Pyrene-Doped Polyorganosiloxane Layers over Commercial Glass Fibers

Commercial glass fibers have been subjected to different activation treatments under neutral and acidic conditions to achieve different coating degrees when silanized with -aminopropyltriethoxisi lane (APES). A fluorescent sulfonamide (PSA) was formed between the amine residue and a fluorescent probe, pyrenesulfonyl chloride (PSC). Reflectance UV–Vis spectra of the pyrene-doped fibres show that pyrene is present in the form of preassociated dimers when the coating degree is low. Emission and excitation fluorescence spectra reveal the existence of a charge transfer ground-state complex with exciplex emission at 460–515 nm and absorption red-shifted with respect to the S₀ S₁ transition. Lifetime measurements yield three lifetimes, which are assigned to dimer, exciplex, and monomer emission. From the photophysical data it is concluded that the fibers with the highest silane content have an open structure with the highest fraction of isolated fluorescent moieties.     

Solvent and pH Effects on the Fluorescence of 7-(Dimethylamino)-2-Fluorenesulfonate

A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2-fluorenesulfonate (2,7-DAFS), was prepared by a three-step reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular charge-transfer (ICT) to π → π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless single band with a large Stokes shift, whereas that of the acidic form, *(⁺HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *(⁺HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence occurs. The pKa* was estimated as −1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15 ∼ 25 times greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant advantages for a variety of applications.     

碲玻璃双芯光子晶体光纤耦合特性研究

以碲玻璃为基质材料,设计了八边形双芯光子晶体光纤.应用全矢量有限元法和模式耦合基本理论分析了八边形双芯光子晶体光纤中结构参数对耦合长度特性的影响.计算结果表明:在波长1.55μm处,减小孔间距可明显减小耦合长度,但只略微改变相对耦合长度;增大空气孔及椭圆率可略微增大耦合长度,但可明显增大相对耦合长度.当相对耦合长度为1时,设计的偏振分束器性能较理想.在此基础上,通过调节结构参数,设计了一种较短传输长度、高带宽、高消光比的偏振分束器,当光纤长度为139μm时,X、Y方向偏振光即可实现分离,消光比达到最小值-53.46dB,且在波长1.49μm~1.61μm,即带宽为120nm范围内,消光比小于-20dB,与同类型的高消光比和极短长度双芯偏振分束器相比,其综合性能比较突出.     

Influence of a Solvent on the Quantum Yield and Duration of the Fluorescence of Tetraazoporphin

In view of the discrepancies between the values available in the literature for the photophysical parameters of tetraazaporphin in solutions, we measured its quantum yield and duration of fluorescence in a number of solvents. It has been found that alcohols (isobutanol and isopropanol) quench the fluorescence appreciably. For a solution in toluene — a stable chemically inactive and low-polar solvent — the measured quantum yield of the fluorescence of tetraazaporphin is equal to 0.180 ± 0.015 and its duration is 3.4 ± 0.1 nsec. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 697–699, September–October, 2005.     

New Insight into the Interfacial Enhancement of Polypropylene Glass Fiber Composites via a Compatibilizer: The Role of Injection Screw Temperature

Polypropylene (PP)glass fiber (GF) composites modified by maleic anhydride-grafted polypropylene (MAH-g-PP) were prepared and the thermal influence on the interfacial properties was characterized and discussed. The results showed that the migration of MAH-g-PP from the PP matrix onto the GF surface was a thermally activated process. To be more specific, with the increasing processing temperature, more MAH-g-PP migrated onto the interface region to bridge PP matrix and GF together and promote the interfacial interaction, resulting in more efficient applied load transfer to GF through the interface. Accordingly, the mechanical properties of PPGF composites were improved with increasing processing temperature. Moreover, based on the content of MAH-g-PP on the surface of the GF and the mobility of MAH-g-PP in the PPGF composites, a temperature-dependent mechanism for the enhanced interface was proposed. We suggest this study not only provides a guide to adjust processing parameters to prepare high-performance PPGF composite, but also would be applicable for other immiscible systems.     

Developing of Fluorescence Probes Based on Stilbazolium Salts for Monitoring Free Radical Polymerization Processes. II

The series of 1-methyl-4-(4-aminostyryl)pyridinium perchlorates was investigated as fluorescent probes for the monitoring of the free radical polymerization progress. The study on the changes in fluorescence intensity and spectroscopic shifts of studied compounds were carried out during thermally initiated polymerization of methyl methacrylate. The purpose of these studies was to find a relationship between the structure of fluorophore and the changes in their fluorescence shape and intensity observed during the monomer conversion into polymer. The probes under the study during the course of polymerization increase their fluorescence intensity at least one order of magnitude. Such increase qualified the tested probes as good fluorescence probes.     

溶剂对TNS与ANS荧光光谱的影响

研究了两种光谱探针TNS与ANS在不同溶剂中的荧光光谱,为此类荧光探针的应用奠定了一定的基础。结果表明溶剂对TNS与ANS荧光光谱的影响是一般溶剂效应与特殊溶剂效应共同作用的结果。     

The Influence of Solvent Viscosity on the Fluorescence Decay and Time-Resolved Anisotropy of Green Fluorescent Protein

This report describes fluorescence decay and time-resolved anisotropy studies of green fluorescent protein (GFP) in various environments. The addition of glucose and fructose, NaCl, or polyethylene glycol changes the viscosity of the medium surrounding the GFP. Both the time-resolved anisotropy and the fluorescence decay of GFP are measured and it is shown that only the time-resolved anisotropy of GFP is affected by the viscosity, but not its fluorescence decay.     

同时测量荧光光纤温度和应变的实验研究

利用掺杂铒元素荧光光纤的试验样品实验测试了荧光寿命的温度特性，并得到荧光寿命在不同温度下的应变响应关系.试验表明，荧光寿命会随着温度的升高而降低；与温度相比荧光寿命随应变的变化很小.提出了一个潜在的同时测量应变和温度的传感器模型.     

外部荧光种子植入法增强液芯光纤中CS2的受激拉曼散射研究

本文报道了运用外部荧光种子(罗丹明6G乙醇溶液)植入法对液芯光纤中CS2受激拉曼散射的增强研究。实验结果表明, CS2的二阶、三阶Stokes波分别获得了1.92和11.71倍的增益。并对外部荧光种子植入法增强液芯光纤中受激拉曼散射的机制进行了分析。     

Fluorescence lifetime characterization of magnesium probes: Improvement of Mg2+ dynamic range and sensitivity using phase-modulation fluorometry

We measured the Mg²⁺-dependent absorption spectra, emission spectra, quantum yields, and intensity decays of most presently available fluorescent magnesium probes. The lifetimes were found to be strongly Mg²⁺ dependent for Mag-quin-1, Mag-quin-2, magnesium green, and magnesium orange and increased 2- to 10-fold upon binding of Mg²⁺. The lifetimes of Mag-fura-2, Mag-fura-5, Mag-fura red, and Mag-indo-1 were similar in the presence and absence of Mg²⁺. Detailed timeresolved measurements were carried out for Mag-quin-2 and magnesium green using phase-modulation fluorometry. Apparent dissociation constants (K _d) were determined from the steady-state and time-resolved data. Their values were compared and discussed. Mg²⁺ sensing is described using phase and modulation data measured at a single modulation frequency. Phase angle and modulation data showed the possibility of obtaining a wider Mg²⁺-sensitive range than available from intensity measurements. A significant expansion in the Mg²⁺-sensitive range was found for Mag-quin-2 using excitation wavelengths from 343 to 375 nm, where the apparentK _d from the phase angle was found to vary from 0.3 to about 100 mM. Discrimination against Ca²⁺ was also measured for Mag-quin-2 and magnesium green. Significant phototransformation and/or photode-composition, which affect the sensitivity to Mg²⁺, were observed for Mag-quin-2 and magnesium green under intense and long illumination.     

滤紫外和红外光的荧光玻璃的研制及其应用

研制出了掺铈、钐的滤紫外和红外光的硼硅酸盐荧光玻璃，测试了该玻璃的吸收光谱和荧光谱，并用其做了固体激光器工作物质的紫外和红外滤光套，能使激光效率提高２５％－５０５，从而促进固体激光器的微型化和实用化。     

Effects of End-Face Tilt Angle on Numerical Aperture for Straight and Bent Plastic Optical Fibers

Numerical aperture (NA) is an important parameter of optical fibers. The larger it is, the greater the amount of light input into the fiber and, hence, the greater the achievable transmission distance. In this article, analytical functions are given for numerical aperture of an angle-ended plastic optical fiber in terms of the tilt angle of its input/output face. This tilt may be intentional, as in biomedical spectroscopic sensors, or otherwise when exploiting the quick interconnectivity potential of plastic fibers. The influence of fiber curvature on its numerical aperture has also been quantified as the functions given cover both straight and curved fiber configurations.     

Mechanical Properties and Morphology of Polypropylene/Polypropylene-g-Maleic Anhydride/Long Glass Fiber Composites

Long glass fiber (LGF)-reinforced polypropylene (PP) was prepared using a self-designed impregnation device. The effect of dicumyl peroxide (DCP) and maleic anhydride (MA) content on the compatibilizer, PP grafted with maleic anhydride (PP-g-MA), was investigated by means of scanning electron microscopy (SEM) and mechanical properties. The experimental results demonstrated that the increase of DCP and MA could effectively improve the interfacial interaction between PP and GF. Good interfacial adhesion between PP and GF in PP/ PP-g-MA /LGF composites was observed from SEM studies for the higher contents of MA. The best mechanical properties of PP/ PP-g-MA /LGF(30%) composites were obtained when the content of DCP and MA were 0.4 and 0.8 wt%, respectively. The storage modulus of the PP/PP-g-MA/LGF composites increased and then decreased with the content of MA. When the content of MA was 0.8 wt%, tan δ had the lowest value, indicating that the corresponding composites had the best compatibility.     

Voltage-Gated Metal-Enhanced Fluorescence II: Effects of Fluorophore Concentration on the Magnitude of the Gated-Current

In this letter we report further findings on the ability of an applied direct current to modulate Metal-Enhanced Fluorescence (MEF). Fluorophores in close-proximity to just-continuous silver films (JCS) show significantly enhanced fluorescence intensities. However, when a current is applied to the films, the enhanced fluorescence can be gated in a manner that depends on both the fluorophore concentration, the magnitude of the applied current and the extent of the protein mono to multi-layer surface coverage. Our results are consistent and indeed further support our previous hypothesis and model that fluorophore-metal near-field interactions can be influenced by an applied direct current.     

磷酸盐钕玻璃的荧光寿命和损耗对激光增益特性的影响

实验研究了目前使用的Ｎ２１２２和Ｎ３１２２掺钕磷酸盐玻璃中不同的ＯＨ基浓度对玻璃荧光寿命的影响，同时从实验和理论上研究了荧光寿命和损耗对激光增益特性的影响，结果表明，增加玻璃的荧光寿命是提高增益性能的一个重要方法，当玻璃的荧光寿命增加１０％时小信号增益系数提高５％左右，提高钕玻璃的荧光寿命，可适当降低对损耗的要求，也能够保持它的增益性能不变。     

压缩CO2中聚合物玻璃化转变温度的实验研究

 玻璃化转变温度（T_g）是聚合物重要的特性参数，压缩CO₂环境中聚合物的玻璃化转变温度的测定，更是超临界流体技术在聚合物科学领域中成功应用的前提条件。根据蠕变柔量实验原理，自建一套测定高压环境下玻璃化转变温度的实验装置。利用该装置对聚对苯二甲酸乙二醇酯（PET）、聚苯乙烯（PS）、聚氯乙烯（PVC）以及聚甲基丙烯酸甲酯（PMMA）在大气中及压缩CO₂环境中的T_g进行了测定。设定实验的平衡吸附温度为室温，平衡吸附压力范围分别为：PET，0~3.5 MPa；PS，0~11.0 MPa；PVC，0~9.0 MPa；PMMA，0~4.5 MPa。在大气中测定的结果与文献中的结果相吻合，表明所设计的实验方法及实验装置是可靠并有效的，可用于高压环境下聚合物的玻璃化转变温度的测定。从压缩CO₂中的聚合物T_g测定结果可以看出，CO₂对聚合物具有较明显的溶胀、增塑作用，可显著降低聚合物的T_g。     

Fluorescence Properties and Dipole Moments of Novel Fused Thienobenzofurans. Solvent and Structural Effects

The electronic absorption, fluorescence excitation and emission spectra, and fluorescence quantum yields of novel fused thienobenzofurans, including thieno[3,2-b][1]benzofuran (1), [1]benzothieno[3,2-b]furan (2), and [1]benzothieno[3,2-b][1]benzofuran (3), were recorded in fourteen solvents of different polarities at room temperature. Compound 2 was not fluorescent. Experimental ground-state dipole moments of compounds 1–3 were measured in benzene at 298 K and compared with the corresponding theoretical dipole moment values. The solvent effects on the electronic absorption and fluorescence spectra of these thienobenzofurans were quantitatively investigated by means of solvatochromic correlations based on the Kawski-Chamma-Viallet and McRae equations. A weak negative solvatochromic behavior was found for these compounds, showing that their dipole moments are slightly lower in the excited singlet-state than in the ground-state. Kamlet-Abboud-Taft multiparameter relationships were also established for electronic absorption and fluorescence wavenumbers, and fluorescence quantum yields in most solvents, demonstrating the occurrence of specific solute-solvent interactions.     

Effect of Solvent Polarity on Fluorescence Quenching of New Indole Derivatives by CCl4

ABSTRACT

The fluorescence quenching of solutes 3-[5′-methyl-3′-phenylindol-2′-yl]-s-triazolo [3,4-b] [1,3,4] thiadiazol-6(5H)-thione (MPITTT) and 3-phenyl-2,5-bis-[thiosemicarbazido] indole (PbisTI) by carbon tetrachloride (CCl₄) in dioxane and acetonitrile mixtures has been studied at room temperature by steady-state fluorescence measurements. The positive deviation from linearity has been observed in the Stern–Volmer (S-V) plots for both fluorophores in different composition of mixed solvents even at moderate CCl₄ concentration (0.10 mol dm^?3). Various quenching parameters of the quenching processes have been determined using the extended S-V equation and have been found to be dependent on the solvent polarity. Further, with the use of the finite sink approximation model, it is concluded that the bimolecular quenching reactions are diffusion limited, and the distance parameter R′ and mutual diffusion coefficient D are estimated independently.     

Fluorescence and Nonlinear Optical Properties of Organic Dye in Inorganic Glass and Xerogel Matrices

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