Solvatochromic Studies of Fluorescein Dianion in N,N-Dimethylformamide/Water and Dimethylsulphoxide/Water Mixtures

Abstract

The absorption, excitation and fluorescence spectra of the fluorescein dianion (FL^2?) in N, N-Dimethylformamide (DMF)/water (H₂O) and Dimethylsulphoxide (DMSO)/H₂O solvent mixtures have been investigated. It is found that the absorption λ_max and emission maxima EX, _nax are both hypsochromic shifted when the H₂O content in the solvent mixtures increases. However, the shoulder peaks λ_s remain constant at 483. 5nm within the range of H₂O mole fraction, x= 0 to 0. 518 in a DMF/H₂O solvent mixture and at 484. 4nm within the range, x=0 to 0. 304, in a DMSO/H₂O mixture. Further increases in H₂O content, cause a hypsochromic shift in λ_s. The molar energies for the electronic transition from the ground state (S₀) to S₁, the first excited singlet state, (E_T(1)) and to S₂, the 2nd excited singlet state, (E_T(2)) of FL^2?in the solvent mixtures are also plotted against x. Linear straight lines and intersection points are observed at x=0. 73 for E_T(1) and at x=0. 51 for E_T(2) in the DMF/H₂O mixture and at x=0. 71 for E_T(1) and at x=0. 31 &; 0. 69 for E_T(2) in the DMSO/H₂O mixture. Hydrogen-bonding stabilization effects are used to explain the above observations. The variation in relative fluorescence quantum yields of S₁ and S₂ of FL^2? with x in the aprotic solvent-H₂O mixtures to FL^2? in pure aprotic solvent are determined and discussed.     

PSⅡ颗粒二聚体中类胡萝卜素向反应中心传能研究

运用瞬态荧光光谱技术在77 K低温下对PSⅡ颗粒复合物中类胡萝卜素（Car）分子的能量传递过程进行研究, 通过不同激发波长473 nm, 481 nm, 507 nm选择性激发PSⅡ颗粒复合物中色素分子, 得到PSⅡ颗粒二聚体中关于Car能量传递的三组时间组分：16.6 ps, 130~183 ps, 217~249 ps. 其中16.6 ps反映了LHCⅡ中的Car分子将能量通过中间体Cars、Chls分子传递到Chl639的过程; 130~183 ps为核心天线中的β-Car分子向RC的能量传递时间; 217~249 ps为LHCⅡ中Car481通过中间Chla分子向RC的传能时间.     

合成双分子膜三元体系的激发态能量转移

在４ （４’ 癸氧基 ４ 氧基联苯）丁基三甲基溴化铵双分子膜体系内,通过静电相互作用使达旦黄、荧光黄和四苯基卟啉磺酸阴离子键合在囊泡表面;研究了达旦黄给体通过荧光黄传递到四苯基卟啉磺酸阴离子受体的三元激发态能量转移。能量转移的结果改善了光的输出,扩展了光波的输出范围。     

胶束体系中荧光素与四溴荧光素间能量转移条件及模型研究

研究了阳离子表面活性剂(CSAA)在水溶液中与阴离子酸性染料四溴荧光素(TBF)的荧光反应,发现当CSAA单体与TBF形成离子缔合物时,TBF的荧光发生猝灭,而CSAA胶束与TBF作用又会产生一个新的、更强的荧光。进而研究了阳离子表面活性剂CTMAB及CPB胶束体系中酸性阴离子荧光染料荧光素与四溴荧光素间的能量转移条件。表明只有在带相反电荷的CSAA形成的胶束中,阴离子染料间的能量转移才可能发生,在2/3临界胶束浓度(CMC)时能量转移效率达到最大。并推测了胶束体系中染料间能量转移模型及染料间能量转移的一般规律。     

The Importance and Use of Energy Transfer in the Liquid-Phase Chemiluminescence

Nonradiative electronic energy transfer (ET) is of great importance and of wide use in studies of chemiluminescence (CL) in solution. Some components of a chemiluminescent system, e. g. reactants, intermediates or products may serve as efficient energy acceptors. In some cases fluorescent energy acceptors, the activators of CL, are necessary components of a CL system. In contrast to the conventional (non-laser) photoexcitation the chemical excitation may produce a triplet state directly, rather than only via the excited singlet state.     

表面增强能量转移效应的研究

通过分析2、2′菁染料水溶液、银胶体以及2、2′菁染料吸附于银胶表面时的吸收光谱得知,2、2′菁染料吸附于银胶表面时,有J聚集体出现,通过分析基频及高阶线性Raman光谱,证实了一些低波数的Raman信号是由J聚集体产生的,从而进一步证实了吸附于银胶表面的2、2′菁染料以单体和J聚集体形式共存.同时,由吸收光谱还可以看出,2、2′菁染料分子及其J聚集体分子的吸收带都处于银胶吸收带的半高宽范围内,满足共振条件,当用不同激发波长(514.5 nm和488 nm)的光激发吸附于银胶表面的2、2′菁染料时,观察到了J聚集体的敏化荧光,而用此激发光激发2、2′菁染料水溶液时,就没有观察到J聚集体的敏化荧光,从而说明了银胶表面的存在,加速了单体2、2′菁染料分子与其J聚集体分子之间的能量转移速率.     

Theory of Directed Electronic Energy Transfer

The migration of electronic energy between molecules or chromophores in molecular solids is a well-studied phenomenon. The ability to exert control over the directionality of this transfer, by a variety of methods involving applied electrical or optical fields, holds promise for advances in fields including nanoelectronics and energy harvesting materials. In this paper, we review in detail a number of methods for directing energy transfer, also identifying potential applications.     

Radiationless Energy Transfer Between Rare-Earth Ions in Solutions and its Application to the Investigation of Complexation Processes

Radiationless energy transfer between rare-earth ions (Ln³⁺) in solutions has some features: 1) the electronic transitions in Ln³⁺ complexes causing the luminescence of energy donor and the absorption of energy acceptors are forbidden by Laporte's rule and are weakly intensive. Therefore the critical radius (R_o) of energy transfer between the rare-earth ions for dipole-dipole mechanism is close to that for exchange-resonant mechanism. This fact presents difficulties for unequivocal interpretation of the energy transfer mechanism. 2) The plus-three lanthanide ions exist in solution as a set of complexes with different number of charged ligands in the inner coordination sphere and hence with different total charge of complexes.     

双掺杂聚合物电致发光中能量传递的光谱分析

将两种荧光染料掺杂到有机聚合物中,制作了双掺杂的电致发光器件ITO/PVK:TPB:Rubrene/LiF/Al, 得到了聚合物与两种荧光染料之间的阶梯式的能量传递。当PVK作为能量给体,Rubrene为能量受体时,能量传递不是很有效。但通过研究共掺杂体系的发光性质,发现辅助染料TPB的加入,作为能量传递的桥梁,提高了能量传递的效率,从而增加了器件的色纯度。     

Electronic Energy Transfer from Sinclet Molecular Oxygen to Carotenoids

Abstract

Aerated benzene solutions containing anthracene together with one of the carotenoids, β-carotene, β-apo-8′-carotenal, ethyl β-apo-8′-carotenate and canthaxanthin were subjected to laser photolysis. Under these conditions oxygen quenching of triplet anthracene produces the excited singlet state of molecular oxygen O₂? (¹δ_g) which in turn transfers energy to the carotenoid thereby yielding its triplet state, the absorption of which was monitored thereby confirming electronic energy transfer as the mechanism of quenching of O₂ ?(¹δ_g) by these carotenoids and enabling the bimolecular quenching constansts which vary from 1.2 – 1.45 × 10¹⁰ 1 mol^?1s^?1 to be measured.     

Time-Resolved Detection of Hot Electron-Induced Electrochemiluminescence of Fluorescein in Aqueous Solution

Strong electrogenerated chemiluminescence (ECL) of fluorescein is generated during cathodic pulse polarization of oxide-covered aluminum electrodes and the resulting decay of emission is so sluggish that time-resolved detection of fluorescein is feasible. The present ECL in aqueous solution is based on the tunnel emission of hot electrons into the aqueous electrolyte solution, which probably results in the generation of hydrated electrons and hydroxyl radicals acting as redox mediators. The successive one-electron redox steps with the primary radicals result in fluorescein in its lowest excited singlet state. The method allows the detection of fluorescein (or its derivatives containing usable linking groups to biomolecules) over several orders of magnitude of concentration with detection limits well below nanomolar concentration level. The detection limits can still be lowered, e.g., by addition of azide or bromide ions as coreactants. The results suggest that the derivatives of fluorescein, such as fluorescein isothiocyanate (FITC), can be detected by time-resolved measurements and thus be efficiently used as electrochemiluminescent labels in bioaffinity assays.     

Detection and Characterization of Membrane Microheterogeneity by Resonance Energy Transfer

The application of resonance energy transfer (RET) in the study of heterogeneity in membrane systems is described. Useful formalisms for monophasic and biphasic systems are presented, together with quantitative studies. Evidence for reduction of dimensionality, probe segregation, and microdomain sizes in these systems is discussed. Selected examples of multicomponent systems (natural membranes or model systems including proteins) are also referred, as well as recent work using RET under the microscope.     

核黄素与蒽酮衍生物之间的能量传递现象的研究

依据Förster的能量传递理论,研究了核黄素和蒽酮衍生物之间的能量转移。研究结果表明：核黄素与蒽酮衍生物之间存在着显著的能量转移,而且二者的能量转移效率受加热温度、加热时间和质量配比的影响;核黄素与蒽酮衍生物最佳质量比为1∶3;随着加热温度和加热时间的增大,能量转移效率减小。     

从捕光天线到反应中心分子能量传递研究

利用飞秒时间分辨光谱技术研究了PSⅡ中捕光天线LHCⅡ内Chla分子和β-Car分子传递光能到反应中心的时间特性,实验测得Chla分子用了25 ps,β-Car分子用了250 ps.理论研究得出:25 ps是相邻Chl分子之间随机转移传能的时间常数,250 ps是LHCⅡ内相邻β-Car分子,通过Chla分子单步FÖrster共振传递、Dexter电子交换机制、激子转移把能量转移到反应中心的总时间.理论计算与实验结果基本符合,激子随机转移传递激发能快而有效.     

从核心天线到反应中心分子传能研究

利用飞秒时间分辨光谱技术研究了PSⅡ核心复合物内β-Car分子和Chla分子传递光能到反应中心的时间特性.实验测得,在CP47中的β-Car分子用了150 ps,Chla分子用了15 ps;在CP43中β-Car分子用了160 ps,Chla分子用了20 ps.利用超快光谱动力学实验曲线,理论计算出在核心天线中β-Car分子到Chla 662之间的能量传递速率为1.18×10¹²s^-1,β-Car分子到相邻β-Car分子之间按速率 1.14×10¹²s^-1传递能量.理论研究得出,在核心天线中β-Car分子接收到光能,以Dexter电子交换机制和Frster共振传能机制进行激发能传递,最后由Chla分子把能量传递到反应中心,在CP47中用了139 ps,在CP43中用了152 ps.理论研究表明,在核心天线中,Chla分子接收到光能之后,以随机转移方式将能量迅速传递到反应中心P680,在CP47中用了16.8 ps,在CP43中用了18 ps.理论研究与实验研究基本符合.     

H原子与CO2分子碰撞的化学反应与能量转移

用时间分辨傅立叶红外发射光谱的方法对H原子与CO2分子的碰撞动力学进行了实验研究．用紫外激光光解的方法分别制备出三个不同平动能为174．7、241．0和306．2 kJ／mol的氢原子,并引发H CO2→OH CO反应．观察到了反应的产物,即振动激发的CO (v≤2)．同时也看到了在H原子与CO2分子的碰撞中发生高效的T- V能量转移．CO2的反对称伸缩模的最高振动能级为v=4．化学反应与能量转移的速率之比大约为10．     

二维相关光谱探测荧光能量转移现象

以EuCl₃和NdCl₃混合水溶液为研究对象,按正交浓度序列以浓度为外部扰动构建紫外可见-荧光二维相关光谱。在混合溶液的二维相关光谱中,观察到了Eu3+的荧光发射谱峰与Nd^{3+的吸收谱峰之间存在交叉峰。交叉峰的出现表明Eu3+和Nd3+的荧光发射与吸收之间存在能量传递。二维相关光谱中交叉峰的产生并非由于溶剂水分子与溶质(Eu3+或Nd3+)之间相互作用;若以单一溶质的EuCl₃和NdCl₃的水溶液构造模拟的“混合溶液”的拟合光谱构建二维紫外可见-荧光相关光谱,由于Eu3+和Nd3+在空间上相互分离,无相互作用发生,交叉峰并不存在。二维相关光谱的交叉峰可为从光谱学角度探测复杂体系能量传递及其相关机制提供一条新思路。}     

基于荧光共振能量转移的核酸适体传感器研究

基于荧光共振能量转移的原理,以修饰于核酸适体上的FAM作为能量供体,以氧化石墨烯作为能量受体,构建了荧光适体传感器,分别对不同浓度的胰岛素和多巴胺进行检测.结果表明,胰岛素的线性检测范围为0.05~10μmol/L,多巴胺的线性检测范围为1~500μmol/L,当胰岛素和多巴胺检测浓度相同时,胰岛素检测信号远强于多巴胺.对胰岛素和多巴胺分别进行特异性实验,发现该传感器对胰岛素和多巴胺有较强的特异性.说明基于荧光共振能量转移的核酸适体传感器不仅可实现多种物质的微量检测,还具有较强的选择性,在生物和医药检测领域应用前景广阔.     

碳量子点/罗丹明B分子复合体系中的能量和电子转移过程研究

本文采用荧光光谱结合稳态和瞬态吸收光谱技术,研究了碳量子点(CQDs)/罗丹明B(RhB)分子复合体系o-CQDs/RhB和m-CQDs/RhB中的能量转移和电子转移过程以及它们之间的关系. 研究发现在能量转移效率为73.2%的o-CQDs/RhB体系中,电子转移过程可以忽略;而在能量转移效率低于33.5%的m-CQDs/RhB体系中,电子转移过程则较为显著. 在这个由碳量子点和染料分子组成的典型复合体系中所揭示的能量转移与电子转移过程之间的内联关系,将为与激子猝灭相关的应用提供有用的视角.     

PAR-吖啶黄能量转移荧光猝灭法测定痕量铁(Ⅱ)的研究

对 4 (2 吡啶偶氮 ) 间苯二酚 (PAR)与吖啶黄间荧光能量转移进行了探讨 ,研究了其能量转移的最佳条件 ,并应用该体系测定痕量铁 (Ⅱ ) ,由此建立了能量转移荧光测定痕量铁的新方法。在λex/em =46 5nm/5 0 5nm ,十二烷基硫酸钠 (SDS)作用下 ,pH =9 2时 ,吖啶黄与PAR 铁 (Ⅱ )络合物间能发生有效能量转移 ,使吖啶黄的荧光猝灭。铁的量在 0～ 10 μg·L-1范围内呈良好的线性关系。最低检出限 0 0 6 μg·L-1。该方法用于水样、发样中痕量铁的测定 ,结果满意。