Systhesis, phase transformation and photoluminescence properties of Eu:La(1-x)Gd(x)VO4 nanofibers by electrospinning method

One dimensional Eu:La(1-x)Gd(x)VO(4) nanofibers were successfully prepared via an electrospinning method. Thermogravimetry and differential scanning calorimeter (TG-DSC), X-ray diffraction, Raman spectroscopy, scanning electron microscopy and photoluminescence were used to characterize the samples. The nanofibers crystallized well below 600 °C and with the increase of Gd contents, the nanofibers crystallized in a zircon-type structure. The Raman spectra shifted to higher frequency with the increase of Gd content for zircon Eu:La(1-x)Gd(x)VO(4). The peaks of photoluminescence spectra shift towards longer wavelength when Gd replaces La and when x = 0.4, the photoluminescence intensity reaches its maximum value. The band structure and density of states of m-LaVO(4), t-LaVO(4), t-LaGdVO(4) and t-GdVO(4) were calculated by local-spin density approximation (LSDA) band theory with Hubbard term of U. The band gap of t-LaGdVO(4) is just the average of t-LaVO(4) and t-GdVO(4). In t-LaGdVO(4), La 5p states are highly localized.     

Strongly exchange coupled inverse ferrimagnetic soft/hard, Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4), core/shell heterostructured nanoparticles

Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4) with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (～0.6 nm) have been synthesized. The structural characterization suggests that the particles have an interface with a graded composition. The magnetic characterization confirms the inverted soft/hard structure and evidences a strong exchange coupling between the core and the shell. Moreover, larger soft core sizes exhibit smaller coercivities and loop shifts, but larger blocking temperatures, as expected from spring-magnet or graded anisotropy structures. The results indicate that, similar to thin film systems, the magnetic properties of soft/hard core/shell nanoparticles can be fine tuned to match specific applications.     

Electrospinning-derived Tb2(WO4)3:Eu(3+) nanowires: energy transfer and tunable luminescence properties

One-dimensional Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires have been prepared by a combination method of sol-gel process and electrospinning. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. The as-obtained precursor samples present fiber-like morphology with uniform size, and Tb(2)(WO(4))(3) and Tb(2)(WO(4))(3):Eu(3+) nanowires were formed after annealing. Under ultraviolet excitation and low-voltage electron beams excitation into WO(4)(2-) and the f-f transition of Tb(3+), the Tb(2)(WO(4))(3) samples show the characteristic emission of Tb(3+) corresponding to (5)D(4)-(7)F(6, 5, 4, 3) transitions due to an efficient energy transfer from WO(4)(2-) to Tb(3+), while Tb(2)(WO(4))(3):Eu(3+) samples mainly exhibit the characteristic emission of Eu(3+) corresponding to (5)D(0)-(7)F(0, 1, 2) transitions due to an energy transfer occurs from WO(4)(2-) and Tb(3+) to Eu(3+). The increase of Eu(3+) concentration leads to the increase of the energy transfer efficiency from Tb(3+) to Eu(3+). The PL color of Tb(2)(WO(4))(3):x mol% Eu(3+) phosphors can be tuned from green to red easily by changing the doping concentration (x) of Eu(3+), making the materials have potential applications in fluorescent lamps and color display fields.     

水热法对Eu3＋掺杂CaMoO4微纳米荧光体的制备及其发光性能

采用水热法成功的制得了不同形貌的CaMoO4：Eu3＋微纳米荧光体。实验结果表明,溶液的pH值在控制产物形貌上起了决定性的作用。用X射线粉末衍射（XRD）、场发射扫描电镜（FE—SEM）和荧光光谱（PL）等分析手段研究了荧光体的结构和光致发光性能。结果表明,CaMoO4：Eu3＋荧光体的激发光谱由两部分组成：1个宽的激发带（240～360nm）和属于Eu3＋的f—f跃迁的锐线谱（395nm、465nm）,它的发射光谱只出现常见的2个发射峰：592nm（5D0→F1）、615nm（5D0→7F2）,中5D0→7F2跃迁发射峰强度明显高于5D0→7F1跃迁发射峰强度,这表明Eu3＋在CaMoO4基质中处于无反演中心或偏离反演中心的格位上。本文还对造成发射峰强度变化的原因进行了分析,认为影响发射峰强度的原因有两个：表面积和对称性,材料的表面积越大,发光的猝灭越严重,荧光发射越弱;材料的结构对称性越差,跃迁戒律打破地越彻底,荧光发射越强。     

Lanthanide ion-doped GdPO4 nanorods with dual-modal bio-optical and magnetic resonance imaging properties

Here, dual-modal bioprobes for combined optical and magnetic resonance (MR) imaging are reported. Gadolinium orthophosphate (GdPO(4)) nanorods co-doped with light-emitting lanthanide ions have been successfully prepared through a hydrothermal method. An efficient downconversion luminescence from Ce/Tb or Eu doped GdPO(4) nanorods and upconversion luminescence from Yb/Er co-doped GdPO(4) nanorods are observed, respectively, which offers the optical modality for the nanoprobes. Notably, we first report the upconversion phenomenon based on the GdPO(4) matrix under 980 nm near infrared irradiation. The possibility of using these nanoprobes with downconversion and upconversion luminescent emissions for optical cell imaging is also demonstrated. Furthermore, these Gd(3+)-containing nanophosphors show good positive signal-enhancement ability when performed under a 4.7 T MR imaging scanner, indicating they have potential as T(1) MR imaging contrast agents. Thus, nanoprobes based on GdPO(4) nanophosphors are shown to provide the dual modality of optical and MR imaging.     

Core-shell Fe3O4@SiO2 nanoparticles synthesized with well-dispersed hydrophilic Fe3O4 seeds

Silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with controlled silica shell thicknesses were prepared by a modified St?ber method using 20 nm hydrophilic Fe3O4 NPs as seeds. The core-shell NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), and UV-Vis adsorption spectra (UV-Vis). The results imply that NPs consist of a crystalline magnetite core and an amorphous silica shell. The silica shell thickness can be controlled from 12.5 nm to 45 nm by varying the experimental parameters. The reaction time, the ratio of TEOS/Fe3O4, and the concentration of hydrophilic Fe3O4 seeds were found to be very influential in the control of silica shell thickness. These well-dispersed core-shell Fe3O4@SiO2 NPs show superparamagnetic properties at room temperature.     

Synthesis and characterization of polypyrrole‐au coated SiO2@poly(4‐vinylpyridine) composites

Microspheres with silica as core and poly(4‐vinylpyridine) (P4VP) as shell were synthesized. AuCl ions were bound by P4VP chains to form the complex, which acted both as an oxidant of pyrrole monomers and as a source of Au atoms. By vapor phase polymerization, the PPy and Au nanoparticles were simultaneously formed on the surfaces of SiO₂@P4VP microspheres. The core‐shell structure was confirmed by transmission electron microscopy. The surface morphologies of the composites were observed by scanning electron microscopy. The molecular structures of composites were characterized in detail by Raman spectra, X‐ray diffraction, and X‐ray photoelectron spectroscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Y_2O_3：Eu~（3＋）@Gd_2O_3核壳结构发光材料的制备与浓度猝灭

采用均相沉淀法制备均匀球形的Y2O3：Eu3＋@Gd2O3核壳结构纳米发光材料,用X射线衍射、红外光谱、扫描电镜、X射线光电子能谱及荧光光谱等表征样品的形貌、结构及发光性能。结果表明：Y2O3：Eu3＋表面成功包覆了Gd2O3,包覆后仍为均匀的球形,包覆层厚度约为5nm;包覆前后样品的猝灭浓度均为7%（摩尔分数）,包覆...     

水热法制备铁锡纳米复合氧化物及表征

以Fe(NO3)3·9H2O,SnCl4·5H2O为原料,通过改变水热反应的条件合成了铁锡纳米复合氧化物.用X射线衍射仪和透射电镜对产物的结构和微观形貌进行了表征.结果表明:在水热制备铁锡复合氧化物的过程中,通过分步控制温度法和使用不同的沉淀剂可以控制产物的粒径大小和形貌.最终得到以棒状的α-Fe2O3晶体为核,附着有SnO2粒子的纳米复合氧化物.并对复合物形成机理进行了初步探讨.     

Synthesis and characterization of cross-linked poly(acrylic acid)-poly(styrene-alt-maleic anhydride) core-shell microcapsule absorbents for cement mortar

We synthesized core-shell microcapsule absorbents with cPAA (cross-linked poly(acrylic acid)) as the core and PSMA (poly(styrene-alt-maleic anhydride)) as the shell by precipitation polymerization, where the shell served to delay the absorption of excess water in cement mortars. To control shell thickness, the cPAA-PSMA capsules were synthesized with core monomer mass to shell monomer mass ratios of 1/0.5, 1/1, and 1/1.5. We observed the hydrolysis of the PSMA polymer in a cement-saturated aqueous solution by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, core-shell structures were observed for 1/1 (cPAA-PSMA #3) and 1/1.5 (cPAA-PSMA #4) core/shell monomer mass ratios, whereas no core-shell structures were observed for the 1/0.5 (cPAA-PSMA #2) microcapsules by transmission electron microscopy (TEM).     

Preparation and characterization of poly(styrene)/metal composites via reversible addition-fragmentation chain transfer (RAFT) polymerization

The expectant dithiocarbamate group end-functional poly(styrene) (PS) with a controlled molecular weight and low molecular weight distribution was synthesized conveniently via reversible addition-fragmentation chain transfer (RAFT) polymerization and was used to prepare polymer/metal composites with coordination chemistry. By the self-assembly technique, PS coordinated with the rare earth metal in N,N-dimethylformamide (DMF) to generate the fluorescent Eu–PS and Sm–PS complexes. Furthermore, PS-coated spherical silver nanoparticles (AgNPs) were prepared by reducing Ag⁺ to Ag⁰ under ultrasound irradiation in the presence of DMF and H₂O. The well core/shell structure of the AgNPs was characterized by transmission electron microscopy (TEM).     

Synthesis of Aqueous CdTe/CdS/ZnS Core/shell/shell Quantum Dots by a Chemical Aerosol Flow Method

This work described a continuous method to synthesize CdTe/CdS/ZnS core/shell/shell quantum dots. In an integrated system by flawlessly combining the chemical aerosol flow system working at high temperature (200–300°C) to generate CdTe/CdS intermediate products and an additional heat-up setup at relatively low temperature to overcoat the ZnS shells, the CdTe/CdS/ZnS multishell structures were realized. The as-synthesized CdTe/CdS/ZnS core/shell/shell quantum dots are characterized by photoluminescence spectra, X-ray diffraction (XRD), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fluorescence and XRD results confirm that the obtained quantum dots have a core/shell/shell structure. It shows the highest quantum yield above 45% when compared to the rhodamine 6G. The core/shell/shell QDs were more stable via the oxidation experiment by H₂O₂.     

Microwave-Assisted Synthesis of Glutathione-Capped CdTe/CdSe Near-Infrared Quantum Dots for Cell Imaging

These glutathione (GSH)-conjugated CdTe/CdSe core/shell quantum dot (QD) nanoparticles in aqueous solution were synthesized using a microwave-assisted approach. The prepared type II core/shell QD nanoparticles were characterized by UV–Vis absorption, photoluminescence (PL) spectroscopy, X-ray powder diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). Results revealed that the QD nanoparticles exhibited good dispersity, a uniform size distribution and tunable fluorescence emission in the near-infrared (NIR) region. In addition, these nanoparticles exhibited good biocompatibility and photoluminescence in cell imaging. In particular, this type of core/shell NIR QDs may have potential applications in molecular imaging.     

Fabrication of core–shell hybrid nanoparticles by mineralization on poly(ε-caprolactone)-b-poly(methacrylic acid) copolymer micelles

Polymer micelles containing calcium phosphate (CaP) minerals on the shell domain were developed by nanotemplate-driven mineralization. The polymer micelle nanotemplate was prepared by self-assembly of a poly(ε-caprolactone)-b-poly(methacrylic acid) (PCL-b-PMAA) copolymer. PMAA formed the anionic outer shell, and PCL constructed the hydrophobic inner core. Subsequent addition of calcium and phosphate ions to micellar solutions induced CaP mineral deposition within the PMAA shell domain. Transmission electron microscopy (TEM) showed the well-defined nanostructure consisting of the CaP nanoshell and the PCL inner core. Energy-dispersive X-ray spectroscopy (EDS) confirmed CaP deposition on polymer micelles. Dynamic light scattering (DLS) study showed CaP mineralization greatly enhanced the micellar stability.     

Room temperature synthesis of hydrophilic Ln(3+)-doped KGdF4 (Ln = Ce, Eu, Tb, Dy) nanoparticles with controllable size: energy transfer, size-dependent and color-tunable luminescence properties

In this paper, we demonstrate a simple, template-free, reproducible and one-step synthesis of hydrophilic KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) nanoparticles (NPs) via a solution-based route at room temperature. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra are used to characterize the samples. The results indicate that the use of water-diethyleneglycol (DEG) solvent mixture as the reaction medium not only allows facile particle size control but also endows the as-prepared samples with good water-solubility. In particular, the mean size of NPs is monotonously reduced with the increase of DEG content, from 215 to 40 nm. The luminescence intensity and absolute quantum yields for KGdF(4): Ce(3+), Tb(3+) NPs increase remarkably with particle sizes ranging from 40 to 215 nm. Additionally, we systematically investigate the magnetic and luminescence properties of KGdF(4): Ln(3+) (Ln = Ce, Eu, Tb and Dy) NPs. They display paramagnetic and superparamagnetic properties with mass magnetic susceptibility values of 1.03 × 10(-4) emu g(-1)·Oe and 3.09 × 10(-3) emu g(-1)·Oe at 300 K and 2 K, respectively, and multicolor emissions due to the energy transfer (ET) process Ce(3+)→ Gd(3+)→ (Gd(3+))(n)→ Ln(3+), in which Gd(3+) ions play an intermediate role in this process. Representatively, it is shown that the energy transfer from Ce(3+) to Tb(3+) occurs mainly via the dipole-quadrupole interaction by comparison of the theoretical calculation and experimental results. This kind of magnetic/luminescent dual-function materials may have promising applications in multiple biolabels and MR imaging.     

(AgSt)_(1-x)/(AgI)_x复合颗粒的制备及其性能研究

分别以碘化钾(KI)为碘源以及硬脂酸银(AgSt)为本体,用原位法合成了负载型的(AgSt)1-x/(AgI)x复合颗粒。利用红外光谱仪(FTIR)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱仪(UV-Vis)、X射线衍射仪(XRD)以及差示扫描量热仪(DSC)对复合颗粒的微观结构、形貌、光吸收、晶型以及热相变行为进行了表征。结果表明,(1)(AgSt)1-x/(AgI)x复合颗粒由本体AgSt颗粒及其表面上负载的尺寸为30~50nm的AgI粒子构成;(2)相对于AgSt,(AgSt)1-x/(AgI)x复合颗粒的光谱吸光范围从265 nm拓展到425 nm左右,是由AgI的吸收造成;(3)(AgSt)1-x/(AgI)x复合颗粒在82~88℃左右就出现第一相变峰,显著低于本体AgSt的122.9℃,体现了AgSt与AgI两相界面的作用。     

Improving the hydrophobic,water barrier and crystallization properties of poly(ethylene terephthalate) by incorporating monodisperse SiO2 particles

This paper details an improvement in the properties of poly(ethylene terephthalate) (PET) with respect to its use in petroleum engineering by incorporating uniform (monodisperse; 35 to 380 nm) silica (SiO₂) particles and polystyrene? SiO₂ core–shell particles by melt mixing. The resulting high‐performance nanocomposite (SNPET) films are presented. The results of contact angle and water absorption tests showed that the contact angle of the amorphous SNPET films increased from 72° to 118.5° as the core–shell particle load increased from 0 to 6.0 wt%. The contact angle reached 128.0° when the films were annealed. Decreasing the SiO₂ particle size demonstrably improved the SNPET film hydrophobicity and lowered the water diffusion coefficient, i.e. SiO₂ particles of 35 nm in size gave the greatest enhancement of water barrier properties. Results of transmission electron microscopy, scanning electron microscopy, atomic force microscopy and optical measurements showed the homogeneous particle dispersion and nanostructure in the SNPET films. Their transparency and haziness increased as the particle size decreased. Use of such core–shell structures meant that the uniform (monodisperse) SiO₂ particles could be dispersed homogeneously in PET, and effectively improved the surface, thermal and crystallization behavior of SNPET films to produce materials with high barrier stability against water. Copyright © 2010 Society of Chemical Industry     

Ethyl vinyl acetate copolymer—SrAl2O4:Eu,Dy and Sr4Al14O25:Eu,Dy phosphor‐based composites: Preparation and material properties

New photoactive composite based on ethyl vinyl acetate (EVA) and SrAl₂O₄:Eu,Dy or Sr₄Al₁₄O₂₅:Eu,Dy were prepared by melt mixing or extrusion methodologies. The phosphorescent behavior and material properties of the polymer‐phosphor composites were studied. The morphology of the polymer and the composites were studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X‐ray spectroscopy (EDS). The SEM shows that the physical and chemical behavior of the matrix and the extrusion conditions were primarily responsible for the surface morphology. TEM and EDS show that the phosphor particles were uniformly dispersed in the EVA matrix. A broad band of ultraviolet (UV)‐excited phosphorescence of SrAl₂O₄:Eu,Dy and Sr₄Al₁₄O₂₅:Eu,Dy phosphors and the respective composites were observed at wavelengths of 516 nm and 490 nm, respectively. The photoluminescence (PL) spectra showed less intense phosphorescence but no shift in the wavelength of the emission peak for all the composites. The Hamburg wheel test was done on all the composites and the PL measurements before and after the test showed almost no change in the intensity of the emission. Thermal studies showed that the presence of the phosphors in the matrix slightly increased the crystallinity of EVA, which leads to higher melting enthalpies. Tensile testing shows very little change in the tensile strength and flexibility of the ethylene vinyl acetate copolymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

聚苯乙烯-聚4-乙烯基吡啶-稀土铕(Ⅲ)发光配合物的微观结构及荧光性能表征

含共轭结构氮杂环的非离子嵌段共聚物能与铕(Ⅲ)络合反应形成发光配合物,研究了该发光配合物的配位结构及其荧光性能。以聚苯乙烯-聚4-乙烯基吡啶(PS-b-P4VP)作为高分子配体,以邻菲罗啉(Phen)作为小分子配体,通过吡啶环的氮原子与Eu(Ⅲ)离子配位发生络合反应形成了以网状的Eu(Ⅲ)-P4VP核层以及PS链段为壳层的共聚物-稀土配合物,通过电子透射电镜(TEM)分析了其微观形态结构。用荧光分光光度计分别表征了嵌段聚合物-稀土铕(III)配合物不同链段的荧光发光强度并且进行了荧光强度的对比。此外,还研究了不同的Eu(Ⅲ)离子浓度对荧光强度的影响,得到了制备共聚物-稀土配合物荧光的最佳Eu(Ⅲ)离子浓度。     

(1-x)Ba(Mg1/3Nb2/3)O3-xBaSnO3陶瓷的微波介电性能

用传统陶瓷制备方法制备了(1-x)Ba(Mg1/3Nb2/3)O3-xBaSnO3[0.0≤x≤0.3,(1-x)BMN-xBS]体系微波介质陶瓷,研究了该陶瓷的微观结构和微波介电性能.用X射线衍射仪研究陶瓷的晶体结构.用扫描电镜观察陶瓷的显微结构.用网络分析仪测试陶瓷的微波介电性能.结果表明:晶格常数c和a均随x值的增加而增加;晶格常数比(c/a)随x值的增加而减小.当x≥0.1时,1∶2有序衍射峰消失.陶瓷的平均晶粒尺寸在0.7～2 μm之间.随x值的增加,陶瓷的相对介电常数(εr)和谐振频率温度系数(τr)呈线性减小;品质因数与谐振频率的乘积(Qf)呈非线性变化.当x=0.15时,Qf达到最大值,为86 200 GHz.当x=0.3时,在此体系中可以获得τf接近零的微波介质陶瓷Ba(Sn0.3Mg0.233Nb0.467)O3,其微波介电性能如下:εr=26.1;Qf=42 500GHz;τr=4.3×10-6/℃.