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991.
Cr(Ⅵ)-4CP(4-氯苯酚)共存污染体系中Cr(Ⅵ)离子的紫外光致还原主要是由于Cr(Ⅵ)与4CP光解产物之间的氧化还原反应而引起的。Cr(Ⅵ)离子还原受光强和体系酸度影响较大,还原速率呈零级反应。随体系pH值增大,Cr(Ⅵ)离子还原速率下降。中性条件下,光反应结束后有沉淀产物生成,这对于采用光化学方法消除环境污染提供了很有意义的结果。4CP存在对Cr(Ⅵ)离子在TiO2表面的暗态吸附没有影响。Cr(Ⅵ)-4CP-TiO2体系中Cr(Ⅵ)离子的紫外光致还原主要包括了两种反应:Cr(Ⅵ)与4CP之间的均相反应以及Cr(Ⅵ)离子在TiO2表面的光催化还原反应。一定波长紫外光下,排除Cr(Ⅵ)-4CP-TiO2体系中的均相反应,使得4CP对Cr(Ⅵ)离子光催化还原反应的促进作用得以证实。 相似文献
992.
本工作对硝酮化合物猝灭9-氰蒽荧光的机制进行了研究,发现不同的9-氰蒽/硝酮体系可能经历包括电子转移、能量转移及竞争吸收等不同的猝灭过程。其中α,N-二苯基硝酮对荧光猝灭遵循电子转移机制,分别形成猝灭剂和敏化剂的离子自由基,但硝酮正离子自由基不能导致环化反应发生,结果还表明:硝酮化合物的四π电子1,3偶极结构在猝灭过程中起主要作用,因此当光环化反应破环1,3偶极结构生成氧氮丙啶时,即失去其原有的猝灭能力,导致已被猝灭的荧光重新回复。 相似文献
993.
Peijie Zheng Xiao Hu Xiongyan Zhao Lin Li Kam Chiu Tam Leong Huat Gan 《Macromolecular rapid communications》2004,25(5):678-682
Summary: Novel azobenzene‐functionalized hydroxypropyl methylcellulose (AZO‐HPMC) polymers and their α‐cyclodextrin (α‐CD) complexes have been prepared. These polymers show interesting sol‐gel transition behavior in aqueous solutions. In the absence of α‐CD, the gelation temperature increases after UV irradiation, while in the presence of α‐CD, the gelation temperature decreases after UV irradiation. The difference in the gelation temperatures between the trans and cis samples of AZO‐HPMC opens a wide operating window for reversible regulation of the sol‐gel transition behavior by photoirradiation.
The UV‐induced cis/trans isomerism of azobenzene‐functionalized hydroxypropyl methylcellulose and its α‐cyclodextrin complexes. 相似文献
994.
Masaaki Suzuki Okio Nishimura Hideaki Nagai Yoshinori Nakata Takeshi Okutani 《应用有机金属化学》2000,14(6):325-329
The synthesis of silicon‐based polymer films was studied by excimer laser (248 nm)‐induced photo‐reaction of phenylsilane and methyl‐phenylsilane at reduced pressure. IR and UV–VIS results showed that the films were composed of Si–C network structures with phenyl rings. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
995.
光热折变体光栅是在光敏玻璃材料中利用光热折变效应记录的折射率型体全息光栅,具有波长和角度选择性好、衍射效率高、热稳定性好和抗损伤阈值高等特点,在激光器技术领域中具有独特的优势。在自行制备的光敏玻璃材料中,用325nm波长的紫外光曝光记录透射型体全息光栅,基于变波长读出的原理设计实验,对热显影后的光热折变体光栅在532nm波长的激光照射下的衍射读出特性以及其在恒定光功率密度的激光照射下的稳定性进行了实验研究。研究结果表明,热显影后的光热折变体光栅在激光辐照下具有光致饱和效应。根据实验结果定量计算出了光热折变体光栅的选择角和描述光致饱和效应的特征时间常数。 相似文献
996.
997.
《Journal of Polymer Science.Polymer Physics》2018,56(5):355-361
Using sequential RAFT polymerization, single monomer insertion, and “click” chemistry, a series of triblock copolymers, poly(ethylene oxide)‐b‐polystyrene‐b‐poly(ethylene oxide), PEO‐b‐PS‐b‐PEO, were synthesized, where one of the two junction points is a UV cleavable ortho‐nitrobenzyl (ONB). Ordered patterns of PEO‐b‐PS‐b‐PEO were produced by solvent vapor annealing. Upon exposure to ultraviolet (UV) light, the PEO‐b‐PS‐b‐PEO was converted into a mixture of a PEO homopolymer and a PS‐b‐PEO diblock copolymer. It was found that the microdomain spacing could be tuned by adjusting the UV exposure time, due to the change in the copolymer architecture and the swelling of the PEO microdomain by the PEO homopolymer produced. By selective area exposure of the PEO‐b‐PS‐b‐PEO thin films, the domain spacing was changed over selected locations across the film, generating patterns of different microdomain sizes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 355–361. 相似文献
998.
Junki Yano Kazuhiko Ishihara Shin‐ichi Yusa 《Journal of polymer science. Part A, Polymer chemistry》2017,55(15):2432-2439
A diblock copolymer (P98N100) composed of a biocompatible water‐soluble block (PMPC) and a lower critical solution temperature (LCST) type thermo‐responsive block (PNIPAM) was prepared via controlled radical polymerization. To dissolve fullerene (C60) in water, the C60/P98N100 complex was prepared by mixing C60 and P98N100 powders. The maximum solubilized C60 concentration in water was 1.39 g/L, as estimated from UV–vis adsorption, when the polymer concentration was 5.0 g/L. The percent transmittance of the aqueous solution of the C60/P98N100 complex decreased above 36 °C due to inter‐complex association above the LCST for the PNIPAM block. While the hydrodynamic radius of C60/P98N100 complex was 135 nm at 20 °C, it increased to 161 nm at 50 °C. Despite the observation of 1H NMR signals from PMPC and PNIPAM blocks for the C60/P98N100 complex in D2O at room temperature, the signals from PNIPAM disappeared above 35 °C due to restricted motion of PNIPAM. Generation of singlet oxygen (1O2) from the C60/P98N100 complex by photo‐irradiation was confirmed using 9,10‐anthracene dipropionic acid (ADPA). The absorbance of ADPA decreased with increasing irradiation time due to oxidation of ADPA by 1O2. It is expected that the C60/P98N100 complex can be applied as a thermo‐responsive carrier for photodynamic therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2432–2439 相似文献
999.
1000.
pH‐ and β‐cyclodextrin‐responsive micelles based on polyaspartamide derivatives as drug carrier
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Huan Yu Jian Sun Yunti Zhang Guangyan Zhang Yanfeng Chu Renxi Zhuo Xulin Jiang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(11):1387-1395
A novel kind of graft polymer poly(aspartic acid)‐ethanediamine‐g‐adamantane/methyloxy polyethylene glycol (Pasp‐EDA‐g‐Ad/mPEG) was designed and synthesized for drug delivery in this study. The chemical structure of the prepared polymer was confirmed by proton NMR. The obtained polymer can self‐assemble into micelles which were stable under a physiological environment and displayed pH‐ and β‐cyclodextrin (β‐CD)‐responsive behaviors because of the acid‐labile benzoic imine linkage and hydrophobic adamantine groups in the side chains of the polymer. The doxorubicin (Dox)‐loaded micelles showed a slow release under physiological conditions and a rapid release after exposure to weakly acidic or β‐CD environment. The in vitro cytotoxicity results suggested that the polymer was good at biocompatibility and could remain Dox biologically active. Hence, the Pasp‐EDA‐g‐Ad/mPEG micelles may be applied as promising controlled drug delivery system for hydrophobic antitumor drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1387–1395 相似文献