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.     

半花菁分子激发态的动力学特性研究

本文利用不同波段的时间分辨荧光和三维荧光谱对半花菁分子激发态的动力学特性进行了研究。在半花菁／花生酸交替的Y型多层膜中,半花菁分子形成的H－聚集体引起其三维荧光谱蓝移,并且荧光峰随时间的变化逐渐向红光方向移动。由于聚集体内所有分子间的相互作用（耦合）相干叠加,使得LB膜中的半花菁分子的激发态寿命比溶液寿命要短,由激发态较高振动能级向低能级过渡较快,因而不同波段的起始发光时间相差也较小。     

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。     

半花菁LB膜的时间分辨荧光研究

利用紫外－可见吸收,稳态和时间分辨荧光等方法研究了半花菁与花生酸交替Ｙ型ＬＢ膜中分子聚集体的性质;吸收光谱和稳态荧光光谱峰位的蓝移说明ＬＢ膜中Ｈ聚集体的存在。从荧光衰工线得到了聚集体的组份含量、大小和寿命。     

Solvent Effects on the Spectroscopic Properties of Styrylquinolinium Dyes Series

The study on the relationship between the structure and spectroscopic properties of styrylquinolinium dyes were carried out by measuring the electronic visible absorption, steady-state and time-resolved fluorescence spectra of quinoline based hemicyanine dyes. The influence of the solvent on absorption and emission spectra and the solvatochromic properties, observed for both ground and first excited states, for all the dyes were applied for the evaluation of their excited state dipole moments. The ground state dipole moments of dyes under the study were established by applying ab initio calculations. The measured, using solvatochromic methods, excited state dipole moments of tested hemicyanines are in the range from 5.38 to 18.90 D and the change in the dipole moments caused by excitation were found to differ from 1.88 to 6.64 D. It was observed that for all tested dyes the dipole moments of the excited states were higher than those of a ground states. The fluorescence lifetime measurements with picosecond resolution was performed for entire series of hemicyanine dyes possessing different dialkylamino groups attached to the phenyl ring. The average lifetimes of the dye fluorescence, determined from the measured data by multi-order exponential decay curve fitting, were in the range from about 120 to 1200 ps at the fluorescence peak wavelength. The fluorescence lifetime measurements were performed for dyes in ethyl acetate solutions. The time-resolved fluorescence spectra measurements allowed to propose the mechanism of the dyes excited states deactivation.     

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.     

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.     

A UV–Visible–NIR fluorescence lifetime imaging microscope for laser-based biological sensing with picosecond resolution

This article describes the design and characterization of a wide-field, time-domain fluorescence lifetime imaging microscopy (FLIM) system developed for picosecond time-resolved biological imaging. The system consists of a nitrogen-pumped dye laser for UV–visible–NIR excitation (337.1–960 nm), an epi-illuminated microscope with UV compatible optics, and a time-gated intensified CCD camera with an adjustable gate width (200 ps-10^-3 s) for temporally resolved, single-photon detection of fluorescence decays with 9.6-bit intensity resolution and 1.4-μm spatial resolution. Intensity measurements used for fluorescence decay calculations are reproducible to within 2%, achieved by synchronizing the ICCD gate delay to the excitation laser pulse via a constant fraction optical discriminator and picosecond delay card. A self-consistent FLIM system response model is presented, allowing for fluorescence lifetimes (0.6 ns) significantly smaller than the FLIM system response (1.14 ns) to be determined to 3% of independently determined values. The FLIM system was able to discriminate fluorescence lifetime differences of at least 50 ps. The spectral tunability and large temporal dynamic range of the system are demonstrated by imaging in living human cells: UV-excited endogenous fluorescence from metabolic cofactors (lifetime ∼1.4 ns); and 460-nm excited fluorescence from an exogenous oxygen-quenched ruthenium dye (lifetime ∼400 ns). Received: 23 February 2003 / Published online: 22 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-734/9361-905, E-mail: mycek@umich.edu     

互变异构激光染料奇通红发光特性研究

本文报道应用微微秒脉冲技术测量奇通红染料荧光寿命,发现该体系荧光衰减呈现双指数衰减形式,证实了奇通红染料分子的互变异构特性.     

异丙醇-水配合液的荧光偏振和时间分辨特性

研究了紫外光照射下异丙醇-水配合液的偏振荧光光谱,以及不同荧光峰处光子强度随时间的衰变过程,计算了偏振度并讨论了其偏振特性,测试了不同峰位对应的荧光寿命并分析了其荧光发射特性.结果表明,异丙醇-水配合液在紫外光激励下发射的荧光为具有确定分子取向的部分偏振光,偏振度和各向异性度分别为0.542和0.441.在波长为220...     

血啉甲醚的时间分辨荧光光谱研究

实验研究了用于肿瘤光动力学诊断的第二代新型光敏剂血啉甲醚(HMME)分别在不同血型人血清和生理盐水环境中的时间分辨光谱,同时还研究了在不同荧光发射峰处的荧光寿命以及光敏剂浓度对荧光寿命的影响。结果表明:HMME在625和690nm处的荧光寿命基本相同,无显著差异。HMME在生理盐水和人血清环境中的荧光寿命具有显著差异,分别为14.6和16.6ns,同时实验结果还表明光敏剂浓度对荧光寿命没有影响。结论对于开展肿瘤的时间分辨药物荧光光谱诊断与成像技术具有重要的指导意义。     

Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects

The radiative and nonradiative decay rates of lissamine dye molecules, chemically attached to differently sized gold nanoparticles, are investigated by means of time-resolved fluorescence experiments. A pronounced fluorescence quenching is observed already for the smallest nanoparticles of 1 nm radius. The quenching is caused not only by an increased nonradiative rate but, equally important, by a drastic decrease in the dye's radiative rate. Assuming resonant energy transfer to be responsible for the nonradiative decay channel, we compare our experimental findings with theoretical results derived from the Gersten-Nitzan model.     

Double 3-Ethyl-2,4-dimethylpyrrole Configured Fluorescent Dye with Fluorine-Boron as the Bridge

Dipyrrolydiketones BF₂ complex was synthesized and characterized by NMR, HRMS, and single crystal diffraction. In non-polar environment, this BF₂ containing dye emitted bright blue-green fluorescence. No significant spectra shift was observed both in absorption and emission spectra, which indicates the insensitivity of absorption/emission toward environment. The alkyl substituted pyrrole rings lead to its highly emission character in solid state by enhancing the distance between dye molecules. Absolute quantum yields were determined to be 0.51–0.78/0.36 in selected organic medium and solid state, respectively. The emission dynamics was investigated by fluorescence lifetime and both monoexponential and bi-exponential decay was observed.

     

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     

Interaction of cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin with mono-and polynucleotides: A study by picosecond fluorescence spectroscopy

The interaction of water-soluble cationic 5,10,15,20-tetrakis(4-N-methyl pyridyl) porphyrin (H₂TMPyP4) with some mono-and polynucleotides is studied by time-resolved and steady-state fluorescence spectroscopy, as well as by steady-state absorption spectroscopy. The fluorescence decay kinetics are analyzed by reconstructing the decay time distributions, which made it possible to describe in more detail than previously the complexes formed due to the interaction. The main effect of binding of H₂TMPyP4 adenosine 5′-monophosphate and to poly(dA-dT)₂ is shown to be an increase in the fluorescence lifetime from 4.6 ns in the solution to 8.3 and 12.3 ns, respectively. This effect is explained by a less polar (in comparison with water) environment of porphyrin in complexes, which leads to a decrease in the quenching action of the intramolecular charge transfer state between the porphyrin macrocycle and methyl pyridyl groups. In the case of complex formation with guanine-containing nucleotides (guanosine 5′-monophosphate and poly(dG-dC)₂), the effect of decrease in the quenching action of the intramolecular charge transfer state caused by a decrease in the medium polarity is superimposed by a stronger effect of decrease in the fluorescence lifetime of porphyrin as a result of intermolecular electron transfer from guanine to excited porphyrin. A high sensitivity of this intermolecular quenching to the mutual arrangement of the electron donor and the electron acceptor makes it possible to reveal four types of complexes between H₂TMPyP4 and guanosine 5′-monophosphate, which differ in the positions of four broad peaks in the porphyrin fluorescence decay time distribution (0.1, 0.7, 2.4, and 6.1 ns). For the complex with poly(dG-dC)₂, a narrow peak at 2.8 ns prevails in the fluorescence decay time distribution, with the contributions from two additional narrow peaks at 1.0 and 6.2 ns being small.     

某些稠环芳香碳氢化合物的荧光寿命测量

应用时间相关单光子计算仪器,测量了八个对荧光光谱学和生物化学重要的稠环芳烃.所有溶液在测量前均通高纯氮除氧,对所有化合物都使用337nm激发波长,对荧蒽还在351nm激发,以验证上述两组作者所给数值之间的分歧.我们的实验对于荧蒽在337nm激发给出荧光寿命39ns,在351nm激发给出36ns,表明两个激发波长不应导致寿命数值的实质性差异.我们对其余稠环芳烃所测得的寿命值或者与文献相符,或者看起来是合理的.     

Studies of Interaction Between Cyanine Dye T-284 and Fibrillar Alpha-Synuclein

A key feature of Parkinson’s disease is the formation and accumulation of amyloid fibrils of the natively unfolded protein α-synuclein (ASN) inside neurons. Recently we have proposed novel sensitive monomethinecyanine dye T-284 as fluorescent probe for quantitative detection of ASN amyloid fibrils. In this study the T-284 dye complex with ASN fibril was characterized by means of fluorescence anisotropy, atomic force microscopy and time-resolved fluorescence techniques to give further insights into the mode of dye interaction with amyloid fibrils. The fluorescence anisotropy of T-284 was shown to noticeably increase upon addition of aggregated proteins indicating on stable dye/amyloid fibril complex formation. AFM imaging of fibrillar wild-type ASN revealed differences in heights between ASN fibrils alone and in presence of the T-284 dye (6.37 ± 1.0 nm and 8.0 ± 1.1 nm respectively), that is believed to be caused by embedding of T-284 dye molecules in the “binding channel” running along the fibril. Fluorescence decay analysis of the T-284 in complexes with fibrillar ASN variants revealed the fluorescence lifetime values for T-284/fibril complexes to be an order of magnitude higher as compared to the free dye. Also, the fluorescence decay of free T-284 was bi-exponential, while dye bound to protein yields tri-exponential decay. We suppose that in complexes with fibrillar ASN variants T-284 dye might exist in different “populations” due to interaction with fibrils in different conformers and ways. The exact binding mode of T-284 with ASN fibrils needs further studies. Studied parameters of dye/amyloid fibril complexes are important for the characterization and screening of newly-developed amyloid-sensitive dyes.     

Fluorescent polystyrene microspheres with large Stokes shift by fluorescence resonance energy transfer

We prepared fluorescent microspheres with notably large Stokes shift and long-wavelength fluorescence by applying fluorescence resonance energy transfer (FRET) between two common julolidine dyes. Short distance between dye molecules caused by high dye concentration results in efficient FRET in microspheres. However, adequate dye concentration and moderate molar ratio of the donor and acceptor should be chosen to avoid aggregation of dye molecules, which leads to the decrease of fluorescent intensity. Microrspheres with average distance between dye molecules of 1.94 nm and molar ratio of 3.08:1 realize highly efficient FRET with no fluorescence of donor and intense long-wavelength emission of acceptor. In addition, the applied solvent evaporation method for preparing microspheres provided better protection of dyes from ambient medium than traditional surface-labeled method. These results demonstrate the feasibility of applying FRET in microspheres to expand useful fluorescent probes, and reveal their potential application in bioassays field.     

多环芳烃时间分辨荧光光谱特性研究

利用时间分辨荧光光谱技术,研究了菲、荧蒽、芴、蒽、芘等五种多环芳烃的荧光时间分辨发射光谱特性。以289 nm受激拉曼光作为激发光源,研究了289 nm激发光作用下五种多环芳烃的延时特性和门宽特性。并以多环芳烃随延时时间的荧光峰强度衰减关系曲线,得到菲、荧蒽、芴、芘的荧光寿命分别为37.0, 32.7, 10.9, 147.0 ns。不同荧光物质具有特定的荧光光谱特性,多环芳烃时间分辨荧光光谱特性的研究可以为复杂水体中不同种类多环芳烃的诊断提供依据。