核黄素与碘离子相互作用的光谱分析

研究了核黄素与I-相互作用的荧光光谱和吸收光谱变化,得出I-可以使核黄素的荧光发生有规律的猝灭,它们之间的相互作用属于动态猝灭机制。根据Stern-Volmer方程,求出了动态猝灭常数Ksv=44.72L.mol-1,荧光猝灭速率常数Kq=6.4×1010L.mol-1.s-1。I-对核黄素荧光的这种动态猝灭引起了吸收光谱的变化,吸收峰从373nm蓝移到了369nm,而443nm处吸收峰却红移到了447nm;并且核黄素的吸收强度随I-浓度的增大不断增强,是由于I-重原子效应的影响,使核黄素分子的自旋角动量与轨函角动量强烈的相互作用,S0→S1的吸收跃迁概率增大而造成的。     

Solvent Polarity and Excitation Wavelength Dependence of the Dual Fluorescence in N,N-Diethyl-4-Nitrosoaniline

Dual fluorescence in N,N-Diethyl-4-nitrosoaniline (DENA) has been studied employing absorption, excitation and emission spectroscopic techniques and computational methods. The absorption and fluorescence spectra of DENA were measured in solvents of various polarities at room temperature. The emission spectra of DENA were found to exhibit a single emission band in non polar solvent (cyclohexane) and in a highly polar solvent (acetonitrile). In the contrary, two emission bands were observed in medium polar solvents (tetrahydrofuran, 1,2-dichloroethane and dichloromethane) whereby the short (local excited; LE) and long (charge transfer; CT) emission maxima correspond to the emission maxima of the compound observed in cyclohexane and acetonitrile solutions, respectively. Moreover, the two emission bands have shown strong excitation wavelength dependence, and area normalization resulted in an iso-emissive point. The two emission maxima were in addition found to correspond to two excitation maxima in 3D fluorescence spectra. Further, two minima were obtained in potential energy surface calculation of DENA. From the experimental and computational results it was concluded that the dual fluorescence may be attributed to the presence of two different ground state structural conformers of DENA in equilibrium that are stabilized through solute-solvent interaction.     

Special Features of Quenching of Fluorescence in the 1-Naphthol and Coumarin 1 Molecules in Binary Mixtures

The work studies the effect of intermolecular interactions on the relation between the rate constants of radiative processes and internal intercombination conversion in particlular molecule - solvent systems. The 1-naphthol complexes in binary mixtures with hydrogen bonding and those of coumarin 1 with nitrogen-nitrogen bonding are examined. The Stern - Volmer curves for the complexes with additions of nitromethane are shown to deviate from linearity.The interaction of coumarin 1 and 1-naphthol with nitromethane was simulated by the INDO/SP method to show that the lower singlet state is associated with nitromethane. The experimentally observed fluorescence band of the coumarin 1 and 1-naphthol molecules belongs to the third singlet state. The quantum yield of fluorescence from the S₃ state is decreased by an order of magnitude for the complexes under study. The quantum yield from the lower singlet state in the 1-naphthol - nitromethane complex is decreased by an order of magnitude, while in the coumarin 1 - nitromethane complex - by two orders. It is found that there is a possibility of photoprotonation in the S₁ and S₂ states for the 1-naphthol molecule along with the foregoing processes of quenching of fluorescence.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 17–23, January, 2005.     

水溶性量子点荧光探针用于帕珠沙星的含量测定

文章采用荧光光谱和紫外光谱研究了CdTe量子点(CdTe QDs)与广谱抗菌药物帕珠沙星的相互作用。结果表明,随着帕珠沙星浓度的增加,CdTe QDs荧光强度有规律的降低,但通过透射电镜图对QDs及加入帕珠沙星后的QDs进行比较,发现QDs仍然均一单分散,表明反应的作用机理可能是帕珠沙星促使QDs表面键合的有机分子发生变化,在Cd空位表现出的表面缺损上形成了碲氧复合物,致使荧光猝灭。因此该反应可作为一种新颖的快速检测帕珠沙星含量的方法。在一定条件下,帕珠沙星溶液的浓度与量子点荧光强度成线性关系,线性范围为10.0～850 μg·mL-1,相关系数r为0.995 4,检测限(S/N=3)为3.254×10-3 μg·mL-1。药物对量子点的猝灭常数为2.188×104 L·mol-1。应用到冻干粉针剂和氯化钠注射液中帕珠沙星的含量测定,所得结果与标示量一致。该方法较常用检测方法具有简便、快捷、灵敏、线性范围宽的优点,并有望进一步开展发药物体内显像及作用机理的研究。     

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.     

一种可溶喹吖啶酮衍生物LB膜的光谱特性

采用表面压-分子面积(π~A)等温曲线、紫外-可见吸收谱和荧光光谱的方法研究了一种喹吖啶酮衍生物材料LB膜的制备及其光谱特性。实验表明,这种喹吖啶酮衍生物能够在水面上形成稳定的单分子膜,它与花生酸(AA)混合后不仅可以形成很好的单分子膜,而且可以较好的转移到固体基片上制备成LB膜多层膜。这种喹吖啶酮衍生物LB膜的紫外-可见吸收谱的吸收峰位较稀溶液发生了红移,这是由极性溶剂分子与其相互作用的结果。其溶液有很强的荧光效应,但LB膜没有荧光现象,原因是在LB膜中QAC16的浓度过高发生“自我猝息”而失光。它在溶液和LB膜中都是以单体的形式存在。     

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。     

Synthesis,X-ray crystal structure and optical properties research of novel diphenyl sulfone-based bis-pyrazoline derivatives

A series of novel bis-pyrazoline derivatives were synthesized by the reaction of chalcone and (sulfonylbis(3,1-phenylene))bis(hydrazine) in 20–34% yields. The structures of the compounds were determined by IR, ¹H NMR, HRMS spectra, and a representative compound 3b was confirmed based on the X-ray crystallographic analysis. Absorption and fluorescence spectra of these compounds in dichloromethane solution were investigated. The results showed that the emission maxima varied from 415 to 444 nm mainly depending on C3 substituents of pyrazoline moiety. The compounds had higher quantum yields, when C3 substituent was an electron-withdrawing p-chlorophenyl group. Moreover, absorption spectra and emission spectra exhibited a blue-shift and a red-shift with increasing the polarity of solvents, respectively. Fluorescent molecules happened to collide with each other and resulted in quench of the fluorescence when the concentration increased over to 10^?5 M.     

Photophysical Properties of some 1,3,4-Oxadiazole Derivatives Containing Phenolphtalein,Fluorene and Bisphenol A Units

The photophysical properties of the three 1,3,4-oxadiazole derivatives containing fluorene (Ox-FL); fluorene and phenolphtaleine (Ox-FL-FF); or fluorene and bisphenol A (Ox-FL-BPA) moieties in the main chain were investigated by the fluorescence and absorption spectroscopy in different solvents and in the solid state. The electronic absorption spectra included a strong absorption band located in the 270–395 nm region, with a maxima around at 302 nm. The fluorescence excitation spectra were also characterized by one broad band, appearing in the wavelength range of 220–340 nm. All samples displayed the emission bands around 356–373 nm and exhibit high quantum yields ranged from 31.61 to 90.77%, in chloroform solution. The sensitivity of the emission spectra on medium characteristics (polarity, acidity and basicity) were evaluated by using the Catalan solvent scale and the fluorescence titration with a dilute acid solution.     

Spectral Properties of Thioflavin T and Its Complexes with Amyloid Fibrils

Comparative analysis of the absorption and fluorescence spectra and fluorescence excitation spectra of thioflavin T (ThT) in various solvents and in the composition of amyloid fibrils has shown that ThT, when excited in the region of the long-wavelength absorption band, fluoresces in the spectral region with a maximum at 478–484 nm. The appearance in aqueous and alcohol solutions of a fluorescence band with a maximum near 440 nm has been attributed to the presence in the composition of the ThT preparations of an impurity with an absorption band in the 340–350-nm range. The literature data showing that in glycerol ThT has a wide fluorescence spectrum with two maxima are due to the artifact connected with the use of a high concentration of the dye. It has been suggested that the cause of the low quantum yield of ThT aqueous and alcohol solutions is the breakage of the system of conjugated bonds due to the reorientation of the benzothiozole and benzaminic rings of ThT in the excited state with respect to one another. The main factor determining the high quantum yield of fluorescence of ThT incorporated in fibrils is the steric restriction of the rotation of the rings about one another under these conditions. The suggestions made have been verified by the quantum-chemical calculation of the ThT molecule geometry in the ground and excited states.     

Tryptophan Fluorescence Yields and Lifetimes as a Probe of Conformational Changes in Human Glucokinase

Five variants of glucokinase (ATP-D-hexose-6-phosphotransferase, EC 2.7.1.1) including wild type and single Trp mutants with the Trp residue at positions 65, 99, 167 and 257 were prepared. The fluorescence of Trp in all locations studied showed intensity changes when glucose bound, indicating that conformational change occurs globally over the entire protein. While the fluorescence quantum yield changes upon glucose binding, the enzyme’s absorption spectra, emission spectra and fluorescence lifetimes change very little. These results are consistent with the existence of a dark complex for excited state Trp. Addition of glycerol, L-glucose, sucrose, or trehalose increases the binding affinity of glucose to the enzyme and increases fluorescence intensity. The effect of these osmolytes is thought to shift the protein conformation to a condensed, high affinity form. Based upon these results, we consider the nature of quenching of the Trp excited state. Amide groups are known to quench indole fluorescence and amides of the polypeptide chain make interact with excited state Trp in the relatively unstructured, glucose-free enzyme. Also, removal of water around the aromatic ring by addition of glucose substrate or osmolyte may reduce the quenching.     

水溶性酞菁类光敏剂的合成及其光谱性质研究

以3-硝基邻苯二甲腈与3-巯基-1-丙磺酸钠为原料,在醋酸盐存在下通过四环化合成了三种带四个3-磺基丙基磺酰基的水溶性酞菁。利用紫外-可见吸收光谱,荧光光谱等对其光谱性质进行了测量,并计算了其荧光量子产率和单线态氧量子产率。引入吸电子基团所合成的水溶性酞菁与ZnPc相比,其荧光发射光谱的形状并未改变,但其最大荧光发射波长均发生10 nm以上的红移。三种水溶性酞菁中锌酞菁的荧光量子产率最高,铜酞菁的荧光量子产率最低;它们在水溶液中的荧光呈双指数衰减,这可归结为激发态质子化或去质子化的结果。单线态氧量子产率锌酞菁最大,空心酞菁次之,铜酞菁最小。光谱分析结果表明,合成的锌酞菁和空心酞菁具有高的单线态氧量子产率和高的光稳定性,有望用作光动力治疗和光免疫治疗的光敏剂。     

Green and Cost Effective Synthesis of Fluorescent Carbon Quantum Dots for Dopamine Detection

Carbon quantum dots (CQDs) due to its high fluorescent output is evolving as novel sensing material and is considered as future building blocks for nano sensing devices. Hence, in this investigation we report microwave assisted preparation and multi sensing application of CQDs. The microwave derived CQDs are characterized by Dynamic Light Scattering (DLS) experiment and Fourier Infrared spectra (FTIR) to investigate the size distribution and chemical purity respectively. Fluorescent emission spectra recorded at varying pH shows varying fluorescence emission intensities. Further, emission spectra recorded at different temperatures shows that fluorescence emission of CQDs greatly depends on temperature. Therefore, we demonstrate the pH and temperature sensing characteristics of CQDs by fluorescence quenching behaviour. In addition, the interaction and sensing behaviour of CQDs for dopamine is also presented in this work with a detection limit of 0.2 mM. The steady state and time-resolved methods have been employed in fluorescence quenching methods for sensing dopamine through CQDs at room temperature. The bimolecular quenching rate constants for different concentration have been measured. The interaction between CQDs and dopamine indicates fluorescence quenching method is an elegant process for detecting dopamine through CQDs.     

Spectroscopic Characterization of the Interaction of Phenosafranin and Safranin O with Double Stranded, Heat Denatured and Single Stranded Calf Thymus DNA

Interaction of phenosafranin and safranin O with double stranded, heat denatured and single stranded calf thymus DNA has been studied by fluorescence, absorbance and circular dichroic techniques. Binding to the double stranded and heat denatured DNA conformations induced strong quenching in the fluorescence spectra of both dyes. Linear Scatchard plots indicated the binding to be of one type and the affinity evaluated to be of the order of 10(5) M(-1) with double stranded and heat denatured DNAs. Fluorescence quenching was much weaker with the single stranded DNA and the binding affinity was one order lower. Ferrocyanide quenching studies revealed that the fluorescence emission of the dye molecules bound to the double stranded and heat denatured DNAs was quenched much less compared to that bound to the single stranded DNA. Further, there was significant emission polarization for the bound dyes and strong energy transfer from the DNA base pairs to the dye molecules indicating intercalative binding. Salt dependence of the binding phenomenon revealed that electrostatic forces have significant role in the binding process. The intercalation of these molecules to double stranded and heat denatured DNA and simple stacking to single strands was proved by these fluorescence techniques. Support to the fluorescence results have been derived from absorption and circular dichroic results. Phenosafranin was revealed to be a stronger binding species compared to safranin O.     

Laser study of the photophysical properties of UF6

The purpose of this paper is to review the most relevant theoretical and experimental results reported in recent years, on the photophysical properties of the uranium hexafluoride molecule in the gas phase. Details of the structure of the molecular orbitals of UF₆ are discussed with reference to theoretical calculations of the electronic states. Tentative assignments of the electronic transitions in the experimental visible-uv absorption spectrum are also considered. The fluorescence properties of the excited states of UF₆ are critically reviewed. The use of laser beams to excite the fluorescence emission of UF₆ is shown to be a fruitful experimental technique. The measurement of fluorescence parameters (i.e. the emission and excitation spectra, the decay time and quantum yield) is a particularly valuable and sensitive way of studying the dynamics and structure of the excited electronic states. The different mechanisms of fluorescence quenching that have been proposed are also critically reviewed.     

Laser study of the photophysical properties of UF6

The purpose of this paper is to review the most relevant theoretical and experimental results reported in recent years, on the photophysical properties of the uranium hexafluoride molecule in the gas phase. Details of the structure of the molecular orbitals of UF₆ are discussed with reference to theoretical calculations of the electronic states. Tentative assignments of the electronic transitions in the experimental visible-uv absorption spectrum are also considered. The fluorescence properties of the excited states of UF₆ are critically reviewed. The use of laser beams to excite the fluorescence emission of UF₆ is shown to be a fruitful experimental technique. The measurement of fluorescence parameters (i.e. the emission and excitation spectra, the decay time and quantum yield) is a particularly valuable and sensitive way of studying the dynamics and structure of the excited electronic states. The different mechanisms of fluorescence quenching that have been proposed are also critically reviewed.     

Fluorescence properties of biochemicals in dry NaCl composite aerosol particles and in solutions

Several fluorophores, such as tryptophan, NADH, NADPH, and riboflavin are found in airborne micro-organisms. In this work, the fluorescence properties of these biochemicals were studied both in dry NaCl composite aerosol particles and in saline solutions by means of laser-induced fluorescence. Fluorescence spectra were measured from individual, airborne aerosol particles and from solutions in cuvette. The excitation wavelength was varied in steps from 210 nm to 419 nm and the fluorescence was detected within a wavelength band of 310–670 nm. For each sample, the measured fluorescence emission spectra were combined into fluorescence maps. The fluorescence maximum of riboflavin in a dry NaCl composite particle is 20 nm red-shifted compared with the solution, whereas the maxima are blue-shifted by about 25 nm for tryptophan and 15 nm for NADH and NADPH. The molecular fluorescence cross sections have significant differences between the aerosol particles and the solutions, except for tryptophan. For NADH and NADPH the cross sections are over 20 times larger in the aerosol particles than in the solutions probably as a result of partial quenching of fluorescence in solution caused by the collision or stacking with the adenine moiety. The fluorescence cross section of riboflavin is almost 60 times larger in the solution than in the dry NaCl composite aerosol. This is probably caused by the different microenvironment around the fluorophore molecule and by the concentration quenching in the particles where the fluorescing molecules are relatively close to each other.     

柿子叶制备碳量子点的光谱性质及对Fe3+的荧光探针

碳量子点作为碳纳米材料中的新成员,具有较高的光学稳定性、低毒性、良好水溶性、原料来源广泛、制备方法多样等多种优点,在分析检测、生物标记、光催化降解以及环境监测等领域具有广泛的应用前景, 对碳量子点的研究引起了国内外学者极大兴趣。水中Fe3+含量的超标会对生活饮用和工业生产造成一定的危害,所以准确快速地检测水中Fe3+的含量,对人体健康具有重要的意义。目前,对Fe3+进行检测的方法有伏安法、荧光光谱法、电化学法以及火焰原子吸收光谱法等,其中荧光光谱法具有快速响应和方法简便的特点,比其他方法更有优势。以柿子叶为碳源,采用水热法制备了发蓝绿色荧光的碳量子点,通过X射线衍射、高分辨透射电子显微镜、傅里叶变换红外光谱、紫外-可见吸收光谱及荧光光谱等技术对碳量子点的结构、微观形态和光谱学性质进行了详细表征。柿子叶制备的碳量子点呈现为分散均匀的球形颗粒,颗粒平均直径大约5.9 nm,碳量子点颗粒表面具有丰富的含氧官能团,在277 nm有明显的紫外吸收,可归因于C═O的n→π*跃迁。碳量子点的发射波长和荧光强度具有明显的激发依赖性,在410 nm光激发下,发射波长峰值为498 nm且荧光峰最强,荧光寿命为4.59 ns。采用多种金属离子对柿子叶制备的碳量子点在荧光传感方面进行了探究,分析发现该碳量子点对金属Fe3+具有极高的选择性,可作为荧光探针检测水中微量的Fe3+含量,其荧光猝灭率F₀/F与金属Fe3+浓度在1~120 μmol·L-1范围内呈现良好的线性关系（R2 = 0.992）,猝灭常数和最低检出限分别为8.84×103 L·mol-1和0.21 μmol·L-1,最低检出限数值明显小于最近一些文献的报导结果。该工作提供了一种原料天然、操作简单、成本低廉的制备工艺,开发了荧光检测水中微量金属铁离子的新方法。     

Luminescent ‘On-Off’ CdSe/ZnS Quantum Dot Chemodosimeter for Hydroxide Based on Photoinduced Electron Transfer from a Carboxylate Moiety

A CdSe-ZnS quantum dot (QD) has been surface functionalised by a place exchange reaction with p-mercaptomethyl benzoate synthesized by a three-step procedure. The resulting lumophore-spacer-receptor QD-conjugate was characterized by IR, UV-visible and fluorescence spectroscopy. The emission profile of the QD reveals a narrow emission peak centred at 542 nm. Addition of hydroxide to the solution containing the QD-conjugate results in quenching of the original fluorescence, which is attributed to a photoinduced electron transfer reaction from the electron-rich benzoate moiety to the QD valence band. This is the first reported example of fluorescent quenching of a CdSe-ZnS QD luminescence by an aryl carboxylate moiety.     

Quenching of fluorescence of porphyrin molecules in their association in binary solutions

It has been established that the absorption and fluorescence spectra of octaethylporphin (OEP), mesotetraphenylporphin (TPhP), and its complex with zinc (Zn-TPhP) in glycerol doped with dimethylformamide (DMF) or ethanol differ from the analogous spectra of these compounds in ethanol or DMF, which is due to the formation of associates of porphyrin molecules in solutions of OEP, TPhP, and An-TPhP with glycerol. For TPhP and Zn-TPhP, these differences are small, the maxima of the bands are shifted toward longer wavelengths by 3–5 nm, and their halfwidths are increased by ∼ 16%; for OEP these changes are more significant. It is shown that the duration of fluorescence of associates is much shorter than that of monomers. The probable mechanisms of quenching of the fluorescence of dimers (oligomers) of molecules were considered. It has been suggested that one of the reasons for the increased rates of deactivation of the excited states of dimers (oligomers) may be the decreased energy interval between the excited and ground states of associates as compared with that of monomers. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 21–25, January–February, 2000.