Search results for "Blue"
showing 10 items of 487 documents
Pressure and temperature dependence of the band-gap in CdTe
2003
In this paper we report on isothermal compression measurements (up to 5 GPa and 500 K) of the optical absorption edge of 1 μm epitaxial layers of CdTe growth by metalorganic chemical vapor deposition (MOCVD) on GaS substrates. The isothermal blue shift under pressure of the direct energy gap (Γ v 15 → Γ c 1 ) in the zinc-blende phase is about 7.1 × 10 -2 eV GPa -1 and is found to be independent of temperature within the experimental errors. The isobaric red shift in the stability range of the zinc-blende phase is about -3.76 × 10 -4 eV K -1 . Regarding the phase transitions, no discontinuity in the energy gap has been found in the narrow pressure range where the cinnabar phase can be presen…
Temperature Dependence of Electronic Transitions of Single-Wall Carbon Nanotubes: Observation of an Abrupt Blueshift in Near-Infrared Absorption
2007
Near-infrared (NIR) absorption spectra of single-wall carbon nanotube (SWNT) films are studied between 10 and 293 K. The most prominent effect is the shift of bands with temperature. Some nanotubes show a redshift of transition upon increasing temperature while some show blueshift and others show no shift. The shift is interpreted to originate mainly from the effect of strain induced in the tubes because of interaction with the environment. In particular, at temperatures T = 175−225 K, for some bands, there is an abrupt large blueshift, which is interpreted to originate from interaction of the nanotubes with water. Two models could be considered to explain the effect: (1) strain induced by…
Detection and correction of interferences in spectroscopy techniques
2001
By combining the apparent content curves method and the Youden method, we have developed a strategy for detecting constant and proportional errors in spectroscopy techniques. A method for elimination of spectral interferences (different of blank) is also proposed. To apply of this method there must be a matrix effect that varies with the amount of sample or a simulated matrix effect provided working under different experimental conditions that induce a variation of the analytical signal of the analyte. The proposed procedures have been applied to the determination of methyl orange in presence of phenol red, bromothymol blue and bromocresol purple.
Haloperoxidase Mimicry by CeO2−xNanorods Combats Biofouling
2016
CeO2-x nanorods are functional mimics of natural haloperoxidases. They catalyze the oxidative bromination of phenol red to bromophenol blue and of natural signaling molecules involved in bacterial quorum sensing. Laboratory and field tests with paint formulations containing 2 wt% of CeO2-x nanorods show a reduction in biofouling comparable to Cu2 O, the most typical biocidal pigment.
Recombination luminescence in aluminum nitride ceramics
2013
Photoluminescence (PL) and afterglow luminescence (AGL) produced by UV laser irradiation with varied intensity were studied in AlN ceramics in the 10–300 K temperature range. Luminescence spectra of AlN ceramics contain the UV–blue band built up of two components – the UV (3.18 eV) and Blue (2.58 eV) bands, which are presumably ascribed to recombination luminescence involving oxygen-related centers in the bulk and on the surface of AlN, correspondingly. It was found that position of the emission band maximum of AlN ceramics depends on such factors as excitation density, temperature, and delay time after excitation ceasing – in the case of AGL. In PL spectra, the excitation density growth pr…
Optical properties of ultrathin Al2O3/ZnO nanolaminates
2015
Abstract Because of their high resistance against ultraviolet and high energy particles, ultrathin amorphous nanolaminates can be very attractive for aerospace application. Here we report on the optical and structural properties of ultrathin Al2O3/ZnO nanolaminates deposited by Atomic Layer Deposition. Structural properties of nanolaminates were studied by GIXRD and AFM. Optical characterization was performed by transmittance, spectroscopic ellipsometry and photoluminescence (PL) spectroscopy. Regression analysis of ellipsometric spectra has shown that absorption peak decreases and blue shifted with the decrease of bilayer thickness in the stack. On the basis of the analysis of structural a…
Nature of the blue luminescence bands in PbWO4
1997
Abstract The photoluminescence spectrum of PbWO 4 is composed of blue and green bands, previously attributed to the regular WO 4 group and to the defect-related WO 3 group, respectively. Untill now only green emission was observed in the thermostimulated luminescence (TSL) above 77 K. Investigation of the TSL spectra starting from 20 K indicates that the blue band, being definitely present at least in the 28 K TSL peak, is also due to recombination emission at defect sites.
Vertical stacks of small InAs/GaAs self-assembled dots: resonant and non-resonant excitation
2003
4 páginas, 2 figuras.-- PACS: 78.67.Hc; 73.21.La; 78.55.Cr.-- Proceedings of the International Conference on Superlattices, Nano-structures and Nano-devices ICSNN 2002.
Nonlinear magneto-optical rotation in rubidium vapor excited with blue light
2015
We present experimental and numerical studies of nonlinear magneto-optical rotation (NMOR) in rubidium vapor excited with resonant light tuned to the $5^2\!S_{1/2}\rightarrow 6^2\!P_{1/2}$ absorption line (421~nm). Contrary to the experiments performed to date on the strong $D_1$ or $D_2$ lines, in this case, the spontaneous decay of the excited state $6^2\!P_{1/2}$ may occur via multiple intermediate states, affecting the dynamics, magnitude and other characteristics of NMOR. Comparing the experimental results with the results of modelling based on Auzinsh et al., Phys. Rev. A 80, 1 (2009), we demonstrate that despite the complexity of the structure, NMOR can be adequately described with a…
Laser Speckle Size And Temporal Transfer Function In Human Vision
1988
Using a blue laser stimulus we measured TMTF with speckle sizes of 19.1 µm, 3.3 µm and absence of speckle. Our results indicate, if we compare the TMTF curves obtained for different speckle sizes, a gain of modulation due fundamentally to the presence of the spec kle; in the low frequency region this gain of modulation can be explained in terms of inhibitory effects. On the other hand, we observe by using the diffusion-inhibition model, that the presence of speckle in the test-field produces a delay of 12 ms and a reduction of the height of the response, with respect to that obtained in the uniform test (with absence of speckle).