Preparation and luminescent properties of cubic Eu3+ : Y2O3 nanocrystals and comparison to bulk Eu3+ : Y2O3

Y2O3:Eu3+ nanocrystals were prepared by combustion synthesis. The particle size estimated by X-ray powder diffraction (XRD) was about 10 nm. A blue-shift of the charge-transfer (CT) band in excitation spectra was observed in Y2O3:Eu3+ nanocrystals compared with bulk Y2O3:Eu3+. The electronic structure Of Y2O3 is calculated by density functional method and exchange and correlation have been treated by the generalized gradient approximation (GGA) within the scheme due to Perdew-Burke-Ernzerhof (PBE). The calculated results show that the energy centroid of 5d orbital in nanocrystal has increasing trend compared with that in the bulk material. The bond length and bond covalency are calculated by chemical bond theory. The bond lengths of Y2O3:Eu3+ nanocrystal are shorter than those of the bulk counterpart and the bond covalency of Y2O3:Eu3+ nanocrystal also has an increasing trend. By combining centroid shift and crystal-field splitting, the blue-shift of the CT band is interpreted.

Sol-gel derived silicate oxyapatite phosphor films doped with rare earth ions

Rare-earth (Eu3+, Tb3+)-doped Ca2Y8(SiO4)(6)O-2 luminescent thin films were dip-coated on silicon and quartz glass substrates through a sol-gel route. X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resultant films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC, and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM micrographs, where particles with various shape and average size of 250 nm can be resolved. The Eu3+ and Tb3+ ions show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4)-F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime of Eu-3divided by increases with the heat treatment temperature front 700 to 1100 degreesC.

Studies on the interaction of porphyrin with antibody with fluorescent spectrum and UV-Vis differential spectra

After meso-tetra (alpha, alpha, alpha, alpha-O-phenylacetyl benzene)porphyrin combined with McAb 1F2, there was a significant hyperchromic effect, indicating that the combination of porphyrin and antibody is rigid and compact, aromatic amino acids exist at the combining sites of antigen in antibody. These aromatic amino acids are Trys and Trps, but the numbers of Trp are more than that found for Trys. The stochiometric ratio of porphyrin to 1F2 is 1:1, the disassociation constant was determined as(2.084+/-0.216) x 10(-10) mol/L by a method of fluorescence quenching, showing that both have a high affinity.

Preparation of europium induced conformation-specific anti-calmodulin monoclonal antibody

Monoclonal antibody technique was employed to detect the conformational difference of CaM induced by metal ions. A trivalent europium ion induced conformation-specific anti-calmodulin monoclonal antibody was successfully prepared with europium-saturated calmodulin as antigen.

Preparation and characterization of luminescent thin films doped with rare earth (Tb3+, Eu3+) complexes derived from a sol-gel process

Sol-gel derived luminescent thin films doped with rare earth (RE) complexes were prepared using an in-situ synthesis method with a two-step hydrolysis process and the luminescence spectra were measured. Fluorescence Lifetime and thermal stability were investigated. The results show that a broad excitation band indicates the formation of RE complexes in the solid thin films. RE ions, which are restrained in a silica matrix, present longer lifetime and higher thermal stability than that in DMF/PVB films containing the corresponding pure complexes. (C) 2000 Elsevier Science B.V. All rights reserved.

环化丁苯橡胶的表征

在SBR中加入环化试剂AlEt2Cl-C6H5CH2Cl,在120℃ ,20min条件下制备了环化SBR ,并借助IR ,1H -NMR ,DSC ,GPC等方法对产物性能进行了表征。结果表明 ,二甲苯溶剂参与了环化反应 ,且随环化度增加 ,参与反应的二甲苯量也逐渐增加 ,并确定了环结构的形成。利用 1H -NMR谱图导出了环化SBR的环化度和溶剂参与量的计算公式

Synchronous fluorescence spectra of hemoglobin: A study of aggregation states in aqueous solutions

The synchronous fluorescence spectra of hemoglobin solutions are reported for the first rime. The main fluorescence peaks observed in the spectra are assigned. The effect of the concentration of hemoglobin solution on the spectra is studied. Characteristic fluorescence peaks due to the dimer and tetramer of hemoglobin molecules are recognized. (C) 1998 Academic Press.

杂质分布对多晶硅薄膜电性能的影响

报道了多晶硅薄膜的制备方法及光生截流子在多晶硅晶界区域的收集、复合情况，并采用剖面分析方法研究了杂质的分布对多晶硅薄膜太阳电池电性能的影响。

A1对M2高速钢凝固过程的作用

研究了A1在M2高速钢凝固过程中的行为及其对凝固组织的影响．结果表明，A1具有扩大δ铁素体区，促进以往状树枝晶方式结晶的作用；A1在M2钢中呈负偏析分布，并参与形成M2C共晶碳化物．A1还降低共晶碳化物的分解温度，使共晶碳化物在高温加热时易于分解和粒化.

INTERACTION OF LANTHANUM AND CALCIUM WITH HUMAN ERYTHROCYTE-MEMBRANES

The effect of lanthanum and calcium on the structure and function of human erythrocyte membranes was investigated by fluorescence polarization, spin- labeled electron spin resonance (ESR) and laser Raman spectroscopy. The results showed that low concentration of La3+ (0.5 mu mol/L) activated a Little (Na++K+)-ATPase and Mg2+-ATPase activities, and it inhibited obvi ously the ATPase activities with increasing its concentrations. La3+ lowered the lipid fluidity of human erythrocyte membranes and decreased the vibration intensity of alpha-helix of the protein in the Amide I '. The effect of Ca2+ on the lipid fluidity and alpha-helix of the protein in the Amide I ' was smaller than that of La3+.

烷烃异构体的结构排序与热力学性质的变化规律

应用分子链状片断(C—C—C,C—C—C—C,C—C—C—C—C)数P_2、P_3、P_4研究了烷烃异构体系列的结构排序及其热力学性质的规律性.每个烷烃分子表达为二维平面(mP_2+P_4,P_3)上的一个点(对辛烷,m=2,壬烷m=4,癸烷m=5),沿着坐标轴方向连结相同m点,得到相应烷烃的异构体周期表.在此基础上,提出了分子异构体序数的概念,并分析了多种热力学性质的变化趋势及其对结构的依赖关系.

细胞色素P-450模拟体系的活性中间体—亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离、表征和氧化反应

铬(Ⅲ)四苯基卟啉-亚碘酰苯体系在温和条件下能催化氧化碳氢化合物,是细胞色素P-450很好的模拟体系。分离和表征细胞色素P-450模拟体系的活性中间体,不仅能解释细胞色素P-450模拟体系催化氧化碳氢化合物的反应机理,而且也有助于深入了解细胞色素P-450催化氧化碳氢化合物的反应机理及其活性中间体的结构。我们首先分离和表征的细胞色素P-450模拟体系的一种活性中间体-氧配位铬(V)四苯基卟啉配合物,具有氧化碳氢化合物的活性。这篇论文报道细胞色素P-450模拟体系的另一种活性中间体-亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离,表征和对环已烯的氧化性质。