Sol-gel combustion synthesis and luminescent properties of nanocrystalline YAG : Eu3+ phosphors

EU3+ -doped Y3Al5O12 (YAG:Eu3+) phosphors were synthesized by a facile sol-gel combustion method. In this process, citric acid traps the constituent cations and reduces the diffusion length of the precursors. YAG phase is obtained through sintering at 900 degrees C for 2h. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed. The charge transfer band of nanocrystalline phosphors shows a shift toward the high-energy side, compared with that of amorphous ones due to lower covalency of Eu-O bond for nanocrystalline phosphors. The higher concentration quenching in YAG:EU3+ nanophosphors may be caused by the confinement effect on resonant energy transfer of nanocrystalline. It also indicates that the sol-gel combustion synthesis method provides a good distribution of Eu3+ activators in YAG host. (c) 2005 Elsevier B.V. All rights reserved.

Structural and optical properties of YAG : Ce3+ phosphors by sol-gel combustion method

High-quality Ce3+-doped Y3Al5O12 (YAG:Ce3+) phosphors were synthesized by a facile sol-gel combustion method. In this sol-gel combustion process, citric acid acts as a fuel for combustion, traps the constituent cations and reduces the diffusion length of the precursors. The XRD and FT-IR results show that YAG phase can form through sintering at 900 degrees C for 2 h. This temperature is much lower than that required to synthesize YAG phase via the solid-state reaction method. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed in the sintering process. The average grain size of the phosphors sintered at 900-1100 degrees C is about 40 nm. With the increasing of sintering temperature, the emission intensity increases due to the improved crystalline and homogeneous distribution of Ce3+ ions. A blue shift has been observed in the Ce3+ emission spectrum of YAG:Ce3+ phosphors with increasing sintering temperatures from 900 to 1200 degrees C. It can be explained that the decrease of lattice constant affects the crystal field around Ce3+ ions. The emission intensity of 0.06Ce-doped YAG phosphors is much higher than that of the 0.04Ce and 0.02Ce ones. The red-shift at higher Ce3+ concentrations may be Ce-Ce interactions or variations in the unit cell parameters between YAG:Ce3+ and YAG. It can be concluded that the sol-gel combustion synthesis method provides a good distribution of Ce3+ activators at the molecular level in YAG matrix. (c) 2005 Elsevier B.V. All rights reserved.

凝胶-燃烧法合成YAG：Eu^3＋纳米荧光材料的结构和发光性能

Y3Al5O12:Eu nanophosphors were synthesized by a gel combustion method. The structure of phosphors was characterized by XRD and FTIR. YAG phase came to occur when YAG:Eu precursors were sintered at 800 ℃, although the phase was mainly amorphous. The organ

Solution combustion synthesis, structure and luminescence of Y3Al5O12 : Tb3+ phosphors

The synthesis and optical properties of Y3Al5O12:Tb3+ phosphors are reported in this paper. Y3Al5O12:Tb3+ phosphors were synthesized by a facile solution combustion method. Citric acid traps the constituent cations and also acts as a fuel. Y3Al5O12 (YAG) phase can crystallize through sintering at 900 degrees C for 2 h, and there were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) in the sintering process. The excitation spectra of crystalline Y3Al5O12:Tb3+ are different from that of amorphous one due to the crystal field effect. The emission spectra mainly show D-5(4) -> F-7(6) transition under UV excitation. The higher concentration quenching in Y3Al5O12:Tb3+ nanophosphors may be due to the confinement effect on resonant energy transfer of nanocrystalline. It is also indicated that the solution combustion synthesis method provides a good distribution of Tb3+ activators in Y3Al5O12 host. (c) 2005 Published by Elsevier B.V.

Phylogenetic relationships among the genera of the Penaeidae (Crustacea : Decapoda) revealed by mitochondrial 16S rRNA gene sequences

The phylogenetic relationships within the family Penaeidae are examined based on mitochondrial 16S rRNA gene sequence analysis of 30 species from 20 genera. The analysis generally supports the three- tribe scheme proposed by Burkenroad ( 1983) but it is not consistent with the five- group classification of Kubo ( 1949). Three clades are resolved: ( Penaeus sensu stricto + Fenneropenaeus + Litopenaeus + Farfantepenaeus + Marsupenaeus + Melicertus + Funchalia + Heteropenaeus), ( Metapenaeus + Parapenaeopsis + Xiphopenaeus + Rimapenaeus + Megokris + Trachysalambria) and ( Metapenaeopsis + Penaeopsis + Parapenaeus), corresponding to the Penaeini, Trachypenaeini and Parapenaeini respectively, while the affinities of Atypopenaeus and Trachypenaeopsis are obscure. The molecular data support that Miyadiella represents the juvenile stage of Atypopenaeus. Within the Trachypenaeini, Trachypenaeus sensu lato is clearly paraphyletic, while the monophyly of Penaeus sensu lato in the Penaeini is questionable.

中药穿龙薯蓣、黄山药和盾叶薯蓣的分子鉴别研究

为建立对中药穿龙薯蓣、黄山药和盾叶薯蓣分子鉴别的方法，我们首先研究薯蓣叶绿体psbA-trnH片段遗传多样性，探讨该片段用于中药穿龙薯蓣、黄山药和盾叶薯蓣种间分子鉴别和系统学研究中的意义。在对不同类群薯蓣种的叶绿体psbA-trnH基因间区进行ＰＣＲ扩增并测序，获得了该区间的完整序列的基础上，将所得序列用软件MEGA3.0进行相关分析。穿龙薯蓣的psbA-trnH片段全长274bp，黄山药全长279bp，盾叶薯蓣植物个体内的叶绿体DNA则有两种psbA-trnH片段，长度分别为241bp和503bp。MEGA3.0软件分析，三种薯蓣种间psbA-trnH片段序列的遗传距离（p-distance）为0.00350-0.04545，各个薯蓣种内的不同类群该序列无差异。用UPGMA法根据psbA-trnH序列的遗传距离建立系统发生树，每个种不同产地的薯蓣很明确地聚在一起，和形态分类一致。所得结果显示psbA-trnH片段序列在所研究的三种薯蓣种内保守，在种间具有明显的较大差异，而三种薯蓣及薯蓣属的系统发生关系尚须进一步研究。 以穿龙薯蓣、黄山药和盾叶薯蓣的psbA-trnH片段序列分析结果为基础，我们根据三种薯蓣在该片段上的特征序列位点设计了用于识别三种薯蓣的寡核苷酸片段并作为PCR反应的引物，将三种薯蓣的特征标记引物与psbA-trnH片段引物配合使用建立了相互识别三种薯蓣的显性和共显性两种检测方式，辅以NaOH碱法快速提取薯蓣干燥根茎总DNA，为三种薯蓣药材相互间快速准确鉴别创造了条件。 To establish molecular method for identifying Chinese medicine Dioscorea nipponica/panthaica/zingiberensis, we firstly study the Genetic diversity of psbA-trnH of Dioscorea and discuss the value of the fragment to molecular identity and systematology to three Dioscorea species (Dioscorea nipponica/panthaica/zingiberensis). The psbA-trnH fragments of different species of Dioscorea are amplified and sequenced，analyzing by software MEGA3.0. The length of Dioscorea nipponica and panthaica are 274bp and 279bp; two psbA-trnH fragments exist in Dioscorea zingiberensis individual, length of the shorter fragment is 241bp and the longer is 503bp. The interspecific Genetic distance (p-distance) of the three species is 0.00350-0.04545, and no intraspecific diversity exists. According to the Genetic distance, phylogenetic tree is built by UPGMA Method, each species of different place gather obviously, which is same to the shape classification. Results show that the psbA-trnH fragment is highly conservative at intraspecific level and obvious diversity at interspecific level, however, phylogenetic study is necessary for the Dioscorea in the future. Based on analysis to psbA-trnH fragment of Dioscorea panthaica, nipponica and zingiberensis, according to the special point of the three Yam species, primers as marker are designed for distinguishing the three species. Cooperating with primer pair psbAf-trnHr, dominant and codominant way is established for discriminating them. Moreover, assisted with NaOH method to extract total DNA of Dry stenophora of Yam, rapid and correct identity to the three species can be done.

Nucleic Acid-Induced Aggregation and Pyrene Excimer Formation

Nucleic acid was found to induce the aggregation of the positively charged pyrene probe (compound 1); as a result, strong pyrene excimer emission was observed. The intensity of the excimer emission was dependent on the concentration of the pyrene probe and the oligonucleotide length, sequence, and concentration. These results suggest a new strategy for label-free nucleic acid-based biosensing applications.

Sol-gel synthesis and luminescence of Y4Al2O9:RE3+(RE=Eu, Tb)

Y4Al2O9 (YAM) was prepared by a sol-gel process, using yttrium and aluminum citrate complexes as precursors. The sol-gel process produced single-phase YAM at 900 degrees C, as opposed to the conventional solid-state reaction, which led to the formation of other phases, even if at 1600 degrees C. The emission and excitation spectra of Eu3+ and Tb3+ in YAM showed the existence of two luminescence centers, agreeing with the crystal structure of YAM. The spectral properties of the samples are discussed.

钙钛矿型铝酸钇(YAP)晶体在还原气氛中的稳定性

关于YAP的相文献上有不同的报导。相图研究说明,在较低温度它将分解成YAG(Y_3Al_5O_(12))和YAM(Y_4Al_2O_9)。Abell等报导分解产物是YAG和未鉴别出来的x相,并推测可能是体系缺氧,而x相不能表示在膺二元体系相图中。我们认为在还原气氛中YAP是不稳定的。本文对石墨加热器处理的YAP晶体粉末通过化学分析和x线相分析进一步证实此推论。

On the crangonidae (Crustacea : Decapoda : Caridea) of the Philippines from the PANGLAO 2004 and PANGLAO 2005 expeditions

Eleven species of the caridean family Crangonidae are reported from the material collected by the Philippine PANGLAO 2004 and PANGLAO 2005 expeditions. Although they have been reported from the Philippines before, all the species have their colouration described and illustrated here for the first time.

Deep-sea pontoniines (Decapoda : Palaemonidae) from the philippine "PANGLAO 2005" expedition, with descriptions of four new species

Ten species belonging to three genera of the subfamily Pontoniinae were colleted by the deep-sea expedition "PANGLAO 2005" in the Philippines, including four new species of the genus Periclimenes, i.e., P. boucheti n. sp., P. leptunguis n. sp., P. ngi n. sp., and P. panglaonis sp. nov., and one newly recorded species from the Philippines, Periclimenes laccadivensis. They are reported with color photographs except one species, Plesiopontonia monodi. The possible synonymy of Periclimenes foresti and P. granuloides is discussed.