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121.
Ioannis?M.?KalogerasEmail author Aglaia?Vassilikou-Dova 《Materials Research Innovations》2003,7(5):263-268
The dielectric response of poly(methyl methacrylate) (PMMA) in solid solutions of perylene derivative laser dyes in PMMA and
PMMA + SiO2 has been studied by means of the thermally stimulated depolarization currents (TSDC) technique, with the aim to isolate molecular
and phase interactions in the dye blends. The changes in characteristics of the β-relaxation mode of PMMA are interpreted
with respect to the dissimilar local environments of the polar carboxy-methyl pendant groups of PMMA. An important "chemical"
effect on the β relaxation mechanism recorded in the organic-inorganic composites, is the formation of hydrogen bonds between
the acidic pore surfaces of SiO2 and the acetate side-groups. Several "physical" effects produced by the chromophores and the geometrical confinement, like
the modification of the monomer-to-polymer conversion rates, the polymer's free volume and the extent of the PMMA-SiO2 interaction, are discussed. 相似文献
122.
为了解C60(OH)x经呼吸道进入体内后的分布情况,用放射性标记技术和单光子发射计算机断层(Single photon emission computed tomography,SPECT)成像技术,研究了99mTc-C60(OH)x经气管滴注后在SD大鼠体内分布、吸收和代谢的情况,及其与纳米颗粒粒径的依赖关系.用99mTc标记了富勒烯多羟基衍生物C60(OH)x(x=22,24),标记率为93%.标记物在体外和体内都有良好的稳定性.比较了99mTc-C60(OH)x和Na99mTcO4经气管滴注后在SD大鼠体内的SPECT成像.结果表明,与水溶性的小分子Na99mTcO4不同,纳米尺度的99mTc-C60(OH)x标记物大多滞留于肺中,且清除缓慢;少部分99mTc-C60(OH)x能迅速通过肺泡-毛细管屏障进入血液,主要分布于肝、骨和脾中,并通过肾代谢排泄,显示了纳米颗粒生物分布的主要特征.由此可见,纳米颗粒穿越气血屏障的能力与颗粒物的粒径相关.研究结果为纳米颗粒的呼吸毒性研究提供了重要基础资料. 相似文献
123.
从理论上分析了高功率双包层光纤激光器的受激布里渊散射效应,建立了考虑受激布里渊散射的光纤激光器速率方程,并采用打靶法对其求解,对数值求解算法进行了详尽的描述。通过比较不同的纤芯直径、光纤长度以及掺杂浓度的情况下输出激光功率极限值的不同,发现增大纤芯直径、减小光纤长度以及降低掺杂浓度可以有效地减少受激布里渊散射的影响。 相似文献
124.
125.
光子晶体及其应用 总被引:2,自引:0,他引:2
祁建霞 《西安邮电学院学报》2007,12(5):138-141
光子晶体是一种具有光子带隙的新型功能材料。文章介绍了光子晶体的基本概念,物理特性及其在光学、微波等方面的应用。 相似文献
126.
F. He L. L. Tian X. Y. Tian H. Xu Y. H. Wang W. J. Xie M. Hanif J. L. Xia F. Z. Shen B. Yang F. Li Y. G. Ma Y. Q. Yang J. C. Shen 《Advanced functional materials》2007,17(9):1551-1557
1,4‐di(4′‐N,N‐diphenylaminostyryl)benzene (DPA‐DSB) is a well known compound with a large two‐photon absorption (TPA) section and strong fluorescence in solution. However, the ease with which it crystallizes results in the formation of discontinuous crystalline phases during vacuum deposition processes, thereby greatly limiting its applicability in solid‐state devices. A cruciform dimer of DPA‐DSB, 2,5,2′,5′‐tetra(4′‐N,N‐diphenylaminostyryl)biphenyl (DPA‐TSB) is reported, wherein two DPA‐DSB molecules are linked through a central biphenyl bond. The DPA‐TSB molecules take on a cruciform configuration because of the steric crowding around the central biphenyl core, which has the effect of efficiently suppressing crystalline and intermolecular interactions. The neat DPA‐TSB solid shows strong green–blue fluorescence because of both steady‐state absorption as well as TPA. The DPA‐TSB solid exhibits a photoluminescence (PL) efficiency (ηsolid) of 29 % and a solid‐state two‐photon action cross section (δηsolid) of 954 GM (1 GM = 1 × 10–50 cm4 s photon–1 molecule–1), which is much greater than for the model compound DPA‐DSB (ηsolid = 16 % and δηsolid = 150 GM, where δ is the TPA cross section and η is the fluorescence quantum yield). Based on its high PL efficiency, good film‐forming ability, and strong TPA, DPA‐TSB seems to be a good candidate for applications in solid‐state optical devices. 相似文献
127.
Y. Tian C.‐Y. Chen Y.‐J. Cheng A. C. Young N. M. Tucker A. K.‐Y. Jen 《Advanced functional materials》2007,17(10):1691-1697
A series of new hydrophobic two‐photon absorbing (2PA) chromophores with varied electron‐donating groups in quasi‐linear and multibranched structures are synthesized to correlate their structure/photophysical property relationships. The feasibility of using these large two‐photon absorption cross‐sectional (δ, expressed in GM = 1 × 10–50 cm4 s photon–1 molecule–1) materials in aqueous solution is also explored. All four hydrophobic 2PA materials can be encapsulated into micelles generated by dispersing an amphiphilic block copolymer, poly(methacrylic acid)‐block‐polystyrene (PMAA‐b‐PS), into water. The micellar nanostructures are characterized using dynamic light scattering, atomic force microscopy, and transmission electron microscopy. After these dyes are incorporated into micelles, they exhibit strong fluorescence in water. It is found that the quantum yield and δ values of these chromophores are strongly dependent on the diameters of the micelles, concentrations of the PMAA‐b‐PS, and molecular structures of the 2PA chromophores. One of the compounds that has a strong triarylamino donor and a multibranched structure exhibits a large δ value of 2790 GM and high quantum yield (0.56) in micelle‐containing water. Although this value is smaller than the original value of 5300 GM in toluene, it is still substantially larger than the values of most water‐soluble 2PA materials, which have δ values of less than 100 GM. 相似文献
128.
Silole‐Based Red Fluorescent Organic Dots for Bright Two‐Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging
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Bin Chen Guangxue Feng Bairong He Chiching Goh Shidang Xu Gabriel Ramos‐Ortiz Laura Aparicio‐Ixta Jian Zhou Laiguan Ng Zujin Zhao Bin Liu Ben Zhong Tang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(6):782-792
Robust luminescent dyes with efficient two‐photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation‐caused quenching. In this work, a red fluorescent silole, 2,5‐bis[5‐(dimesitylboranyl)thiophen‐2‐yl]‐1‐methyl‐1,3,4‐triphenylsilole ((MesB)2DTTPS), is synthesized and characterized. (MesB)2DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation‐enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2DTTPS within lipid‐PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two‐photon absorption cross section of 3.43 × 105 GM, which yields a two‐photon action cross section of 1.09 × 105 GM. These (MesB)2DTTPS dots show good biocompatibility and are successfully applied to one‐photon and two‐photon fluorescence imaging of MCF‐7 cells and two‐photon in vivo visualization of the blood vascular of mouse muscle in a high‐contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network. 相似文献
129.
Victor Chernomordik Amir H. Gandjbakhche Leonardo Dagdug 《Journal of Modern Optics》2013,60(20):2048-2053
Biomedical applications of near infrared radiation (NIR) techniques (i.e. based on light wavelengths roughly between 400 and 1100?nm) require that a preliminary estimate of the tissue volume being investigated be found. One possible estimate is the depth to which a photon penetrates a tissue before eventually emerging at a separating plane at a given time. A simple model for this problem can be based on a lattice random walk and was initially analyzed when the associated optical coefficients are isotropic with respect to the geometrical configuration. Here we include the effects of anisotropy in the optical coefficients, finding that at long times the statistical properties of the depth of penetration can be accounted for by very simple scaling factors while at short times the anisotropy effects can be quite noticeable. 相似文献
130.
A recurrent stochastic binary network 总被引:1,自引:0,他引:1
赵杰煜 《中国科学F辑(英文版)》2001,44(5):376-388
Stochastic neural networks are usually built by introducing random fluctuations into the network. A natural method is to use stochastic connections rather than stochastic activation functions. We propose a new model in which each neuron has very simple functionality but all the connections are stochastic. It is shown that the stationary distribution of the network uniquely exists and it is approxi-mately a Boltzmann-Gibbs distribution. The relationship between the model and the Markov random field is discussed. New techniques to implement simulated annealing and Boltzmann learning are pro-posed. Simulation results on the graph bisection problem and image recognition show that the network is powerful enough to solve real world problems. 相似文献