Aromatic compounds in molecular phase of Baltic amber-synchronous luminescence analysis

Synchronous luminescence analysis was performed in order to identify aromatic compounds in solvent extracts of Baltic amber. The investigated extracts were obtained, for comparisons, as products of extraction by various techniques and solvents. Methylene chloride and ethanol were applied independently for extraction at the ambient temperature (conservative extraction), as well as at the temperature of solvent boiling (extraction in Soxhlet apparatus). Ethanol, as the solvent, was also used for extraction in an ultrasonic bath and for the decoction process. The extraction, by techniques mentioned, of the analysed amber has resulted in products generally containing the same groups of aromatics: mainly naphthalenes, phenanthrenes and anthracenes. Among phenanthrenes, in all samples the retene was also identified, being one of the characteristic links of the diagenetic chain of chemical transformations of vegetal precursors. The identification of a series of individual compounds made, using the synchronous luminescence technique, was verified by the record of conventional emission and excitation spectra. Presented identified compounds were also confirmed by the results of GC-MS analysis. The luminescence analysis was also performed comparatively for fossil resin from Galicia, Spain (Cretaceous) older than Baltic amber (Tertiary, Eocene). The obtained preliminary results of synchronous luminescence analysis suggest the possibility of diversification in this manner of fossil resins of various ages by characterisation of aromatisation degree and alkyl substitution of aromatic rings. It is since well known that aromatisation progress is an indicator of a natural process of maturation of fossil organic matter. However, a greater number of samples should be taken to further testify to the investigations.     

Synchronous fluorimetric determination of salicylic acid and diflunisal in human serum using partial least-squares calibration

The simultaneous determination of salicylic acid and diflunisal in human serum has been accomplished by synchronous fluorimetry, in combination with partial least-squares multivariate calibration. The total luminescence information of the analytes has been used to optimize the spectral data set for the calibration, by analysis of the three-dimensional excitation-emission matrices. The synchronous spectrum, maintaining a constant difference of Deltalambda = 128 nm between the emission and excitation wavelengths, has been selected as optimum to perform the determination. The method is based on the fluorescence of these compounds in chloroform containing 1% (v/v) acetic acid. Serum samples are treated with trichloroacetic acid to remove the proteins, and both analytes are extracted into chloroform-1% (v/v) acetic acid prior to the determination. For concentrations ranging from 60-240 mug ml(-1) of each drug, analytical recoveries range from 96% to 103% for salicylic acid and from 97% to 105% for diflunisal.     

Classification of edible and lampante virgin olive oil based on synchronous fluorescence and total luminescence spectroscopy

Total luminescence and synchronous fluorescence spectroscopies were tested as regards their ability to differentiate edible from lampante virgin olive oils. Total luminescence spectra were recorded by measuring the emission spectra in the range 350-720 nm at excitation wavelengths from 320 to 535 nm. The synchronous fluorescence spectra of 41 edible and 32 lampante virgin olive oils were acquired by synchronous scanning the excitation and emission monochromator maintained at an offset value of 80 nm. Classification of virgin olive oils based on their synchronous fluorescence spectra was performed by hierarchical cluster analysis and principal component analysis using the spectral range of 429-545 nm. Principal component analysis provided better discrimination between the two classes, without any classification error, while hierarchical cluster analysis allowed 97.3% correct classification. These results indicate the capability of fluorescence techniques to differentiate virgin olive oils according to their quality.     

Identification of polycyclic aromatic hydrocarbons (PAHs) in suspended particulate matter by synchronous fluorescence spectroscopic technique

The synchronous fluorescence (SF) technique has been used in the identification of polycyclic aromatic hydrocarbons (PAHs) from air particulate sample in an urban environment of Delhi, Jawaharlal Nehru University. Suspended particulate matter samples of 24h duration were collected on glass fiber filter papers. PAHs were extracted from the filter papers using dichloromethane (DCM)+hexane with ultrasonication method. Qualitative measurements of the polycyclic aromatic hydrocarbons (PAHs) were carried out using the SF technique at various wavelength intervals (Deltalambda). Due to the difference in chemical structure, each PAH gives specific characteristic spectrum for each Deltalambda. Following PAHs were detected in our measurement: benz(a)anthracene (BaA), pyrene (Pyr), chrysene (Chry), fluoranthene (Flan), phenanthrene (Phen), and benz(ghi)perylene (BghiP). This is in agreement with our earlier work for determination of these PAHs using gas chromatography (GC). The seasonal variation of the PAHs was found to be maximum in winter and minimum during the monsoon.     

Analysis of binary mixtures of flufenamic, meclofenamic and mefenamic acids by derivative synchronous fluorescence spectrometry

Second-derivative synchronous fluorescence spectrometry was used to develop a simple, rapid and sensitive spectrofluorimetric method for the determination of binary mixtures of the nonsteroidal antiinflammatory drugs flufenamic (FFA), meclofenamic (MCFA) and mefenamic (MFA) acids in serum and pharmaceutical formulations. The method is based on the intrinsic fluorescence of these compounds in chloroform. A Deltalambda=105 nm was used for the resolution of FFA-MFA and MFA-MCFA mixtures, whereas the FFA-MCFA mixture was determined at Deltalambda=40 nm. Serum samples are treated with trichloroacetic acid to remove the proteins, and the analytes are extracted in chloroform prior to determination. Pharmaceutical preparations were analysed without prior separation steps.     

固定能量同步发光光谱测定法

本文介绍一种分子发光分析新技术——固定能量同步发光光谱测定法(CESLS)。该法系在激发波长和发射波长的同时扫描过程中保,持两者间有一个固定的能量差。它具有比经典发光分析法和固定波长同步发光光谱测定法更为优越的特点,是一种有潜力的多组分分析方法。尤其在PAHs分析中,可望获得广泛应用。本文还讨论了CESLS参数选择的理论优化问题。     

Application of radiochemical neutron activation and flame atomic absorption spectrometry for the determination of manganese in blood

The triplet-triplet absorption spectra of various aromatic compounds in benzene solution were studied by pulse radiolysis. It has been found that methylation of naphthalene characteristic absorption band in this group of compounds at 430±10 nm (naphthalene, 2-methylnaphthalene, 2,6-dimethylaphthalene, anthracene, phenanthrene, pyrene and fluorene); new bands appeared with phenanthrene and pyrene at 495 and 525 nm respectively. The decay remains of the first order in the whole group with similar rate constant values. Diphenyl and 1,1-dinaphthyl show significant changes in their T-T spectra in comparison with the preceding group of compounds. T-T spectrum of o-terphenyl differs significanly from those of p-and m-isomers, which can be caused by greater overlapping of electron orbitals in o-isomer molecule. Aromatic ketones show a complex picture both in spectra and decay kinetics.     

全二维气相色谱-飞行时间质谱联用技术分析重馏分油中芳烃组成

通过对升温速度、二维补偿温度、调制周期等关键实验参数的优化,建立了全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)分析重馏分油中芳烃组分的方法,得到了重馏分油芳烃组分按环数分布的二维点阵图。根据谱库检索、标准化合物对照及文献报道,对重馏分油芳烃组分中菲、甲基菲及芘、苯并蒽等常见多环芳烃(PAH)进行了准确定性,并将该方法应用到重馏分油加氢处理工艺研究中,对菲、芘的加氢处理产物进行了定性分析。该研究为重馏分油芳烃组分的准确定性提供了新的技术手段,为加深对油品加氢规律的认识提供了技术支持。全二维气相色谱与普通一维色谱对比,在重馏分油的芳烃组分分析上体现了极大优势。     

微波法制备纳米碳点反应机制与发光机理

为探讨微波法制备纳米碳点发光性质的影响规律与本质,采用微波加热法通过控制微波功率、反应时间以及pH值合成了一系列纳米碳点,并利用荧光激发光谱与发射光谱测试对纳米碳点的发光性质进行了表征,结合紫外吸收光谱与傅立叶红外光谱对反应产物官能团变化分析,最终揭示了微波加热过程中葡萄糖向纳米碳点转变的机制与发光机理。结果表明,采用微波法制备纳米碳点,当微波功率为560 W,反应时间为2.5 min时,获得纳米碳点发光性能最佳。当采用波长370 nm紫外光激发时,对应451 nm的蓝光发射强度最高。伴随纳米碳点溶液pH值从酸性变为碱性,纳米碳点最强发光峰的激发光波长由350 nm显著向高波长方向移动,且发光峰强度显著升高。紫外吸收光谱与傅立叶红外光谱显示反应过程中形成了多环芳香族碳氢化合物,表明微波加热过程中是葡萄糖单糖向多糖聚合并最终发生碳化的过程。不同pH值下纳米碳点发光性质的差异,源于对纳米碳点中C=C键与C=O键比例的调整,从而实现对纳米碳点的光学带隙宽度及激子束缚能等的综合调控。     

Photophysical properties of praseodymium complexes with aromatic carboxylic acids: double light conversion both in ultraviolet and visible region

A series of luminescent praseodymium complexes with different aromatic carboxylic acids have been synthesized and characterized. The photophysical properties of these complexes have been studied with ultraviolet spectra, phosphorescence spectra and fluorescence spectra. Ultraviolet absorption spectra show that the praseodymium complexes systems with aromatic carboxylate form the more extensive conjugated systems to be suitable for the distribution of electron in the whole coordination environment, resulting in the energy decrease and red-shifts of ultraviolet spectral bands. Phosphorescence spectra suggest that excited triplet state of aromatic carboxylic acids, which can indicate the energy match and intermolecular energy transfer process between the excited triplet state of ligands and the resonant emissive energy level of Pr ions. The emission spectra of all praseodymium complexes show two emission peaks under the excitation band of 245 nm at about 395 and 595 nm, respectively, while one peak at about 595 nm under 415 nm excitation, which attributed to be 1S0-->1I6 (395 nm) transition and the characteristic emission 1D2-->3H4 (595 nm) transition of Pr3+ ion. The 1S0-->1I6 transition can be speculated to belong to the transition of charge transfer state, and the 1D2-->3H4 can be further proved that there exists an antenna effect in the luminescence of praseodymium with aromatic carboxylic acids. In conclusion, the praseodymium complexes systems can realize the double proton light conversion both in the ultraviolet and visible region, which can be further studied to have potential application.     

Analysis of polymers by mass spectrometry: Metastable mapping of transitions from pyrolysis products of an aromatic polyamide

Metastable mapping was applied to the analysis of the mixture of the pyrolysis products obtained from an aromatic polyamide, pyrolysed directly in a mass spectrometer. This technique permits a rapid analysis of the components and provides a method for assigning structures through the study of molecular ions, characteristic fragmentations and comparisons of daughter and parent ions of authentic samples. Collisionally activated decomposition spectra were always obtained in order to induce a higher intensity in the metastable transition. The thermal decomposition mechanism of the aromatic polyamide investigated here occurs via an intramolecular exchange and a concomitant N-H hydrogen transfer process with the formation of compounds with amine and/or succinimide end-groups.     

A flow-through fluorimetric sensing device for determination of alpha- and beta-naphthol mixtures using a partial least-squares multivariate calibration approach

A single flow-through optosensor spectrofluorimetric system is proposed for the resolution of mixtures of alpha- and beta-naphthol at mug l(-1) levels using a partial least-squares (PLS) calibration approach. The sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorimetric detection using Sephadex QAE A-25 resin as an active sorbent substrate in the flow cell and the second derivative of the native synchronous fluorescence spectra of analytes as analytical signal. In the manifold, the solutions of naphthol (at pH 10.0) were injected in a carrier stream of KCl (0.15 M)/NaOH (10(-2) M). Because of the strong spectral overlap, the mixture could not be resolved by conventional spectrofluorimetry. The non-additive behaviour of the fluorescence signals revealed an interaction in the system, which was not found by working in the solution only (without the sorbent support). This interaction, probably due to the environment of the analytes on the solid phase, made impossible their simultaneous determination. So, the use of synchronous fluorescence spectroscopy or even its derivative signal could not resolve satisfactorily the mixture. The simultaneous determination of both naphthol has been carried out by recording the signal of the second-derivative synchronous fluorescence (Deltalambda=170 nm) spectra between 200 and 450 nm and a PLS multivariate calibration treatment. The optimum number of factors was selected by using the cross-validation method. After validating the proposed method, it was applied to the determination of these compounds in natural waters with different amounts of each chemical.     

Three-dimensional total synchronous luminescence spectroscopy criteria for discrimination between normal and malignant breast tissues

Specimens of malignant and normal female human breast tissues were analyzed after surgery by means of synchronous luminescence spectroscopy. Measurements were performed in the ranges of excitation wavelengths from 330 to 650 nm and synchronous wavelengths from 30 to 120 nm to obtain ordinary and first derivative three-dimensional total synchronous luminescence spectra (3d-TSLS) of each specimen. Arithmetic mean of these spectra has been calculated for normal and malignant specimens and analyzed to establish criteria for tissue differentiation. Spectral domain volumes (volumes below luminescence intensity surface) and mean spectral slopes have been calculated and also analyzed as tissue discrimination criteria. The obtained results are discussed in view of the possible relevance of synchronous luminescence spectroscopy in discrimination between normal and malignant breast tissue.     

The synthesis and the solvent and substituent effect on the spectroscopic characteristic of 3-ethyl-2-(p-substitued styryl)benzothiazolium iodides

The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring.     

Tuning the excited-state energy of the organic chromophore in bichromophoric systems based on the Ru(II) complexes of tridentate ligands

A series of new heteroleptic and homoleptic Ru(II) complexes containing variously substituted bis(pyridyl)triazine ligands has been prepared and their absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in a rigid matrix at 77 K) have been investigated. For some compounds, X-ray structures have also been determined. The new bis(pyridyl)triazines incorporate additional chromophores, such as biphenyl, phenanthrene, anthracene and bromoanthracene derivatives, so the Ru(II) species can be considered as multichromophoric species. The absorption spectra and redox properties of all the metal complexes have been assigned to features belonging to specific subunits, thus suggesting that these species can be regarded as multicomponent, supramolecular assemblies from an electronic coupling point of view. Whereas most of the complexes exhibit luminescence properties that can be attributed to metal-to-ligand charge-transfer (MLCT) states involving the metal-based subunit(s), the species containing the anthryl and, even more, the brominated anthryl chromophores exhibit complicated luminescence behaviour. For example, 2 d (the anthryl-containing heteroleptic metal compound) exhibits MLCT emission at room temperature and emission from the anthracene triplet at 77 K; 2 e (the bromo-substituted anthryl-containing heteroleptic metal compound) exhibits anthryl-based emission at 77 K and MLCT emission at room temperature, but with a prolonged lifetime, thus suggesting equilibration between two triplet states that belong to different chromophores. The equilibration regime between MLCT and aromatic hydrocarbon triplet states is therefore reached by suitable substitution on the organic chromophore.     

Simultaneous fluorometric determination of nalidixic acid and 7-hydroxymethylnalidixic acid by partial least squares calibration

The resolution of binary mixtures of nalidixic acid (NA) and 7-hydroxymethylnalidixic acid (OH-NA) has been accomplished by partial least squares (PLS) and principal component regression (PCR) multivariate calibration. The method of determination is based on the fluorescence emission of these compounds in the presence of gamma-cyclodextrin (gamma-CD). The formation of the inclusion compounds gives rise to an increase of the fluorescence emission compared to aqueous solution. The total luminescence information of the compounds has been used to optimize the spectral data set to perform the calibration. A comparison between the predictive ability of three multivariate calibration methods, PLS-1, PLS-2 and PCR, on three spectral data sets, excitation, emission and synchronous spectra has been performed. The PLS-1 method, applied to the emission spectra, has been selected as optimum. The proposed method has been applied to the simultaneous determination of NA and OH-NA in urine. Recovery values from urine samples containing (NA) and (OH-NA) range from 91 to 103% (mean 97%), and from 92 to 105% (mean 99%), respectively.     

Heterocyclic Schiff Bases of 3-Aminobenzanthrone and Their Reduced Analogues: Synthesis,Properties and Spectroscopy

New substituted azomethines of benzanthrone with heterocyclic substituents were synthesized by condensation reaction of 3-aminobenzo[de]anthracen-7-one with appropriate aromatic aldehydes. The resulting imines were reduced with sodium borohydride to the corresponding amines, the luminescence of which is more pronounced in comparison with the initial azomethines. The novel benzanthrone derivatives were characterized by NMR, IR, MS, UV/Vis, and fluorescence spectroscopy. The structure of three dyes was studied by the X-ray single crystal structure analysis. The solvent effect on photophysical behaviors of synthesized imines and amines was investigated. The obtained compounds absorb at 420–525 nm, have relatively large Stokes shifts (up to 150 nm in ethanol), and emit at 500–660 nm. The results testify that emission of the studied compounds is sensitive to the solvent polarity, exhibiting negative fluorosolvatochromism for the synthesized azomethines and positive fluorosolvatochromism for the obtained amines. The results obtained indicate that the synthesized compounds are promising as luminescent dyes.     

Novel cyclopenta[def]phenanthrene based blue emitting oligomers for OLEDs

Novel blue emitters, oligo-MCPPs (tri-MCPP, tetra-MCPP, and penta-MCPP), have been synthesized and characterized. The introduction of cyclopenta[def]phenanthrene (CPP) units into the structure of oligo-MCPPs gave LEDs with high efficiency and pure blue emission. UV-visible absorption spectra of the thin films of these compounds appear at 333-354 nm, and their maximum PL emission at 416-447 nm. Multilayer organic EL devices with oligo-MCPPs as an emitting layer showed the turn-on voltage of about 4.8 V, the maximum brightness of 1076 cd/m² (at 8.2 V), the maximum luminescence efficiency of 0.81 cd/A, and the CIE coordinates of (0.17, 0.14) with blue color.     

Total synchronous fluorescence scan spectra of petroleum products

Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan (TSFS) spectral measurement gives the total synchronous fluorescence characteristics of a multifluorophoric sample at various possible wavelength intervals (Deltalambda), which could help to characterize multifluorophoric systems better. TSFS spectra of petroleum products such as diesel, kerosene, petrol, engine oil etc., available in the Indian market, are reported. Fluorescence in these samples is due to the presence of polycyclic aromatic hydrocarbons (PAHs) of various ring sizes. The TSFS contour plot profiles of the neat samples measured at right-angle geometry is a result of various energy-degrading photophysical processes such as inner filter effect, light attenuation, resonance energy transfer, collisional quenching etc. TSFS plots make it easy to obtain the optimized Deltalambda of an unknown sample of analytical interest. TSFS and the excitation-emission matrix (EEM) techniques are similar, but the contour profiles generated are different. The response of the TSFS contour profiles to dilution is different from that in the EEM contour profiles. Thus, TSFS can provide an alternative way of presenting the fluorescence response of concentrated multifluorophoric samples.     

Synthesis and photophysical investigation of a series of push-pull arylvinyldiazine chromophores

A new series of push-pull arylvinyldiazines has been efficiently prepared by aldol condensation between the appropriate methyldiazine and aromatic aldehyde. The optical absorption and emission properties of these chromophores were studied in different solvents and media. These compounds act as polarity sensors with a strong positive emission solvatochromism. This behavior suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. These molecules also exhibit halochromic properties and are potential colorimetric and luminescence pH sensors. The second-order nonlinear properties have been investigated for some of the compounds, and large and positive μβ are obtained, in particular, for pyrimidine derivatives.