PREPARATION AND CHARACTERIZATION OF PVA COATED MAGNETIC NANOPARTICLES*

Polyvinyl alcohol coated magnetic particles (PVA ferrofluids) have been synthesized by chemical co-precipitationof Fe(Ⅱ)/Fe(Ⅲ) salts in 1.5 mol/L NH_4OH solution at 70℃ in the presence of PVA. The resultant colloidal particles havecore-shell structures, in which the iron oxide crystallites form the cores and PVA chains form the shells. The hydrodynamicdiameter of the colloidal particles is in the range of 108 to 155 nm, which increases with increasing PVA concentration from5 wt% to 20 wt%. The size of the magnetic cores is ca. 5～10 nm, which is relatively independent of PVA concentration.Under transmission electron microscopic (TEM) examination, the magnetic cores exhibit somewhat irregular shapes varyingfrom spherical, oval, to cubic. Magnetometry measurement revealed that the PVA coated magnetic particles aresuperparamagnetic. The saturation magnetization of 5 wt% and 20 wt% PVA ferrofluids at 300 K is 54 and 49 emu/g.respectively. All the PVA ferrofluids exhibited excellent colloidal stability in pure water and phosphate buffer saline (PBS,pH=7.4). The ferrofluids can remain stable in above solutions for more than three months at 4℃.     

Fe_3O_4/P(NaUA-St-BA)核-壳纳米磁性复合粒子的合成与表征

以表面包敷有反应型的表面活性剂NaUA(十一烯酸钠)的Fe3O4磁性胶体粒子为种子,运用无皂乳液聚合方法原位制备出Fe3O4P(NaUAStBA)核壳纳米磁性复合粒子.Fe3O4磁性胶体粒子的粒径为10nm左右.IR和TG结果分析表明,苯乙烯、丙烯酸酯和NaUA在Fe3O4粒子的表面发生了聚合反应,形成P(NaUAStBA);TEM和激光粒度分析仪测试结果显示,Fe3O4P(NaUAStBA)复合粒子具有核壳结构而且粒子分布均匀、平均粒径60nm;TG测试的结果表明,NaUA在Fe3O4粒子的包覆率为13.83%,P(NaUAStBA)共聚物的包覆率71.85%;振动样品磁强仪(VSM)测试的磁滞回线则表明由无皂乳液聚合得到的Fe3O4P(NaUAStBA)复合粒子具有超顺磁性,可避免磁性微球在磁场中的团聚.另外,合成的磁性胶乳可稳定存放数月.     

Fe3O4/P(NaUA-St-BA)核-壳纳米磁性复合粒子的合成与表征

以表面包敷有反应型的表面活性剂NaUA（十一烯酸钠）的Fe3O4磁性胶体粒子为种子,运用无皂乳液聚合方法原位制备出Fe3O4／P（NaUA-St-BA）核-壳纳米磁性复合粒子,Fe3O4磁性胶体粒子的粒径为10nm左右,IR和TG结果分析表明,苯乙烯、丙烯酸酯和NaUA在Fe3O4粒子的表面发生了聚合反应,形成P（NaUA-St-BA）;TEM和激光粒度分析仪测试结果显示,Fe3O4／P（NaUA-St-BA）复合粒子具有核-壳结构而且粒子分布均匀、平均粒径60nm;TG测试的结果表明,NaUA在Fe3O4粒子的包覆率为13．83％,P（NaUA-St-BA）共聚物的包覆率71．85％;振动样品磁强仪（VSM）测试的磁滞回线则表明由无皂乳液聚合得到的Fe3O4／P（NaUA-St-BA）复合粒子具有超顺磁性,可避免磁性微球在磁场中的团聚。另外,合成的磁性胶乳可稳定存放数月。     

STUDY ON FLUORESCENCE BEHAVIOUR OF EU~(3+) CONTAINING POLY(METHYL METHACRYLATE)

Fluorimetry has been used to characterize ionomers synthesized by copolymerization ofmethyl mehacrylate, methacrylic acid and europium methacrylate (EMA). Under excita-tion of UV light at 375 nm no seif-quenching was found in fluorescence of EMA containingionomers at 615nm within the concentration range of 1.6×10~(-2) to 11.49×10~(-2) mol%.This means that the distance between two Eu~(3+) ions is larger than 5nm. In the sameconcentration range seif-quenching took place in europium octanoate (EOA) containingpoly(methyl methacrylate) in which EOA was doped as an additive.     

无皂乳液聚合制备含铕荧光共聚物乳液的研究及其表征

以丙烯酸(AA)为第一配体、邻菲罗啉(Phen)为第二配体、Eu3+为中心离子,合成了一种可聚合的稀土铕配合物.以配合物单体、甲基丙烯酸甲酯、丙烯酰胺和对苯乙烯磺酸钠为共聚单体,通过无皂乳液聚合的方法,制备了含铕荧光共聚物乳液.采用红外光谱对共聚物的结构进行了表征,并探讨了配合物单体含量对共聚物乳液性能的影响.透射电子显微镜(TEM)和激光光散射粒度仪(PCS)测试结果表明,共聚物乳液形成了相对均一的球状结构,但随着配合物单体含量增加,共聚物微球粒径逐渐增大、分散性变差.采用荧光分光光度计测试了共聚物乳液的荧光性能,在594和619 nm处出现Eu3+的特征发射光谱,且荧光强度随着配合物单体含量增加而增强.     

交联核壳结构PBA/PS和PBA/PMMA纳米微球的制备与应用

考察了聚丙烯酸丁酯/聚苯乙烯(PBA/PS)以及聚丙烯酸丁酯/聚甲基丙烯酸甲酯(PBA/PMMA)交联核壳结构纳米高分子微球的制备方法,并对其在尼龙复合材料中的应用进行了初步研究.结果表明,通过交联剂的引入使粒子核层和壳层内部均形成了高度交联的结构,可以限制亲水性较小的聚苯乙烯(PS)壳层向粒子内部迁移的趋势;制备出的微球平均粒径为40~50 nm,粒径分布很窄.采用饥饿态加料方式加入第二单体不仅可以使微球具有较高的产率和凝胶率,而且可以使其具有更理想的核壳结构和更窄的粒径分布.此外,将合成出的PBA/PMMA核壳粒子对尼龙6基体进行复合的结果表明,由于该微球表面与尼龙6基体之间具有较强的界面相互作用且微球具有较大的形变能力,可以在基体中形成良好的分散,在保持材料强度的同时有效地提高了其刚性和韧性.     

掺希土离子Eu3+的BaTiO3超细微粉的制备及物性表征

近年来人们对材料及由材料制备的元件提出了高可靠性、多功能等要求。为了达到这种要求,人们从多种途径进行了探索,其中,对现有材料进行掺杂就是很有效的方法之一［１,２］。本文报道对ＢａＴｉＯ３超细微粉进行Ｅｕ３＋的有效掺杂并对其进行了物性表征。１实验部分１...     

核壳乳剂的制备及其性质

本工作制备了内核碘含量分别为0、2、4、6、8、10、15、25和35mol%的单分散八面体核壳乳剂并对它们的感光性能作了研究。发现二次乳化法是较好的包壳方法。讨论了保证单分散颗粒形成的加料速度范围.将Markocki和Zaleski研究碘含量及pBr对Ag(Br,I)晶体形状影响的结果扩展到碘含量达35mol%。发现有一个生成扁平颗粒的区域。本文采用两种方法:X线衍射以及腐蚀和X线荧光分析颗粒成份结合对所制备的核壳颗粒的双结构进行了实验验证。内核碘含量在0到35mol%范围内,核壳乳剂对光能的吸收量随着碘含量的增加而增加但显影活性不损失,因此有较高的感光度。发现化学增感时核壳乳剂的敏化中心首先在颗粒内部生成。     

PREPARATION AND CHARACTERIZATION OF POLYAMIDE 11/CLAY NANOCOMPOSITES

INTRODUCTIONIn recent years, polymer/clay nanocomposites have attracted great interest from researchers since they frequentlyexhibit unexpected hybrid properties synergistically derived from the two components. Compared to their microcounterparts and the pristine polymer matrix, polymer/clay nanocomposites exhibit improved tensile strength andmodulus, decreased thermal expansion coefficient, decreased gas permeability, increased swelling resistance,enhanced ion conductivity, and reduced fl…     

Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉的制备与发光性能

为了探究在Dy~(3+)掺杂Ba_3Y(PO_4)_3荧光粉中共掺Eu~(3+)离子对其发光性能的影响,我们采用传统高温固相法制备了一系列Dy~(3+)、Eu~(3+)单掺杂和共掺杂Ba_3Y(PO_4)_3荧光粉。通过X射线衍射(XRD)、荧光发射光谱和荧光衰减曲线对样品进行了表征。结果表明,所制备的荧光粉呈闪铋矿立方相。在近紫外光激发下,Ba_3Y(PO_4)_3∶Dy~(3+)发射光谱在487和578 nm处有两个窄带发射峰,呈冷白光发射;Ba_3Y(PO_4)_3∶Eu~(3+)发射光谱的窄带发射位于594和616 nm处,呈发橙红光。在Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)中,由于Eu~(3+)离子补偿Dy~(3+)冷白光发射所缺的红色组分,从而实现了色纯度高、色温适中的暖白光发射。进一步探索了Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)荧光粉发光机理。所制备的Ba_3Y(PO_4)_3∶Dy~(3+),Eu~(3+)单基质白光荧光粉在白光近紫外激发白光二极管(UVWLED)领域具有潜在应用价值。     

STRUCTURE AND PROPERTIES OF POLY (N-VINYLCARBAZOLE) OBTAINED VIA ASYMMETRICALLY STEREOSELECTIVE POLYMERIZATION

The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtainedvia asymmetrically stereoselective polymerization have been studied by using ~1HNMRspectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the contentof isotactic sequences was found to be increased by using AIBN to (-)Sp~+(+)CSA~- asthe initiators or catalysts and the mole extinction coefficient to be decreased. Bimodalmolecular weight distribution (MWD)s of the obtained PVCZs were caused by two propa-gating species of the free ions and the ion-pairs associated with the organic salts duringpolymerization.     

CONFIGURATION-DEPENDENT PROPERTIES OF POLY(DIMETHYLSILOXANE) CHAIN*

The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains aredirectly obtained from a priori probability P_(αβ). Here the differing statistical weight matrices for the Si-Oand O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, asthe same statistical weight matrices for the Si -O and O- Si bonds are adopted, there exists a large deviationof αpriori probability P_(αβ) between the theory and the molecular dynamics (MD) simulation. Our model givessatisfactory agreement with experiment on the mean-square unperturbed end-to-end distance, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants fordimethylsiloxane oligomers. This new rotational isomeric state approach can be widely applied to otherchains, such as -CH_2-C[(CH_2)_mH]_2- and -O-Si[(CH_2)_mH]_2 for arbitrary m.     

Fluorescence Quantum Efficiency Enhancement in CaWO4:Eu3+,Na+ Nanocrystals by Tridoping with F- Ions

We demonstrated that tridoping with F- ions is an effective way to improve the fluorescence quantum efficiency of CaWO4:Eu3+,Na+ nanocrystals. F--tridoped samples with different F- concentrations were synthesized by a hydrothermal process. The fluorescence spectra and decay curves were measured at room temperature. The fluorescence intensity of F--tridoped samples is about 3 times that for the non F--doped sample. The fluorescence quantum efficiency can be enhanced by 21% when the atomic ratio of F to W was 0.7.     

STRUCTURAL INVESTIGATION OF A NEW POLYORGANOSILOXANE CONTAINING NANOTUBULAR CAVITIES USING ORGANIC FLUORESCENT PROBES*

Fluorescent molecules - p-dimethylaminobenzonitrile (DMABN) and trans-stilbene (TSB) -were used as probes to investigate the inner structure of the nanotubular cavities contained in a newpolyorganosiloxane (POS) which was prepared by the hydrosilylation coupling reaction of cis-isotacticladderlike polyvinylsilsesquioxane (Vi-T) with 1, 1,3,3-tetramethyldisiloxane (H-MM) as coupling agent inthe presence of catalyst dicyclopentadienyldichloroplatin (Cp_2PtCl_2). The results from FTIR spectra andfluorescence spectra in combination with molecular simulation revcal that the cross-section of thenanotubular cavity is nearly rectangular in shape, and is about 0.62 nm in width and about 0.38 nm in height.This work gains in-depth knowledge into the inner structure of the nanotubular cavities of POS andfurthermore provides a guide to the selection of proper guest molecules in constructing functionalsupramolecular clathrate based upon POS.     

PREPARATION AND PROPERTIES OF EPOXY RESIN MODIFIED BY LIQUID CHLOROPRENE-HYDROXYETHYLMETHACRYLATE COPOLYMER

The epoxy resin modified by liquid chloroprene-hydroxyethylmethacrylate copolymer (CP-HEMA) is a new kind of structural adhesives with good mechanical properties. By changing its mole-cular structure, it may also have such desirable properties as retardation of combustion, enduringweather aging, inert oils and chemicals. A series of the thermosets of the epoxy resin modifiedby CP-HEMA used as a toughener were prepared. The effects of CP-HEMA content, catalyst con-tent and curing temperature on the mechanical properties of modified epoxy resin system were studied.The thermal weight-loss curves were examined. The two-phase morphology was observed and dis-cussed.     

Eu3+/Tb3+和Eu3+/Pr3+共掺杂P(MMA-co-St)的荧光性能的研究

将不同荧光性能的铽(Tb)、镨(Pr)离子分别与铕(Eu)离子混合，以三异丙氧基稀土的形式掺杂P(MMA-CO-St)共聚物，研究Eu^3 ／Tb^3 和Eu^3 ／pr^3 共掺杂P(MMA-CO-St)的荧光性能的变化情况．结果表明，Eu^3 ／Tb^3 掺杂的P(MMA-CO-St)中，Tb^3 作为能量给予体，Eu^3 作为能量接受体，能量转移的结果使Eu^3 特征荧光显增强；Eu^3 ／pr^3 掺杂的P(MMA-CO-St)中，Eu^3 的能量向pr^3 转移，致使Eu^3 的特征荧光猝灭，pr^3 的荧光略为增强．     

Ag@YF3:Eu3+核壳结构纳米材料的制备与性能研究

采用乙二醇法制备了单质Ag纳米粒子,并通过直接沉淀法合成了均匀球形的Ag@YF3∶Eu3+核壳结构复合纳米发光粒子,对产物的结构和性能进行了表征。XRD分析表明:Ag表面包覆上了结晶良好的正交晶系的YF3∶Eu3+。TEM照片表明:所得的纳米复合粒子具有明显的核壳结构和均匀的球形,中间Ag粒子的尺寸在80~100 nm之间,Ag@YF3∶Eu3+的粒径尺寸约为150~180 nm,表面粗糙且包覆完全。电子衍射表明复合样品为多晶。荧光光谱表明:该纳米复合粒子具有良好的发光性,以593 nm附近的5D0→7F1磁偶极跃迁为最强发射峰,但是比纯的YF3∶Eu3+的发光强度要弱,其荧光寿命有所增强,这表明Ag纳米粒子对外层的YF3∶Eu3+的发光有猝灭作用。     

Li2O-Ln2O3-SiO2:Eu3+,Bi3+体系的结构

采用ｓｏｌ－ｇｅｌ法合成了系列发光体Ｌｉ２Ｏ－Ｌｎ２Ｏ３－ＳｉＯ２：Ｅｕ＾３＾＋，Ｂｉ＾３＾＋，并确定了发光体的物相结构。当Ｌｎ＾３＾＋＝Ｙ＾３＾＋和Ｌｎ＾３＾＋＝Ｌａ＾３＾＋时，紫外光激发下Ｅｕ＾３＾＋的发射分别以红光和橙光为主，只存在一种Ｅｕ＾３＾＋发光中心；Ｌｎ＾３＾＋＝Ｇｄ＾３＾＋时，至少存在两种Ｅｕ＾３＾＋发光中心和两种Ｂｉ＾３＾＋发光中心（共掺杂Ｅｕ＾３＾＋，Ｂｉ＾３＾＋的吸收和发射所     

Electrode kinetics of Eu3+/Eu2+ reaction by cyclic voltammetry

The cyclic voltammetric behaviour of Eu³⁺/Eu²⁺ couple at hanging mercury drop electrode (HMDE) has been studied in chloride, bromide, iodide, thiocyanate and EDTA supporting electrolytes. The apparent rate constant and transfer coefficient for these systems have been calculated at various voltage scan rates, without using the data for standard or formal potential. The values have been compared with those obtained by earlier workers through other electrochemical methods.