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Luminous properties play an essential role in phosphor-converted white light-emitting diodes for high-quality illumination, where the self-reducing behavior of doped activators and their excellent thermal stability have received significant attention. Here, we prepared NaY9Si6O26:Mn2+ red phosphors by a high-temperature solid-state reaction method, which achieved self-reduction of Mn4+ → Mn2+ and excellent thermal stability (luminous intensity at 420 K is 98% of that at room temperature) under ambient conditions. First-principles calculations and X-ray photoelectron spectroscopy elucidated a self-reduction mechanism from Mn4+ to Mn2+. The defect types were calculated in conjunction with thermoluminescence, verifying that the low thermal quenching properties originated from the transfer of electrons from the defect energy level to the Mn2+ excited state center induced by the cationic vacancy defect, which suppressed the luminescence loss from thermal quenching. In this work, the effect of defects on luminescence properties is highlighted and the further exploration of defect control is stimulated, opening up a new avenue for new types of highly thermally stable materials. [ABSTRACT FROM AUTHOR]

A series of Ce-doped YAG-Al2O3 eutectics were grown by the micro-pulling-down (μ-PD) method, for the purpose of high power white light emitting diodes. The eutectic structure was investigated. A calibrated integrating sphere spectrometer setup was used to measure the white LED properties of eutectic samples. The CIE color coordinates can be regulated easily by altering the Ce3+ doping concentration and sample thickness of the Ce:YAG-Al2O3 eutectics. A 1 W white LED device based on Ce:YAG-Al2O3 eutectics at a rated current of 350 mA emitted a bright white light with a CIE coordinate of (0.319, 0.334), a luminous efficacy of 83.0 lm W−1 and a Duv value of 0.003. The results showed that Ce:YAG-Al2O3 eutectics have better luminescence properties than commercial powder phosphors at a high current density. [ABSTRACT FROM AUTHOR]

Hybrid Bi12TiO20/Bi4Ti3O12 composites with different Bi : Ti molar ratios were successfully fabricated using a one-step solid-state calcination. These samples were characterized using X-ray diffraction, specific surface area analysis, scanning electron microscopy, high-resolution microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence analyses, and photocurrent and electrochemical impedance spectroscopy. Some specified techniques were also used to investigate the photocatalytic properties and the formation of radical species under UV-vis irradiation. The composites provide an efficient pathway for photo-produced electrons and holes to diffuse and transfer to the exterior of the particles for photodegradation, because of the good contact between hybrid Bi12TiO20 and Bi4Ti3O12. Therefore, the hybrid Bi12TiO20/Bi4Ti3O12 can prolong the carrier lifetime as compared to any individual material (Bi12TiO20 or Bi4Ti3O12). In particular, the hybrid Bi12TiO20/Bi4Ti3O12 composite with a Bi : Ti ratio of 12 : 6 had the longest photo-generated carrier lifetime and produced the maximum amount of hydroxyl radicals during UV-vis irradiation; therefore, it demonstrated the best photo-catalytic properties. A Z-scheme mechanism was proposed to explain the hydroxyl radical yield and photodegradation. [ABSTRACT FROM AUTHOR]

Novel Z-scheme structured Sr 0.8 La 0.2 (Ti 1- δ 4+ Ti δ 3+ )O 3 /Bi 2 MoO 6 (LSTBM) composites were prepared via a facile two-step solvothermal method. Several characterization techniques were employed to investigate the phases, microstructures, compositions, valence states, oxygen vacancies, surface oxygen absorption, energy band structures and lifetime of photoproduced carriers. It was found that the lifetime and transfer of the photoproduced carriers of LSTBM were better than those of Bi 2 MoO 6 (BMO) and Sr 0.8 La 0.2 (Ti 1- δ 4+ Ti δ 3+ )O 3 (LSTO). The LSTBM with a molar ratio of BMO/(LSTO + BMO) = 0.07 (denoted as LSTBM7) showed 1.9 and 3.1 times removal rates than those for BMO and LSTO, respectively. Importantly, the built-in electric field in the heterojunction of LSTBM and O v -s, especially in O v -s on the higher-Fermi-level side of the heterojunction, had co-played roles in prolonging the lifetime and improving the transfer of photogenerated carriers. The photoproduced e - played a dominant role in reducing Cr(vi) to Cr(iii) and the produced Cr(iii) tends to form Cr(OH) 3 and adsorb onto the surface of the photocatalyst to decrease the nucleation energy. The possible reduction route for Cr(vi) to Cr(iii) over LSTBM7 was figured out. This study implies that inducing O v -s on the higher-Fermi-level side of the Z-scheme heterojunction is a more effective route for separating the photogenerated electrons and holes and improving the transfer of photogenerated carriers., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

It's highly desired to design and fabricate an effective Z-scheme photo-catalyst with excellent charge transfer and separation, and a more negative conduction band edge ( E CB ) than O 2 /·O 2 - (-0.33 eV) and a more positive valence band edge ( E VB ) than ·OH/OH - (+2.27 eV) which provides high-energy redox radicals. Herein, we firstly designed and synthesized a core-shell-heterojunction-structured Z-scheme system BaTiO 3 @In 2 S 3 (BT@IS, labelled as BTIS) through a hydrothermal method, where commercial BT was used as the core and In(NO 3 ) 3 · x H 2 O together with thioacetamide as the precursor of IS was utilized as the shell material. In this system, the shell IS possesses a E CB of -0.76 eV and visible-light-response E g of 1.92 eV, while the core BT possesses a E VB of 3.38 eV, which is well suited for a Z-scheme. It was found that the as-prepared BTIS possesses a higher photocatalytic degradation ability for methyl orange (MO) than commercial BT and the as-prepared IS fabricated by the same processing parameters as those of BTIS. Holes (h + ) and superoxide radicals (·O 2 - ) were found to be the dominant active species for BTIS. In this work, the core-shell structure has inhibited the production of ·OH because the shell IS has shielded the OH - from h + . It is assumed that if the structure of BTIS is a composite, not a core-shell structure, ·OH could be produced during photocatalysis, and therefore a higher photocatalytic efficiency would be obtained. This current work opens a new pathway for designing Z-scheme photocatalysts and offers new insight into the Z-scheme mechanism for applications in the field of photocatalysis., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Hybrid Bi 12 TiO 20 /Bi 4 Ti 3 O 12 composites with different Bi : Ti molar ratios were successfully fabricated using a one-step solid-state calcination. These samples were characterized using X-ray diffraction, specific surface area analysis, scanning electron microscopy, high-resolution microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence analyses, and photocurrent and electrochemical impedance spectroscopy. Some specified techniques were also used to investigate the photocatalytic properties and the formation of radical species under UV-vis irradiation. The composites provide an efficient pathway for photo-produced electrons and holes to diffuse and transfer to the exterior of the particles for photodegradation, because of the good contact between hybrid Bi 12 TiO 20 and Bi 4 Ti 3 O 12 . Therefore, the hybrid Bi 12 TiO 20 /Bi 4 Ti 3 O 12 can prolong the carrier lifetime as compared to any individual material (Bi 12 TiO 20 or Bi 4 Ti 3 O 12 ). In particular, the hybrid Bi 12 TiO 20 /Bi 4 Ti 3 O 12 composite with a Bi : Ti ratio of 12 : 6 had the longest photo-generated carrier lifetime and produced the maximum amount of hydroxyl radicals during UV-vis irradiation; therefore, it demonstrated the best photo-catalytic properties. A Z-scheme mechanism was proposed to explain the hydroxyl radical yield and photodegradation.