Layer-by-layer assembly of long-afterglow self-supporting thin films with dual-stimuli-responsive phosphorescence and antiforgery applications

The assembly of thin films (TFs) having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors,anti-counterfeiting materials,and information-encryption systems.However,such films are limited compared with their powder and solution counterparts.In this study,by exploiting the self-organization of phosphors in the two-dimensional (2D) galleries between clay nanosheets,we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer (LBL) process.Compared with the pristine powder,the TFs exhibit high polarization and up-conversion room-temperature phosphorescence (RTP),as well as enhanced quantum yields and luminescence lifetimes,allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen.Moreover,modified day-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays.We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic-organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.     

Size dependent ferromagnetism in dodecyl amine capped ZnO nanoparticles

We investigated the size dependent ferromagnetism in dodecyl amine capped zinc oxide nanoparticle. X-ray diffraction and X-ray photoelectron spectroscopy analysis demonstrated that density of oxygen vacancies was enhanced due to an increase in compressive strain concomitant with the decrease in particle size. Magnetic measurements showed increased ferromagnetic ordering in ZnO nanoparticles with reduced particle size. It was also found that the increase in coercive field, saturation magnetization and magnetic hysteresis loop area were invariably associated with increased oxygen defect population. The observed ferromagnetism in organic capped zinc oxide nanocrystals has therefore been assigned to defect induced phenomena. Results of sample characterization using optical absorption spectroscopy, photo luminescence spectroscopy and high resolution transmission electron microscope have also been presented.     

Japanese Evaluated Nuclear Data Library (JENDL)

Three versions of Japanese Evaluated Nuclear Data Library (JENDL) are briefly explained. The first version, JENDL-1, was made aiming mainly at application to fast reactors. The second version, JENDL-2, was built as a bigger general purpose evaluated nuclear data library. It stores nuclear data for 181 nuclides. It has, however, some drawbacks particularly for fusion neutronics calculation. To remove these drawbacks of JENDL-2 and further extend its applicability, the third version, JENDL-3, has now been made. JENDL-3 includes photon-production data for some nuclides, in addition to the data contained in JENDL-2.     

Measurements of Photon Mass Attenuation Coefficients for Ge and BGO Crystals at 10 Me V

The photon mass attenuation coefficients of the important materials for γ-ray detection, Ge and BGO (Bi₄Ge₃O₁₂) crystals, have been measured for 10.0 MeV γ-rays. The measurement system using the laser-Compton backscattering γ-rays and the high-resolution high-energy photon spectrometer has been developed and utilized. The effectiveness of the system achieving the total systematic uncertainties of 0.5% for the measurements of the photon mass attenuation coefficients was demonstrated. It was shown that the measured photon mass attenuation coefficients, 318.1 ± 1.7 [cm²/g] for the Ge crystal and 425.2 ± 2.4 [cm²/g] for the BGO crystal, agree within the achieved experimental uncertainties with the evaluated values including atomic and nuclear processes at 10.0 MeV.     

Determination of diffusion coefficients in film systems on the basis of Fe/Cr and Cu/Cr

This paper presents the results of investigation of condensation stimulated (CSD) and thermal stimulated (TSD) diffusion in nanoscale film systems on the basis of Fe/Cr and Cu/Cr by Auger-electron spectroscopy method. The film systems were built in ultrahigh vacuum. Auger spectrum was traced during condensation after each increase in thickness of 0.5-1 nm or during film systems annealing from 300 to 683 K over 5 h. According to experimental data the concentration profiles were built and the effective coefficients of CSD and TSD were computed by several mathematical methods. The efficiency of these techniques in different cases was analyzed. The most accurate results were obtained with Weeple and Gauss error methods that take into account the thickness of the diffusant source.     

Comprehensive study on structural,thermal, morphological and luminescence (RL,PL, TL) properties of CaLa2(WO4)4: Tb3+, Dy3+ phosphors synthesized via sol-gel method

Tb³⁺/Dy³⁺ co-doped CaLa₂(WO₄)₄ (CLW: Tb³⁺/Dy³⁺) and its derivatives were synthesized by the sol-gel method. The morphology, thermal, structure and luminescent-optical properties the as-prepared light-emitting phosphors were characterized by utilizing scanning electron microscopy (SEM), differential thermal analysis (DTA)-thermogravimetric analysis (TG), X-ray diffraction (XRD) and radioluminescence (RL or X-ray luminescence) - photoluminescence (PL) –thermoluminescence (TL or TSL) - optical absorption spectrometry. The Tb³⁺ and Dy³⁺ ions were singly or doubly doped and the results were examined in detail. Moreover, for these phosphors, the energy transfer mechanisms which depend on RL and PL spectra were determined. The samples excited by X-ray demonstrate characteristic luminescence peaks of Dy³⁺ (422, 480, 575, 663 and 747 nm) and Tb³⁺ (489, 544, 586, 620, 652 and 675 nm). These emissions are similar for RL and PL measurements. It could be said that the energy transfer efficiency of the host material is perfect for rare-earth ions. The synthesized phosphors exhibit various colors from yellow to blue under UV excitation. The optical band gaps of host CLW, CLW: Tb³⁺, CLW: Dy³⁺ and co-doped CLW: Tb³⁺/Dy³⁺ were calculated at values 3.83 eV, 3.44 eV, 3.64 eV and 3.52 eV, respectively. From the results obtained, the CaLa₂(WO₄)₄: Tb³⁺, Dy³⁺phosphors may be one of the potential candidates for light-emitting diode.     

Design modelling and measured performance of the vacuum system of the Diamond Light Source storage ring

A one-dimensional diffusion model of the Diamond Light Source storage ring vacuum system is described and its predictions are compared with actual measured static (without beam) and dynamic (with beam) pressures over more than 2000 A h of beam conditioning at 3 GeV. An average specific thermal outgassing yield of 1·10⁻¹¹ mbar l/(s cm²) during initial beam circulation is obtained, which reduces to 2·10⁻¹² mbar l/(s cm²) after an accumulated beam dose of 1000 A h and an elapsed time of 769 days. In the presence of stored electron beam, the pressure rises as expected due to photon stimulated desorption (PSD). The PSD yield reduces with beam dose according to a (−2/3) power law as was applied in the model. Predicted and measured dynamic pressures generally agree within a factor of 2 over the whole range of beam conditioning dose studied.