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1.
Laxman Singh Ravikant Sharma Narayan Singh Atendra Kumar Dev K Mahato Youngil Lee Mikhael Bechelany KD Mandal 《Progress in Crystal Growth and Characterization of Materials》2021,67(4):100542
This review paper covers the low temperature wet growth of nano-engineered particles of ZnO-based mixed metal oxides, their growth mechanism, and characterization using X-ray diffraction, SEM, TEM and IR, UV–visible, and XPS spectral techniques. Main focus of this article is centered on low temperature semi-wet methods of synthesis that are suitable for large scale production of zinc oxide-based systems mixed with iron oxide, copper oxide, nickel oxide and cobalt oxide. These mixed metal oxides have broad industrial applications as catalyst, semiconductors, adsorbents, superconductors, electro-ceramics, and antifungal agents in addition to extensive applications in medicines. This paper discusses the low-cost and environment friendly synthesis of these mixed metal oxides, measurement of properties and applicability of these materials systems. 相似文献
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Luminescence and thermoluminescence properties of nominally pure LiF and CaWO4 crystals are compared with those of the crystalline system LiF/CaWO4. Evidence is found which clearly indicates that from the various emission bands of CaWO4 crystals only the blue one is of intrinsic nature. Luminescence decay measurements are reported. Within the spectral range of the blue tungstate band in LiF/CaWO4 four different decay times are obtained. This result is interpreted as arising from WO2-4 luminescence centres with different environments in the LiF host. 相似文献
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The blue luminescence of pure and Al-, Au-, Ag-, Cu-, and Mn-doped ZnS crystals has been studied in the temperature range between LNT and RT and for different wavelengths of the exciting UV-light. All investigated crystals emit two blue bands. The energies of the maxima of these emission bands are independent of the temperature. The temperature dependence of the intensity ratio of the two blue luminescence bands can simulate a temperature shift of the blue emission. The experimental results support the assumption of an essentially uniform structure of the luminescence complex responsible for the visible luminescence of pure and doped ZnS phosphors. 相似文献
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Influence of low and high temperature annealing on the blue and green emission bands of ZnS crystals
R. Grasser K. Hermanns A. Scharmann W. Schwedes 《Zeitschrift für Physik B Condensed Matter》1976,24(1):25-32
After annealing at 350 °C, in the luminescence spectra of pure and Cu-doped ZnS crystals a reversible blue-green conversion has been obtained. The blue-green conversion of luminescence is correlated with analogous reversible variations in the optical transmission and thermoluminescence properties. Besides these low temperature results, in the fluorescence spectra of undoped ZnS crystals, which are annealed at 1,000 °C in sealed evacuated quartz ampoules, a reversible blue-blue conversion has been observed. All these effects, induced by distinct heat treatments, seem to be mainly controlled by changes in the structural disorder or/and by the evaporation of lattice atoms from the surface of the crystals.Dedicated to Prof. Dr. Dr. Ing. E.h.W. Hanle on occasion of his 75th birthdayPart of thesis, Gießen 1974 (D26) 相似文献
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We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the
central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density
distribution. 相似文献
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Nadine S Simons-Weidenmaier Maruschka Weber Claudia F Plappert Peter KD Pilz Susanne Schmid 《BMC neuroscience》2006,7(1):38
Background
Short-term habituation of the startle response represents an elementary form of learning in mammals. The underlying mechanism is located within the primary startle pathway, presumably at sensory synapses on giant neurons in the caudal pontine reticular nucleus (PnC). Short trains of action potentials in sensory afferent fibers induce depression of synaptic responses in PnC giant neurons, a phenomenon that has been proposed to be the cellular correlate for short-term habituation. We address here the question whether both this synaptic depression and the short-term habituation of the startle response are localized at the presynaptic terminals of sensory afferents. If this is confirmed, it would imply that these processes take place prior to multimodal signal integration, rather than occurring at postsynaptic sites on PnC giant neurons that directly drive motor neurons. 相似文献8.
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Matthias A. Grasser Tobias Pietsch Jan Blasius Dr. Oldamur Hollóczki Prof. Dr. Eike Brunner Prof. Dr. Thomas Doert Prof. Dr. Michael Ruck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103770
Elemental tellurium readily dissolves in ionic liquids (ILs) based on tetraalkylphosphonium cations even at temperatures below 100 °C. In the case of ILs with acetate, decanoate, or dicyanamide anions, dark red to purple colored solutions form. A study combining NMR, UV-Vis and Raman spectroscopy revealed the formation of tellurium anions (Ten)2− with chain lengths up to at least n=5, which are in dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an ionic liquid reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. Although the spectroscopic detection of tellurium cations in these solutions is difficult, the coexistence of tellurium cations, such as (Te4)2+ and (Te6)4+, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient to stabilize both types of tellurium ions in solution. 相似文献