Methanation of carbon dioxide over Ru/Titania at room temperature: explorations for a photoassisted catalytic reaction

The methanation of CO₂ has been investigated over a special Ru/TiO₂ catalyst suggested by Thampi, Kiwi and Graetzel [4]. This paper deals with the analysis of the material and the investigation of the reported photoenhancement of the activity. The catalyst is characterised by in situ UV-VIS spectroscopy and by XPS. Conversion experiments at atmospheric pressure were carried out with and without UV light irradiation. The irradiation increases the conversion significantly. From various experiments it can be shown, however, that this effect is due to a thermal effect and does not involve an intrinsic photochemical step. Localised Ti³⁺ states sensitise the support to convert visible light into heat resulting in the observed increase in conversion.     

类胡萝卜素的紫外可见光谱特性及其应用

对类胡萝卜素紫外可见吸收光谱(UV—VIS)的部分特性进行了综述。重点讨论了类胡萝卜素UV—VIS最大吸收峰的位置、形状及影响因素，类胡萝卜素异构化对UV—VIS的影响，与类胡萝卜素UV—VIS有关的化学测试反应在其结构鉴定中的应用。     

MoO_2Br_2-Al(i-Bu)_2OPhCH_3-Allyl-X体系催化丁二烯聚合的紫外可见吸收光谱

用紫外可见光谱法考察了MoO_2Br_2-Al(i-Bu)_2OPhCH_3(-m)催化体系中添加第三组分-烯丙基卤(A11yl-X),对丁二烯聚合的影响.结果表明,MoO_2Br_2的乙酸乙酯溶液在340nm和780nm处有两个特征吸收峰.其中780nm处归属为Mo(V)的自旋允许d-d跃迁吸收峰.烯丙基卤能与Mo形成π络合物,随Al/Mo增加,其电荷迁移峰由340nm移向380nm,且烯丙基卤和丁二烯可分别与Mo(Ⅲ)形成的π络合物,其特征吸收峰均在380nm处.同时表明,Al(i-Bu)_2OPhCH_3(-m)易与烯丙基溴反应,可使烯丙基溴-Mo(Ⅲ)络合物解络合.     

苯乙烯 - 马来酸酐无规共聚物/银纳米微粒的合成及表征

金属纳米材料能够产生量子尺寸效应及表面效应，在许多领域具有很好的应用前景.以DMF(N,N-二甲基甲酰胺)为溶剂及还原剂，苯乙烯-马来酸酐无规共聚物为大分子稳定剂，在不同的反应条件下，合成制备了银纳米微粒.通过紫外-可见吸收光谱、透射电子显微镜等测试手段对所合成的纳米银样品进行了表征.结果表明：通过上述反应所得到的银纳米微粒的DMF溶液可以在420 nm处出现纳米银所具有的特征吸收峰，增加了反应前驱体浓度及反应时间，使银纳米微粒的特征吸收峰变得更加明显.透射电子显微镜的结果表明，所得到的银纳米微粒具有较窄的尺寸分布，从而证明苯乙烯-马来酸酐无规共聚物可以对纳米银表面进行较好的修饰.     

Interactions between anthocyanins and organic food molecules in model systems

The interactions between different glucosidic anthocyanins (pelargonin, cyanin, delphinin, malvin and petunin) and some organic compounds (lactic, galacturonic, tannic, phenolic and sinapic acids; pyrogallol, furfural, pectin, cellulose, hydrolitic lignin) which are present in food‐stuffs were investigated at pH 3.0–4.3 and 25 °C. The interactions were monitored by means of u.v.‐VIS spectra and their different behaviours were highlighted by following changes in absorbance over a range of wavelengths (Δλ and ΔA). Significant effects on absorbance were detected and are discussed in terms of the phenomenon of co‐pigmentation.     

巴西Minas Gerais彩色电气石的宝石矿物学特征

利用电子探针、X射线光电子能谱仪、紫外-可见光光度计和傅里叶变换红外光谱仪对产自巴西MinasGerais地区、不同颜色的彩色电气石样品进行了宝石矿物学特征研究。电子探针测试结果显示,该电气石样品中Al2O3和Na2O的质量分数较高,FeO的质量分数相对较低,且含有一定量的MnO和Cr2O3;X射线光电子能谱分析初步证实该样品为锂电气石;结合化学成分与紫外-可见光透过光谱的分析结果认为,微量元素Fe^2＋,Fe^3＋,Mn^3＋,Ti^4＋和Cr^2＋是巴西Minas Gerais彩色电气石样品致色的主要因素之一;红外吸收光谱测试结果显示,该样品在1200～1450cm。范围内存在强的B-O基团致伸缩振动带,含有BO3原子团;其在3000-3750cm。范围内具有H2O和羟基离子致双峰伸缩谱带。比较不同颜色电气石样品的红外吸收光谱发现,其光谱频带数及位置与电气石中的类质同象和化学成分有关。     

Structural,thermal, spectral,optical and surface analysis of rare earth metal ion (Gd3+) doped mixed Zn–Mg nano-spinel ferrites

The present work reports the structural, thermal, spectral, optical and surface analysis of rare earth metal ion (Gd³⁺) doped mixed Zn–Mg nano-spinel ferrites. The samples of Gd³⁺ doped Zn–Mg nano ferrites with equi-amount chemical composition i.e. Zn_0.5Mg_0.5Fe_2-xGd_xO₄ (0.00 ≤ x ≤ 0.10 in step of 0.02) were prepared by self-ignited sol-gel route. The variance in the thermal behaviour and spinel phase development with weight loss percentage in the prepared samples was investigated by TG-DTA technique. The powder X-ray diffraction (P-XRD) patterns ensured the nanocrystalline mono-phasic formation and spinel-cubic structure of all the samples. The trend of increment in lattice constant (a) and decrement in crystallite (t) size was observed with the doping of Gd³⁺ ions. The appearance of two requisite vibrational stretching modes was affirmed by the FT-IR spectral studies. The UV–Vis optical analysis displayed the augmentation in absorbance and drastic decrement in energy band gap value (1.96 eV–1.83 eV) with Gd³⁺ doping. The photo-luminescent (PL) studies revealed the broad near band-edge emission in visible wavelength range (523 nm–528 nm) for all the samples. The surface parameters investigation was undertaken with the help of BET isotherms recorded by the N₂-physisorption and BJH model. The various surface parameters such as BET surface area, volume and radius of the pores, distribution of the pore sizes etc were construed from the BET data. The enhancement in these surface parameters via Gd³⁺ doping was noted for all the samples. The outcomes of the present work reflects the influential doping of Gd³⁺ ions in Zn–Mg nano ferrites, which can be implementable for bio-applications as thermal seeds in magnetic hyperthermia or as contrast enhancer in medical MRI imaging.     

Determination of Antioxidant Properties of Fruit Juice by Partial Least Squares and Principal Component Regression

The multivariate calibration methods—principal component regression and partial least squares—were employed for the prediction of antioxidant capacities of fruit juices. High-performance liquid chromatography and spectrophotometric approaches were used to determine the antioxidant capacities of fruit juices. The importance of calibration design was investigated by calculating the prediction and validation errors. The influences of using independent validation sets were emphasized. Calibration design is shown to have major effect on principal component regression and partial least squares errors. The models developed on the basis of the mean-centered data were able to predict the total antioxidant activity with a precision comparable to that of the reference [2,2-azino-di-(3-ethylbenzothialozine-sulfonic acid)] method. The partial least squares model seems preferable because of its predictive and describing abilities and good interpretability of the contribution of compounds to the antioxidant capacity. The contribution of individual phenolic compounds to the antioxidant capacity was identified by high-performance liquid chromatography.     

Structural, thermal and optical behavior of 84 MeV oxygen and 120 MeV silicon ions irradiated PES

In order to study structural, thermal and optical behavior, thin flat samples of polyethersulfone were irradiated with oxygen and silicon ions. The changes in properties were analyzed using different techniques viz: X-ray diffraction, thermo-gravimetric analysis, Fourier transform infrared, UV-visible and photoluminescence spectroscopy. A noticeable increase in the intensity of X-ray diffraction peaks was observed after irradiation with 84 MeV oxygen ions at low and medium fluences, which may be attributed to radiation-induced cross-linking in polymer. Fourier transform infrared and thermo-gravimetric analysis corroborated the results of X-ray diffraction analysis. No noticeable change in the Fourier transform infrared spectra of oxygen ion irradiated polyethersulfone were observed even at the highest fluence of 1 × 10¹³ ions cm⁻², but after irradiation with silicon ions, a reduction in intensity of almost all characteristic bands was revealed. An increase in the activation energy of decomposition of polyethersulfone was observed after irradiation with 84 MeV oxygen ions up to medium fluences but degradation was revealed at higher fluences. Similar trends were observed by photoluminescence analysis.     

Spectrophotometric Measurement of Asphaltene Concentration

Abstract

Typically, when ultraviolet and visible absorbance of asphaltenes is employed to measure asphaltene concentration, linear calibrations of absorbance vs. asphaltene concentration are prepared from a sample of asphaltenes in a given solvent. This calibration is shown to be sensitive to: (a) the inorganic solids content of the asphaltenes; (b) physical–chemical differences between asphaltenes from different sources or extracted with different methods; and (c) selective adsorption of asphaltenes on liquid–liquid or solid–liquid interfaces. Calibration constants were determined at wavelengths of 288 and 800 nm for samples of Athabasca and Cold Lake asphaltenes obtained using different extraction methods, from precipitation experiments, and from adsorption experiments on water-in-hydrocarbon emulsions and on powdered metals. It was found that the inorganic solids content did not affect absorbance but the asphaltene concentrations must be corrected to a solids-free basis for accurate results. Calibration constants were found to correlate to the average associated molar masses of the asphaltenes. Therefore, any change in molar mass of asphaltenes during the course of an experiment may change the calibration constant. Partial precipitation and the selective adsorption of asphaltenes can lead to a change in the molar mass of asphaltenes left in solution. The corresponding change in the calibration constants can lead to errors of 5–25% in the estimated concentration.