[en] The tritium resistivity of multiple tritium resistant materials was determined through the technique of trapping the permeating tritium with water. The principle and the arrangement of the technique was described. The results showed that the gas tritium permeability through the different multiple materials ranged from 1/29 - 1/16 relative to the 74 neoprene. Instead of neoprene, these multiple materials could be used for better performance of tritium protective gloves, clothing and other appliances

[en] More recently, Ce³⁺ activated γ-Ca₂SiO₄ has been reported and it shows great potential application as a yellow-emitting phosphor for white LEDs. However, β-Ca₂SiO₄, another known phase of Ca₂SiO₄, doped with Ce³⁺ is not available. It is interesting to know if β-Ca₂SiO₄:Ce³⁺ can also be suitable for white LEDs. For this reason, we synthesized a series of β-Ca₂SiO₄:Ce³⁺ phosphors by solid state reaction. β-Ca₂SiO₄:Ce³⁺ exhibits an intense blue emission band peaked at 425 nm with a bandwidth of 68 nm which is attributed to the typical Ce³⁺ 4f⁰5d¹→4f¹ transitions. The integral intensity of the concentration-optimized β-Ca₂SiO₄:Ce³⁺ can be as high as 71% of the commercial BAM blue phosphor upon 360 nm excitation. The excitation spectra of β-Ca₂SiO₄:Ce³⁺ consist of three broad bands with maxima at 252, 289 and 348 nm , which are ascribed to the 4f¹→4f⁰5d¹ transitions of Ce³⁺. Thermal quenching property of β-Ca₂SiO₄:Ce³⁺ was evaluated and the results show that the integral PL intensity at 150 °C maintains about 93% of that at room temperature. The excellent thermal stability and intense emission upon NUV light excitation suggest that β-Ca₂SiO₄:Ce³⁺ can be used as a potential blue-emitting phosphor for NUV white LEDs. - Highlights: • The photoluminescence properties of β-Ca₂SiO₄:Ce³⁺, Li⁺ were investigated. • It can be efficiently excited by NUV light. • It presents excellent thermal stability. • An intense blue-emitting silicate phosphor for white LEDs was obtained

[en] In this paper, we demonstrate a method to improve the photoluminescence of CaO: Ce³⁺ phosphor and delineate its first use in blue-pumped white LEDs. The results show that the yellow emission of Ce³⁺ is enhanced by a factor of 1.88 by adding Li⁺ into CaO host at 474 nm blue light excitation. On analyzing the diffuse reflection spectra and fluorescence decay curves, we reveal that the photoluminescence enhancement is originated from the rise of absorbance to the excitation photons but not from the improvement of the luminescent efficiency. Li⁺-improved CaO: Ce³⁺ exhibits more red component when it is compared with the commercial Y₃Al₅O₁₂: Ce³⁺ (YAG: Ce³⁺) phosphor, indicating its potential application for high color rendering white LEDs. Thus, a white LED is fabricated by combining blue InGaN LED chip with CaO: Ce³⁺, Li⁺ phosphor and a warm white light with high color rendering index (R_a) of 80, low correlated color temperature (T_c) of 4524 K, and sufficient luminous efficiency of 50 lm W⁻¹ is obtained. -- Highlights: • The photoluminescence of Ce³⁺ in CaO host was enhanced by Li⁺ co-doping. • A CaO: Ce³⁺, Li⁺ based white LED was fabricated for the first time. • An efficient warm white light was obtained. • CaO: Ce³⁺, Li⁺ is expected to be used as a yellow phosphor for blue-pumped white LEDs

[en] Photoluminescence (PL) and time-resolved spectroscopic studies on plasmonically coupled semiconductor nanoparticles (SNPs) have demonstrated the PL quenched and lifetime enhanced of SNPs in the presence of metal nanoparticles (MNPs). The hybrid colloidal CsPbBr₃ perovskite SNPs/Pt MNPs (S-M) structures exhibit novel optical properties due to the synergetic interaction between the individual components. In hybrid S-M nanostructures colloidal chemistry incorporates SNP and MNP into a single unit resulting in the formation of plexciton (or excimon) which has now been established in a series of hybrid structures. The experimental results of femtosecond transient absorption (TA) spectroscopy based on the time-resolved pump−probe confirm the transformation from excitons to plexcitons. It was found that the experimental data can’t be well described by the theory based on conventional Fӧster resonance energy transfer (FRET). The differences between theory and experiment may be due to the missing some PbBr₂ PL peaks, the reason will be revealed further. (paper)

[en] The photoluminescence (PL) behavior of γ-Al₂O₃ nanopowder is studied. Two emission peaks at 343 and 378 nm and a broadband ranging between 400 and 600 nm are observed. The peaks are attributed to F⁺ center, while the broadband is attributed to impurities. It is found that irradiating the sample with intense ultraviolet (UV) light can cause significant decrease in the intensity of the two peaks, but has no effect on the broadband. A simple model is proposed to explain the kinetics of UV irradiation-induced PL degradation

[en] We reported a facile route to fabricate a tin dioxide (SnO_2)-based light-emitting diode (LED) and obtain an electrically pumped band-edge ultraviolet (UV) emission. We first investigated the photoluminescence (PL) properties of the SnO_2 thin films deposited on quartz substrates annealed at various temperatures. It was found that SnO_2 nanocrystals were embedded in the SnO_2 amorphous matrix after annealing at 400 °C to form a SnO_2 nanoparticle/amorphous hybrid film; the band-edge UV emission was observed from the hybrid film due to the hybrid structure breaking the dipole-forbidden rule of bulk SnO_2. This hybrid SnO_2 film was then deposited on a p-type GaN substrate to form a SnO_2 hybrid film-based LED and a band-edge UV electroluminescence (EL) was observed. Our results suggest that this easy and effective approach may find extensive application in the field of optoelectronics, displays and solid-state lighting. (paper)

[en] We report that a band-tail emission at 3.08 eV, lower than near-band-edge energy, is observed in photoluminescence measurements of bulk Na-doped CuAlO_2. The band-tail emission is attributed to Na-related defects. Electronic structure calculations based on the first-principles method demonstrate that the donor-acceptor compensated complex of Na_A_l-2Na_i in Na-doped CuAlO_2 plays a key role in leading to the band-tail emission and bandgap narrowing. Furthermore, Hall effect measurements indicates that the hole concentration in CuAlO_2 is independent on Na doping, which is well understood by the donor-acceptor compensation effect of Na_A_l-2Na_i complex. (paper)

[en] A series of compressively strained AlGaInAs quantum well (QW) structures with different annealing treatment durations at 170 °C were investigated by temperature-dependent photoluminescence (PL). An abnormal S-shaped behavior in emission energy and a non-monotone evolution in spectral band width were observed at low temperature. A significant negative linear correlation between full width at half maximum (FWHM) and emission energy at different test temperature was exhibited in samples with different heat treatment durations. The highly linear relation demonstrated that the dependencies and relationships between PL peak energy and FWHM vs temperature are consistent. The anomalous blue shift and concomitant narrowing of FWHM in AlGaInAs QW were affected by lattice strain fluctuations due to the difference of thermal expansion coefficients between adjacent layers and strong carriers’ localization at low temperature.

[en] The oxidation kinetics of polymer-derived SiAlCN ceramics are determined at 1400 deg. C by measuring oxide-scale thickness as a function of oxidation time. The results reveal that the SiAlCN ceramics possess much better oxidation resistance than polymer-derived SiCN without Al, pure SiC and Si₃N₄. X-ray diffraction studies reveal that the oxide scales consist of cristobalite, plus a small amount of mullite for the sample with high aluminum-content. The reason that the SiAlCNs exhibited better oxidation resistance is discussed

[en] The step energy transfers from Pr³⁺ 4f5d state to Ce³⁺ 5d state followed by energy back transfer from Ce³⁺ 5d state to Pr^{3+ 1}D₂ level are studied. The Ce³⁺→Pr³⁺ energy back transfer upon Pr³⁺ 4f5d excitation is found to be more efficient than the normal Ce³⁺→Pr³⁺ energy transfer upon Ce³⁺ 5d excitation. The efficient energy back transfer is attributed to preferential excitation of the Ce³⁺ ion with an adjacent Pr³⁺ surrounding in Pr³⁺→Ce³⁺ energy transfer of the first step, whereas Ce³⁺ is excited randomly in the normal energy transfer. The efficiencies of Ce³⁺→Pr³⁺ energy back transfer as a function of Ce³⁺ and Pr³⁺ concentration are evaluated, respectively.