含铕配合物荧光纳米纤维的制备及光学性质的研究

通过静电纺丝技术,将发光良好的稀土配合物Eu(DBM)₃·H₂O和Eu(DBM)₄·CPC纳米微粒复合到水溶性的聚乙烯基吡咯烷酮中,制备了具有稀土铕离子红色特性荧光的聚合物纳米纤维。通过对稀土配合物以及聚合物纳米纤维样品扫描电镜和透射电镜的测试,发现当稀土配合物复合到聚合物纳米纤维中后,由于与聚乙烯基吡咯烷酮乙醇溶解性良好,其微观结构发生了变化,得到了50～100 nm左右的比较均匀的线状结构。同时,通过对稀土配合物以及聚合物纳米纤维样品的荧光激发、发射光谱及荧光寿命进行研究,表明稀土配合物在聚合物纳米纤维中比其在粉末状有更高的发光强度及更长的荧光寿命,其原因在于高分子纳米纤维为稀土配合物提供了较稳定的化学环境。     

Rapid wavelength scans over one octave and application to laser-induced fluorescence

Rapid excitation scans of laser-induced fluorescence (LIF) have been demonstrated. Broadband light was generated in a photonic crystal fiber and transmitted through a long fiber. Due to group-velocity dispersion in the long fiber, a wavelength scan emerged from the fiber in time. The wavelength was swept over approximately one octave in approximately 150 ns. The generated light was used to excite LD 700 Perchlorate diluted in methanol. The LIF excitation scan had a spectral resolution of approximately 15 nm, and the integrated fluorescence spectrum was found to be within 7% of the integrated absorption spectrum of the dye molecule. The method presented makes possible spatially and spectrally resolved LIF excitation scans with scanning speeds up to the limits set by the excited-state lifetime of the dye molecule.     

Influence of morphology on the emissive properties of dye-doped PVP nanofibers produced by electrospinning

Dye-doped polymer micro- and nanofibers with tailored light emission properties have great potential for applications in optical, optoelectronic, or photonic devices. In this study, these types of structures were obtained by electrospinning rhodamine 6 G-doped polyvinylpyrrolidone (PVP) using a polymer solution of 10% (mass) concentration in ethanol. Polymer nanofibers with different morphologies (smooth and beaded) and diameters of about 500 nm were obtained using different electrospinning conditions with the same solutions. Fluorescence optical microscopy observations showed that the dye was distributed uniformly in the doped PVP nanofibers. Different shifts were observed when we compared the wavelength of the dye emission band peak of the smooth nanofibers (566 nm) and the wavelength of the dye emission band peak of the beaded fibers (561.5 nm) produced by electrospinning in different conditions with the wavelength of the emission band peak for transparent thin films produced by spin coating (558 nm) using the same polymer solution. This demonstrates that it is possible to tune the optical properties of electrospun dye-doped polymer nanofibers simply by modifying the morphology of the material, i.e., the parameters of the electrospinning process.     

Photobleaching on Photonic Crystal Enhanced Fluorescence Surfaces

The effect of resonant fluorescent enhancement from a photonic crystal surface upon the fluorescent photobleaching rate of Cyanine-5 labeled protein has been investigated. We show that the enhanced excitation mechanism for photonic crystal enhanced fluorescence, in which the device surface resonantly couples light from an excitation laser, accelerates photobleaching in proportion to the coupling efficiency of the laser to the photonic crystal. We also show that the enhanced extraction mechanism, in which the photonic crystal directs emitted photons approximately normal to the surface, does not play a role in the rate of photobleaching. We show that the photobleaching rate of dye molecules on the photonic crystal surface is accelerated by 30x compared to an ordinary glass surface, but substantial signal gain is still evident, even after extended periods of continuous illumination at the resonant condition.     

Effect of concentration on optical properties of dyes incorporated into polyvinyl alcohol films

The quantum yield, lifetime and anisotropy of fluorescence emitted by molecules of neutral red dye incorporated into polyvinyl polymer films were studied as a function of dye concentration. From the data a mechanism of excitation quenching by dye monomers bound to the polymer matrix is suggested.     

高分子添加剂对激光染料荧光的增强效应

本文研究以水作溶剂的Rh-6G激光染料中加入高分子添加剂——聚乙二醇(分子量为6000)引起的染料荧光的增强效应。通过荧光光谱,吸收光谱与染料浓度,添加剂含量的关系的实验研究,定量地给出了不同添加剂量对荧光的增强作用。表明了荧光增强效应的机理主要是添加剂抑制了二聚物的形成。     

Fluorescence as a Probe of Energy Dependence of Electron–Molecule Interaction

The fluorescence intensity dependences on electron kinetic energy, or fluorescence excitation functions, for some aromatic (perylene and p-terphenyl) and heterocyclic (biphenylfuran, oxazoles, and oxadiazoles) compounds are studied. It is found that the addition of phenyl rings to the above molecules result in a moderate decrease in excitation function. On the other hand, introducing heteroatoms such as oxygen or nitrogen leads to a substantial decrease in excitation function.     

Modification of the spontaneous emission of quantum dots near the surface of a three-dimensional colloidal photonic crystal

This paper demonstrates experimentally and numerically that a significant modification of spontaneous emission rate can be achieved near the surface of a three-dimensional photonic crystal.In experiments,semiconductor core-shell quantum dots are intentionally confined in a thin polymer film on which a three-dimensional colloidal photonic crystal is fabricated.The spontaneous emission rate of quantum dots is characterised by conventional and time-resolved photoluminescence (PL) measurements.The modification of the spontaneous emission rate,which is reflected in the change of spectral shape and PL lifetime,is clearly observed.While an obvious increase in the PL lifetime is found at most wavelengths in the band gap,a significant reduction in the PL lifetime by one order of magnitude is observed at the short-wavelength band edge.Numerical simulation reveals a periodic modulation of spontaneous emission rate with decreasing modulation strength when an emitter is moved away from the surface of the photonic crystal.It is supported by the fact that the modification of spontaneous emission rate is not pronounced for quantum dots distributed in a thick polymer film where both enhancement and suppression are present simultaneously.This finding provides a simple and effective way for improving the performance of light emitting devices.     

蒽、苝和1-氨基蒽醌水溶胶的制备及其荧光性能的研究

用再沉淀法分别制备了蒽、苝和1-氨基蒽醌水溶胶,研究了三者在水溶液中的荧光光谱,通过与其对应的分子荧光光谱比较,发现蒽和苝的水溶胶荧光光谱发生了红移,而1-氨基蒽醌分子从无荧光到它的水溶胶有荧光的转变,根据荧光和分子结构关系,得出3种溶胶是通过分子之间相互重叠聚集而成。同时因为他们为平面型分子,因此π电子共轭度大,使得荧光容易激发和发射,荧光光谱向长波方向移动。     

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.     

Molecular third-harmonic-generation microscopy through resonance enhancement with absorbing dye

This paper reports a facile and effortless method to realize three-dimensional (3D) molecular third-harmonic-generation (THG) microscopy through the technique of resonance enhancement with absorbing dye. Hematoxylin, a popular absorbing stain, is applied as an example to verify the multiphoton resonant enhancement based on the 1230 nm excitation light and can selectively enhance THG yield at cell nuclear sites in the studied specimens, serving as a cell nucleus contrast agent. It is concluded that combining THG microscopy with the mature staining technique can readily achieve 3D molecular imaging without using fluorescence.     

The molecular aggregation of pyronin Y in natural bentonite clay suspension

The molecular aggregation and spectroscopic properties of Pyronin Y (PyY) in the suspension containing natural bentonite clay were studied using molecular absorption, steady-state and time-resolved fluorescence spectroscopy techniques. Interaction between the clay particles and the cationic dye compounds in aqueous solution resulted in significant changes in spectral properties of PyY compared to its molecular behavior in deionized water at the same concentration. These changes were due to the formation of dimer and aggregate of PyY in the clay suspension as well as the presence of the dye monomer. The H-type aggregates of PyY in the clay suspension were identified by the observation of a blue-shifted absorption band of the dye compared to that of its monomer. In spite of diluted dye concentrations, the H-aggregate of PyY in the clay suspension was formed. The intensive aggregation in the clay suspension attributed to the localized high dye concentration on the negatively charged clay surfaces. Adsorption sites of PyY on the clay particles were discussed by deconvulated absorption and excitation spectra. Fluorescence spectroscopy studies revealed that the fluorescence intensity of PyY in the clay suspension is decreased by H-aggregates drastically. Moreover, the presence of H-aggregates in the clay suspension resulted in the decrease of fluorescence lifetime and quantum yield of PyY compared to those in deionized water.     

Fluorescence switch of dye-infiltrated SiO<Subscript>2</Subscript> inverse opal based on acid-base vapors or light

The acid-base vapors/light double responsive dye-infiltrated SiO₂ inverse opal photonic crystals (PCs) were fabricated by sacrificial template method and a subsequent infiltration of spiropyran derivative dye molecules. The fluorescence of ring-open dye molecules infiltrated in PCs can be switched on/off based on different fluorescence properties of spiropyran dye under stimuli of acid-base vapors or light, when PCs with suitable stopband were selected. The fluorescence switch behavior based on PCs has potential applications in data storage, color displays, chemical and biological sensors.     

Enhanced two-photon biosensing with double-clad photonic crystal fibers

A double-clad photonic crystal fiber was used to improve detection efficiency over a standard single-mode fiber in a two-photon fluorescence detection scheme in which the dye was excited and the fluorescence was detected back through the same fiber.     

Fluorescence Study of DNA–Dye Complexes Using One-Photon and Two-Photon Picosecond Excitation

Preliminary results of investigation of one-photon- and two-photon-induced fluorescence of acridine orange (AO), epirubicin (ER), hypericin (HYP), and ethidium bromide (EB) in complexes with DNA are presented. A spectrofluorometer based on a picosecond Nd:YAG laser was used for investigations of two-photon (1064-nm, 1-mJ, 40-ps) and one-photon (532- and 355-nm) dye excitation. The spectra of two-photon-induced fluorescence of dyes and their complexes with DNA as well as the kinetics of dyes' fluorescence intensification during their interactions with DNA in dependence on the biomacromolecule concentration were obtained. The intensities of AO, HYP, and EB fluorescence were increased 2.4, 3.2, and 8 times, respectively, after binding with DNA at two-photon excitation, while at one-photon excitation the corresponding values were 2.5, 3.7, and 10 times. The difference in fluorescence enhancement during DNA–dye complex formation at linear and nonlinear excitation may possibly be associated with the fact that the cross sections of one-photon and two-photon absorption, in general, change unequally during the binding of dyes to organic molecules and bathocromic shift of the electronic transitions. It was shown that the peak of AO fluorescence shifted to a longer wavelength on 10 nm after two-photon excitation at 1064 nm in comparison with one-photon excitation at 532 nm.     

Far-field fluorescence microscopy with repetitive excitation

We introduce the concept of repeatedly exciting an excited state of a photostable fluorescent entity to generate a nonlinear fluorescence signal which is solely based on the linear susceptibility of the molecule. The excitation cycle between the fluorescent state and another state prolongs the average lifetime of , with emphasis on those molecules that are in the center of the focus. The photons emitted by the long-lived molecules in the center are recorded by a temporal filter and constitute fluorescence that depends nonlinearly on the excitation intensity. Theoretical analysis reveals that this concept can provide three-dimensional imaging and improve the spatial resolution in far-field fluorescence microscopy. We show that despite the presence of diffraction the effective focal waist can in principle be narrowed down to the molecular scale at the expense of signal. Received: 3 December 1998     

Highly Enhanced Emission of Visible Light from Core–Dual‐Shell‐Type Hybridized Nanoparticles

Core–dual‐shell‐type hybridized nanoparticles (NPs) having Au‐core/dye‐doped silica inner shell/Au outer shell are successfully fabricated by developing a biphasic process that is a kind of so‐called “one‐pot” method. The resulting hybridized NPs exhibit evidently about 20‐fold enhancement of fluorescence intensity, increase in fluorescence quantum yield, and decrease in fluorescence lifetime. These effects depend on the metal nanostructure being optimized, compared with the reference hybridized NPs with neither a Au‐core nor a Au outer shell, due to the gap‐mode effect induced by localized surface plasmon resonance in the core–dual‐shell‐type MIM‐like nanostructure. More detailed elucidation concerning the enhancement mechanism will provide the possibility of photonic device application, for example as a high‐performance point light source, nanolaser, or sensor for bioimaging in the visible region in the near future.     

Simultaneous antigen detection using multiplex dyes

To detect several antigens simultaneously, antibodies directed against different antigens were immobilized on a quartz surface. The antigens were tagged with multiplex, dyes, which show different fluorescence lifetimes but similar excitation and emission spectra. The antigens were detected by recognizing the characteristic fluorescence lifetime. Furthermore, the effect of labeling of the dye on the antigen molecules was examined.     

掺钕镉铝硅酸盐玻璃的Judd-Ofelt理论分析与光谱特性

以掺杂光子晶体光纤为介质的光纤激光器一直受到科研工作者的广泛关注,应用于光子晶体光纤纤芯的掺稀土元素玻璃的制备成为研制掺杂光子晶体光纤的关键问题。利用高温熔融工艺制备钕离子掺杂的40SiO_2-14Al_2O_3-(40-x)CdO-2Li2O-2K2O-2Na_2O-xNd_2O_3(x=0.07,0.14,0.21,0.35,0.42,0.56mol)重金属硅酸盐玻璃系统,测试了其吸收光谱和荧光光谱。采用Judd-Ofelt理论,计算了玻璃样品的强度参数Ωt(t=2,4,6)以及钕离子的自发辐射概率、荧光分支比、荧光辐射寿命等参数。利用测得的荧光光谱计算了钕离子能级跃迁4 F3/2→4 I11/2的受激发射截面及荧光有效线宽。结果表明:当掺Nd_2O_3的摩尔分数为0.42时,制备的镉铝重金属硅酸盐玻璃具有较大的受激发射截面和比较宽的荧光有效线宽,且与相关文献中的钕离子掺杂玻璃相比,具有良好的激光性能和增益性能,有望在研制掺杂光子晶体光纤中得到应用。     

银纳米颗粒对四苯基卟啉Q带荧光寿命的延长

文章报道了吸附在银纳米颗粒表面的四苯基卟啉(TPP)的Q带荧光寿命的变化.实验发现将银纳米颗粒的表面等离激元共振吸收峰调至与TPP的Q吸收带共振时,会使TPP的Q带荧光寿命得到延长.这是由于银纳米颗粒对表面的光电场有较大的表面等离激元共振增强效应,而处于激发态的TPP分子有较高的极性,这种增强的光电场会对有较高极性的TPP分子有稳定作用,所以延长了其Q带寿命.这对于以卟啉为光敏剂的光动力治疗有重要的意义.