共查询到20条相似文献,搜索用时 812 毫秒
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采用红外光谱、热重分析、紫外光谱和荧光光谱对侧链含查尔酮基团的聚(4-甲基丙烯酰氧基-4'-二甲氨基查尔酮)(PMADMAC)和聚(4-丙烯酰氧基查尔酮)(PAC)的光交联特性进行了研究。随着光照时间的增加,PMADMAC和PAC聚合物光致环加成反应迅速进行,波长短的紫外线更易使得聚合物发生[2+2]环加成反应。与溶液状态相比,固体薄膜状态下的光交联反应速率较慢。PMADMAC聚合物更容易发生光致环加成反应,其光交联速率要比PAC聚合物快,环加成反应也更彻底。采用荧光光谱研究了聚合物的发光特性,发现PAC聚合物无荧光,而PMADMAC聚合物具有溶剂极性敏感的荧光特性。在PMADMAC聚合物的稀溶液中,随着365 nm紫外光照时间的增加,荧光强度迅速降低,其荧光特征波长在紫外光照射后发生蓝移。 PMADMAC和PAC聚合物的热稳定性较好,光交联后形成热不稳定的环丁烷结构,其热稳定性有所降低。 相似文献
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利用迈克尔加成反应合成了2,7-二溴-9,9-二-(3-丙基酰胺-2-甲基丙磺酸)芴(FSO3H),并通过Suzuki偶合反应制备了9,9-二-(3-丙基酰胺-2-甲基丙磺酸)芴-9,9-二己基芴共聚物(PF6SO3H)和9,9-二-(3-丙基酰胺-2-甲基丙磺酸)芴-4,4'-联苯共聚物(PFDBSO3H)。通过核磁共振氢谱(1H NMR)、凝胶渗透色谱(GPC)、紫外-可见吸收光谱对聚合物的结构进行了表征,利用荧光发射光谱对聚合物在各种条件下的荧光发光性能进行了研究。结果表明,上述两种磺酸型聚芴已被成功合成,这些聚合物具有较高的分子量并能够很好地溶于甲醇和水/醇混合溶剂中。荧光发光光谱研究表明:溶剂的极性、溶液的浓度和p H值、溶液中的金属离子都对磺酸型聚芴的发光性能有很大的影响。荧光发射光谱随着溶剂极性的增加逐渐红移。荧光强度随着溶液浓度的增加先增加后降低。当溶液p H从1增加到7.5时,荧光强度逐渐增加;当p H从7.5增加到12.5时,荧光强度降低直至猝灭。离子猝灭剂Mv+、Ag+、K+、Na+和Li+等对两种聚合物具有明显的猝灭效应,且对PF6SO3H的猝灭效应比对PFDBSO3H更强,这与磺酸型聚芴分子的刚性及离子的相互作用有关。 相似文献
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在聚合物溶液中,聚合物单体和溶剂分子之间的相互作用会影响聚合物高分子的尺寸和结构。本文使用动态光散射实验系统研究了聚环氧乙烷在水+TBA二元混合溶液中的分子尺寸变化,实验结果表明聚环氧乙烷分子会呈现出收缩-膨胀的奇异性构型变化。本文也系统分析了产生该现象的原因,依次分析了在二元混合溶液中可能对聚合物分子尺寸产生影响三个原因:溶剂非理想性影响(Shultz-Flory理论)、临界涨落影响以及水+醇溶液所呈现出来的奇异性性质。结合这三个因素,本文较好地解释了实验所观测到的奇异现象。 相似文献
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首次用二氧化钛(TiO2)纳米材料修饰的547孔微结构聚合物光纤(MPOF)二次预制棒作为阵列化微管式光催化反应器对亚甲基兰的光催化分解进行研究.将高光催化活性的P25型二氧化钛纳米粒子均匀分散在TiO2溶胶中,对547孔微结构聚合物光纤孔洞内壁进行铺膜,得到了负载光催化剂的阵列化微管材料.该TiO2MPOF有序复合的阵列化微管不仅对二氧化钛纳米粒子起到负载作用,还可以作为光波导介质(rolling-up薄膜波导,聚光、导光进入二氧化钛薄膜层)、污染物反应流体通道.以有机染料亚甲基兰为模拟污染物,研究了TiO2负载量、亚甲基兰的初始浓度及溶液pH值等因素对光降解效果的影响.该反应器547个孔道的内表面用于负载光催化剂,不仅增加了固-液接触面积,也提高了光的吸收效率,从而提高了光催化效率.迄今为止,这种兼具导光、聚光、传质、负载功能于一体的光催化反应器还未见报道. 相似文献
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Falko Riechert Guy Verschaffelt Georg Bastian Ingo Fischer 《Optics Communications》2008,281(17):4424-4431
We present a technique to reduce the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can be obtained when using the proper driving conditions. We evaluate the efficiency of this technique to reduce the speckle contrast by comparing it with the speckle characteristics in multimode emission under cw operation. Depending on the illumination setup, the incoherent emission regime can lead to a strongly reduced speckle contrast down to 1.3%. This is in agreement with estimates of the expected speckle contrast reduction when three contrast reducing effects are taken into account. These low contrast values make the investigated sources attractive for several applications that suffer from speckle noise. 相似文献
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Tatiana Gorelik Ute Kaiser Thomas Kuhlmann Sergey Yulin Wolfgang Richter 《Applied Surface Science》2004,230(1-4):1-7
The structure of multilayers of ultrathin scandium (Sc) and chromium (Cr) films has been characterized by means of transmission electron microscopy (TEM). Face centered cubic Sc was found both in magnetron sputtered thin Sc layers on Si(0 0 1) and in Cr/Sc multilayers for soft X-ray mirrors. The single Sc and Cr layers are polycrystalline with randomly oriented grains, while Sc and Cr within the Cr/Sc multilayer show a strong [0 0 1] texture in the deposition direction. From high-resolution images the orientation-relationship at the Cr/Sc interfaces could be deduced as: Sc[110]//Cr[100] and Sc[010]//Cr[110], which was confirmed by image simulations. 相似文献
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This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers. 相似文献
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《Current Applied Physics》2020,20(1):78-81
Doping is one of the most powerful methods amongst the various performance improvement ways. Doping affects the energy levels of the host layer by the energy level of the dopant. This allows the energy bandgap to be adjusted to a desired level and thus generates light corresponding to that energy level. Alternatively, it can act as an energy barrier between the interfaces to change the flow of carriers. In this study, the voltage dependences of undoped and doped devices were observed. Bis(2-phenylquinoline) iridium(III) (acetylacetonate) (Ir(pq)2acac) was doped in 4,4′-N, N′-dicarbazole-biphenyl (CBP) as the emission layer. The light intensity changes with the doping concentration, and the efficiency was also studied. When a high voltage was applied, the effect of triplet-triplet annihilation (TTA) adversely affected the electron-hole recombination. We analyzed the optimal operating conditions and the effect of doping concentration on OLEDs. 相似文献
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The grain boundary potential and interface state charge density at the grain boundaries of silver sulfide (Ag2S) thin films prepared by chemical conversion of cadmium sulfide (CdS) films have been determined from the dc resistance of the material and are found to be sensitive to annealing. A reduction in the grain boundary potential and the grain boundary charge density of the film has been noticed when the source CdS film is annealed at different temperatures prior to chemical conversion. The variation in the grain boundary charge density of the grown Ag2S film with source annealing temperature has been found to be similar to that of thin cadmium sulfide film, reported earlier. An additional low temperature heat treatment of the sample results in an enhancement in the charge density at the grain boundaries. The change in the silver vacancy and/or oxygen and sulfur content of the films as revealed from the energy dispersive spectra of the films suggests possible role of film composition on the grain boundary charge density. 相似文献
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三螺旋DNA分子Poly(dT)·Poly(dA)·Poly(dT)碱基振动模式 总被引:1,自引:0,他引:1
利用晶格动力学方法计算了三螺旋 DNA分子 poly(d T)· poly(d A)· poly(d T)碱基振动模式 ,并根据势能分布矩阵对碱基振动模式进行了指定。计算的模式频率同拉曼光谱实验相符合 相似文献
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SHEN Cheng-Ping 《中国物理C(英文版)》2010,34(6):615-620
In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X(3872), X(3915),Y(4140), X(4350), and the charged Z states. 相似文献
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利用在Υ(nS)(n=1,2,4,5)共振态及其附近采集的大量数据,Belle实验测量了末态中含两个矢量粒子的双光子过程γγ→J/ψ和ωJ/ψ.在这两个过程中,发现了两个窄共振结构X(4350)和X(3915).这两个新结构的性质目前尚不清楚,可能是普通粲偶素粒子,也可能是含一对粲夸克和一对轻夸克的四夸克态,或含一对粲夸克和一个激发胶子的混杂态,或是由其他未知的动力学原因造成的奇特结构.Belle同时发现在γγ→J/ψ过程中,不存在显著的Y(4140)的信号,实验结果与将Y(4140)解释为四夸克态的部分理论预期有较大差异. 相似文献
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Sarla Sharma Rishi VyasSubodh Shrivastava Y.K. Vijay 《Physica B: Condensed Matter》2011,406(17):3230-3233
We report a study on the SHI induced modifications on structural and optical properties of ZnO/PMMA nanocomposite films. The ZnO nanoparticles were synthesized by the chemical route using 2-mercaptoethanol as a capping agent. The structure of ZnO nanoparticles was confirmed by XRD, SEM and TEM. These ZnO nanoparticles were dispersed in the PMMA matrix to form ZnO/PMMA nanocomposite films by the solution cast method. These ZnO/PMMA nanocomposite films were then irradiated by swift heavy ion irradiation (Ni8+ ion beam, 100 MeV) at a fluence of 1×1011 ions/cm2. The nanocomposite films were then characterized by XRD, UV-vis absorption spectroscopy and photoluminescence spectroscopy. As revealed from the absorption spectra, absorption edge is not changed by the irradiation but the optical absorption is increased. Enhanced green luminescence at about 527 nm and a less intense blue emission peak around 460 nm were observed after irradiation with respect to the pristine ZnO/PMMA nanocomposite film. 相似文献
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Previous studies have shown that anisotropy in phonon transport exist because of the difference in phonon dispersion relation due to different lattice directions, as observed by a difference in in-plane and cross-plane thermal conductivities. Our current work intends to study the effect of anisotropy scattering on silicon thermal conductivity at 300 K and 400 K. We adopt the Henyey and Greenstein probability density function in our phonon Monte Carlo simulation to investigate the effect of highly forward and backward scattering events. The impact of applying the anisotropy scattering using this approach is discussed in detail. While the forward and backward scattering will increase and decrease thermal conductivity respectively, the extent of the effect is non-linear such that forward scattering has a more obvious effect on thermal conductivity than backward scattering. 相似文献