Spectral Analysis of Poly(propyleneamine) Dendrimers Peripherally Modified with 1,8-Naphthalimides

Seven newly synthesized poly(propyleneamine) dendrimers, modified with 1,8-naphthalimides, have been investigated by infrared, UV-vis, and fluorescence spectroscopy. The influence of the nature of the substituents at the C-4 position of the naphthalene ring on the spectral properties of the dendrimers is discussed.     

Phase transitions and molecular motions in [Cd(H2O)6](BF4)2 studied by DSC, H and F NMR and FT-MIR

Two solid phase transitions of [Cd(H₂O)₆](BF₄)₂ occurring on heating at T_C2=183.3 K and T_C1=325.3 K, with 2 K and 5 K hysteresis, respectively, were detected by differential scanning calorimetry (DSC). High value of entropy changes indicated large orientational disorder of the high temperature and intermediate phase. Nuclear magnetic resonance (¹H NMR and ¹⁹F NMR) relaxation measurements revealed that the phase transitions at T_C1 and T_C2 were associated with a drastic and small change, respectively, of the both spin-lattice relaxation times: T₁(¹H) and T₁(¹⁹F). These relaxation processes were connected with the “tumbling” motions of the [Cd(H₂O)₆]²⁺, reorientational motions of the H₂O ligands, and with the iso- and anisotropic reorientation of the BF₄⁻ anions. The cross-relaxation effect was observed in phase III. The line width and the second moment of the ¹H and ¹⁹F NMR line measurements revealed that the H₂O reorientate in all three phases of the title compound. On heating the onset of the reorientation of 3 H₂O in the [Cd(H₂O)₆]⁺², around the three-fold symmetry axis of these octahedron, causes the isotropic reorientation of the whole cation. The BF₄⁻ reorientate isotropically in the phases I and II, but in the phase III they perform slow reorientation only about three- or two-fold axes. A small distortion in the structure of BF₄⁻ as well as of [Cd(H₂O)₆]²⁺ is postulated. The temperature dependence of the bandwidth of the O-H stretching mode measured by Fourier transform middle infrared spectroscopy (FT-MIR) indicated that the activation energy for the reorientation of the H₂O did not change much at the T_C2 phase transition.     

海藻多糖的组成及结构光谱分析

海藻多糖具有抗凝血等多种生物活性,其活性与多糖的组成结构有关。本文对近年来红藻、褐藻及少量绿藻多糖的单糖组成及含量研究以及FT-IR和12^C NMR两种主要光谱手段对多糖结构研究的结果进行了介绍。     

光谱法研究钢铁表面彩色Mo-S-Fe簇合物膜

研究MoS4^2-在钢铁表面发生配位反应形成的具有装饰效果的多种彩色Mo-S-Fe簇合物膜。FT-IR、F-IR、FT-Raman、XPS和AES分析表明,簇合物膜以Fe(Ⅲ)、Mo(Ⅵ)状态存在,膜内层以Fe(Ⅱ)、Mo(Ⅳ)和Mo(Ⅵ)共存,S和O都-2价,膜表面含少量 4、 6价硫。从AES深度分布曲线的组成恒定区求得各组成元素的相对原子百分比浓度和膜层厚度,反应时间越长,膜越厚,膜为多分子层结构。加热后膜层所含元素种类及价态不变,但元素分布有所改变。     

聚乙烯尼龙共混物的PGC-MS和FT-IR联用鉴别

采用裂解气相色谱-质谱法和红外光谱法研究聚乙烯和尼龙共混物的组成;据此建立鉴别聚乙烯共混物组分的方法;红外光谱法可以准确鉴别出尼龙组分,裂解气相色谱-质谱法可以准确鉴别出聚乙烯组分以及尼龙的具体结构;二种方法结合使用,可以准确鉴别聚乙烯和尼龙共混物的组分。     

FT-IR and FT-FIR studies of vanadium,molybdenum and tungsten oxides supported on different carriers

In the far IR region at low molybdenum loadings, Mo-SiO₂ catalysts present a pseudomolybdate or a polymolybdate species, while bulk-like MoO₃ appears at loadings close to the geometrical monolayer coverage. W-SiO₂ and V-SiO₂ spectra show bands close to those observed on the corresponding bulk oxides.In the case of TiO₂, Al₂O₃, ZrO₂ supported catalysts, a band is observed near 1000 cm^–1 which is assigned to the Mo=O stretching vibration of coordinatively unsaturated Mo ⁿ⁺ ions showing a stronger interaction with the support than one observed on silica.     

Characterization of tension and normally lignified wood cellulose inPopulus maximowiczii

We have investigated unlignified tension wood and normally lignified wood celluloses inPopulus maximowiczii with particular reference to the composition of two crystalline phases I/I (triclinic/ monoclinic). Four independent techniques, which enable us to detect the two phases, CP/MAS¹³C NMR, Fourier transform infrared microscopy, selected-area electron diffraction, and X-ray diffraction were applied. Because of the low crystallinity of wood celluloses, particularly in the case of celluloses in the lignified cell wall, no single method was decisive enough to be able to determine the composition of the two phases as one can with highly crystalline materials. The I dominant structure (monoclinic crystal type) was, however, preferred for both tension and normal wood celluloses.     

傅里哀变换红外发射光谱法研究金属氧化物催化剂——Ⅰ.实验建立及氧化钼的还原-氧化研究

本文报导了傅里哀变换红外发射光谱法研究多相氧化物催化剂的实验装置的建立及实验条件的考察。设计加工了一个温度范围宽,可在各种气氛和真空条件下原位研究氧化物催化剂的红外发射池。以MoO_3为例,考察了样品厚度,测试温度对发射光谱的影响。当样品量小于1mm·cm~(-2)时,随样品量增加,谱峰强度线性增加,但峰形不发生变化。当样品量高于1mg.cm~(-2)时,随样品量增加,谱图严重畸变。随样品温度升高,谱峰强度近似线性增加。并用该方法研究了MoO_3在还原和再氧化过程中表面氧物种的变化。结果表明桥式MO?O?Mo物种比端基Mo=O物种较易还原,再氧化时,Mo=O物种比Mo?O?Mo物种优先形成。     

稀土Pr_6O_(11)表面上低碳烃氧化反应的原位FT-IR研究

前文报道了CO与Pr_6O_(11)表面反应的结果.已发表的关于烃类与氧化物表面反应的研究,旨在了解烃类的活化和表面氧化机理,而且大部分工作都是在过渡金属氧化物上进行的.近年来的研究表明,稀土氧化物将是有潜力的甲烷氧化偶联制乙烯的催化剂,在消除环境污染的烃类完全氧化催化剂中,稀土氧化物也常被用作助剂或活性组分,但对于稀土氧化物本身的催化表面研究尚不多见.作者曾较系统地研究了CeO_2的表面催化性质,发现表面上存在多种氧物种,这些氧物种与烃类的反应活性差异很     

Citrate - Nitrate route for the synthesis and characterization of TAG using sol-gel techniques

Terbium Aluminum Garnet (TAG) is an important optically active material and is one of the best materials known for the fabrication of optical isolators. TAG has a large Verdet constant and has good transmission in the region of 350–1500 nm of the electromagnetic spectrum. It is also known that TAG melts incongruently at 1840°C. This makes efficient synthesis of TAG important and challenging and forms the motivation of the present work to develop techniques for the synthesis of TAG at lower temperatures. In the present work we report the synthesis of TAG using sol-gel techniques following the citrate-nitrate route. The prepared sample is sintered at various temperatures in presence of air and characterized using X-ray diffraction, FT-IR spectroscopy, energy dispersive X-ray Analysis and the morphology is observed using the scanning electron microscopy.