Effect of Oxygen Vacancies on the Reduction of Eu³⁺ in Mg₃Ca₃(PO₄)₄ in Air Atmosphere

The paper reported the synthesis of mixed-valence Eu-doped Mg₃Ca₃(PO₄)₄ by solid-state reaction in the air atmosphere. The luminescence measurements indicated that the obtained phosphors exhibit a broad bluish-green fluorescence of Eu²⁺ and a sharp orange-red emission of Eu³⁺ excited by 395 nm. The abnormal reduction mechanism could be explained by a charge compensation model. A tunable luminescence was realized based on the reduction of Eu³⁺ to Eu²⁺ changed along with increasing the sintering time. The reduction of Eu³⁺ to Eu²⁺ in Mg₃Ca₃(PO₄)₄ host was effected by the oxygen vacancy defects when the samples sintered in different atmosphere and sintered for different lengths of time, and the oxygen vacancies which act as the electron traps were investigated with thermoluminescence. All of the results almost indicated the oxygen vacancy could weaken the reduction of Eu³⁺ to Eu²⁺. Our investigation of Mg₃Ca₃(PO₄)₄:Eu could provide a practical basis and theoretical basis to study the effect of oxygen vacancy on the emission of Eu ions

Commendable Eu²⁺-Doped Oxide-Matrix-Based LiBa₁₂(BO₃)₇F₄ Red Broad Emission Phosphor Excited by NUV Light: Electronic and Crystal Structures, Luminescence Properties

In this work, we synthesized a new Eu²⁺-doped oxide-matrix-based LiBa₁₂(BO₃)₇F₄ broad red emission phosphor. It can emit red light peaking at ∼644 nm under NUV excitation with the coordinate at (0.6350, 0.3586) and a sensitive color gamut for eyes. This phosphor with a special kind of tunnel crystal structure and layered distribution of Ba²⁺ is contributed to longer wavelength emission. By theoretical calculation and analysis using local state density energy band structure simulation of Eu²⁺ doped in different site, the origin of the observed emission center was distinguished. Furthermore, decay curves analysis also indicated there are three possible Ba²⁺ sites for Eu²⁺ to occupy. Temperature-dependent PL spectra appeared anomalous phenomena that the intensity increases first and then decreases, which is due to the traps energy level’s contribution of electron’s transition. The phosphor also has cathodoluminescence (CL) property which the spectra take on typical current saturation phenomenon. The CL curves indicated that this phosphor has a very good stability under much electron beam bombardment time. After fabricated combining with BAM, (Sr, Ba)₂SiO₄ and our red phosphor excited under 405-nm NUV chips, warm light LED was obtained. Its CIE coordinate is (0.3475, 0.3416) and the CCT, Ra, and luminous efficiency are 4856 K, 84.1, and 72.6 lm/W, respectively

One-Pot Solvothermal Synthesis of ZnSe·<i>x</i>N₂H₄/GS and ZnSe/N-GS and Enhanced Visible-Light Photocatalysis

Doped-graphene has attracted considerable attention in many fields because doping element can alter the electrical properties of graphene. In this paper, we synthesized ZnSe·<i>x</i>N₂H₄/graphene (ZnSe·<i>x</i>N₂H₄/GS) and ZnSe/nitrogen-doped graphene (ZnSe/N-GS) nanocomposites with p-n junctions via one-pot solvothermal process. The structure, morphologies and catalytic performance of the ZnSe·<i>x</i>N₂H₄/GS and ZnSe/N-GS are characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and cathodoluminescence spectrum (CL), respectively. Our experiments show that the as-prepared nanocomposites ZnSe·<i>x</i>N₂H₄/GS and ZnSe/N-GS exhibit remarkably enhanced photocatalytic activities for methylene blue (MB) dye under visible light irradiation. Even importantly, ZnSe/N-GS would make this degradation process more effective. Overall, this facile and catalyst-free synthesize method in this work could provide new insights into the fabrication of other composites based on doped graphene with high performance photocatalysts, which show their potential applications in producing of hydrogen through water splitting, environmental protection issues

Persistent Fluorescence-Assisted TiO_2‑<i>x</i>N_<i>y</i>-Based Photocatalyst for Gaseous Acetaldehyde Degradation

Photocatalytic technologies were utilized to develop an environment-friendly system that is capable of removing and oxidizing organic pollutants from an air stream. A series of long-afterglow phosphors emitting long lifetime fluorescence was adapted to prepared TiO₂-based composite photocatalysts for the photodegradation of gas-phase acetaldehyde. Although the photocatalytic reaction by an undoped titania (Degussa P25) was stopped immediately after turning off the irradiation light, the long-afterglow phosphor/nitorogen-doped TiO₂ (TiO_2‑<i>x</i>N_<i>y</i>) composites maintained the acetaldehyde photodegradation ability even after turning off the light for a long time. This novel photocatalytic property may be attributed to the presence of the long-afterglow phosphor, which can reserve the light energy and generate the persistent fluorescence afterward as the light source for the photocatalytic reaction with the visible-light responsive TiO_2‑<i>x</i>N_<i>y</i>. The substitution of the undoped TiO₂ with TiO_2‑<i>x</i>N_<i>y</i> was essential to use the fluorescence as a light source for photocatalysis. Such a self-fluorescence-assisted system could enhance the performance of photocatalysts for environmental cleanup

Synthesis of Alumina-Supported RhSn Alloy Nanocatalysts by Using Rh@Sn Core–Shell Nanoparticle Precursors for Toluene Catalytic Hydrogenation

In this work, alumina-supported RhSn alloy nanocatalysts were prepared for toluene hydrogenation. Rh@Sn core–shell nanoparticles were first synthesized through a sequential reduction method and then in situ transformed into RhSn alloy on alumina by calcination and H2 reduction. Relative to Rh/Al2O3, Rh1Sn0.7/Al2O3 catalysts demonstrate enhanced catalytic efficiency for hydrogenation of toluene. At a toluene/Rh molar ratio of 118/1, 0.1 MPa of H2 pressure, and 45 °C, 99.2% of methyl cyclohexane yield was achieved at 2.0 h. The enhanced catalytic efficiency of Rh1Sn0.7/Al2O3 can be ascribed to the synergistic effect between Rh and Sn

A Garnet-Based Ca₂YZr₂Al₃O₁₂:Eu³⁺ Red-Emitting Phosphor for n‑UV Light Emitting Diodes and Field Emission Displays: Electronic Structure and Luminescence Properties

A series of Ca₂Y­Zr₂Al₃­O₁₂:Eu³⁺ (CYZA) phosphors were successfully synthesized through conventional solid-state method. The electronic structure and their photoluminescence or cathodoluminescence properties were investigated in detail. Under n-UV excitation, the CYZA:Eu³⁺ exhibits more intense red emission than the commercial Y₂O₃:Eu³⁺ phosphor. A WLED lamp with good color render index was obtained by fabricating the phosphor with BAM:Eu²⁺ and LuAG:Ce³⁺ phosphors. The phosphor also exhibits red emission with high current saturation and high resistance under low voltage electron bombardment. The degradation resistance can be compared to the commercial Y₂O₃:Eu³⁺ phosphor. All the results indicate that the CYZA:Eu³⁺ has potential applications in both white LEDs and FEDs

Enhanced Photoluminescence and Thermal Properties of Size Mismatch in Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ for High-Power White Light-Emitting Diodes

In this Study, Mg²⁺ and Ba²⁺ act to enhance the maximum emission of Sr_2.97SiO₅:0.03Eu²⁺ significantly and redshift the emission band to the orange-red region in Sr_{2.97–<i>x</i>–<i>y</i>}Mg_<i>x</i>Ba_<i>y</i>SiO₅:0.03Eu²⁺. Size mismatch between the host and the doped cations tunes the photoluminescence spectra shift systematically. A slight blue shift when increasing the amount of Mg²⁺ occurs in the Sr_{2.97–<i>x</i>}Eu_0.03Mg_<i>x</i>SiO₅ lattices, and a rapid red shift occurs when Ba²⁺ is codoped in the Sr_{2.57–<i>y</i>}Eu_0.03Mg_0.4Ba_<i>y</i>SiO₅ lattices. The emission spectra were tuned from 585 to 601 nm by changing the concentration of Ba²⁺. Accordingly, we propose the underlying mechanisms of the changes in the photoluminescence properties by adjusting the cation composition of phosphors. The influence of the size mismatch on the thermal quenching is also observed. This mechanism could be widely applied to oxide materials and could be useful in tuning the photoluminescence properties, which are sensitive to local coordination environment. The emission bands of Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ show the blue shift with increasing temperature, which could be described in terms of back tunneling of the excited electrons from the low-energy excited state to the high-energy excited state. Thus, the Sr_{2.97–<i>x</i>–<i>y</i>}Eu_0.03Mg_<i>x</i>Ba_<i>y</i>SiO₅ phosphors could have potential applications in the daylight LEDs or warm white LEDs

Additional file 1: of Visible Light-Driven Photocatalytic Activity of Oleic Acid-Coated TiO2 Nanoparticles Synthesized from Absolute Ethanol Solution

Supplementary information. Figure S1. XRD patterns of as-prepared samples by adding Sr source (SrCl2) into starting material (a) oleic acid-ethanol and (b) acetic acid-ethanol solutions with a large amount of Ti source. Figure S2. DeNOx abilities of different TiO2 samples. Figure S3. Crystalline morphology properties of nitrogen-doped TiO2 nanoparticles. Figure S4. DRS spectrum of nitrogen-doped TiO2 and P25 TiO2. Figure S5. DeNOx abilities of nitrogen-doped and TOS-TiO2 samples

Nonequivalent Substitution and Charge-Induced Emitter-Migration Design of Tuning Spectral and Duration Properties of NaCa₂GeO₄F:Mn²⁺ Persistent Luminescent Phosphor

We combine nonequivalent substitution and charge-induced emitter-migration approaches and design an efficient method to optionally tune the spectral and duration properties of NaCa₂GeO₄F:Mn²⁺ phosphor. A series of representative codopants have been investigated in detail and classified into two categories: R_A (R_A = Li⁺, Al³⁺, N^3–, Ga³⁺, B³⁺) and R_B (R_B = Mg²⁺, F^–, Bi³⁺, Zn²⁺, Cd²⁺, Sc³⁺, Tm³⁺). Results reveal that the nonequivalent substitution of R_A codopants would induce foreign negative defects and stabilize Mn²⁺ emitters at octahedral Na/Ca sites for red emission. In constrast, the R_B codopants would generate foreign positive defects and make Mn²⁺ emitters migrate to tetrahedral Ge⁴⁺ sites for green-yellow emission. At the same time, the R_A codopants are in favor of the generation of intrinsic positive traps with shallow trap depth and thus efficiently improve the duration properties of phosphors. On the basis of the experimental results, a possible nonequivalent substitution and charge-induced emitter-migration model has been proposed, and we can optionally tune the spectral (568 ↔ 627 nm) and the duration (minutes to more than 6 h) properties according to this model

Inhibitory effects of low dose 5FU and Taxol on naïve and resistant tumor growth in a nude mouse model.

<p>When the tumors reached 100 mm³, animals received designated treatment every second day five times via tail vein injection. KB-3-1 (A) and KB-8-5 (B) tumors received 5mg/kg Taxol, while H460 (C) and H460/Tax-R (D) tumors received 10mg/kg Taxol. The ratio of paclitaxel to 5FU was 2.3:1 (w/w) for each treatment. Statistical analysis was performed using two-way ANOVA (*<i>p</i><0.05; ***<i>p</i><0.001).</p