Polymer microenvironmental effects on the photophysics of cinchonine dication

Photophysical properties of cinchonine dication (C⁺⁺) have been studied in protic and aprotic polymers by monitoring steady state and time resolved measurements. It is found to be sensitive towards the microenvironment of polymers. Edge excitation red shifted emission (EERS) is observed in all polymeric matrices. However, the magnitude of EERS is relatively high in protic as compared to aprotic polymer. Isobestic point in excitation spectra and three decay components in time resolved measurements indicate more than two trapped chemical species in the heterogeneous environment of the polymer. Solute-polymer interactions are found to produce the third decay channel, unlike in solution phase and may be useful to understand the polymer microenvironment.     

Structural Transition in the Micellar Assembly: A Fluorescence Study

Structural transition can be induced in charged micelles by increasing the ionic strength of the medium. Thus, spherical micelles of sodium dodecyl sulfate (SDS) that exist in water at concentrations higher than the critical micelle concentration assume an elongated rod-like structure in the presence of an increased electrolyte concentration. This is known as sphere-to-rod transition. In this paper, we characterize the change in organization and dynamics that is accompanied by the salt-induced sphere-to-rod transition in SDS micelles using wavelength-selective fluorescence and other steady-state and time-resolved fluorescence parameters. Since the change in micelle organization during such structural transition may not be limited to one region of the micelle, we have selectively introduced fluorophores in two distinct regions of the micelle. We used two probes, N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (NBD-PE) and 25-[N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-methyl]amino]-27-norcholesterol (NBD-cholesterol), for monitoring the two regions of the micelle. NBD-PE monitors the interfacial region of the micellar assembly, while NBD-cholesterol acts as a reporter for the deeper regions of the micellar interior. Our results show that wavelength-selective fluorescence, in combination with other fluorescence parameters, offers a powerful way to monitor structural transitions induced in charged micelles. These results could be significant to changes in membrane morphology observed under certain physiological conditions.     

Modulation of Fluorophore Environment in Host Membranes of Varying Charge

The net electrical charge of the biological membrane represents an important parameter in the organization, dynamics and function of the membrane. In this paper, we have characterized the change in the microenvironment experienced by a membrane-bound fluorescent probe when the charge of the phospholipids constituting the host membrane is changed from zwitterionic to cationic with minimal change in the chemical structure of the host lipid. In particular, we have explored the difference in the microenvironment experienced by the fluorescent probe 2-(9-anthroyloxy)stearic acid (2-AS) in model membranes of zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cationic 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (EPOPC) which are otherwise chemically similar, using the wavelength-selective fluorescence approach and other fluorescence parameters. Our results show that the microenvironment experienced by a membrane probe such as 2-AS is different in POPC and EPOPC membranes, as reported by red edge excitation shift (REES) and other fluorescence parameters. The difference in environment encountered by the probe in the two cases could possibly be due to variation in hydration in the two membranes owing to different charges.     

人工湿地中水溶性有机物三维荧光光谱特性的分析

采用三维荧光技术,结合荧光区域一体化积分的分析方法,研究了一个表面流+垂直流复合人工湿地处理两条污染河流废水中水溶性有机物的荧光特征变化,结果表明:(1)该人工湿地中水溶性有机物腐殖质的主要来源为生物代谢输入而非陆源输入;(2)在表面流人工湿地的后段,部分类蛋白类物质转化为类富里酸类物质,表明经过表面流人工湿地处理之后,水溶性有机物的组成成分发生显著变化,并且有机物结构趋于稳定。而垂直流人工湿地对类腐殖酸物质峰具有明显的削弱作用;(3)表面流人工湿地对水溶性有机物的结构转化意义重大,可以显著提高水溶性有机物的稳定性。表面流+垂直流的复合人工湿地工艺对水溶性有机物具有良好的去除效果。     

拉曼激发激光诱导电子荧光流场测量系统中标记过程的研究

研制了一套拉曼激光发激光诱导电子荧光空气流场测速系统,利用Nd:YAG激光器的二次谐波及其抽运的氧气受激拉曼散射作为标记光源,以ArF准分子激光作为荧光再现光源,并用像增强CCD摄像机（ICCD）记录荧光图像,成功地获得了纯氧及空气中的标记线的荧光图像,并进行了氧气喷流速度测量的初步研究。     

二(2-苯基-8-羟基喹啉)锌和喹啉锌的合成和荧光性质

合成了一种新型二(2-苯基-8-羟基喹啉)锌配合物。利用元素分析、红外吸收光谱等方法表征了结构,并对比研究了二(2-苯基-8-羟基喹啉)锌和喹啉锌的荧光性质,前者的激发光谱在465nm处出现了较强的吸收,并且发射峰位置发生了明显的红移,由喹啉锌的495nm移至2-苯基-8-羟基喹啉锌和喹啉锌的521nm处。对有关的吸收峰的归属进行了讨论,初步认为苯环的取代增加了有机配体π-π键的共轭程度,使HOMO-LUMO之间能隙变小,引起发射峰红移。     

污泥内层和外层胞外聚合物的三维荧光光谱特性研究

运用三维荧光光谱技术对污泥LB-EPS和TB-EPS的荧光特性进行了研究.实验结果表明,在污泥LB-EPS和TB-EPS中都有三个明显的荧光峰,分别为Peak B(λex/λem=270～280 nm/345～360 nm),Peak C(λex/λem=330～340 nm/410～430 am)和Peak D(λex/λem=390 nm/450～470 nm).其中Peak B为类蛋白荧光(Protein-like)、Peak C为可见区类富里酸荧光(Visible fulvic-like)、Peak D为类腐殖酸荧光(Humic-like).从各荧光峰的荧光强度来分析,LB-EPS和TB-EPS中的主要成分都为类蛋白,然后依次为富里酸和腐殖酸.浓度和pH值对污泥LB-EPS和TB-EPS的三维荧光特性都有很大的影响,但影响程度略有区别,表明作为外层的胞外聚合物,LB-EPS表现出与TB-EPS不全相同的化学结构.     

Fluorescence Characterization of the Hydrophobic Pocket of Cyclophilin B

Human cyclophilin B is a monomeric protein that contains two tryptophan residues, Trp104 and 128. Trp128-residue belongs to the binding site of cyclosporin A and is the homologous of Trp 121 in CyPA, while Trp104 residue belongs to the hydrophobic pocket. In the present work, we studied the dynamics of Trp residue(s) of cyclophilin B and of the CyPB_w128A mutant and of TNS-mutant complex. Our results showed that Trp-104 and TNS show restricted motions within their environments and that energy transfer between the two fluorophores is occurring.     

Spectroscopic studies on the interaction and sonodynamic damage of neutral red (NR) to bovine serum albumin (BSA)

In this paper, the interaction of neutral red (NR) with bovine serum albumin (BSA) and the sonodynamic damage to BSA under ultrasonic irradiation was studied by means of ultraviolet-visible (UV-vis) and fluorescence spectra. The quenching constant (K_SV=5.749×10⁴ L/mol), binding constant (K_A=3.19×10⁴ L/mol) and binding site number (n=0.9462) were measured. The binding distance (r=2.47 nm) between NR and BSA was obtained according to Föster’s non-radiative energy transfer theory. The damage process of BSA molecules was detected by the hyperchromic effect of UV-vis spectra and quenching of intrinsic fluorescence spectra. In addition, the influencing factors such as ultrasonic irradiation time and NR concentration on the damage to BSA molecules were also considered. The results showed that the damage degree is enhanced with the increase of ultrasonic irradiation time and NR concentration. The possible mechanism of sonodynamic damage to BSA molecules was mainly mediated by singlet oxygen (¹O₂). Otherwise, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. The results indicated that the NR is more vicinal to tryptophan (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residues. The research result will bring a certain significance to use sonosensitive drugs in the fields of tumor treatment.     

Solid-state NMR studies of some tin(II) compounds

High-resolution NMR spectra of [Formula: see text] nuclei, particularly (119)Sn and (31)P, in solid tin(II) phosphite, SnHPO(3), and tin(II) phosphate, SnHPO(4), are presented. The results are discussed in relation to the crystal structures. Spinning sideband analysis has been carried out for both nuclei, giving information on the shielding tensors. Satellite peaks allow the indirect Sn,Sn coupling constants to be determined. Surprisingly large values of 2600+/-200Hz and 4150+/-200Hz are reported for SnHPO(3) and SnHPO(4) respectively. The satellite peaks were investigated by using a single Hahn echo for each refocusing time, which showed that the observed splittings result from (119)Sn, (117)Sn coupling. For SnHPO(3), the calculated relative intensities of the satellites for six intra-layer coupling interactions are in agreement with the experiment values, but for SnHPO(4) the coupling appears to be inter-layer in nature. Tin-119 (and in one case phosphorus-31) shielding tensor data derived from MAS NMR are also reported for four other crystalline tin(II) compounds, namely tin diphosphate, tin oxalate, tin sulphate and calcium tin ethylenediamine tetraacetate.     

胶束中的若丹明6G荧光增强和激光行为

使用阴离子表面活性剂十二烷基硫酸钠 (SDS)有效的增强了若丹明 6G染料水溶液的荧光 ,在若丹明 6G浓度分别为 5 47× 10 -7和 5 47× 10 -4 mol·L-1时 ,最大增强比率分别为 1 95和 9 7。在后一浓度下SDS的加入使若丹明 6G染料激光阈值降低 ,能量转化效率提高。不加SDS时的激光阈值功率密度约为 6 5MW·cm-2 ,加入 4 1× 10 -2 mol·L-1的SDS后 ,激光阈值功率密度降为 0 8MW·cm-2 。泵浦光功率密度为 6 5MW·cm-2 时 ,能量转化效率达到 2 5 %。同时还观察到SDS的加入使溶液吸收谱、荧光谱和染料激光发生了红移。对以上现象的物理机制进行了讨论。     

Fluorescence anisotropy of cyanobacterial phycobilisomes oriented in polyvinyl alcohol (PVA) films

Polarized absorption (at 296 and 85 K), fluorescence, and photoacoustic (at 296 and 85 K) spectra of antenna complexes—phycobilisomes isolated from cyanobacteriaTolypothrix tenuis andOscillatoria and embedded in isotropic and anisotropic polyvinyl alcohol films—were measured. From the sets of polarized components of emission, the anisotropy of fluorescence for the pools of differently oriented molecules was calculated. On the basis of polarized photoacoustic and emission spectra, the competition between the process of thermal deactivation of excitation and excitation energy transfer in a chain of excitation donor and acceptor chromophores of phycobilisomes is discussed.     

室温下吡啶溶液中的富勒稀荧光研究(英文)

室温下,在C6 0 -吡啶溶液中观察到了3 99nm到75 0nm范围内C6 0 丰富的荧光峰。C6 0 和吡啶之间的相互作用,破坏了C6 0 分子的高度对称性,从而放松了选择定则,使得荧光辐射率增强。这种相互作用也被C6 0 -吡啶溶液中C6 0 的电化学还原和表面增强拉曼散射证实。     

Minimization of the pulse's timing jitter in a dispersion-compensated WDM system

We address the problem of the collision-induced crosstalk between pulses in a dispersion-compensated WDM system composed of a periodic array of cells that include two or three fiber segments. Both the cross- and self-phase-modulation nonlinearities are taken into account. A semi-analytical approximation and direct simulations are used to calculate the frequency shift (FS) of colliding pulses, and to search for conditions which provide for minima of the FS and the temporal shift (TS), including the most promising possibility of minimizing both shifts simultaneously. Semi-analytical results, obtained by means of the perturbation theory, are in qualitative agreement with the numerical findings, especially in regimes near the optimum. In searching for the FS and TS minima, we investigate the effect of changing the initial width and chirp of the pulse, position of the amplifier within the dispersion–compensation period, group-velocity difference between the channels, allocation of the group-velocity-dispersion (GVD) inside the cell, and the average GVD. We conclude that a more sophisticated dispersion–compensation map, with three different local values of GVD, may be significantly more efficient than the one based on two different segments. A global FS minimum, with respect to the variation of all the parameters, is found.     

Effect of Host Medium on the Fluorescence Emission Intensity of Rhodamine B in Liquid and Solid Phase

In this work, we study the effect of concentration, host medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a host medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 × 10⁻² M and 5 × 10⁻⁶ M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 × 10⁻⁴ M. Comparison studies were investigated for different host medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about ≈0.82.     

海草生态系中DOM的三维荧光光谱特征

利用荧光激发-发射矩阵光谱(EEMs)技术研究了海南省陵水县新村湾海草生态系中溶解有机物(DOM)的三维荧光光谱特征。EEMs谱图表明, 海草生态系中的DOM存在3个类腐殖质荧光A(230/430 nm), C(350/440 nm), M(300/380～400 nm)和2个类蛋白质荧光R(230/355～375 nm), N(280～300/365～380 nm)。各荧光信号平均荧光强度的变化规律为R(0.304 RU)>A(0.194 RU)>M(0.147 RU)>N(0.125 RU)>C(0.051 RU)。类腐殖质荧光和类蛋白质荧光均表现为离岸近含量高;2个明显的低值区, 分别出现在该湾海草茂密的西南部和东南部。各荧光信号在该湾的分布特征表明, 控制类腐殖质荧光和类蛋白质荧光的动力学因素相同。荧光N与M和R之间以及荧光C与A之间具有较好的正相关关系, 表明这些荧光具有相同的来源属性及地化行为。较高的荧光指数FI(均值为1.81)、较高的自生源指标BIX(均值为1.44)和较低的腐殖化指标HIX(HIXa和HIXb的均值分别为4.2和0.81)均表明海草生态系中DOM的强自生来源贡献和弱腐殖化程度。研究结果表明, 海草生态系中DOM具有非常独特的荧光特征, 不同于其他水生生态系。     

Fluorescence spectroscopy of polynuclear aromatic compounds in environmental monitoring

The occurrence of polynuclear aromatic compounds (PAC) in the environment and experimental techniques suitable for the detection of PAC in environmental compartments are briefly reviewed. The specific requirements for on-site andin situ environmental analysis are outlined. Particular emphasis is given to fluorescence spectroscopic techniques for the investigation of humic acid- and soil-containing samples. Some examples of studies in the literature on Shpol'skii and jet spectroscopy and on laser-induced fluorescence (OF) measurements of PAC and mineral oils are highlighted. Contaminants in the environment are usually encountered as multicomponent mixtures in very complex matrices. Total fluorescence analysis in combination with the chemometrical technique of rank annihilation factor analysis (RAFA) was employed for the evaluation of a six-component PAC mixture in toluene. It was shown that even in the presence of strong spectral overlap the qualitative identification of all compounds and the reliable quantification of five substances was possible. Results are presented from our stationary and time-resolved fluorescence investigations of the interactions between pyrene and humic acid in water. The Stern-Volmer analysis showed a significant effect of pH on the static quenching efficiency which can be explained by the pH-dependent macromolecular structure of humic acids. Preliminary results from studies of the deactivation of triplet PAC and quenching of delayed fluorescence by humic acid are reported. LIF measurements of mineral oils directly from soil surfaces and of a model oil in a soil column were performed with a fiber-optic coupled multichannel spectrometer. The fluorescence intensity/ concentration relationships were established for a crude and a fuel oil; the corresponding lower limits of detection (LOD) were determined to be 0.025 and 0.125% m/m (mass/mass percentages). These detection limits are compared with realistic oil contaminations of soils. In a soil column designed to mimic fixed-bed bioreactors the distributions of fluorescence signal intensities from a perylene-doped model oil before and after water flooding were determined. These results fromin situ measurements can provide a quantitative basis for the modelling of temporal and spatial contaminants' distributions in reactor design.     

Silane-modified polymers as interphases in glass-fibre-reinforced composites: 1. Synthesis and characterisation of alkoxy-silane functionalized polymers

This paper presents techniques for the functionalization of polymer materials with alkoxy-silane groups. Alkoxy-silane groups are key intermediates in bonding organic materials onto glass-fibre surfaces. Two reaction routes are described: (1) Chain copolymerization of butyl acrylate (BuA) and γ-methacryloxypropyltrimethoxy-silane (MPS) and (2) grafting of MPS onto polyethylene (PE) and poly(styrene-block-ethylene-co-1-butene-block-styrene) (SEBS). It is concluded that chain copolymerization is the superior route since it gives almost unlimited possibilities of adjusting the degree of alkoxy-silane functionality. The paper also demonstrates the advantage of performing graft copolymerization in the melt instead of in solution. Solution grafting is of low efficiency and is probably directed to chains having reactive sites, e.g. branch points. It is proposed that the primary cause is the lower temperatures used in solution grafting in comparison to the melt reaction.     

Yielding of glassy polymers in the second quadrant of principal stress space

Second quadrant crazing and shear yielding studies were performed on glassy poly(methyl methacrylate) by means of combined torsion-tension loading. The results are in quantitative agreement with the shear and normal stress yielding criteria proposed by Sternstein and Ongchin. It is shown that four distinct regions of material response exist in the second quadrant and, depending on the stress state, 1) no crazing and no shear yielding, 2) crazing alone, 3) shear yielding alone, or 4) crazing and shear yielding can occur. An analysis of stress field induced brittle-ductile transitions is presented which is in agreement with other studies of high-pressure yielding.     

一种校正XRF光谱基体吸收效应的新方法

根据校正XRF光谱基体吸收效应的基本理论,提出了一种用基本参数法校正基体吸收效应的新方法,该法既不需要标准,又对样品和衬底靶无特别要求,仅用一些基本的物理参数(ω,J,τ)和荧光强度的测量值便可算得样品中待分析元素的含量,方便简单。用岩石标准SY-2,SY-3和MRG-1检验该法,其结果与文献报道的值相符。