一种新型卟啉侧链聚合物的飞秒荧光动力学

研究了一种新型的卟啉侧链聚合物丙烯腈丙烯酸卟啉酯共聚物{poly[porphyrin acrylate-acrylonitrile](p[(por)A-AN]}的链间和链内的卟啉分子的相互作用对聚合物薄膜发光性质的影响。通过采用飞秒荧光光谱技术测量了p[(por)A-AN]薄膜的荧光动力学过程。测量结果表明:纯p[(por)A-AN]薄膜(~450ps)显示出了比混合物薄膜p[(por)A-AN]/polystyrene(PSE)(~1.3 ns)快得多的荧光弛豫过程。而p[(por)A-AN]/PSE混合物薄膜显示出较纯p[(por)A-AN]薄膜增强的荧光效率。增加p[(por)A-AN]分子内卟啉侧链基团的浓度导致纯p[(por)A-AN]薄膜和p[(por)A-AN]/PSE混合物薄膜的荧光效率的增强和寿命(由近26~36 ps)的增加。分子间和分子内卟啉侧链基团之间的无辐射能量转移和分子内卟啉侧链基团的旋转运动在p[(por)A-AN]的荧光动力学过程中起着重要的作用。     

分子链间距离对于卟啉侧链聚合物稳态及瞬态发光性能的影响

采用荧光光谱技术,测量了一种卟啉侧链聚合物:卟啉丙烯酸酯-苯乙烯共聚物(P[(por)A-S])的稳态和瞬态的发光性能.通过将聚合物P[(por)A-S]掺杂到有机玻璃(PMMA)中,研究了链间距离对于P[(por)A-S]发光性能的影响.结果表明:随着聚合物分子浓度增大,即链间距离减小,导致卟啉侧链基团之间的相互间作用增加,使其激发态无辐射跃迁几率增加,聚合物荧光强度减弱,激发态寿命缩短.讨论了上述过程产生的原因.     

侧链基团对聚合物薄膜瞬态发光性能的影响

采用飞秒激光光谱技术比较研究了两种卟啉侧链聚合物:卟啉丙烯酸酯-苯乙烯共聚物P[(por)A-S]和卟啉铁(Ⅲ)丙烯酸酯-苯乙烯共聚物P[(por)FeA-S]的瞬态发光性能。并采用纳秒激光光谱技术测量了小分子卟啉(TPP)的荧光动力学过程。结果表明:P[(por)FeA-S]具有比P[(por)A-S]快得多的荧光弛豫过程,而P[(por)A-S]的荧光寿命远小于小分子卟啉的荧光寿命。对上述过程进行了分析,P[(por)A-S]的荧光衰变主要来源于聚合物分子链间的相互作用;而P[(por)FeA-S]的荧光衰变除了来源于聚合物分子链间的相互作用外,中央金属离子与配位体之间的电荷转移也对卟啉发色基团的激发态超快无辐射弛豫具有重要的影响,对上述过程的产生机理进行了讨论。     

F?rster双分子猝灭作用对卟啉侧链聚合物荧光衰变的影响

通过采用时间分辨荧光光谱技术测量了一种卟啉侧链聚合物薄膜：卟啉丙烯酸酯—苯乙烯共聚物poly［porphyrin acrylate-styrene］ (P［(por)A-S］)在高激发密度下的瞬态荧光特性.实验发现,P［(por)A-S］样品的荧光衰减随聚合物分子浓度的增大而加快.利用Frster机制的双分子猝灭理论对其浓度猝灭的原因进行了分析,理论结果与实验结果符合较好.研究表明,在高激发密度的情况下,Frster机制的双分子作用是加快卟啉侧链聚合物初始荧光衰减和降低其发光效率的主要因素. 关键词： 双分子猝灭 Frster机制 瞬态荧光 卟啉侧链聚合物     

F(o)rster双分子猝灭作用对卟啉侧链聚合物荧光衰变的影响

通过采用时间分辨荧光光谱技术测量了一种卟啉侧链聚合物薄膜:卟啉丙烯酸酯-苯乙烯共聚物poly[porphyrin acrylate-styrene] (P[(por)A-S])在高激发密度下的瞬态荧光特性.实验发现,P[(por)A-S]样品的荧光衰减随聚合物分子浓度的增大而加快.利用Frster机制的双分子猝灭理论对其浓度猝灭的原因进行了分析,理论结果与实验结果符合较好.研究表明,在高激发密度的情况下,Frster机制的双分子作用是加快卟啉侧链聚合物初始荧光衰减和降低其发光效率的主要因素.     

共轭高分子中激子演化过程的非绝热动力学研究

有机共轭高分子受光激发或被电荷掺杂后可能会产生各种激发状态的激子,激子的演化过程对有机发光光谱有着至关重要的影响.通过非绝热动力学演化的方法模拟了受光激发后有机高分子中激子驰豫的动力学过程,结果表明高激发态激子不稳定,由于电声耦合作用,高激发态激子会持续向低激发态激子演化,同时,低激发态激子的复合发光会发生红移.稳定的激子复合发光光谱中,基态激子发光强度最大,可高达70-80%;第一激发态激子及其它激发态激子发光强度的总和不超过20%.     

窄带系聚合物APFO3的激发态光物理特性 (cited: 1)

化学计算证实了光致激发窄带系聚合物APFO3后,会发生链内电荷转移(ICT)过程,同时这一特性还影响了吸收光谱中的第一吸收带. 瞬态吸收结果再一次表明了当聚合物在单分散体系中确实存在ICT特性,而且这种特性会同振动弛豫竞争. 在聚集态中,受链间相互作用的影响,ICT特性会消失,而且激子弛豫过程将在光致激发后的弛豫过程中占据主导地位. 混有PC₆₁BM的APFO3薄膜的光致激发动力学显示,当PC₆₁BM 的含量超过50%时,激子解离已经达到饱和. 基于此异质节的光     

卟啉和钌二元体的超快能量转移

采用超快时间分辨的荧光光谱技术测量了一种由柔性链连接的卟啉-钌二元体分子内的能量转移动力学过程.通过在钌的吸收峰(～453nm)对二元体进行光激发,实验上观测到了从钌基团到卟啉基团的超快能量转移过程(～400ps).而在卟啉的吸收峰(～400nm)对二元体进行光激发,实验上没有观测到从卟啉基团到钌基团的能量转移.采用Frster理论对二元体系能量转移过程的产生机理进行了分析,结果表明,钌和卟啉之间的能量转移来源于基于光谱重叠的偶极-偶极相互作用. 关键词： 卟啉-钌二元体 能量转移 超快激光光谱技术     

聚合物发光器件中激子的解离与复合效率

对聚合物发光器件中极化子激子的形成与解离过程进行了详细探讨,提出了极化子激子解离的理论模型及解离概率的解析式,分析了激子解离后正、负极化子的输运过程,认为是极化子的链间跃迁实现了聚合物的电导,计算并讨论了内量子效率随外加电场、温度及杂质浓度的变化关系.该模型较好地解释了有关实验现象. 关键词： 聚合物发光器件 极化子激子 激子解离 内量子效率     

神经网络法研究多溴代二苯胺热力学性质

通过时间分辨光谱技术详细地研究了ZnCuInS/ZnSe/ZnS量子点的激子弛豫动力学. 基于速率分布模型,波长依赖的发射动力学表明本征激子、界面缺陷态中的激子、给-受体对态中的激子都会参与量子点的发光过程,整个发光过程主要依赖于给-受体对态发射. 瞬态吸收数据表明激发后本征激子和界面缺陷物种可能会同时出现,在高激发光强下,光强依赖的俄歇复合过程也存在于量子点中     

The effect of intermolecular interactions on photoluminescence of a porphyrin side-chain polymer

Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile (abbreviated p[(por)A-AN]), have been investigated by femtosecond time-resolved photoluminescence spectroscopy. All the luminescences of p[(por)A-AN] films are due to the emissive decay of the photoexcited singlet excitons in the porphyrins. The luminescence efficiencies and lifetimes are increased for samples from pure films to dilute blend films. However, they are increased as the intrachain concentration of the porphyrin sidechain groups is decreased. The intrachain rotation motions of porphyrin sidechain groups result in the initial ultrafast luminescence decays, which are much faster than those due to the interchain interactions. All the samples show no significant red-shift and broadening of the transient luminescence spectra. The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the p[(por)A-AN] films. The possible origin of different intrachain and interchain dynamic behaviours in p[(por)A-AN] films is discussed.     

Fluorescence and Time-Resolved Delayed Luminescence of Porphyrins in Organic Solvents and Polymer Matrices

Porphyrin dyes fulfill an essential function in photosynthesis and are important in photodynamic therapy and in a range of electronic devices. Their spectroscopic characteristics may play a crucial role in these processes. The spectral properties of two porphyrin dyes: tetraphenylporphyrin and tetraphenysulfporphyrin in organic solvents (acetone, chloroform, methyl alcohol, and dimethyl-sulfoxide) and in polyvinyl alcohol and poly(methylmethacrylate) films have been investigated. Absorption, fluorescence, and microsecond time-resolved delayed luminescence spectra have been measured at room temperature. The existence of different aggregated dye forms in the ground and excited states has been demonstrated. The manifold of dye species depends on the solvent/polymer. In the case of the polymers, it also depends on the solvent used to coat the polymer film. Delayed luminescence spectra and decay times of the two porphyrins in the different solutions and in polymeric matrices suggest that different mechanisms of deexcitation of the singlet excited states may be responsible for their generation in these and other porphyrin dyes.     

Luminescence diagnostics of malignant tumors in the IR spectral range using Yb-porphyrin metallocomplexes

The creation and application of new low-toxic photosensitizers for the luminescence diagnostics of cancer are considered. The new photosensitizers weakly generate singlet oxygen, exhibit developed luminescence, and retain the tumor-tropic properties of the therapeutic photosensitizers. Twenty one ytterbium complexes of porphyrin compounds that differ by the substituents at the periphery of the porphyrin ring are synthesized. The absorption and luminescence spectra and the luminescence decay curves of these substances are studied. The primary toxicological and pharmacokinetic investigations are performed for the most promising compounds in the organisms of experimental animals. The experimental data prove that the Yb-porphyrin complexes are promising as low-toxic markers for the luminescence diagnostics of malignant tumors in the IR spectral range (975–985 nm) that are free of the phototoxicity typical of the conventional porphyrins at a relatively high luminescence contrast and the selective accumulation in tissue.     

Rotational Relaxation of Linear π-Systems with Flexible Side Chains in Solution

The classical hydrodynamic theory for Brownian rotational motion is applied to model compounds of conjugated polymers with alkoxy side chains of variable length. Theory predicts two rotational relaxation times for these types of molecules with the dipole transition moment parallel to the longest axis whereas experiments reveal only one. The rotational relaxation times and their relative amplitudes were calculated for a wide span of axial ratios of a general ellipsoid. In this way, the range in the axial ratios is obtained such that there is a chance to detect both rates experimentally. Rotational relaxation times of five particular molecules were measured in liquid n-butane. Theoretical calculations using ellipsoid parameters obtained from molecular dynamics calculations compare well with experimental results. Calculation of the rotational relaxation times from the autocorrelation function of the transition dipole moment vector requires significantly greater computational effort.     

Effect of energy transfer on the kinetics of the decay and anisotropy of luminescence of prodan molecules

The temporal characteristics of the decay and polarization of luminescence of prodan solutions with different concentrations, excited by a picosecond laser radiation, are studied. The kinetics of the emission decay and polarization depend on the spectral range of luminescence recording and on the luminophore concentration and reflect the relaxation processes (leading to a long-wavelength shift of the entire emission band) and, in the case of sufficiently high concentrations, nonradiative energy transfer between the prodan molecules. It was found that the evolution of luminescence anisotropy in a diluted solution depends on the recording wavelength, which allowed us to calculate the average times of the Brownian rotational diffusion for prodan in glycerol, whose maxima were determined to be about 40 ns in the spectral region near 520 nm and to decrease to 14 and 17 ns at the edges of the emission region at 450 and 560 nm, respectively.     

Inhomogeneous spectral broadening and the decay kinetics of the luminescence spectra of prodan

The selectively excited steady-state luminescence spectra, as well as the decay time characteristics of the luminescence, of prodan in polar solvents excited by picosecond radiation are studied. The steady-state luminescence spectra exhibit a strong inhomogeneous broadening, which is the most pronounced at elevated solution viscosities. The temporal characteristics of the luminescence decay in different spectral ranges and the instantaneous spectra suggest the presence of relaxation processes resulting in a long-wavelength shift of the emission spectrum during the lifetime of the excited state. A relation between the relaxation shift of the emission spectrum and the intermolecular orientational relaxation of solvate molecules is established.     

EPR studies of photoinduced electron transfer in triad model compounds of photosynthesis

Time-resolved EPR spectra are reported for porphyrin-quinone-quinone and porphyrin-porphyrin-quinone triads obtained after photoexcitation in the nematic and soft glass phase of liquid crystals. Spin-polarized EPR spectra were observed for the triplet states of the porphyrin created by spin-selective intersystem crossing (ISC) from the excited singlet state and those of the charge-separated radical pair states (RP) generated by electron transfer (ET) processes. The EPR polarization patterns of the RP are discussed in terms of the favored decay channel of the photoexcited singlet state of the porphyrin donor. The decay pathway may either be singlet ET to the quinone(s) followed by singlet/triplet mixing to yield RPs with triplet character or triplet ET after ISC from the porphyrin singlet to the triplet state, or a superposition of both pathways. It is demonstrated that the nature of the linking bridge between donor and acceptor, i.e., aliphatic cyclohexylene or aromatic phenylene, significantly influences the ET mechanism and thus the polarization patterns of the RP spectra. Using liquid crystals, information about the orientation of the guest molecules in the liquid crystal matrix with respect to the long axes of the liquid crystal molecules can be obtained. In the porphyrin-porphyrin-quinone triads the energy and ET processes strongly depend on the type of metallation of the porphyrins, specifically, whether the distal, the vicinal or both porphyrins bear a zinc atom.