Search

This work analyzes the crystal structural properties and photoluminescence properties of six Eu2+‐activated thiogallates: CaGa2S4:Eu2+, SrGa2S4:Eu2+, EuGa2S4, BaGa2S4:Eu2+, Sr2Ga2S5:Eu2+, and Eu2Ga2S5. Photoluminescence parameters such as the absorption energy (Eabs), emission energy (Eem), zero‐phonon line energy (E0), Stokes shift (ΔS), and red shift (D) are discussed. This work is the first report on the photoluminescence parameters of these six Eu2+‐activated thiogallates and therefore provides important information about these materials. [ABSTRACT FROM AUTHOR]

The near-IR spectra of thioacetamide were recorded for the investigation of hydrogen bonding between thioacetamide (TA) and N,N-dimethylalkylamides (DMF, OMA, DMP) in chloroform over the range of 5°C to 55°C. The v0 + amide II combination band has been resolved into contributions from monomeric TA, 1:1 hydrogen bonded complex and 1:2 complex by the parameterized matrix modeling method. The association constants

(Ca1‐xEux)Ga2S4 (x = 0.10, 0.40, 0.70, 1.0) phosphors were synthesized from CaS, EuS, and Ga2S3 via a solid‐state reaction, and their crystal structures were investigated by X‐ray diffraction analysis. Cathodoluminescence (CL) spectra of these phosphors under moderate electron‐beam voltages from 4 to 10 kV were investigated to assess their applicability in carbon nanotube field‐emission displays. The wavelength at maximum intensity (λmax) of the CL spectra changed gradually from 557 to 546 nm with increasing europium‐ion mole fraction (x) in the (Ca1‐xEux)Ga2S4 phosphors. These bands were attributed to the transitions from the lowest energy level of the 4f65d1 excited state to the 4f7 (8S7/2) ground state of the Eu2+ ions. The blue shift of this wavelength was interpreted on the basis of the crystal structures of the phosphors. The color of light emitted from the (Ca1‐xEux)Ga2S4 phosphors was confirmed to be tunable. [ABSTRACT FROM AUTHOR]

A new method to synthesize the YVO4:Eu phosphor by reacting a Y(OH)CO3:Eu precursor with NH4VO3 was described. X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and photoluminescence spectroscopy were used to analyze the Y(OH)CO3:Eu precursor and the YVO4:Eu product. The photoluminescence spectrum of the YVO4:Eu product showed a strong and broad absorption peak at approximately 300 nm, which was attributed to charge transfer in the host lattice and the strongest and sharp emission peak at 618 nm due to the5D0→7F2 transition of the Eu3+ activator ion. To find the brightest emission of the YVO4:Eu phosphor, the optimal conditions of the concentration of Eu3+ activator ion in the Y1 − xVO4:xEu composition and calcination temperature were examined. Among the investigated compositions, the Y0.92VO4:0.08Eu phosphor showed the brightest red emission under UV excitation. [ABSTRACT FROM AUTHOR]

We determined the effects of varying the structural parameters of two-dimensional (2D) square lattice SiO2 photonic crystal (PC) arrays on the efficiency of extraction of the photoluminescence (PL) of sputter-deposited Y2O3:Eu3+ thin films, in which the interface between the phosphor layer and the quartz substrate was modified with the 2D SiO2 PC pattern. The structural parameters of the 2D PC pattern were optimized according to their effects on the light extraction efficiency and similar trends were found for both the as-grown and the post-annealed samples; the samples with lattice constants in the range 400-600 nm exhibit the largest enhancement, there is increased enhancement with pattern height increases up to ∼420 nm, and the samples with a filling ratio of ∼0.20 exhibit the maximum enhancement of the extraction efficiency. For 2D PC patterns with a depth of 420 nm, a lattice constant of 600 nm, and a filling ratio of 0.2, the optimum PL extraction efficiencies of as-grown (350 °C) and post-annealed (900 °C) Y2O3:Eu3+ thin-film phosphors were improved by factors of more than 8.6 and 4.8, respectively, with respect to those of flat Y2O3:Eu3+ thin films. We investigated the reasons for this difference between the enhancements of the extraction efficiencies of the as-grown and post-annealed Y2O3:Eu3+ thin films deposited on 2D PC quartz substrates, in order to determine the factors affecting the extraction efficiencies of 2D PC layer assisted thin-film phosphors. [ABSTRACT FROM AUTHOR]

Various morphologies of Cu2S and Cu2MoS4 were synthesized from an octahedral Cu2O template in the presence of various concentrations of sodium molybdate and thioacetamide by carrying out solvothermal reactions in an ethylene glycol solvent. The morphology varied from hollow octahedral Cu2S structures, through small pieces of P‐Cu2MoS4, and finally to thin square‐like plates of I‐Cu2MoS4, depending on the concentrations of sodium molybdate and thioacetamide. The XRD data indicated that the Cu2MoS4 structural phases changed from P4¯2m to I4¯2m the concentrations of sodium molybdate and thioacetamide increased. [ABSTRACT FROM AUTHOR]

The rotational and vibrational quantum state distributions for the H2 products of the H+HR→H2+R reactions (HR=C2H6 and C3H8 ) at 1.6 eV collision energy have been measured using coherent anti-Stokes Raman scattering. Total reaction cross sections have also been determined. For the total cross sections we find 1.5±0.5 Å2 for the ethane reaction and 2.9±0.8 Å2 for the propane reaction. Although several vibrational states are energetically accessible, we observe H2 products only in v’=0 and v’=1, with the majority in the ground vibrational state. The H2 products are on average rotationally cold as well, and 20% or less of the total energy is partitioned to H2 internal energy. However, the quantum state distributions show a positive correlation of H2 product rotational and vibrational energy. That is, the average rotational energy of the H2 in v’=1 is substantially greater than the average rotational energy of the H2 in v’=0. Comparison with state-to-state dynamics results previously obtained for the kinematically and energetically similar H+CD4→HD+CD3 and H+HCl→H2+Cl reactions seems to indicate that this anomalous energy disposal is an intrinsic characteristic of H + alkane hydrogen atom abstraction reactions at high collision energy. We speculate that this anomalous behavior is the result of inelastic encounters between the nascent H2 and alkyl radical products in the reaction exit channel. [ABSTRACT FROM AUTHOR]