The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysis. Lutetium, ytterbium, cerium(III), scandium, gadolinium, terbium, dysprosium, holmium, erbium, and thulium florides can be hydrolyzed in 30 min or less. Yttrium, lanthanum, praseodymium, neodymium, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U₃O₈), chromium(III) oxide, and a mixture of these oxides have been used successfully to reduce the tune required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium and neodymium.     

A study on the formation mechanism of graphite fluorides by Raman spectroscopy

Raman spectra were measured of highly fluorinated graphite samples prepared at room temperature, 380 and 515 °C. C_xF prepared at room temperature showed a novel downshifted band at 1555–1542 cm⁻¹ along with G band at 1593–1583 cm⁻¹. Similar behavior is also observed for samples prepared at 380 and 515 °C at early stages of fluorination, after which the Raman shifts completely disappeared. Raman spectra as well as X-ray diffraction (XRD) analysis suggest that graphite fluorides, (CF)_n and (C₂F)_n are formed via fluorine-intercalated phase with planar graphene layers.     

NMR parameters in alkali, alkaline earth and rare earth fluorides from first principle calculations

(19)F isotropic chemical shifts for alkali, alkaline earth and rare earth of column 3 basic fluorides are measured and the corresponding isotropic chemical shieldings are calculated using the GIPAW method. When using the PBE exchange-correlation functional for the treatment of the cationic localized empty orbitals of Ca(2+), Sc(3+) (3d) and La(3+) (4f), a correction is needed to accurately calculate (19)F chemical shieldings. We show that the correlation between experimental isotropic chemical shifts and calculated isotropic chemical shieldings established for the studied compounds allows us to predict (19)F NMR spectra of crystalline compounds with a relatively good accuracy. In addition, we experimentally determine the quadrupolar parameters of (25)Mg in MgF(2) and calculate the electric field gradients of (25)Mg in MgF(2) and (139)La in LaF(3) using both PAW and LAPW methods. The orientation of the EFG components in the crystallographic frame, provided by DFT calculations, is analysed in terms of electron densities. It is shown that consideration of the quadrupolar charge deformation is essential for the analysis of slightly distorted environments or highly irregular polyhedra.     

煤焦油的拉曼光谱表征和组分识别

用355 nm激光作为激发光源检测了煤焦油常温拉曼光谱;应用两种量子化学计算程序(Gaussian-DFT和ADF)模拟了占总量1%以上的15种煤焦油组分的拉曼光谱,模拟结果与实验光谱能较好匹配,并对振动模式进行了归属分析。研究表明,煤焦油组分主要由共轭六元环构成,其拉曼光谱特征谱带主要在1 660、1 420和1 265 cm^-1附近,当共轭六元环成链式结构时,1 420 cm^-1谱带特征明显;五元环嵌入共轭六元环链式结构会导致其拉曼光谱在1 265和1 660 cm^-1谱带相对强度增大;五元环、杂原子基团和甲基侧链依附在共轭六元环上,则对组分的拉曼光谱影响不显著。     

Spectroscopic studies of the f↔d ultraviolet transitions of Pr in alkaline earth fluorides

Absorption and UV fluorescence spectra of Pr³⁺ weakly doped alkaline earth fluoride single crystals have been recorded and interpreted in terms of f↔d transitions. Short fluorescence lifetimes have been measured. The emission spectra and the decay profiles of Pr-doped BaF₂ have been studied as a function of photon excitation energy. This latter system exhibits cross-luminescence and excitonic fluorescence in addition to d↔f luminescence of Pr³⁺.     

Production of phenol compounds by alkaline treatment of technical hydrolysis lignin and wood biomass

Aqueous alkaline depolymerization of technical hydrolysis lignin (THL) was carried out with a 5% NaOH solution at a temperature of 180°C for 6 hours, the ratio between the biomass and depolymerizing agent being 1:8. The poplar wood sawdust was treated under the same conditions for 2 hours, where anthraquinone was added as a catalyst (0.5 wt %). The poplar wood bark was treated for 4 hours, without anthraquinone. Compounds contained in the aqueous phase were extracted three times by means of toluene for a ratio between the organic and aqueous phases equal to 1:5, 1:5 and 1:5. The compounds 2-methoxyphenol, 2,6-dimethoxyphenol, 4-hydroxy-3-methoxybenzaldehyde, 1-(4-hydroxy-3-methoxyphenyl)ethanone, 4-hydroxy-3,5-dimethoxybenzaldehyde, etc., were identified through GC-MS analysis in obtained extracts. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 144–146, March–April, 2008.     

Chemotaxonomical identification of spores of macrofungi: possibilities of Raman spectroscopy

Confocal Raman spectroscopy is a non-destructive analytical method which is useful to obtain detailed information about the molecular composition of biological samples. Its high spatial resolution was used to collect spectra of single basidiospores of macrofungi of the genera Collybia, Gymnopus, Laccaria, Lactarius, Mycena and Russula. These spectra can be divided into three major taxon-related groups, with general compositional differences, such as the relative amount of lipids compared to proteins. In this study, collapsing of thin-walled spores during storage was often observed, a phenomenon which has been given little attention in the literature. The Raman spectra are treated with different chemometric preprocessing techniques, including Savitsky–Golay, standard normal variate (SNV) preprocessing and extended multiplicative scatter correction (EMSC). By using linear discriminant analysis, approximately 90% of the spectra can be assigned to the correct genus, but identification on the species level was not possible.     

A combination of thin-layer chromatography and emission spectroscopy for the microdetermination of alkaline earth metals

Summary Thin-layer chromatography of alkaline earth metals on cellulose has been modified. After detection of the metal ions with an oxine spray, identification and semiquantitative determination was carried out by liquid emission spectroscopy. The sensitivity of the method is 0.05 ppm for all cations tested. The smallest detectable change in concentration corresponds to about ±5% in a medium concentration range. Analysis errors were below 10%.

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Zusammenfassung Die Dünnschichtchromatographie der Erdalkalimetalle auf Zellulose wurde modifiziert. Die Metallionen werden durch Sprühen mit Oxin nachgewiesen, identifiziert und halb quantitativ durch Emissionsspektroskopie ihrer Lösungen bestimmt. Die Empfindlichkeit dieser Methode beträgt für alle untersuchten Kationen 0,05 ppm. Die geringsten im mittleren Bereich nachweisbaren Konzentrationsunterschiede betragen ±5%. Die Fehler liegen unter 10%.

     

负载氧化钒催化剂的多波长拉曼光谱研究:结构识别和定量

探究负载金属氧化物的结构是确立催化剂结构和催化性能之间相互关系的首要条件. 在众多表征技术中,多波长拉曼光谱结合了共振拉曼和由不同波长激发的非共振拉曼,不仅在识别负载金属氧化物团簇的结构,而且在定量方面已经成为强有力的工具. 本文以两个负载氧化钒体系(VOx/SiO2,VOx/CeO2)为例,阐述了如何利用该技术研究活性氧化物团簇的多相结构,并理解氧化物团簇和载体之间复杂的相互作用. 由多波长拉曼光谱得到的定性和定量信息能为设计更有效的负载金属氧化物催化剂提供基本的依据.     

Tumour cell identification by means of Raman spectroscopy in combination with optical traps and microfluidic environments

Raman spectroscopy has been recognized to be a powerful tool for label-free discrimination of cells. Sampling methods are under development to utilize the unique capabilities to identify cells in body fluids such as saliva, urine or blood. The current study applied optical traps in combination with Raman spectroscopy to acquire spectra of single cells in microfluidic glass channels. Optical traps were realized by two 1070 nm single mode fibre lasers. Microflows were controlled by a syringe pump system. A novel microfluidic glass chip was designed to inject single cells, modify the flow speed, accommodate the laser fibres and sort cells after Raman based identification. Whereas the integrated microchip setup used 514 nm for excitation of Raman spectra, a quartz capillary setup excited spectra with 785 nm laser wavelength. Classification models were trained using linear discriminant analysis to differentiate erythrocytes, leukocytes, acute myeloid leukaemia cells (OCI-AML3), and breast tumour cells BT-20 and MCF-7 with accuracies that are comparable with previous Raman experiments of dried cells and fixed cells in a Petri dish. Implementation into microfluidic environments enables a high degree of automation that is required to improve the throughput of the approach for Raman activated cell sorting.     

Systematization of the effective ionic charges in the oxides,oxide fluorides,and fluorides of the rare earth metals

Conclusion We can compare the values obtained above and in [9] for the effective ionic charges e^* for all three types of REM compound examined: fluorides, oxides, and oxide fluorides.In spite of the difference in composition, all these substances can be divided into two groups by separating the cubic (or pseudo-isotropic) crystals and the anisotropic compounds. The average values of the effective charges for each of the structural groups are given in Table 7, which also gives in parentheses the values of the ionic character of the bond, calculated according to Pauling's scheme with allowance for only the nearest homogeneous coordination sphere (for example, for CN=5 instead of 11 for the hexagonal LnF₃, etc.).It can be seen from the Table that the effective charges increase on going from the oxides to the fluorides of the REM, as expected in view of the fact that the electronegativity of fluorine is greater than that of oxygen. In all cases, the increase in the values of e^*, noted above, is observed on going from the anisotropic to the cubic crystals of these compounds. This last feature can be attributed to a decrease in the immediate coordination sphere around the REM atoms with change in the structure of the crystal; in this case the coordination sphere is understood to consist of the nearest ligands. Calculation of the degree of ionic character by the EN method with allowance for only the atoms situated at the shortest distances shows much better agreement with experiment than the classical calculation using the formal CN [8].All-Union Scientific-Research Institute for Physicotechnical and Radiotechnical Measurements. Translated from Zhurnal Strukturnoi Khimii, Vol. 14, No. 3, pp. 541–547, May–June, 1973.     

Automatic identification of novel bacteria using Raman spectroscopy and Gaussian processes

Raman spectroscopy is successfully used for the reliable classification of complex biological samples. Much effort concentrates on the accurate prediction of known categories for highly relevant tasks in a wide area of applications such as cancer detection and bacteria recognition. However, the resulting recognition systems cannot always be directly used in practice since unseen samples might not belong to classes present in the training set. Our work aims to tackle this problem of novelty detection using a recently proposed approach based on Gaussian processes. By learning novelty scores for a large bacteria Raman dataset comprising 50 different strains, we analyze the behavior of this method on an independent dataset which includes known as well as unknown categories. Our experiment reveals that non-parametric methods such as Gaussian processes can be successfully applied to the task of finding unknown bacterial strains, leading to encouraging results motivating their further utilization in this area.     

Towards detection and identification of circulating tumour cells using Raman spectroscopy

Body fluids are easily accessible and contain valuable indices for medical diagnosis. Fascinating tools are tumour cells circulating in the peripheral blood of cancer patients. As these cells are extremely rare, they constitute a challenge for clinical diagnostics. In this contribution we present the Raman spectroscopic-based identification of different single cells in suspension that are found in peripheral blood of cancer patients including healthy cells like leukocytes and erythrocytes, and tumour cells like leukaemic cells and cells originating from solid tumours. Leukocytes and erythrocytes were isolated from the peripheral blood of healthy donors while myeloid leukaemia cells (OCI-AML3) and breast carcinoma derived cells (MCF-7, BT-20) were obtained from cell cultures. A laser emitting 785 nm light was used for optical trapping the single cells in the laser focus and to excite the Raman spectrum. Support vector machines were applied to develop a supervised classification model with spectra of 1210 cells originating from three different donors and three independent cultivation batches. Distinguishing tumour cells from healthy cells was achieved with a sensitivity of >99.7% and a specificity of >99.5%. In addition, the correct cell types were predicted with an accuracy of approximately 92%.