Preparation, characterization and infrared emissivity study of helical polyurethane@SiO2 core-shell composite

Helical polyurethane@SiO₂ (HPU@SiO₂) core-shell composite was prepared after surface modification of SiO₂ nanoparticles. HPU@SiO₂ was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified SiO₂. HPU@SiO₂ composite exhibits clearly core-shell structure. The ultraviolet absorption and crystallizability of HPU@SiO₂ are changed due to the shell of helical polyurethane, which possesses regular single-handed conformation and inter-chain hydrogen bonds. The infrared emissivity of HPU@SiO₂ was also investigated. The result indicates that the interfacial interactions between organic shell and inorganic core induce the infrared emissivity value being reduced from 0.781 for SiO₂ to 0.503 for HPU@SiO₂.     

Amplification properties of Tb (III) green emission in polymeric waveguide doped with Tb-Al nanocluster

This paper describes optical amplification properties in a polymeric waveguide doped with Tb-Al nanoclusters. The Tb-Al nanocluster is a promising fluorescent material for polymeric waveguides, which can be uniformly dispersed in polymer matrices while restraining the concentration quenching of Tb³⁺. Under the continuous optical pumping by 488 nm laser light, optical amplification for the green emission of Tb³⁺ was achieved. The optical gain coefficients were estimated to be as high as 0.25 and 0.56 mm⁻¹ at the Tb-Al nanocluster concentrations of 4.5 and 5.0 wt%, respectively. Taking into account our previous works for the polymeric waveguide doped with Eu-Al nanocluster, the rare-earth-metal nanocluster is believed to be a promising candidate for various photonic applications such as multicolor polymer lasers and waveguide-type optical amplifiers.     

CaTiO3:Pr3+长余辉玻璃的制备与发光性能

用二次熔融法制备了CaTiO3：Pr^3＋红色长余辉玻璃。测量了样品的发射光谱,其发射光谱峰值为611．7,614．5nm,对应于Pr^3＋的4f-4f（^1D2→^3H4）跃迁,与CaTiO3：Pr^3＋晶态长余辉发光粉的发射光谱峰值相一致。玻璃粉与发光粉的质量配比在95：5～80：20时,都可以形成玻璃态并得到红色长余辉发光。研究了气氛和熔融温度对发光性能的影响,在空气环境下,800℃即可得到性能良好的样品。     

掺镨GaN薄膜的微结构与光致发光

利用背散射／沟道（RBS／C）技术、原子力显微镜（AFM）和光致发光（PL）谱研究了掺镨GaN薄膜的微结构和可见光发光特性。RBS／C结果表明,注入Pr后,在注入层引入了晶格损伤;注入样品经1050℃退火后,部分损伤得到恢复,但是晶体质量没有恢复到注入前的状态。AFM结果表明,注入Pr后,表面凹凸不平,而且在注入区引起了膨胀,膨胀幅度达到23．368nm左右。PL结果表明,在850—1050℃退火,发光强度按e指数增加;当退火温度达到1050℃,发光强度最强,经过数据拟合可得Pr^3＋的热激活能为5．8eV。     

Cross-aldol Condensation of Cycloalkanones and Aromatic Aldehydes in the Presence of Nanoporous Silica-based Sulfonic Acid (SiO2-Pr-SO3H) under Solvent Free Conditions

The aromatic aldehydes underwent cross aldol condensation with cycloalkanones in the presence of a catalytic amount of nanoporous silica-based sulfonic acid (SiO2-Pr-SO3H) under solvent-free conditions to afford the corresponding α,α’-bis(substituted benzylidene)cycloalkanones in excellent yields with short reaction time without any side reactions. This method is very general, simple and environmentally friendly in contrast with other existing methods. SiO2-Pr-SO3H was proved to be an efficient heterogeneous solid acid catalyst, which could be easily handled and removed from the reaction mixture by simple filtration, and also recovered and reused without loss of reactivity.     

Mg2+、Al3+离子增强SrTiO3∶Pr3+荧光体发光性能的研究

采用溶胶凝胶法成功制备了SrTiO3∶Pr3+、SrTiO3∶Pr3+, Mg2+ 及SrTiO3∶Pr3+, Al3+荧光粉.通过XRD、PL谱及第一性原理计算对样品的晶体结构、光谱特性及发光增强机制进行了研究.研究结果表明：共掺杂后,SrTiO3∶Pr3+荧光粉为单一组成的SrTiO3立方相,主发射锋位于617 nm, 对应于Pr3+离子的1D2→3H4跃迁发射.SrTiO3∶Pr3+, Mg2+ 及SrTiO3∶Pr3+, Al3+荧光粉的发光强度分别是SrTiO3∶Pr3+荧光粉发光强度的7倍和2倍,但主要发光机制没有改变.Mulliken布局分析表明,Mg2+、Al3+离子的掺入使SrTiO3∶Pr3+荧光粉中Ti-O及Pr-O键的化学键增强、键长变短,SrTiO3∶Pr3+基质向Pr3+离子发光中心的能量传递效率提高,导致SrTiO3∶Pr3+, Mg2+ 及SrTiO3∶Pr3+, Al3+荧光粉的发光效率提高.     

Energetics of dioxygen binding into graphene patches with various sizes and shapes

Density functional theory (DFT) calculations were employed to investigate the electronic properties of an H-atom terminated graphene patch (hydrographene) smaller than a rhombic C96H26 structure with zigzag edges. Depending on shapes and sizes of hydrographenes, some hydrographenes have the triplet ground state where unpaired electrons are localized on their zigzag edges. The stability of the triplet spin state is diminished, decreasing the hydrographene sizes. The existence of the localized spin densities allows triplet dioxgen to bind into a hydrographene. According to the DFT calculations, the energetics of the dioxygen bindings is negatively influenced by downsizing hydrographenes, as well as depends on their shapes. The size-and shape-dependences of the dioxygen bindings reflect from the stability of the triplet state of a hydrographene, because its localized unpaired electrons can be utilized to be attached to an unpaired electron of triplet dioxygen.     

CF4 decomposition over solid ternary mixture NaF-Si-MO（MO=La2O3,CeO2,Pr6O-（11）,Nd2O3,Y2O3）

A solid ternary mixture consisting of NaF,silicon and one metal oxide such as La2O3,CeO2,Pr6O11,Nd2O3,and Y2O3 was prepared and usedas de-fluorinated reagent for CF4 decomposition.The results show that 90% conversion of CF4 can be reached initially over NaF-Si-La2O3,NaF-Si-CeO2,NaF-Si-Nd2O3,and NaF-Si-Y2O3 at 850 C.The fresh and used reagents were characterized using XRD and XPS techniques.It was found that the active components of NaF and metal oxides in NaF-Si-CeO2,NaF-Si-Pr6O11,NaF-Si-Nd2O3,and NaF-Si-Y2O3 weretransformed into inert phases of mixed metal fluorides and silicates,respectively,resulting in an ineffective utilization of these de-fluorinatedreagents,whereas no inert phases from NaF and La2O3 can be observed in the used NaF-Si-La2O3,indicating the NaF-Si-La2O3 reagent couldbe utilized more efficiently than the other reagents in CF4 decomposition.     

Ca4LaNbMo4O20:Pr3+荧光粉的发光性质

采用高温固相法成功制备出荧光粉Ca₄LaNbMo₄O₂₀:Pr³⁺,通过X射线衍射分析了样品的结构,其结构与CaMoO₄结构相似。在Ca₄LaNbMo₄O₂₀:Pr³⁺的激发光谱中出现了NbO₄^3-和MoO₄^2-的电荷迁移(CTS)吸收和Pr³⁺离子的4f→4f5d激发跃迁,以及Pr³⁺-金属离子的价间电荷迁移(IVCT)吸收;另外在420~520 nm处,还观测到属于Pr³⁺离子的典型f-f激发跃迁。发射光谱中,在452 nm激发下,主要出现绿光和红光两种发射,其峰值位于490 nm和607 nm处,分别是Pr³⁺的³P₀→³H₄和¹D₂→³H₄的跃迁作用;在紫外287 nm激发下出现NbO₄^3-和MoO₄^2-发射和Pr³⁺离子的4f5d→4f跃迁宽带,以及Pr³⁺离子的4f→4f发射峰。     

pr3+ 激活的CaMoO4红色荧光粉的发光性质

采用高温固相法制备了稀土pr3+激活的Ca1-xPrxMoO4(0.005≤x≤0.02)系列红色荧光粉.荧光光谱表明:在453 nm激发下,样品产生了红光发射,其中对应于pr3+的特征跃迁3 P0→3F2位于654 nm的红色发射峰最强.分析了pr3的掺杂摩尔分数x对样品发光强度的影响,确定pr3+的最佳掺杂摩尔分数...