduction approach using two or three reducing agents simultaneously. By this approach, the shape-/size-controlled silver nanoparticles (plates and spheres) can be generated under mild conditions. It was found that the reaction temperature could play a key role in particle growth and shape/size control, especially for silver nanoplates. These nanoplates could exhibit an intensive surface plasmon resonance in the wavelength range of 700â1,400 nm in the UVâvis spectrum depending upon their shapes and sizes, which make them useful for optical applications, such as optical probes, ionic sensing, and biochemical sensors. A detailed analysis conducted in this study clearly shows that the reaction temperature can greatly influence reaction rate, and hence the particle characteristics. The findings would be useful for optimization of experimental parameters for shape-controlled synthesis of other metallic nanoparticles (e.g., Au, Cu, Pt, and Pd) with desirable functional properties
Bioinspired Magneto-optical Bacteria
âTwo-in-oneâ magneto-optical bacteria have been produced using the probiotic Lactobacillus fermentum for the first time. We took advantage of two features of bacteria to synthesize this novel and bifunctional nanostructure: their metal-reducing properties, to produce gold nanoparticles, and their capacity to incorporate iron oxide nanoparticles at their external surface. The magneto-optical bacteria survive the process and behave as a magnet at room temperature.This work was funded by Biosearch S.A. (POSTBIO project-Agency for Innovation and Development of Andalucia IDEA) and by MINECO and FEDER (project CTQ2012-32236)
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. VI. Variability of NGC 3783 from ground-based data
The Seyfert 1 galaxy NGC 3783 was intensely monitored between 1991 December
and 1992 August. We present the results from the ground-based observations in
the optical and near-IR, which complement the data-set from the IUE, discussed
elsewhere. Spectroscopic and photometric data from many observatories were
combined in order to obtain well sampled light curves of the continuum and of
H-Beta. During the campaign the source varied significantly. The light curves
of the optical continuum and of H-Beta are similar to those obtained with the
IUE. The near-IR flux did not vary significantly except for an increase at the
end of the campaign. The optical continuum and the flux of H-Beta lag the UV
continuum by 1 day or less and by 8 days respectively. These results confirm
that the continuum variations are simultaneous or have a very small lag across
the entire UV-optical range, and that the lines of NGC 3783 respond to ionizing
continuum variations with less delay than those of NGC 5548. As in NGC 5548,
the lag of H-Beta is greater than those of the high ionization lines.Comment: 34 pages in LaTeX, 7 postscript figures available on request from
[email protected] or 37907::stirpe, BAP#10-1993-035-OA
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