Advanced Materials Research Vols. 557-559

Abstract: Co (t nm)/TiO₂ (200 nm) films were prepared by DC facing-target magnetron reactive sputtering system onto glass substrates at room temperature. The influence of the Co distribution on microstructure and magnetic properties of films was investigated in detail. The results indicate that CoTiO₂ thin films with t= 2 nm island-type deposited showed a homogeneous structure, and pure ferromagnetic properties of thin films are only attributed to the CoTiO₂ phases. On the other hand, in case of thin films above t= 2nm, the overall ferromagnetic properties depended on both CoTiO₂ and CoTi phases.

Abstract: We herein report the synthesis of bis-(5,10-diphenyltripyrrin)nickel(II), which is the first meso-substituted tripyrrin metal complex. The use of tripyrrane as the starting material provides a new synthetic route to tripyrrins. The functionalization on the meso positions endows this type of compound a brighter perspective in synthetic chemistry. Meanwhile, the fluorescent property of the compound has been detected, indicating that this type of compound a strong candidate for fluorescent materials.

Abstract: A simple and convenient method to make a novel material of DNA-coated magnetic-fluorescent composite particles was presented in this article. Hydrothermal synthesis was used for obtaining Fe3O4 magnetic nanoparticles. After modified by oleic acid, the nanoparticles were coated by the macromolecular shell, which came form the polymerization of ethyleneglycol dimethacrylate and methacrylic acid. With the help of ethylenediamine as linker molecules and the condensation effect of ethyl (dimethylaminopropyl) – carbodiimide and N-Hydroxysuccinimide (EDC/NHS) reaction system, salmon DNA were linked to the surface of the shell. After labeling a fluorescent dye Syber Green Ⅰ®, the magnetic-fluorescent composite particles were produced.

Abstract: The combinatorial material library approach is an excellent innovation for inorganic functional material research, and it can discover and screen new materials efficiently. In this paper, it is used to quickly find and improve Tb₃₊ activated gadolinium aluminate perovskite phosphors (Gd_1-x-yAlO₃: Tb_x, RE_y, RE ion vary among Ce^3+,4+, Dy³⁺, abbreviate as GAP:Tb,RE). Under UV light excitation, Gd_1-x-yAlO₃: Tb_x, RE_y gradational combinatorial library indentifies the “lead” green luminescent compound as GAP:Tb_0.1 from all the GAP:Tb_x (x=0.05~0.15) candidates in a quick way. Then the relationship between sensitizers and activators can be also mapped out quickly, that Dy³⁺, is a good sensitizer for Tb³⁺,activator while Ce^3+,4+ is not a suitable one. The photoluminescent excitation (PLE) and photoluminescent emission (PL) spectral indicate the resonance energy transfer between the activator and sensitizer must have happened, which leads to Ce^3+,4+ co-doping decrease Tb³⁺ green luminescence（⁵D₄→⁷F₅，544nm） while Dy³⁺ co-doping increase green luminescence. The candidates in the library are prepared in powder form by nitric-citric method for more detailed characterization. All the screening results, obtained from the combinational library, are coherent with the powder phosphor experiments.

Abstract: The magnetization, ac susceptibility and magnetic relaxation of Nd_0.90Sr_0.10CoO₃ polycrystalline sample were systematically investigated in this paper. The experimental studies of susceptibility and magnetic relaxation evidence the existence of a low-temperature spin-glass. A dynamic analysis of ac susceptibility implies a spin-glass transition temperature TSG =12.17 K and the dynamical exponent zv=8. Moreover, low-temperature zero-field cooling and field cooling magnetic relaxation show perfectly mirror symmetry, and field cooling processes relaxation obeys a stretched exponential form. Therefore, our study confirms that the phase separation in Nd_0.90Sr_0.10CoO₃ originates from both the ferromagnetic clusters interaction and the spin glasslike phase at low temperature.

Abstract: The Silver nanoparticles with chiroptical feature have been prepared via chiral transfer through supramolecular interaction during the photoirradiation of silver salt with the assistance of chiral environment provided by sodium deoxycholate at pH 9.7. The pH value plays a significant role for the formation of optically active silver nanoparticles, which may be due to the changes in distance and conformation caused by the addition of hydroxy anion. The as-synthesized silver nanoparticles exhibit the typical surface plasmon absorption, and most importantly, the positive circular dichroism signal in CD spectrum. This finding may be fundamentally important, on the one hand, in term of the fact that chiral photochemistry is extendable to the hot field of inorganic nanomaterials. On the other hand, the as-prepared chiral silver nanoparticles may find their application in chiral opto-electronic switches, the catalysts for asymmetric organic synthesis, or the host for chiral organic photochemistry.

Abstract: Tb-Ce ions co-doped SiO₂ matrix nanocomposites were prepared successfully by a modified sol-gel method. High resolution SEM shows that the dried sample (annealed at 120°C for 48 hours) was in a “magnetic-domain” like structure. When the sample was treated at high temperature (800°C for 3 hours), it really forms an amorphous glass state with average grain size of 49.8nm. Under the excitation of 257nm UV light, the very strong emission of green light are observed around 544nm (⁵D₄ - ⁷F₅). The possible mechanism of efficient energy transfer occurred in SiO₂:Ce³⁺-Tb³⁺ phosphor is from Ce³⁺ to Tb³⁺. Various mole ratio of Tb:Ce and their concentrations, different annealing temperature and time have significant influence on PL properties of Tb-Ce ions co-doped SiO₂ matrix nanocomposites.

Abstract: Influences of different amount of La-substituted on structural and magnetic properties of M-type strontium ferrites SrLa_xFe_(12−x)O₁₉ compounds prepared by an aqueous solution method have been systematically investigated by XRD, VSM and TEM. In this work, it is found that only magnetoplumbite structure exists in the sample rather minorphases from the XRD patterns. When the doping content is x≤0.06mol, substituting of La³⁺ for Fe³⁺ occurs, forming SrLa_xFe_(12-x)O₁₉. In contrast, when the doping content is x>0.06mol, Sr2+ is substituted by La³⁺, forming Sr_(1-x)La_xFe₁₂O₁₉. The saturation magnetization (σs) shows its maximum at x=0.04 while the peak value of the intrinsic coercive field (Hjc) presented at x=0.06 as the La substituted content increases. The obtained results also indicated that the shape of the formed SrLa_xFe_(12−x)O₁₉ is oblong with 70nm length and 40nm width.

Abstract: The absorption and transport scattering coefficients of biological material determine the radial dependence of the diffuse reflectance light that is due to a point source. In order to noninvasive determinate the optical scattering and absorption coefficients of biological material, we must know the radial dependence of the diffuse reflectance. The diffusion approximation of the radiative transfer equation is a model used widely to describe photon migration in biological material. An analysis of the steady state diffusion equation together with its solution of the diffuse reflectance light for the slab geometry and for a semi-infinite diffusing biological material is reported. The result has been compared with that obtained from Monte Carlo simulations. The comparison has shown that the solution about the diffuse reflectance light on surface of biological material is the same as that obtained from Monte Carlo simulations.

Abstract: In order to explore low dielectric polymeric materials, two types of cellular polyimide films with different dianhydride units were prepared by phase inversion method, and their dielectric properties were investigated. Polyimide films with various cellular structures were obtained by controlling coagulation bath compositions and temperatures. The effects of chemical structures, cellular structures on dielectric property of cellular polyimide films were studied. The results showed that all of the cellular polyimide films had lower dielectric constants than the polymer matrix. The dielectric properties were influenced dominantly by the morphologies of the films. Cellular Polyimide films filled with uniform small cellular structures behaved excellent dielectric property compared with those large-pore cellular films. These findings would provide potential application for cellular polyimide films in microelectronic devices.