Spontaneous Emission of Singlet Oxygen Near Dielectric Nano-objects and Radiative Diagnostics of Bio-Objects

We investigate modifications of a spontaneous emission rate near the surface of the hemoglobin-like dielectric structure in the long-wavelength limit. We demonstrate that notwithstanding the small size of the dielectric structure, an influence of its shape cannot be neglected. Even for moderate dielectric contrasts one can expect having significant and detectable enhancement or suppression of the spontaneous emission rate near the surface of the biological macromolecule.     

Feasibility Study on Quantitative Measurements of Singlet Oxygen Generation Using Singlet Oxygen Sensor Green

The purpose of this study is to investigate the feasibility for quantitative measurement of singlet oxygen (¹O₂) generation by using a newly developed ¹O₂-specific fluorescence probe Singlet Oxygen Sensor Green reagent (SOSG). ¹O₂ generation from photoirradiation of a model photosensitizer Rose Bengal (RB), in initially air-statured phosphate buffered saline (PBS) was indirectly monitored with SOSG. In the presence of ¹O₂, SOSG can react with ¹O₂ to produce SOSG endoperoxides (SOSG-EP) that emit strong green fluorescence with the maximum at 531 nm. The green fluorescence of SOSG-EP is mainly dependent on the initial concentrations of RB and SOSG, and the photoirradiation time for ¹O₂ generation. Furthermore, kinetic analysis of the RB-sensitized photooxidation of SOSG is performed that, for the first time, allows quantitative measurement of ¹O₂ generation directly from the determination of reaction rate. In addition, the obtained ¹O₂ quantum yield of porphyrin-based photosensitizer hematoporphyrin monomethyl ether (HMME) in PBS by using SOSG is in good agreement with the value that independently determined by using direct measurement of ¹O₂ luminescence. The results of this study clearly demonstrate that the quantitative measurement of ¹O₂ generation using SOSG can be achieved by determining the reaction rate with an appropriate measurement protocol.     

Effect of a Homogeneous Dielectric Medium on the Luminescence of Singlet Oxygen

Russian Physics Journal - Results of an analysis of our and literature data devoted to the study of the effect of a homogeneous dielectric medium on the rate constant of the $$...     

Luminescence Study of Singlet Oxygen Production by Meso-Tetraphenylporphine

The research in the field of the photodynamic therapy of cancer (PDT) is focused on a development of photosensitizers exhibiting high quantum yield of singlet oxygen production. Direct time-resolved spectroscopic observation of singlet oxygen phosphorescence can provide time constants of its population and depopulation as well as photosensitizer phosphorescence lifetime and relative quantum yields. In our contribution, a study of time and spectral resolved phosphorescence of singlet oxygen photosensitized by meso-tetraphenylporphine in acetone together with the photosensitizer phosphorescence is presented. Time constants of singlet oxygen population and depopulation were determined at wide range of photosensitizer concentrations. The time constant of singlet oxygen generation (0.28 ± 0.01) s is slightly shorter then the lifetime of photosensitizer's triplet state (0.32 ± 0.01) s. It is caused by lower ability of TPP aggregates to transfer excitation energy to oxygen. The lifetime of singlet oxygen (50 s) decreases with increasing photosensitizer concentration. Therefore, the photosensitizer acts also as a quencher of oxygen singlet state, similarly to the effects observed in [A. A. Krasnovsky, P. Cheng, R. E. Blankenship, T. A. Moore, and D. Gust (1993). Photochem. Photobiol. 57, 324–330; H. Küpper, R. Ddic, A. Svoboda, J. Hála, and P. M. H. Kroneck (2002). Biochim. Biophys. Acta Gen. Subj. 1572, 107–113]. Moreover, the increasing concentraion of the photosensitizer causes a slight hypsochromic shift of the singlet oxygen luminescence maximum.     

Singlet and Triplet State Properties and Singlet Oxygen Yield of an Amino-Acyl-Quinoxalinone Yellow Dye

Amino-acyl-quinoxalinone yellow dyes are cyclised analogues of the yellow azomethine dyes developed for, and still used in, silver halide colour photography. Unlike image azomethine dyes, which are rapidly deactivated in their excited states by torsion about the azomethine bond, amino-acyl-quinoxalinone dyes have an interesting photophysics because torsion is not possible due to their cyclised structure. We report results from studies on singlet and triplet state properties, and singlet oxygen yields, of the yellow dye, 7-diethylamino-3-(2,2-dimethyl-propionyl)-5-methyl-1-phenyl-1H-quinoxalin-2-one, in polar and nonpolar solvents. The dye photophysics is characterised by a weak fluorescence, with a solvent dependent emission yield (Φ_F?≈?0.002–0.004), and short singlet state lifetime (τ_expt?≈?20–50 ps), both increasing by a factor of ≈2 in going from polar acetonitrile to non-polar dioxane as solvent. DFT ZINDO calculations show a transition involving significant electron transfer from the diethyl-amino group into the carbonyl region of the molecule. In solution, in the presence of oxygen, the triplet state decays almost exclusively by oxygen quenching, and singlet oxygen is produced in high yield (Φ_??≈?0.5–0.55). The triplet state absorbs across the 450–750 nm region with maxima around 480 and 650 nm, and moderate molar absorption coefficients (ca. 6000–8000 M^?1 cm^?1). In a glass at 77 K, triplet decay gives a red phosphorescence, with λ_max?≈?640–650 nm, and a ?≈?0.25 s lifetime. If singlet oxygen yields are a good indication of triplet yields, then internal conversion and intersystem crossing occur with roughly equal efficiency.

     

基于量子化学计算的谷氨酰胺太赫兹吸收谱模拟

利用量子化学计算方法模拟物质的太赫兹吸收谱,可以为目标物质的太赫兹吸收特征匹配分子振动模式,对深刻理解谱的形成机理十分必要。模拟结果的可靠性,主要取决于目标物质初始构型的搭建和振动模式计算方法的选择。首先利用太赫兹时域光谱技术获取了谷氨酰胺固态样品的太赫兹吸收谱,为了在理论模拟过程中体现考虑分子间作用的程度,构建了三种常用于有机物太赫兹吸收谱模拟的谷氨酰胺初始构型,单分子、二聚体、晶胞。使用量子化学计算程序基于密度泛函理论对三种初始构型进行了结构优化和振动模式计算。将计算结果通过洛伦兹线型函数拟合为吸收谱与实验吸收谱进行对比发现,二聚体构型的模拟吸收谱从吸收峰个数上优于单分子构型,在此基础上,晶胞构型模拟结果从吸收峰峰位上又较二聚体构型有了明显的改进,随着初始构型考虑分子间作用的程度提高模拟结果逐步逼近实验吸收谱。在得到了可靠的理论模拟吸收谱的基础上,成功对谷氨酰胺固态样品在0.3～2.6 THz范围内的三个吸收峰匹配了晶胞内各分子的集体振动模式。研究表明,在固体样品的太赫兹吸收谱理论模拟中,在计算能力允许的情况下,应尽可能选择全面反映分子间作用力的晶胞构型作为计算的初始构型。     

射流式单重态氧发生器研究

单重态氧O2 (a1Δg)是迄今唯一能用纯化学反应高效产生的具有长寿命的亚稳激发态分子 .为了考察提出的用两个O2 (1Δ)能量汇集反应生成氧第二单重激发态O2 (b1Σ+ g)以实现近可见短波长化学激光方案的现实性 ,设计和实验了一个氯流量为 3～ 10mmol/s的射流式单重态氧发生器 (JSOG) .考察了三种具有不同孔径和孔数目的喷头、氯气流量和脱水冷阱温度等对JSOG出口的O2 (1Δ)浓度、O2 (1Δ)分压、氯利用率及水蒸气含量的影响 .发现用聚氯乙烯管作冷阱时 ,最佳冷阱介质温度为 - 140～ - 15 0℃ ,对此提出了O2 (1Δ)表面脱活与脱水互相竞争的解释 .在最佳条件下 ,可将O2 (1Δ)气中水分压降低至 4Pa ,这一结果是首次报导     

自发辐射对量子级联激光器发光噪声的影响

为得到量子级联激光器特有的光噪声特性,通过在速率方程中引入Langevin噪声源以及自发辐射因子的方法,在单模与线性增益的情况下讨论了自发辐射因子及与偏置电流等参数与光噪声的强度及带宽等特性之间的关系,计算结果表明,增大自发辐射因子能降低光噪声的强度,增宽光噪声的3-dB截止频率,进一步的研究也表明,自发辐射因子对光噪声的影响与激光器的偏置电流有密切关系,这种影响在偏置电流较小时比较明显,但当偏置电流很大时自发辐射因子对光噪声的影响将变得很弱。     

Synthesis and Characterization of New Fluorene-Based Singlet Oxygen Sensitizers

The synthesis, photophysical characterization, and determination of singlet oxygen quantum yields (Φ_Δ) for a class of fluorene derivatives with potential application in two-photon photodynamic therapy (PDT) is reported. It has been demonstrated that these compounds possess the ability to generate singlet oxygen (¹O₂) upon excitation. A photochemical method, using 1,3-diphenylisobenzofuran (DPBF) as ¹O₂ chemical quencher, was employed to determine the singlet oxygen quantum yields (Φ_Δ) of the fluorene-based photosensitizers in ethanol. Φ_Δ values ranged from 0.35 to 0.75. These derivatives may have potential application as two-photon photosensitizers when pumped via two-photon excitation in the near-IR spectral region.     

亚磷酸三苯酯臭氧化合物分解产生单重态氧的研究

现在世界上功率最大的短波长化学激光、氧碘化学激光是以亚稳态的O2 (a1△)作为储能分子,通过近共振碰撞传能给碘原子,使碘原子激发而发射激光,因此,O2 (a1△)的发生是其主要关键技术.目前使用的方法是H2 O2 的碱溶(BHP)与Cl2 气反应[1] .它具有化学效率高的优点,但此方法产生的O2 (a1△)中含有水份,而水对碘原子具有强的猝灭作用;另外,BHP不能长期保存;氯气还有毒性.196 1年Thompson发现,在- 78℃时亚磷酸三苯酯(TPP)与O3加成为亚磷酸三苯酯臭氧化合物(TPPO3) [2 ] ,并在高于- 35℃分解产生O2 (a1△) .　(C6 H5O) 3P +O3-78℃(…     

利用FCLA特征荧光实现单态氧和超氧的高灵敏检测

活性氧(ROS)的检测对生物学和医学研究很多领域方面具有重要意义,如光动力治疗肿瘤的治疗检测、植物应激反应检测、种子活力检测等。实现活性氧中的单态氧、超氧阴离子高灵敏度的检测,是人们追求的目标。研究发现单态氧、超氧的选择性化学发光探针FCLA(fluoresceinyl cypridina luciferin analog)氧化后,在515 nm处荧光会大大增强。利用这个性质并结合非常成熟的荧光检测方法,可以实现活性氧的高灵敏度检测。尤其在微观检测方面,如单细胞, FCLA的化学发光很微弱而难以检测到,但是却可以灵敏地检测到其荧光变化。FCLA荧光检测不仅灵敏度高而且选择性好,其无毒和易于透膜的性质更适于在细胞和生物体上应用。另外如果同时结合FCLA的化学发光,对单态氧和超氧阴离子的检测将更准确、更具实时性。     

钯酞菁配合物的荧光光谱与单线态氧的生成速率

分别测定了四-α-(2,2,4-三甲基-3-戊氧基)酞菁钯(锌)和四-α-(2,4-二叔丁基苯氧基)酞菁钯(锌)配合物的紫外-可见电子吸收光谱,荧光发射光谱和单线态氧生成速率,结果表明虽然酞菁钯的中心金属离子为开壳层电子结构,但其生成单线态氧(1O₂)的能力与中心金属为闭壳层结构的相应取代酞菁锌相近,这可能是与其荧光发射很弱,系间串跃很强相关。     

The Efficiency of the Formation of Singlet Oxygen by a Sensitizer Based on Zinc Phthalocyanine

Using zinc octa(diethoxyphosphenylmethyl)phthalocyanine as an example, we determined experimentally the quantum yield of generation of singlet oxygen () which makes it possible to evaluate quantitatively the efficiency of photogeneration of ¹O₂ and the influence of biomolecules on this parameter. It is shown that the efficiency of generation of singlet oxygen by the sensitizers used in photodynamic therapy depends on their state in a solution and increases with disaggregation of the dye and its interaction with biomolecules. It is established that phthalocyanine in an aqueous buffer solution sensitizes the formation of ¹O₂ with the quantum yield = 0.16 ± 0.02. On introduction of the detergent Triton X100 into the buffer solution of phthalocyanine, increases up to 0.48 ± 0.07. In a microheterogeneous medium (buffer + albumin) = 0.42.     

Quantum Recoil Effects of Spontaneous Emission on Disentanglement

By taking into account spatial degrees of freedom of atoms, we study theinternal-state disentanglement dynamics of two atoms interacting with avacuum multi-mode noise field. We show that the complete internal-statedisentanglement of the two atoms, caused due to the atomic spontaneousemission can be achieved in a finite time.     

Effect of Spontaneous Emission on Both Atomic Dynamics and Momentum Transfer of an Atom-cavity System

The dynamics of an atom coupling to a quantized cavity field have been studied. The atom is treated as a two-level system with a spontaneous emission rate. The transition probabilities have been given for both adiabatic and non-adiabatic situations. For a special Λ-type atom with dark state, the problem of momentum transfer is discussed in details. The influence of spontaneous emission on validity of the adiabatic approximation is also discussed.     

Correlation between the Efficiency of Singlet Oxygen Generation and the Luminescence Parameters of Photosensitizers

Optics and Spectroscopy - The quantum yield of interconversion to triplet states for free-base 2,3,7,8,12,13,17,18-octaethylporphyrin and 5,10,15,20-tetraphenylporphyrin, as well as of...     

Influence of Substituent and Solvent on the Radiative Process of Singlet Excited States of Novel Cyclic Azacyanine Derivatives

The photophysical properties of novel cyclic azacyanine derivatives have been investigated in acetonitrile, N-butyronitrile, methanol, ethanol, DMF and water. Introduction of electron donating or accepting groups on the cyclic azacyanine has a direct impact on the spectroscopic and photophysical properties. Irrespective of the nature of the substitution, azacyanine shows a general solvent relaxation in accordance with Lippert-Mataga’s prediction; however, in protic solvent, specific interactions are encountered. Fluorescence lifetime decay suggests a relaxation in the nanosecond time scale with monoexponential decay in polar solvents and biexponential decay in non polar solvents. The fluorescence lifetime of azacyanines are found to be longer than popular cy3 dyes. An electron donating substituent increases the fluorescence lifetime and influences the radiative process, whereas an electron withdrawing group marginally increases the excited state lifetime but remarkably enhances the radiative process. The fluorescence quantum yield of substituted cyclic azacyanine in water is noted to be at least five fold higher than the popular cy3 dye.     

有机材料EnBOD的放大自发发射性能研究

在紫外脉冲激光泵浦条件下,研究了有机材料EnBOD的放大自发发射(ASE)性能.EnBOD的甲苯稀溶液样品具有较窄的吸收和荧光光谱,主峰分别位于508 nm和527 nm.其ASE效率随着溶液浓度而变化,浓度为0.008 mol·L-的EnBOD样品具有最高的ASE效率,达到22.6％.其ASE主峰位于542 nm,阈值约为29.5 kW·cm-2.阈值后的ASE半宽约为12.4 nm.经紫外脉冲激光20万次泵浦后,ASE的光强衰减为初始强度的61.2％.结果表明EnBOD是一种ASE阈值较低、光稳定性良好的激光材料.