Effect of the layer charge on the interaction of porphyrin dyes in layered silicates dispersions

Interaction between tetracationic porphyrin, 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP), and layered silicates in aqueous dispersions was studied using absorption, steady-state and time-resolved fluorescence spectroscopies. The charge density of silicates increases in order synthetic laponite (LAP)<Kunipia F montmorillonite (KF)<synthetic fluorohectorite (FHT). Interpretations of the spectra of layered silicate-porphyrin (LSP) systems considered models of dye adsorption on clay mineral colloid particles, analyzing phenomena occurring in similar systems such as structural changes of TMPyP and the formation of dye molecular assemblies. Structural changes of TMPyP, including flattening of the porphyrin molecule, do not fully explain all the spectral observations. One should mention variations of the Q-bands and fluorescence spectra in dependence on the layer charge. The molecular association of the TMPyP molecules is expected to occur to a certain extent in dependence on the layer charge of a clay mineral template. H-aggregates were not observed in any system. Only FHT colloids induced the formation of at least two components with significantly different spectral properties.     

Effect of surfactants on the aggregation of pyronin B and pyronin Y in aqueous solution

Molecular dynamics of pyronin B (PyB) and pyronin Y (PyY) in aqueous solution containing different surfactants were investigated by using absorption and fluorescence spectroscopy techniques. First, the interactions of PyB and PyY with the negatively charged surfactant sodium dodecyl sulphate (SDS) were investigated in the below and above critical micelle concentration (cmc). The H-aggregate formation of the dye compounds was observed for below the cmc of SDS surfactant. The absorbance of H-aggregate absorption band of PyB and PyY decreased according to the aggregate-monomer equilibrium by increasing SDS surfactant concentration towards the cmc. Therefore, equilibrium constants of the aggregate formation and oscillator strengths of monomer and aggregate of the dye compounds were calculated from spectral studies. Moreover, aggregate formation dynamics was discussed in terms of thermodynamic functions by using temperature studies. The interactions of PyB and PyY with the positively charged hexadecyltrimethylammonium bromide (CTAB) and neutral Triton X-100 (TX-100) were also studied and it was observed that there was no aggregate formation on the absorption and fluorescence spectra for below and above the cmc.     

Self-Aggregation Behavior of meso-Tetra-(4-trimethylaminophenyl)porphyrin Encapsulated in Reverse Micelles

The aggregation behavior of cationic meso-tetra-(4-trimethylaminophenyl)porphyrin (TAPP) was investigated in two reverse micelles (RM) of ionic surfactants, cetyltrimethylammonium bromide (CTAB) and bis(2-ethylhexyl)sulfosuccinate (AOT) using absorption spectroscopy, fluorescence spectroscopy, and resonance light scattering spectroscopy. TAPP showed different types of aggregation upon varying the ratio of water concentration to CTAB concentration, ω₀. The charge on the surfactant used to form reverse micelles determines the aggregation of porphyrin. The addition of hydrochloric acid can transform the H-aggregates of TAPP into monomers, while the addition of sodium hydroxide led to J-aggregation. Ionic strength had no significant influence on the aggregation of TAPP.     

光谱法研究七、八元瓜环对亚甲基蓝的分子识别

利用紫外-可见吸收光谱和荧光光谱法考察了七、八元瓜环(Q[7],Q[8])对客体亚甲基蓝染料(g)的分子识别作用.结果表明,Q[7]与g作用形成物质的量比为2:1的主客体配合物,Q[8]与g作用形成的是物质的量之比为1:2的主客体配合物.吸收光谱法测得的包结常数分别为KQ[7]-g=1.34×1012 L2·mol-2,KQ[8]-g=5.34×1012 L2·mol-2;荧光光谱法测得的KQ[7]-g=1.53×1012 L2·mol-2,KA[8]-g=6.11×1012 L2·mol-2,两种方法结果一致.随着Q[7或8]浓度的增加,瓜环对客体有明显的荧光增敏作用,而Q[8]对客体有明显的荧光猝灭作用.从Q[7]和Q[8]分别与客体作用体系的紫外-可见吸光度和荧光强度随pH值改变的变化规律可以看出,体系在pH在0.5～13范围内均能观察到主客体的相互作用,且作用比例不发生变化.     

CEL溶液中二磺酸基二邻苯二甲酰亚胺甲基酞菁锌的电子吸收和荧光光谱

两亲性金属酞菁配合物二磺酸基二邻苯二甲酰亚胺甲基酞菁锌（ＺｎＰｃＳ２Ｐ２）能有效选择地滞留在组织中,是一种新型的光动力治疗肿瘤的光敏剂。有关酞菁化合物治疗肿瘤的机制目前还不清楚,而对ＣＥＬ溶液中该光敏剂状态的研究对阐明其机制有重要意义,本文对不同浓度ＣＥＬ溶液中的二磺酸基二邻苯二甲酰胺甲基酞菁锌的吸收光谱和荧光光谱进行了研究,探讨了它在溶液中的聚集状态,通过分析确定其聚集态为二聚体,并获得其平衡常数和单体的摩尔吸光系数。     

橄榄油的聚集荧光猝灭及吸收光谱特性的研究

素有“液体黄金”之称的橄榄油已成为健康食用油的代名词,不仅身价陡增,而且在非产地市场也已成为一种畅销油。在橄榄油检测技术中光谱法与其他技术相比具有快速、无损、无样品处理等优势而备受关注,而不同的光谱检测方法在检测的物质成分上各有侧重,例如红外光谱法侧重于脂肪酸含量的检测、拉曼光谱法侧重于分子的检测、荧光光谱法侧重于光敏物质的检测以及吸收光谱法侧重于光敏物质和不饱和脂肪酸的检测等。荧光及吸收光谱对光敏物质反应极其灵敏,而橄榄油富含叶绿素等光敏物质,因此荧光及吸收光谱成为一种鉴别橄榄油的有效技术手段。叶绿素是一种含有环卟啉结构的有机分子,该类分子结构具有吸光特性,且不同的叶绿素吸收光谱各异,其中绿色植物的叶绿素a含量最多。为深入研究叶绿素的吸收光谱及荧光特性在橄榄油鉴别中的应用,将特级初榨橄榄油中掺入不同比例的玉米油,已达到间接调控橄榄油中叶绿素含量的目的,测量不同掺伪比例橄榄油的荧光及吸收光谱并研究与叶绿素浓度的相关性,以此来研究叶绿素浓度与掺伪量对橄榄油吸收光谱及荧光特性的影响。取10份同批次的特级初榨橄榄油,将其中9份按照等比例稀释,并对10份样品按照掺伪量依次排序;依次采集这10份样品的荧光及吸收光谱,比较叶绿素浓度与掺伪量的相关性及对这两种光谱技术在橄榄油鉴别中的影响。随着叶绿素浓度的上升,荧光强度由弱变强,并在某一时刻后会出现荧光强度急剧减弱的现象,即聚集荧光猝灭。这种现象主要是由于叶绿素的环卟啉分子结构引起的分子间π-π作用,使未被激发的低能分子与高能分子堆叠在一起,能量的辐射跃迁（荧光）也转变为分子间的能量转移（热能交换）。对于吸收光谱,随着叶绿素浓度的上升,吸收光谱的强度也逐渐增强。橄榄油中叶绿素吸收的能量主要去向包括镁电子辐射跃迁产生荧光以及分子间热能交换两部分,而橄榄油的吸收光谱并未出现类似于聚集荧光猝灭的现象,且吸收光谱强度与掺伪浓度间存在近似线性相关的关系。结果表明：当聚集荧光猝灭出现时,叶绿素吸收的能量仍然与浓度呈线性相关,此时高、低能分子堆叠引起的热能交换效率提高。     

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。     

羧基修饰纳米SiO2荧光指印试剂的制备与应用

指印是一种重要的证据形式，它百年以来持续成为法庭科学领域的研究重点。在实践中，已经得到广泛推广的粉末法和熏显法对环境和工作人员的身体健康构成了重大威胁。近年来发展的纳米悬浮液显现指印的方法能够有效减少纳米粉尘在空气中的悬浮，降低对使用者健康和环境的侵害，并且规避了悬浮液制备过程中分散剂的使用以及有机染料溶液的处理等瓶颈。因此，关注纳米二氧化硅荧光指印显现试剂的制备与应用：首先，利用反相微乳液法制备了掺杂氯化三（2,2’-联吡啶）钌（Ⅱ）·六水化合物的荧光型纳米二氧化硅颗粒；随后，通过氨基硅烷偶联剂的氨基改性以及与丁二酸酐的氨解反应，使用两步法实现了表面羧基化阴离子修饰的荧光二氧化硅纳米材料的合成；此外，利用红外吸收光谱对纳米二氧化硅，以及目标产物的表面氨基、羧基等化学修饰基团进行表征，并测定了不同修饰产物在水相中的表面电性能以其水合半径；通过紫外可见光吸收光谱和分子荧光光谱仪对材料的荧光性能做了检测，测试了不同染料浓度产物的荧光强度；对新型纳米材料在指印显现中的应用条件进行了系统考察，通过正交试验设计法，全面探究了pH值、母液稀释倍数和显现时间等重要因素对于指印显现效果的综合影响，并最终确定了此种显现试剂的最佳显现条件；论文最后依据上述优化实验条件对捺印在玻璃非渗透性光滑客体表面的指印样品的显现效果进行了系统评价。实验结果表明：产物悬浮液与染料溶液的紫外可见吸收光谱之间并未发生明显的红移或蓝移，这意味着二氧化硅包覆对于荧光染料分子结构没有显著影响；根据染料浓度与产物荧光强度之间的变化关系可知，最佳染料掺杂浓度为15 mmol·L-1；纳米材料的表面氨基化和羧基化修饰已经成功，其最佳激发光源波长为375 nm；Zeta电位-DLS测试结果印证了氨基质子化带正电、羧基电离带负电的纳米材料电学性能，此外羧基化前后纳米二氧化硅颗粒负电荷密度的显著改变也为基于静电吸附作用的指印显现方法灵敏度的提升奠定了基础；使用悬浮液法对前述优化后的合成产物进行指印显现方面的应用，其最佳显现条件为溶液pH值为2.8、母液稀释倍数为2倍且显现时间5 min，其对非渗透性客体表面的新鲜指印及陈旧指印均具有良好的显现效果，部分情况下甚至可以实现三级指印特征的理想显现效果。     

LASER FLUORESCENCE SPECTROSCOPY AS A METHOD FOR STUDYING HUMIC SUBSTANCE

This paper summarizes the results obtained by fluorescence spectroscopic techniques with conventional and laser light sources for the characterization of the spectral luminescent properties of aquatic humic substances (AHS). The band profiles of corrected absorption, fluorescence emission, and fluorescence excitation spectra are compared in graphical form with unique functions used for the axes. In order to calculate the quantum efficiency of fluorescence, we used the Raman signal from water molecules as an internal reference. The temperature dependence of the fluorescence spectra of humic matter has been recorded in solid (?160°C to 0°C) and in liquid (0°C to +300°C) aqueous solutions. The behavior of the fluorescence band shape is discussed. A new method of nonlinear fluorimetry is proposed to enhance the capabilities of fluorescence spectroscopy. This method is based on the fluorescence saturation effect manifesting itself under powerful laser pumping (excitation) conditions. The use of the technique allows one to determine certain photophysical properties of molecules, as a complement to the normal spectral data. Using three different samples of aquatic humic substances with very similar fluorescence band shapes, it is demonstrated that these compounds have distinct molecular luminescent parameters and therefore, can be identified. The similarity of the fluorescence band shapes of humic substances in natural water of different types; the absence of any noticeable effect of temperature across a wide range and the fluorescence saturation on the fluorescence band contour can be explained. This assumes that in all of the samples of aquatic humic substances studied, with different molecular weight fractions, that there is a single dominant fluorescent functionality present.     

荷叶中紫云英苷和DNA相互作用的光谱学研究

在pH 7.4 的Tris-HCl的缓冲溶液中,采用紫外及荧光光谱法研究了荷叶中紫云英苷(AST)与DNA之间的相互作用,探讨了离子强度和阴离子猝灭剂KI对紫云英苷及紫云英苷-DNA体系荧光强度的影响,同时考察了紫云英苷和中性红与DNA结合的竞争性。结果表明DNA通过静态猝灭作用机制猝灭紫云英苷的荧光,并测得其在298及308 K时的猝灭速率常数(K_q)分别为3.120 ×1012和2.630×1012 L·mol-1·s-1,结合常数(K_d)分别为3.412×104和1.762×104 L·mol-1,结合位点数(n)分别为1.007和0.962;DNA的存在使紫云英苷的紫外吸收光谱发生减色效应且吸收波长产生红移;发现离子强度的改变对紫云英苷及紫云英苷-DNA体系的荧光强度影响不大;KI对结合形式存在的紫云英苷的荧光猝灭效率明显小于自由形式存在的紫云英苷的荧光猝灭效率;紫云英苷可插入DNA中置换出与DNA结合的中性红。这些结果说明荷叶中紫云英苷以嵌插模式与DNA进行结合。     

取代基对双酞菁铥LB膜及光谱特性的影响

采用紫外-可见吸收光谱的方法研究了三种稀土夹心双酞菁铥化合物在溶液和LB膜中的聚集性和光谱特性。实验结果表明三种稀土双酞菁化合物在氯仿溶液中形成了H-聚集体,但当浓度比较低时,溶液中表现出单体的吸收。取代基OC₈H₁₇的加入使氯仿溶液中双酞菁铥化合物的聚集性减弱,而且使得吸收峰发生红移,对吸收峰的强度也有较大的影响,造成了Soret吸收带的分裂。另外,取代基OC₈H₁₇对LB膜中双酞菁分子的存在状态有较大的影响,在LB膜中,TmPc₂和TmPcPc*分子以H-聚集体的形式存在,而TmPc*₂分子以T-聚集体的形式存在。形成LB膜后,由于双酞菁分子之间排列紧密,相互作用加强,使得薄膜中分子聚集体的吸收峰相对于溶液中聚集体的吸收峰发生了一定的红移,薄膜中分子排列方向的不同对吸收光谱也有一定的影响。     

A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir-Blodgett films mixed with stearic acid

Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir-Blodgett (LB) films. The surface pressure-area (π-A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air-water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air-water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air-water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).     

Quick detection of contaminants leaching from polypropylene centrifuge tubes with surface‐enhanced Raman spectroscopy and ultraviolet absorption spectroscopy

Anomalous surface‐enhanced Raman scattering (SERS) peaks were identified for liquid sample stored in polypropylene (PP) centrifuge tubes for months. We observed unexpected Raman peaks during experiments with thiamine hydrochloride aqueous solutions stored in PP tubes for 2 months. In order to identify the contaminants, we have performed SERS experiments on deionized (DI) water stored in PP centrifuge tubes for 2 months and compared them with those from fresh DI water sample. We have also carried out ultraviolet (UV) absorption spectra for both fresh and contaminated water. We believe that the water is contaminated because of chemicals leaching from the PP tube. From the gas chromatography‐mass spectrometry data, the main contaminants were found to be phthalic acid (PA) and its derivatives. Further SERS and UV absorption experiment for PA correlated well with the anomalous peaks identified earlier. We qualitatively confirmed the identification and quantitatively estimated the concentration of the suspect contaminants as between 1 and 10 µM with both SERS and UV absorption spectroscopy. With UV absorption spectroscopy, we precisely estimated the concentration as 2.1 µM . We have shown that the sample in PP tube can be contaminated by the leaching chemicals upon long‐term storage, and suggest SERS and UV absorption spectroscopy as two quick and simple techniques to detect the contamination. Copyright © 2011 John Wiley & Sons, Ltd.     

Independence of Maximum Single Molecule Fluorescence Count Rate on the Temporal and Spectral Laser Pulse Width in Two-Photon FCS

We investigate the fluorescence emission characteristics of standard dye tetramethylrhodamine (TMR) in two-photon fluorescence correlation spectroscopy for different temporal and spectral properties of the femtosecond excitation pulses. After determining the second-order dispersion of our setup, including the microscope objective, a pulse stretcher was employed to control the temporal width at the location of the specimen. As expected, the fluorescence per molecule and therefore the signal-to-noise ratio of an FCS-measurement can be improved at constant average excitation power by altering either the temporal or spectral width of the excitation pulses. We found however, that the maximum achievable molecular brightness is largely independent of the temporal and spectral width in the regime analyzed. This observation confirms the current working hypothesis for two-photon fluorescence correlation spectroscopy that bleaching and saturation, and thus, the inherent properties of the dye system, are the dominant effects limiting the quality of measurements. As a practical consequence, elaborate optimization of temporal and spectral laser pulse width, e.g. by introducing pulse stretchers in the beam path, is less critical than previously expected.     

Study of concentration-dependent quantum yield of Rhodamine 6G by gold nanoparticles using thermal-lens technique

Tailoring optical properties of the dye molecules using metal nanoparticles is a burgeoning area of research. In this work, we report our results on the studies of how the absorption and emission behavior of Rhodamine 6G dye is tailored using gold nanoparticles. Furthermore, the influence of dye concentration on these properties for a given concentration of nanoparticles in the dye-nanoparticle mixture is investigated. In addition, the difference between the concentration-dependent fluorescence quantum yield of the dye molecules is measured in the absence and presence of nanoparticles using the dual-beam thermal-lens technique. Our absorption spectral studies show additional spectral features due to nanoparticle aggregation on interaction with cationic Rhodamine 6G dye. Dye concentration-dependent steady-state fluorescence studies in the presence of nanoparticles indicate a blue shift in peak fluorescence emission wavelength. The quantum yield value measured using thermal-lens technique exhibit a non-monotonic behavior with dye concentration with substantial quenching for lower dye concentrations. The results are interpreted in terms of dye–nanoparticle interaction and the formation of dye shell around the nanoparticle.     

两亲性光敏剂Al(OH)PcSP在醇水和水溶液中的分子光谱和存在状态

研究了具有光动力抗癌活性的两亲性光敏剂磺基邻苯二甲酰亚胺甲基酞菁羟基铝 (Al(OH)PcSP)在醇水和在水中的电子吸收光谱 ,并探讨了其聚集状态。研究表明 ,Al(OH)PcSP在醇水溶液中以单体形式存在 ,醇的碳链和羟基数对Al(OH)PcSP的单体吸收光谱没有显著的影响。但在水中 ,Al(OH)PcSP存在单体 二聚体平衡 ,二聚平衡常数为 5 730 7× 10 4 mol·L-1。Al(OH)PcSP在水中所形成的二聚体的Q带特征吸收峰位于 740 5nm ,相对于其单体特征吸收峰 (6 76 5nm)红移 ,而一般金属酞菁在水中所形成的聚集体Q带特征吸收光谱均相对于单体兰移至位于 6 30nm附近。研究了Al(OH)PcSP的荧光光谱 ,结果说明 ,二聚体的荧光很弱。     

Study on the competitive reaction between bovine serum albumin and neomycin with ponceau S as fluorescence probe

A competitive reaction exists between bovine serum albumin (BSA) and neomycin (NM) when ponceau S (PS) is chosen as fluorescent probe. This reaction was studied by fluorescence spectroscopy and UV-vis absorption spectroscopy. The static fluorescence quenching process between BSA and PS was confirmed and the binding constant, the number of binding sites and type of interaction forces between BSA and PS were obtained. It was observed that when NM was added into BSA-PS system, the relative fluorescence intensity of BSA was recovered gradually with increase in concentration of NM, which shows that there existed competitive reaction between BSA and NM. According to competitive reaction mechanism, the equilibrium concentration of PS, the binding constant and the type of interaction forces between PS and NM were obtained.     

牛血清白蛋白与槲皮素在不同溶剂中相互作用特征及抗氧化性的研究

槲皮素与牛血清白蛋白的相互作用机理以及影响因素的研究对于生物活性小分子与生物大分子的相互作用方式及其功能改变具有一定理论和实际意义。运用荧光光谱、紫外可见光谱、同步荧光光谱、自由基清除方法(DPPH和ABTS自由基清除率),研究了牛血清白蛋白与槲皮素在水、二甲基亚砜和乙醇三种不同溶剂中的相互作用方式及其对槲皮素抗氧化性的影响。结果表明：槲皮素对牛血清白蛋白有较强的荧光猝灭作用,且为静态与动态并存的复合猝灭方式,相互作用力为疏水作用力。三种溶剂中,牛血清白蛋白与槲皮素的结合常数和结合位点数由大到小依次为：水＞二甲基亚砜＞乙醇,结合距离由大到小依次为：乙醇＞二甲基亚砜＞水。根据结合距离的大小可知,结合作用由强到弱依次为：水＞二甲基亚砜＞乙醇。在三种溶剂中牛血清白蛋白的酪氨酸和色氨酸残基同时参与与槲皮素的相互作用。未结合及结合牛血清白蛋白的槲皮素与DPPH自由基清除率均为30%,未结合及结合牛血清白蛋白的槲皮素与ABTS自由基清除率相比,由80%显著降低到70%。三种溶剂对未结合及结合牛血清白蛋白的槲皮素的自由基清除能力无显著性影响。     

Photophysics of 1-ethynylpyrene-modified RNA base adenine

The photophysical behaviour of a pyrene-modified adenine base is examined. Time-dependent absorption and fluorescence spectroscopy is used to shed light on the fluorescence behavior and the charge transfer between the fluorophore and the nucleobase. The results from TCSPC, fluorescence upconversion and pump-probe absorption spectroscopy are reported, compared and analyzed. This study is a prerequisite for the detailed characterization of RNA dynamics in real time and on a molecular time scale.     

不同物理形态阿奇霉素的远红外与太赫兹光谱鉴别研究

运用THz-TDS技术和Far-FTIR技术在干燥氮气和真空环境下分别测量了阿奇霉素干混悬剂、胶囊、片剂、分散片等不同物理形态的药品在0.2～5.0 THz波段的光谱。其中,阿奇霉素干混悬剂在0.2～15.0 THz波段内存在较为明显的吸收峰,且对比国产和进口产品的特征峰可以发现,国产药品在几个主峰上都表现出谱线增宽,且有部分多余小峰出现,可能是由于结晶度不纯和杂质引起的。而国产阿奇霉素胶囊、片剂、分散片则由于填充辅料、样品颗粒较大、样品含量少等原因致使吸收基线随频率增高而上扬,上述特征峰在0.2～2.7 THz波段发生不同程度的变弱和频移。同时,对不同浓度进口阿奇酶素干混悬剂与聚乙烯的混合物作了分析,根据浓度与吸收强度呈现的线性正相关关系,可以较为准确地分析出有效成分的浓度,从而实现对阿奇霉素类混合体系药品的质量检测和评估。