硝酮化合物对9-氰蒽荧光猝灭作用的研究

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。     

香豆素衍生物与碘鎓盐间的光诱导电子转移研究

研究了3种碘鎓盐对3种香豆素荧光的猝灭,发现猝灭曲线符合Stern-Volmer方程,并且猝灭过程受扩散控制.研究证实了猝灭的机理是由于发生了光诱导电子转移.通过香豆素衍生物-碘鎓盐体系能在光照下引发甲基丙烯酸甲酯单体的聚合进一步证实了这种机理.尽管香豆素有较强的分子内电荷转移倾向,但由于碘鎓盐阳离子很强的拉电子能力,它们间还是能发生快速的电子转移.     

有机电致发光器件中几种常用组分的荧光光谱研究

利用荧光光谱对电致发光器件(OLED)中几种常用化学组分的荧光猝灭和光诱导电子转移问题进行了研究.发现两种常用的空穴传输材料NPB和TPD与常用电子传输材料AlQ₃在光的帮助下可发生电子转移.根据荧光猝灭的Stern-Volmer作图和用单光子记数法测得的荧光寿命而计算得到的猝灭速度常数和扩散速度常数相对应,明确地表明这里的猝灭具有电子转移特征.并对所得的结果进行了讨论.     

用荧光光谱法研究OLED用的新型蓝色发光染料和三-（8-羟基喹啉）铝(AlQ_3)的光诱导电子转移和激基复合物的生成

在合成了三种新型发射蓝光化合物的基础上，对它们在溶液中的光物理行为作 了详细研究。发现它们的荧光能强烈地被三-（8-羟基喹啉）铝所猝灭，并在荧光 光谱的长谱部分出现因发生光诱导电子转移而生成激基复合物的发光。几个方面的 工作-如猝灭常数的测定，电子转移过程自由能的计算，都表明化合物荧光猝灭过 程的电子转移性质。此外，还讨论了因出现光诱导电子转移和激基复合物给OLED器 件带来的影响，特别对三种作为器件发射蓝光化合物的优劣进行了讨论，表明化合 物DPF有着最佳的发光特征。     

光致噻吨酮与胺类、酚类、醇类的电子转移和氢转移反应

利用激光闪光光解方法研究了一系列胺类、酚类、醇类在脱氧乙腈中猝灭噻吨酮(TX)三重态的反应,得到了相应的瞬态吸收光谱和猝灭速率常数(kq).通过对光谱演变特性的分析,推断出三重态噻吨酮与不含有活泼氢的胺发生了电子转移反应,与含有活泼氢的胺发生了电子-质子转移反应.三重态噻吨酮与酚类、醇类反应中观察到噻吨酮加氢自由基的生成,据此推断出三重态噻吨酮与酚类、醇类发生了氢转移反应.胺类的猝灭速率常数随着反应自由能变(ΔG)的增大而减小,说明电子转移影响了噻吨酮三重态的猝灭.酚类的猝灭速率常数先随ΔG增大而减小,后随酚阳离子的酸性增强逐渐增大,可能是猝灭过程中电子转移影响减弱的同时氢转移影响逐渐增强.醇类的猝灭速率常数随着醇的α-C—H键能的增大而减小,说明α-C—H键能是影响噻吨酮三重态猝灭的关键因素.比较以前研究的胺类、酚类、醇类与三重态呫吨酮(XT)、芴酮(FL)反应的结果可知,由于分子结构差异性的影响,相关的猝灭速率常数按照呫吨酮、噻吨酮、芴酮的顺序逐渐减小.     

龙脑烯醛对9,10-二腈蒽荧光的猝灭作用

本文研究了在不同溶剂中龙脑烯醛对DCA荧光的猝灭作用, 通过稳态和瞬态荧光猝灭特性的比较, 溶剂极性对猝灭速度的影响, 自由能变化的估算及其与乙腈中双分子猝灭速率常数相关比较, 证明这是一个电子转移的动态猝灭过程。     

以聚醚链相连的9-氨基吖啶、苯甲酸酯二元体系的合成及分子内光诱导电子转移反应

本文用聚四乙二醇柔性链将9-氨基啶和不同取代基的苯甲酸酯连接起来,合成了一类新型二元分子体系。对各体系中9-氨基啶的电子转移荧光猝灭进行了研究,并根据稳态荧光猝灭计算了体系中的荧光猝灭效率和荧光猝灭速率常数。     

香豆素酮类化合物的瞬态研究——Ⅲ.香豆素酮和碘鎓盐间的电子转移

本工作采用激光闪光光解法对香豆素酮类化合物敏化碘鎓盐化合物问题进行了研究。结果表明:碘鎓盐化合物能通过电子转移机理猝灭香豆素酮的激发三重态。工作中还用甲基紫精(PQ²⁺)为模型化物,观察到它也能使香豆素酮的三重态猝灭,同时可看到在位于610nm处的PQ⁺生成。这些结果说明,在发生电子转移的反应中香豆素酮是电子给体,按Weller公式的计算结果也表明它们之间可发生电子转移反应。     

唑类化合物的荧光猝灭及其与四氯化碳组合时所组成的光诱导引发体系

本工作对 唑类化合物在不同溶剂中的荧光被四氯化碳的猝灭问题进行了研究。发现其荧光猝灭的Stern-Volmer常数与所用溶剂的极性参数E~T(30)值间存在着线性关系, 这一结果表明: 这一猝灭过程具有明确的电子转移性质。在此工作基础上提出唑类化合物与四氯化碳所组成的体系可能是一种新的光诱导引发聚合体系。实验结果表明, 这一体系确能光引发单体化合物进行自由基聚合反应, 对该体系的光引发聚合机理作了初步的讨论。     

唑类化合物的荧光猝灭及其与四氯化碳组合时所组成的光诱导引发体系

本工作对 唑类化合物在不同溶剂中的荧光被四氯化碳的猝灭问题进行了研究。发现其荧光猝灭的Stern-Volmer常数与所用溶剂的极性参数E~T(30)值间存在着线性关系, 这一结果表明: 这一猝灭过程具有明确的电子转移性质。在此工作基础上提出唑类化合物与四氯化碳所组成的体系可能是一种新的光诱导引发聚合体系。实验结果表明, 这一体系确能光引发单体化合物进行自由基聚合反应, 对该体系的光引发聚合机理作了初步的讨论。     

Photopolymerization reactions initiated by a visible light photoinitiating system: Cyanine dye/borate salt/1,3,5‐triazine

New three‐component photoinitiating systems consisting of a cyanine dye, borate salt, and a 1,3,5‐triazine derivative were investigated by measuring their photoinitiation activities and through fluorescence quenching experiments. Polymerization kinetic studies based on the microcalorimetric method revealed a significant increase in polymerization rate when the concentration of n‐butyltriphenylborate salt or the 1,3,5‐triazine derivative were increased. The photo‐induced electron transfer process between electron donor and electron acceptor was studied by means of fluorescence quenching and SrEt change of the fluorescence intensity. The experiments performed documented that an increase of the n‐butyltriphenylborate salt concentration dramatically increases the rate of dye fluorescence quenching, whereas the increasing of the 1,3,5‐triazine derivative concentration slows down the consumption of the dye. We conclude that the primary photochemical reaction involves an electron transfer from the n‐butyltriphenylborate anion to the excited singlet state of the dye, followed by the reaction of the 1,3,5‐triazine derivative with the resulting dye radical to regenerate the original dye. This reaction simultaneously produces a triazinyl radical anion derived from the 1,3,5‐triazine, which undergoes the carbon‐halogen bond cleavage yielding radicals active in initiation of a free radical polymerization chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3626–3636, 2007     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

 本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

Fluorescence Quenching of Poly[2-methoxy-5-(2''''-ethylhexoxy)-p-phenylene vinylene](MEH-PPV) in Solutions

Introduction Poly(1,4-phenylene vinylene) (PPV) has been the subject of explosive interest in these years. It has poten-tial applications in light-emitting diode, light emitting electrochemical cell and plastic laser.1-4 To improve its solubility and optical properties substituents are intro-duced to the PPV main chain. Poly[2-methoxy-5-(2'-ethylhexoxy)-p-phenylene vinylene] (MEH-PPV) is one of derivatives with alkoxy groups on phenyl rings. It exhibits superior solubility in organic sol…     

Radioluminescence quenching of toluene scintillators by methyl methacrylate

It was established that singlet electronic excited state of toluene is quenched by MMA /but is not quenched by PMMA/. The value of quenching rate constant k_g=0.6×10⁹ l.mol^–1.s^–1 indicates that the quenching is a diffusion controlled process. It is assumed that the excitation energy of toluene sensitizes the polymerization process of MMA. The increase of radioluminescence intensity and quantum yield of excitation energy transfer is the result of diminishing the quantity of MMA in the solution during polymerization time.     

Heteroatom‐Doped Carbon Dots (CDs) as a Class of Metal‐Free Photocatalysts for PET‐RAFT Polymerization under Visible Light and Sunlight

A key challenge of photoregulated living radical polymerization is developing efficient and robust photocatalysts. Now carbon dots (CDs) have been exploited for the first time as metal‐free photocatalysts for visible‐light‐regulated reversible addition–fragmentation chain‐transfer (RAFT) polymerization. Screening of diverse heteroatom‐doped CDs suggested that the P‐ and S‐doped CDs were effective photocatalysts for RAFT polymerization under mild visible light following a photoinduced electron transfer (PET) involved oxidative quenching mechanism. PET‐RAFT polymerization of various monomers with temporal control, narrow dispersity (?≈1.04), and chain‐end fidelity was achieved. Besides, it was demonstrated that the CD‐catalyzed PET‐RAFT polymerization was effectively performed under natural solar irradiation.     

Fluorescence Quenching of Poly[2-methoxy-5-（2′-ethylhexoxy）-p-phenylene vinylene] （MEH-PPV） in Solutions

Fluorescence quenching processes of poly[2-methoxy-5-(2‘ethyl-hexoxy)-p-phenylene vinylene] (MEH-PPV) in solution by electron acceptors, O2 and acid, have been studied. Static quenching of the fluorescence from MEH-PPV by an electron acceptor (DDQ or TCNE) occurs due to electron transfer from MEH-PPV to the electron acceptor and this electron transfer quenching can be promoted by chloroform. Photooxidation takes place in the MEH-PPV solution and singlet oxygen is an intermediate in the photooxidation, according to the results of ESR spectroscopy. Acid also plays an important role in the fluorescence quenching process of MEH-PPV, by the protonation of the alkoxy groups in the molecular chain.     

Mechanism of anionic polymerization of phenylacetylene

Anionic polymerization of phenylacetylene in the presence of butyllithium has been studied. It was shown that the process of polymerization is accompanied by the appearance and growth of the ESR signal with pronounced superfine structure. The model of polymerization was suggested according to which formation of low molecular polyphenylacetylene is caused the destruction of the active centers by means of electron transfer from the active center to the conjugated chain. This type of electron transfer may also be the fundamental reaction limiting the chain length in cationic polymerization of acetylene monomers. © 1992 John Wiley & Sons, Inc.     

Excited states quenching of phenosafranine dye by electron donors

The quenching of the excited singlet and triplet states of phenosafranine by aromatic amines, methoxybenzenes and triethanolamine was investigated in acetonitrile and methanol. The rate constants for the aromatic quenchers present a typical dependence of an electron transfer process with the one-electron redox potential of the donor. A Rehm–Weller correlation is obtained with the driving force. The fitting parameters are very similar in both solvents. The electron transfer nature of the quenching reaction is further confirmed by the detection of the radical cations of the quenchers and the semireduced form of the dye in laser flash photolysis experiments. The absorption coefficients of the transient species were estimated, and the quantum yield of the charge separation process was determined.