Preparation,characterization and luminescent properties of spherical CaTiO3:Pr3+ phosphors by spray pyrolysis

In this paper, spherical Pr³⁺-doped CaTiO₃ phosphor particles were fabricated through a two-step spray pyrolysis process, using citric acid and polyethylene glycol (PEG) as additives. X-ray diffraction (XRD), scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), thermogravimetric and differential thermal analysis (TG–DTA), X-ray photoelectron spectra (XPS), photoluminescence (PL), cathodoluminescence (CL) spectroscopy, and lifetime measurements were employed to characterize these samples. The results reveal that the as-prepared CaTiO₃:Pr³⁺ phosphors are spherical with submicron particle size. The particles show a strong red emission corresponding to ¹D₂–³H₄ (612 nm) of Pr³⁺ under the ultraviolet excitation (325 nm) and low voltage electron beams (1–5 kV). Furthermore, the morphology, PL and CL intensities of the CaTiO₃:Pr³⁺ phosphors can be tuned by altering the concentration of PEG, annealing temperature, and acceleration voltage. These phosphors show potential applications in the field of field emission displays (FEDs).     

YAG∶Ce体系中稀土离子掺杂对Ce3+的光谱性能的影响

采用高温固相法合成了一系列的(Y0.95Ln0.01Ce0.04)3Al5O12(简称YAG∶Ce,Ln), 系统地研究了此体系中的Ln3+对Ce3+的发光强度的影响. 结果表明, 在YAG∶Ce的体系中, La3+, Gd3+, Lu3+等光学透明离子的少量掺杂对Ce3+的发光强度的影响不大; 掺入少量的Pr3+, Sm3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+等稀土离子, 由于它们的能级与Ce3+的能级有交叠, 使它们之间存在着竞争吸收或能量转移, 对Ce3+的发光有较明显的变化, 其中, Pr3+和Sm3+的掺入使其在红光区有发射峰, 可以增加YAG∶Ce的红色成分以提高显色性; Nd3+, Eu3+和Yb3+对Ce3+的发光有严重的猝灭作用.     

Ce and La single- and double-substitutional defects in yttrium aluminum garnet: first-principles study

The atomistic structure, energetics, and electronic structure of single-substitutional Ce and La defects and double-substitutional Ce-La defects in Ce,La-codoped yttrium aluminum garnet (YAG) Y(3)Al(5)O(12) have been studied by means of first-principles periodic boundary conditions density functional theory calculations. Single substitution of Y by Ce or by La produces atomistic expansions around the impurities, which are significantly smaller than the ionic radii mismatches and the overall lattice distortions are found to be confined within their second coordination spheres. In double-substitutional defects, the impurities tend to be as close as possible. La-codoping Ce:YAG provokes an anisotropic expansion around Ce defects. The Ce impurity introduces 4f occupied states in the 5.0 eV computed gap of YAG, peaking 0.25 eV above the top of the valence band, and empty 4f, 5d, and 6s states starting at 3.8 eV in the gap and spreading over the conduction band. La-codoping produces very small effects on the electronic structure of Ce:YAG, the most visible one being the decrease in covalent bonding with one of the oxygen atoms, which shifts 0.05 ? away from Ce and gets 0.04 ? closer to La in the most stable Ce-La double-substitutional defect.     

Catalytic performance of ternary Mg-Al-Ce oxides for ethanol conversion into 1-butanol in a flow reactor

An investigation of hydrotalcite-derived ternary Mg-Al-Ce oxides as catalysts for vapour phase condensation of ethanol to 1-butanol in a flow reactor under atmospheric pressure was carried out. The Mg-Al-Ce oxide systems with Mg/(Al +Ce) ratio from 1 to 4 were synthesized and characterized by XRD, SEM, NMR, and XPS. The study of acid-base characteristics of the systems with different Mg/(Al+Ce) ratio by NH_3/CO_2 quasi-equilibrium thermal desorption techniques shows that the ratio of the catalyst oxide components(Mg, Al, Ce) can provide acid/base capacity ratio close to 3 for the effectivity of the target process. The highest selectivity 68% is reached over Mg-Al-Ce oxide catalyst with the ratio of Mg/(Al+Ce) = 2.     

掺杂Ce的TiO_2纳米粒子的光致光及其光催化活性

采用sol-gel法制备了纯的和掺杂不同量Ce的TiO_2纳米粒子，并利用XRD， TEM，BET，XPS和PL光谱对样品进行表征，主要考察焙烧温度和含量对掺杂Ce的 TiO_2纳米粒子性质以及光催化降解苯酚活性的影响，并探讨了Ce的掺杂对TiO_2相 变的作用机制以及PL光谱与光催化活性的关系，结果表明，掺杂的Ce~(4+)没有进 入到TiO_2晶格中，而是以小团簇的CeO_2化学态均匀地弥散在TiO_2纳米粒子中， 这可能导致了Ce的掺杂对TiO_2的相变有很大的抑制作用；Ce的掺杂没有引起新的 光致发光现象，而适量Ce的掺杂能够降低TiO_2纳米粒子PL光谱的强度，这是因为 掺杂的Ce~(4+)易于捕获光生电子而生成Ce~(3+);600℃处理的掺杂Ce的TiO_2纳米 粒子表现出较高的光催化活性，这说明600℃是比较合适的焙烧温度，而掺杂不同 量的Ce的TiO_2样品的光催化活性顺序是：3 mol%＞4 mol%＞2 mol%＞5 mol%＞1 mol%＞0 mol%，这与它们的PL光谱强度的顺序是相反的，即PL光谱强度越低，其 光催化活性越高，这说明PL光谱与其光催化活性间有着必然的联系，这是因为掺杂 剂Ce~(4+)能够捕获光生电子，在光致发光过程中使PL光谱强度下降，而在光催化 反应过程中使有机污染物加快氧化。     

Visible light-emitting and temperature-sensitive copolymer gel/ZnO nanocomposites loaded with surface-modified ZnO nanoparticles having polyethylene glycol chains

New visible light-emitting and temperature-sensitive poly(VCL-co-SA)/ZnO gel nanocompsites (GNs) 4 loaded with surface-modified ZnO nanoparticles NPs 3 with polyethylene glycol (PEG) chains were successfully prepared by the cross-linking of N-vinylcaprolactam (VCL), sodium acrylate (SA) and tetraethylene glycol dimethacrylate (TEGDM) in the presence of NPs 3. The NPs 3 having nanostructured size were prepared from ZnO NPs 2 with 2-bromo-2-methylpropionyl linkages on the surface, and sodium alcoholate of polyethylene glycol monomethyl ether (PEGME). The NPs 3 and the GNs 4 were characterized by FTIR, UV–vis absorption and photoluminescent (PL) spectroscopies, X-ray analysis measurements, TEM and SEM observations and dynamic light scattering (DLS) measurements. The measurements indicated that the GNs 4 with wurtzite crystal structures based on the ZnO NPs show absorptions and yellow light-emitting properties arising from the NPs 3, except for the GNs 4 containing a high weight % of NPs 3. The size of the GNs 4 drastically decreased with increasing temperature in the range of 20–35 °C, probably because of the induction of steric hindrance and enhancement of hydrophilic PEG chain concentrations inside the GN networks 4.     

弱碱溶液后处理对固相合成铈掺杂钇铝石榴石荧光粉发光性能的改进

为改善高温固相反应制备的铈掺杂钇铝石榴（YAG∶Ce3+）黄光荧光粉的发光性能,分别采用浓氨水、N,N-二甲基乙酰胺(DMAC)、三乙醇胺、聚丙烯酰胺和六次甲基四胺等的水溶液对其进行浸泡处理,比较了处理剂浓度、用量和处理剂类型对荧光粉发光强度、荧光粉温度、猝灭性能和形貌的影响,确定了以30%氨水在50 ℃浸泡50 min为优化的处理工艺,YAG∶Ce3+荧光粉发光强度比处理前约提高9.5%,荧光粉分散程度也得到改善,处理后粒径分布更加均匀。     

Controlled fabrication and shape-dependent luminescence properties of hexagonal NaCeF4, NaCeF4:Tb3+ nanorods via polyol-mediated solvothermal route

Hexagonal monodisperse NaCeF(4) and NaCeF(4):Tb(3+) nanorods have been successfully synthesized by a polyol-mediated solvothermal route with ethylene glycol (EG) as solvent. The crystalline phase, size, morphology, and luminescence properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra as well as dynamic decays. The experimental results indicate that the content of NH(4)F and NaNO(3) are crucial in controlling product morphology and size. Nanorods with different aspect ratios could be controllably obtained under settled conditions. Shape-dependent luminescence and energy transfer routes from Ce(3+) to Tb(3+) in NaCeF(4):Tb(3+) nanorods were observed by the modified local crystal field environment around rare earth ions. The 4f-5d transitions of Ce(3+) ions have much higher sensitivity to the anisotropic shape of samples than that of Tb(3+) ions.     

Synthesis and spectroscopic characterization of gold nanoparticles

Photoluminescent nanoparticles of gold with size 3, 4, 6, and 9nm are prepared by borohydride/citrate reduction in presence of polyethylene glycol (PEG)/tannic acid. The prepared nanomaterials are characterized by UV-vis spectroscopy and dynamic light scattering (DLS) technique. Intense photoluminescence (PL) is observed in nanoparticles prepared by fast reduction with borohydride in presence of PEG. A red shift of PL emission from 408 to 456nm is observed for the change of size from 4 to 6nm. Increase in PL intensity is observed for all the nanoparticles on the addition of KCl. Citrate reduced gold colloid which consists of large particles of size approximately 35nm with anisotropic shapes showing two plasmon peaks is also prepared. The anisotropy is confirmed by TEM measurement. SERS activity of this colloid is tested using glutamic acid as an adsorbate probe. Assignment of the observed bands is given.     

Er3+和Ce3+/Ce4+掺杂β-BaB2O4纳米棒的制备、结构与发光性质

以Ba(NO3)2、NaBH4、Er2O3和CeO2为原料, 在十六烷基三甲基溴化铵(CTAB)表面活性剂辅助下, 采用水热法制备了β-BaB2O4 (β-BBO)纳米棒, 稀土离子Er3+单掺杂的β-BBO(β-BBO:Er3+)及Er3+和Ce3+/Ce4+共掺杂的β-BBO(β-BBO:Er3+/Ce3+/Ce4+)纳米棒. 通过X射线粉末衍射(XRD)、傅里叶变换红外(FTIR)光谱、拉曼光谱、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和光致发光(PL)光谱分别对样品的物相、结构、形貌、成分及光致发光性质进行了表征. 研究结果表明: 微量稀土离子掺杂并不改变β-BBO的结构, 制得的纳米棒尺寸均匀, 长度在200-500 nm 之间, 直径在10-20 nm 之间; β-BBO:Er3+和β-BBO:Er3+/Ce3+/Ce4+纳米棒在400nm光激发下, 在可见光范围内都观察到中心波长为515和542 nm的绿光. 对发光机理的初步研究表明: 发光分别对应于Er3+的2H11/2→4I15/2, 4S3/2→4I15/2跃迁, 铈离子以Ce3+和Ce4+两种形式存在于体系中, Ce3+对Er3+起敏化作用, 可以显著增强β-BBO:Er3+/Ce3+/Ce4+纳米棒的发光强度, 存在Ce3+→Er3+的能量传递过程.     

A facile synthesis of luminescent YVO4:Eu3+ hollow microspheres in virtue of template function of the SDS–PEG soft clusters

Hollow europium-doped yttrium orthovanadate (YVO₄:Eu³⁺) microspheres were fabricated via a sodium dodecyl sulfate (SDS)–polyethylene glycol (PEG)-assisted hydrothermal technique. The as-synthesized hollow YVO₄:Eu³⁺ microspheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The obtained results showed that the morphology and size of the hollow microspheres have a strong dependence on the hydrothermal reaction time of the YVO₄:Eu³⁺ powders. It is believed that the SDS–PEG clusters perform a function of dual soft-template that results in a unique template-induced secondary assembly in the one-pot synthesis of hollow YVO₄:Eu³⁺ microspheres. The photoluminescence measurement revealed that the YVO₄:Eu³⁺ powders with a spherical hollow shape have better red luminescence compared to the YVO₄:Eu³⁺ solid microspheres. As a result, the controlled synthesis of hollow YVO₄:Eu³⁺ microspheres not only has a great theoretical significance in studying the three-dimensional control and selective synthesis of inorganic materials but also benefits the potential applications based on hollow YVO₄:Eu³⁺ microspheres owing to reducing the usage of expensive rare-earth elements.     

铈掺杂对BaFBr:Eu2+光激励发光性能的影响

采用一步反应法制备了BaFBr:Eu2+,Ce3+X射线影像存储材料.通过荧光光谱和光激励发光谱研究了材料的光致发光及其经X射线辐照后的光激励发光性质.结果发现,Ce离子的掺入使得BaFBr:Eu2+的发光性能明显增强,存在Ce3+离子向Eu2+离子的能量传递,Ce离子的掺杂浓度为0.7%(摩尔分数)左右时可得到较高的光致发光及光激励发光强度.且掺入Ce3+后,可以有效的形成能稳定存储的较低能级的电子陷阱,使得在信息读出过程中所需激励光能量降低,从而使得读出光的能量与价廉、便携的长波激光器的读出波长匹配得更好.     

磷灰石结构荧光粉Ba10(PO4)6F2:Ce3+,Tb3+的合成、发光和能量传递

采用高温固相法合成了系列Ce~(3+)和Ce~(3+)/Tb~(3+)激活的具有磷灰石结构荧光粉Ba_(10)(PO_4)_6F_2。用X射线衍射(XRD)、扫描电镜(SEM)、激发和发射(PLE和PL)光谱对样品进行了表征分析。研究结果表明:所合成的荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)具有氟磷灰石结构,样品微观呈现不规则形貌。荧光粉Ba10-x(PO4)6F2∶x Ce~(3+)的相对发射强度随着x增加而增强,当x=0.09时,荧光强度达到最大。荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的激发光谱为240～330 nm的宽带,发射光谱呈现出Ce~(3+)的5d→4f跃迁紫外光(335和358 nm)发射和Tb~(3+)的4f→4f跃迁绿光(542 nm)发射。光谱特性表明,发光过程中存在Ce~(3+)→Tb~(3+)能量传递,能量传递效率可以达到60%。计算Ce~(3+)和Tb~(3+)的临界距离为0.79 nm,能量传递机理是偶极-偶极交互作用。此外,详细论述了Ce~(3+)和Tb~(3+)之间的能量传递和发光的过程。通过调节Tb~(3+)的掺杂浓度,对荧光粉发光色坐标与Tb~(3+)的掺杂浓度之间的关系也进行了研究,随着Tb~(3+)的掺杂量从0增加0.52,荧光粉Ba_(10)(PO_4)_6F_2∶Ce~(3+),Tb~(3+)的发射光谱色坐标可以从(0.149 4,0.045 1)蓝色区变化到(0.280 1,0.585 3)绿色区。     

Infrared and MAS NMR Spectroscopic Studies of Al18B4O33

IntroductionAllsB.O,, is a refractory compound with the melting point of 1 713 K. It has a low density of 2. 94 g/cm' and tends to form a needle--shaped crystal. These characteristics lead to itspotential application in reinforced plastics or metal alloys['j. The investigationL'] in the crystalstructure Of Al,SB,O,, by X-ray study has reve.aled that the material has a 10Al,O,. BZO3type structure. This structure contains AIO.--tetrahedra, AIO,-octahedra, five-oxygen-coordinated Al ato…     

Metal-cation-mediated nanocrystal arrays of sandwich-type (phthalocyaninato) [tetrakis(4-pyridyl)porphyrinato] cerium complex formed at the water-chloroform interface

Regular square, wirelike, quadrate, and rodlike nanocrystal arrays of Cd2+, Hg2+, or Ag+ metal-cation-mediated sandwich-type mixed (phthalocyaninato) [5,10,15,20-tetrakis(4-pyridyl)poprhyrinato] cerium(III) double-decker complex Ce(Pc)(TPyP) have been successfully prepared at the water-chloroform interface. The nanocrystal growth processes were monitored by transmission electron microscopy (TEM), which reveals that different morphologies of nanocrystals have been fabricated from double-decker molecules connected by different kinds of metal cations, forming coordination polymers. These nanoscaled coordination polymers were characterized by FT-IR spectra and energy-dispersive X-ray spectra (EDS). EDS results clearly revealed the elements of the nanocrystals and the FT-IR spectra give evidence for the coordination interaction between the double-decker molecules and metal cations. The UV-vis absorption spectrum indicates the formation of J-aggregates of the double-decker molecules in the nanocrystals formed.     

Hierarchical self-assembly of 3D amphiphilic discrete organoplatinum(Ⅱ)metallacage in water

Here we described the design and synthesis of a discrete 3D amphiphilic metallacage 4,in which the tetragonal prismatic frameworks act as the hydrophobic cores and the poly(ethylene glycol)(PEG)chains as the hydrophilic tails.The structure of 4 was characterized by 1H NMR,31P NMR and electrospray ionization time-of-flight mass spectrometry(ESI-TOF-MS).Notably,4 with its Iong PEG tails was subsequently ordered into micelles at a low concentration(1.20×10^-6 mol/L)in water.As the concentration and cultivation time increased,the micelles can further self-assembly into nanofibers and nanoribbons.Considering the dynamic property of the coordination bond,these structures show reversible transformation under external stimuli.     

Single nanocrystal arrays on patterned poly(ethylene glycol) copolymer microstructures using selective wetting and drying

Single nanocrystal arrays were fabricated on sub-microwells of poly(ethylene glycol) (PEG) copolymer using selective wetting on the hydrophilic regions of the exposed substrate surface and subsequent drying. Templates were produced by molding a thin film of a PEG-based random copolymer on hydrophilic substrates such as glass or silicon dioxide. The polymeric microstructures provide a topographical barrier around the well, which makes it possible to create nanocrystal arrays with controlled geometrical features. The size of the nanocrystal was found to decrease with decreasing well size and also decrease with decreasing topological height. A simple empirical equation was derived to predict the size of the crystal as a function of the pattern size and height, which is in good agreement with the experimental data.     

Influence of combustion reagent and microwave drying method on the characteristics of nano-sized Nd<Superscript>3+</Superscript>:YAG powders synthesized by the gel combustion method

Nanosized Nd³⁺ doped Y₃Al₅O₁₂ (Nd³⁺:YAG) powders have been synthesized by the gel combustion method using different combustion reagent such as citric acid, ethylene diamine tetraacetic acid (EDTA), glycine, glycol and the combination of citric acid and EDTA with different ratio. The pure YAG phase was obtained at relatively low temperature around 950 °C for citric acid or EDTA and 1,050 °C for glycine or glycol as combustion reagent, respectively by the gel combustion method. It was found that citric acid and EDTA are the better combustion reagents and yield rather homogeneous and well dispersed club-shape Nd³⁺:YAG samples, and the particle size synthesized by EDTA is larger than that by citric acid. Moreover, the particle size of Nd:YAG was enlarged when the ratio of EDTA was increased in the combination reagent, and the better dispersion of YAG was obtained when the ratio of citric acid to EDTA was 1:1 compared to that of other ratios and pure one as combustion reagent. On the other hand, the results showed that the microwave assisted in drying process of gel to xerogel produced more smaller Nd³⁺:YAG particles in size, and more homogeneous dispersion of the Nd³⁺:YAG particles than that of the traditional dry method.     

Effect of surface modification on photoluminescence properties of Y3Al5O12:Ce3+, Gd3+ nano-phosphors

In this study, a series of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors were prepared using a simply wet chemical process with polyvinyl pyrrolidone as a modifier. The crystal and bonding structures of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with different weight percentages of polyvinyl pyrrolidone were characterized by X-ray diffractometry and infrared spectrometry. The decomposition process of dried precursor gel with adding 1.37 wt% polyvinyl pyrrolidone was investigated by differential thermal and thermogravimetric analysis. The effect of surface modification on photoluminescence properties for the samples was studied. The results show that the steric hindrance effect of polyvinyl pyrrolidone leads to high dispersion and good crystallinity of Y(3)Al(5)O(12):Ce(3+), Gd(3+) nano-phosphors prepared with adding a proper weight percentages of polyvinyl pyrrolidone. Adding polyvinyl pyrrolidone is beneficial for the photoluminescence enhancement of the samples, which is attributed to the promotion of the incorporation of Ce(3+) and Gd(3+) into the Y(3)Al(5)O(12) nanocrystal and the surface passivation of the nano-particles by the polyvinyl pyrrolidone molecules.     

稀土掺杂氟化镁钾纳米晶的合成及其光谱特性

采用微乳液法合成了Eu²⁺,Ce³⁺单掺和双掺KMgF₃纳米晶,分析了样品的结构与形态. 结果表明,所合成的样品均为单相,颗粒粒度分布均匀. 讨论了光谱特性并与高温固相法合成的产物作了对比. 研究发现,在KMgF₃纳米晶双掺体系中,由于Eu²⁺和Ce³⁺竞争吸收激发能,只能观察到Ce³⁺的发射带; 而在KMgF3多晶共掺体系中,因为存在Ce³⁺→Eu²⁺能量传递过程,只能观察到Eu²⁺的发射峰.