Photophysical studies of PET based acridinedione dyes with globular protein: Bovine serum albumin

Interaction of acridinedione dyes with model transport proteins, bovine serum albumin (BSA) in aqueous solution were investigated by fluorescence spectral studies. A fluorescence enhancement was observed on the addition of BSA to photoinduced electron transfer (PET) based acridinedione dyes, which posses C₆H₄(p-OCH₃) in the 9th position of the basic acridinedione ring. On the contrary, the addition of BSA to non-PET based acridinedione dyes with methyl or phenyl substitution in the 9th position does not result in any fluorescence enhancement. The enhancement in the fluorescence intensity is attributed to the suppression of PET process through space between -OCH₃ group and the acridinedione moiety is elucidated by steady state fluorescence measurements. The fluorescence anisotropy value (r) of 0.40 reveals that the motion of the dye molecule is highly constrained and is largely confined to the rigid microenvironment of the protein molecule. The binding constant (K) was found to be in the order of 6.0×10³ [M]⁻¹, which implies the existence of hydrophobic interaction between the PET based dye and BSA. Time resolved fluorescence lifetime measurements reveal that the PET based acridinedione dye preferably binds in the hydrophobic interior of BSA.     

Photophysical Studies on the Interaction of Formamide and Alkyl Substituted Amides with Photoinduced Electron Transfer (PET) Based Acridinedione Dyes in Water

Interaction of photoinduced electron transfer (PET) based acridinedione dye (ADR 1) with amides like formamide, acetamide and dimethylformamide (DMF) were investigated by fluorescence spectral techniques. A fluorescence enhancement accompanied with a blue shift in the emission maximum was observed on the addition of amides to ADR 1 dye, which possess C₆H₄(p-OCH₃) in the 9th position of the basic acridinedione ring. The extent of fluorescence enhancement and the blue shift in the emission maximum of ADR 1 dye is of the order of DMF > acetamide > formamide. DMF, which is more hydrophobic and less polar, results in a higher extent of fluorescence enhancement and a larger shift in the emission maximum towards the blue region. On the addition of amides, the ADR 1 dye prefers to orient towards a more hydrophobic phase surrounded by more number of amide molecules. The fluorescence enhancement of ADR 1 dye is attributed to the suppression of PET process occurring through space. The influence of the hydrophobic nature and the polarity of the amides on the excited state properties of acridinedione dyes are elucidated by steady-state and time resolved fluorescence measurements.     

Photophysical and Electrochemical Studies of 4-Dicyanomethylene 2,6-Dimethyl-4H-Pyran (DDP) Dye with Amides in Water

Photophysical and electrochemical studies of DDP dye with Formamide and alkyl substituted amides were carried out in water. Addition of Formamide (F), Acetamide (ACM), N,N-Dimethylformamide (DMF), Dimethylacetamide (DMAC) to DDP dye result in an isosbestic point. A fluorescence enhancement of DDP dye is observed on the addition of amides. Apart from the fluorescence enhancement, the addition of formamide result in no significant shift in the position of emission maxima of DDP dye whereas addition of ACM and DMF result in a shift towards the blue and red region respectively. DDP dye exhibits three lifetime components which are unique in lifetime and amplitude. The fluorescence lifetime and relative amplitude of DDP dye varies significantly by addition of amides in aqueous solution which are influenced by amidewater hydrogen-bonding network and hydrophobic influences of the alkyl substituted amides. The nature of interaction between dye and amide be predominantly through hydrogen-bonding wherein the carbonyl oxygen (C=O) of amides are bonded to N-H hydrogen of DDP dye through water molecule. The existence of more than one microenvironment of DDP dye in aqueous phase is elucidated by Electrochemical Impedence Spectroscopy (EIS) through Nyquist plots wherein it signifies that there exist at least three different micro environments which support the existence of different fluorescence lifetimes. Fluorescence spectral technique is used as an efficient tool to elucidate the nature of interaction of water soluble probe with hydrogen-bonding solutes is established in our studies.     

Fluorescence properties of dyes adsorbed to silver islands,investigated by picosecond techniques

The fluorescence properties of dye molecules (rhodamine 6G and erythrosin) adsorbed on pure glass surfaces and on silver islands films are investigated by cw and picosecond time-resolved methods. On pure glass surfaces we observe concentration quenching below a critical intermolecular distance (reduction of the fluorescence power per molecule as well as shortened and non-exponential fluorescence decay). On silver islands films the shortening in fluorescence lifetime is more drastic and is nearly independent of the intermolecular distance. This behavior suggests an electrodynamic interaction between dye monomers and plasmons in the metal particles, modified by a damping influence of dye dimers.     

罗丹明101染料的光谱特性研究

观测了罗丹明101染料在甲醇和酸性甲醇溶液巾的稳态吸收、稳态荧光和时间分辨荧光光谱,得到了吸收与荧光光谱的特征信息以及荧光寿命;通过拉曼光谱、红外光谱和密度泛函理论计算,对罗丹明101染料分子的振动模式进行了指认.研究结果全面系统地表征了罗丹明101染料的光谱特征以及分子结构和振动信息,为罗丹明101染料在染料敏化太阳能电池和生物荧光标记等方面的应用研究提供了依据.     

Fluorescence of organic dyes in lipid membranes: Site of solubilization and effects of viscosity and refractive index on lifetimes

The fluorescence decay of several organic dye molecules intercalated in egg phosphatidylcholine lipid membrane vesicles is consistent with the existence of two or three prominent lifetime components rather than a single continuous distribution of lifetimes. The major lifetime components are identified with different sites of solubilization in the membrane. The variation of the lifetime of the membrane-bound dye was studied as a function of the sucrose concentration, which varied the viscosity and refractive index of the aqueous solution. The combined effect of viscosity and refractive index on the lifetime of the dye was used to identify the site of solubilization of the dye in the membrane. The study was useful to identify dye molecules on the surface which are exposed to the aqueous phase, for which the fluorescence lifetime increased systematically with sucrose (viscosity effect). More importantly, it was possible in a few cases to identify the dye molecules which are oriented in the membrane phase, and the fluorescence lifetime decreased systematically with sucrose (refractive index effect). Anomalous values of order parameters determined from the refractive index effect are explained in terms of an orientational distribution of the linear dye molecule weighted in favor of mutually orthogonal orientations.     

光谱法研究变性剂对苦荞麦蛋白质构象的影响

采用紫外差示光谱和荧光光谱研究了不同浓度的乙醇溶液和盐酸胍溶液对苦荞麦蛋白质(TBWSP31)构象变化的影响.研究表明,TBWSP31的色氨酸残基和酪氨酸残基有的位于分子内部,有的暴露于分子表面.乙醇溶液使TBWSP31变性时,仅仅是分子的外层结构发生了变化,分子内部疏水核的变化较小,高浓度的盐酸胍使位于TBWSP31...     

Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method

The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a three-dimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the three-dimensional nanocylindrical photonic fiber geometry.     

Detection and characterization of single molecules in aqueous solution

Using a confocal microscope with a single-photon avalanche photodiode as detector, we studied photon bursts of single Rhodamine 6G (R6G) and Rhodamin B-zwitterion (RB) molecules in aqueous solution by excitation of the lowest excited singlet stateS ₁ with a frequency-doubled titanium: sapphire laser. Multichannel scaler traces, the fluorescence autocorrelation function and fluorescence decay times determined by time-correlated single-photon counting have been measured simultaneously. The time-resolved fluorescence signals were analyzed with a maximum likelihood estimator. Fluorescence lifetime patterns in steps of 100 ps were generated by convolution with the excitation pulse. The lifetime of theS ₁ state was derived from the Kullback-Leibler minimum discrimination information. We are able to demonstrate for the first time identification of two different single dye molecules via their characteristic fluorescence lifetimes of 1.79 ± 0.33 ns (RB) and 3.79 ± 0.38 ns (R6G) in aqueous solution.Dedicated to Prof. F. P. Schäfer on the occasion of his 65th birthday.On leave from Department of Physics, Mokwon University, Taejon, 301-729, Korea     

Fluorescence Properties of Phenol-Modified Zinc Phthalocyanine that Tuned by Photoinduced Intra-Molecular Electron Transfer and pH Values

Tetra[α-(4-hydroxyphenoxy)] zinc phthalocyanine, ZnPc(α-OPhOH)₄, was synthesized and its photophysics was found to be sharply pH dependent. Dual fluorescence emission around 700 nm was observed when it is dissolved in basic solution. The fluorescence of the phthalocyanine can be sharply switched off at pH 9.1 due to the intramolecular photoinduced electron transfer (PET) in ZnPc(α-OPhONa)₄, formed by the deprotonation of ZnPc(α-OPhOH)₄. The photophysics of both ZnPc(α-OPhOH)₄ and ZnPc(α-OPhONa)₄ were studied in detail by UV-vis absorption, steady state and time-resolved fluorescence and transient absorption (TA) to reveal the fluorescence quenching mechanism. Intra-molecular PET in ZnPc(α-OPhONa)₄ from the donor, PhONa subunits, to the acceptor, ZnPc moiety, was characterized by the much smaller fluorescence quantum yield (0.003) and lifetime (<0.20 ns). PET was further evidenced by the occurrence of charge separation state (CSS) in TA spectra, i.e. the bands due to anion radical of ZnPc and phenol radical. The lifetime of the charge separation state is ca. 3 ns, the efficiency of PET is ca. 99% and the rate constant of PET is 2.3 × 10¹⁰ s⁻¹.     

稀土配合物的时间分辨荧光光谱法研究(Ⅱ)——Eu,Sm-DBM-TOPO体系的荧光衰减动力学特性和激光诱导时间分辨荧光光谱

本文以Nd:YAG泵浦的染料激光器为激发光源,门控光学多道分析仪为检测器,自制的触发器和荧光盒组装成一台激光诱导时间分辨光谱装置。采用此装置研究了在表面活性剂Triton X-100存在下铕、钐-二苯甲酰甲烷-三正辛基氧化膦(Eu、Sm-DBM-TOPO)体系的激光诱导发光光谱特性和荧光衰减动力学特性。讨论了荧光发射过程中的能量传递机制。拟定出测定痕有铕和钐的时间分辨光谱方法,用于高纯稀土氧化物等样品中痕量铕和钐的测定,结果满意。     

Domain Formation in DODAB–Cholesterol Mixed Systems Monitored via Nile Red Anisotropy

The effect of the cholesterol (ch) on liposomes composed of the cationic lipid dioctadecyldimethylammonium bromide (DODAB) was assessed by studying both the steady-state and time-resolved fluorescence anisotropy of the dye Nile Red. The information obtained combined with analysis of the steady-state emission and fluorescence lifetime of Nile Red (NR) for different cholesterol concentrations (5–50%) elucidated the presence of “condensed complexes” and cholesterol-rich domains in these mixed systems. The steady-state fluorescence spectra were decomposed into the sum of two lognormal emissions, emanating from two different states, and the effect of temperature on the anisotropy decay of Nile Red for different cholesterol concentrations was observed. At room temperature, the time-resolved anisotropy decays are indicative of NR being relatively immobile (manifest by a high r _∞ value). At higher temperature, rotational times ca. 1 ns were obtained throughout and a trend in increasing hindrance was seen with increase of Ch content.     

DMANS——一种新型荧光闪烁体染料的寿命与能量转移的研究

本工作对一种新型荧光闪烁体染料——4-二甲胺基—4''硝基芪(DMANS)在不同介质中的光谱行为和能量转移进行了研究,发现介质的极性大小以及介质和染料间的能量转移对该闪烁体染料的荧光量子产率和闪烁发光延迟具有重大影响。研究对选择基体材料和合理组成闪烁材料配方有一定的参考价值。     

DNA介导复合膜中[Ru(bpy)3]2+与Cu(Ⅱ)间光诱导电子转移

由于DNA与[Ru(bpy)₃]2+(bpy=2,2′-联吡啶)及Cu2+间的静电作用,用自铸膜法在铟锡氧化物(ITO)上制备了橙红色[Ru(bpy)₃]2+-DNA-Cu2+复合膜,并应用稳态和暂态荧光光谱、紫外可见光谱、荧光显微镜和扫描电镜对复合膜进行了表征和DNA介导的光诱导电子转移(PET)研究。结果表明,[Ru(bpy)₃]2+-DNA-Cu2+复合膜(摩尔比为10∶20∶1)呈现了明显的吸收特征峰(450 nm)和发射峰(λ_em=595 nm),发光呈单指数衰减,发光寿命为188.6 ns,Cu2+通过DNA介导PET机制猝灭[Ru(bpy)₃]2+发光,猝灭常数为6.94×103 L·mol-1,猝灭速率常数为3.80×1010 L·mol-1·s-1;复合膜中Cu2+摩尔比(10倍)的增大使发射峰蓝移了11 nm,吸收和发射强度衰减至消失,Cu2+通过静态猝灭机制削弱[Ru(bpy)₃]2+发光。此外,对比于溶液和复合膜中Cu2+对[Ru(bpy)₂(tatp)]2+-DNA(tatp=1,4,8,9-四氮三苯)的发光调控,Cu2+仅能因静电作用猝灭复合膜中[Ru(bpy)₃]2+的发光。     

Spectroscopic and photophysical investigations on the nature of localization of rhodamine-123 and its dibromo derivative in different cell lines

Steady-state and time-resolved spectroscopic properties of rhodamine-123 (rh123) and 4,5-dibromorhodamine methyl ester (dbr123) bound to different cell lines are evaluated. Studies are also performed on the dye bound to extracted mitochondria. Results are compared with those obtained in homogeneous and microheterogeneous media. Results suggest that these dyes can specifically bind only with cell mitochondria. As a result of binding, excitation and emission spectra are red shifted by 10 to 12 nm. The fluorescence decay of these dyes bound to mitochondria shows two lifetimes. Values are about 4.0 and 2.0 ns forrh123 and about 1.9 and 0.5 ns fordbr123. Detailed global analysis of emission wavelength and dye concentration dependences of the fluorescence decay is performed. Results indicate that these dyes are bound to two different binding sites at mitochondria. The decay-associated fluorescence spectrum for the species corresponding to each binding site is recovered. Species1, corresponding to the longer lifetime, is found to be more red shifted compared to species2. The fluorescence of species2 is heavily quenched. The origin of this quenching is explained in terms of resonance energy transfer between donor species2 and acceptor species1. The possible nature of the two binding sites is also discussed.     

识别过渡金属离子的1,8-萘二甲酰亚胺多胺衍生物荧光传感器的研究

设计合成了用以检测过渡金属离子的荧光化学敏感器体系,它们是由1,8-萘二酰亚胺为荧光团,多胺衍生物为金属离子受体组成．在室温下对其光物理性质的研究中发现,在没有加入过渡金属离子时,由于体系内存在有效的光诱导电子转移过程使得荧光团的荧光被淬灭．加入过渡金属离子后,金属离子受体中的氮原子和过渡金属离子之间的配位作用阻断了光诱导电子转移过程,体系的荧光增强．不同的金属离子受体表现出了和过渡金属离子不同的配位识别能力,并且通过荧光的变化传递出受体-金属离子作用的信息．     

The third-order optical nonlinearity and upconversion luminescence of CdTe quantum dots under femtosecond laser excitation

The aqueous CdTe quantum dots (QDs) were synthesized by the electrostatic reaction method. The optical properties of CdTe QDs were investigated by femtosecond Z-scan and time-resolved luminescence technique in nonresonant spectral region. The nonlinear absorption and refraction are ascribed to two-photon absorption, and time-resolved upconversion photoluminescence produces biexponential decay pattern at infrared femtosecond laser excitation. Upconversion luminescence is composed of a band-edge excitonic state and a photoinduced trapping state. The short-lived band-edge excitonic emission is independent of the detection wavelengths, and long-lived species becomes even longer with the increase of detection wavelengths, which indicates the size dependence of surface excitonic emission. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Intramolecular photoinduced electron-transfer in azobenzene-perylene diimide

This paper studies the intramolecular photoinduced electron-transfer (PET) of covalent bonded azobenzene-perylene diimide (AZO-PDI) in solvents by using steady-state and time-resolved fluorescence spectroscopy together with ultrafast transient absorption spectroscopic techniques.Fast fluorescence quenching is observed when AZO-PDI is excited at characteristic wavelengths of AZO and perylene moieties.Reductive electron-transfer with transfer rate faster than 10 11 s-1 is found.This PET process is also consolidated by femtosecond transient absorption spectra.     

氧化石墨烯如何猝灭罗丹明6G的荧光

考察了水相溶液中氧化石墨烯对罗丹明6G的高效荧光猝灭．借助稳态及时间分辨荧光光谱测量,结合对该二元体系线性吸收谱变化的细致分析,澄清了相关荧光猝灭机理,即动态猝灭与静态猝灭的联合猝灭机制．提出在静态猝灭过程中罗丹明6G与氧化石墨烯所形成的可能的基态复合物,并进一步讨论了二者之间的光致电子转移过程．     

Probing the Liquid-State Structure and Dynamics of Aqueous Solutions by Fluorescence Spectroscopy

Time-resolved fluorescence spectroscopy of the solvent-sensitive molecule 1,8-anilinonaphthalene sulfonate (ANS) is used to probe the structure and dynamics of an aqueous methanol solution (mole fraction = 0.5). The intensity decay of ANS in the mixed solvent displays single exponential kinetics under ambient conditions. At low temperature, a simple two-state solvent relaxation model describes the fluorescence decay for ANS in both methanol and the mixed solvent. The temperature dependence of ANS fluorescence in the mixed solvent is attributed to the onset of glassy dynamics in the aqueous component at higher temperature, implying a partial demixing of the water and methanol due to self-association. We discuss the absence of more complicated fluorescence decays in such a heterogeneous solvent system.