CO2 Aggregation on Monoethanolamine: Observations from Rotational Spectroscopy

The initial stages of the gas-phase nucleation between CO₂ and monoethanolamine were investigated via broadband rotational spectroscopy with the aid of extensive theoretical structure sampling. Sub-nanometer-scale aggregation patterns of monoethanolamine-(CO₂)_n, n=1–4, were identified. An interesting competition between the monoethanolamine intramolecular hydrogen bond and the intermolecular interactions between monoethanolamine and CO₂ upon cluster growth was discovered, revealing an intriguing CO₂ binding priority to the hydroxyl group over the amine group. These findings are in sharp contrast to the general results for aqueous solutions. In the quinary complex, a cap-like CO₂ tetramer was observed cooperatively surrounding the monoethanolamine. As the cluster approaches the critical size of new particle formation, the contribution of CO₂ self-assembly to the overall stability increases.     

OH自由基与CO反应的研究

用时间分辨-傅立叶变换红外发射光谱法研究了OH自由基与CO的反应.OH自由基由248 nm的激光光解硝酸得到.在实验中首次观测到了产物CO2的非对称伸缩振动(ν3)的激发态.对CO2发射光谱的拟合结果显示,其振动态的布居在量子数v=2时最大 ,而最高振动量子数达到v=6.由实验得到的CO2振动布居与Schatz等人用全量子化计算该反应的中间物HOCO解离动力学得到的CO2布居结果能很好地吻合.     

Investigation of Lignins by FTIR Spectroscopy

Summary: Applying special computer mathematical treatments to increase resolution of experimental spectra there were established a set of stable characteristic bands for isolated softwood lignins. In the 740–1620 cm⁻¹ spectral range the band maximum positions did not change but values of bandwidths and peak intensities were varied in limits 15% and 32%. After analysis of the infrared spectra of 30 investigated samples a softwood lignin spectral model was constituted. This model allowed to clear discrepancies in the bands parameters of different mild isolated (lignins of Bjorkman, Pepper and Freudenberg), dioxane and technical lignin spectra. It was helpful for studying lignin structure changes during degradation procedures.     

聚酰胺酸结构及其亚胺化的红外光谱分析

利用变温透射红外光谱方法,通过跟踪聚酰胺酸（PAA）的亚胺化过程,对由均苯四酸二酐和4,4′-二氨基二苯醚合成的聚酰胺酸及经过加热亚胺化后生成的聚酰亚胺(PI)的红外吸收光谱进行分析,对聚酰胺酸和聚酰亚胺的红外谱峰进行合理的归属,发现聚酰胺酸在亚胺化过程中有-COO-和-NH+2存在,-COO-中羰基的对称与反对称伸缩振动分别位于1607和1406 cm-1,NH+2的伸缩振动则有3200、3133、2938、2880、2820和2610 cm-1等多个精细谱带。 并根据对-COO-和-NH+2谱峰的归属,提出聚酰胺酸生成聚酰亚胺的机理为聚酰胺酸中COOH的H+转移到聚酰胺酸中的NH上,形成NH+2,然后脱水环化生成聚酰亚胺。     

二维红外光谱研究聚碳酸酯薄膜中水的扩散

利用二维衰减全反射红外光谱方法,研究了水在聚碳酸酯(PC)薄膜中的扩散过程,发现水的羟基弯曲振动谱带中可以分辨出分别位于1672、1646和1621 cm-1的吸收峰,而羟基伸缩振动谱带中可以分辨出分别位于3560、3425和3255 cm-1的吸收峰,由此可知水分子在聚碳酸酯薄膜中存在3种状态,分别为与羰基形成强、中强氢键作用的水分子和进入PC微孔中的弱氢键作用的水分子。 经过二维相关分析得到水分子进入PC薄膜的顺序为首先形成中等强度的氢键,然后形成弱和强2种强度的氢键。     

用TR-FTIR研究CH+NO2的反应

CH自由基是烃类燃烧过程中反应活性很高的重要的中间产物[1,2].CH自由基与氮氧化物的反应被认为是通过二次燃烧过程减少氮氧化物的主要反应之一,也是对火焰中氮化物的化学行为建立模型的关键步骤[3].但是,对于CH与NO2反应的研究还不是很深入,到目前为止,只有两篇论文报道了该反应在298 K时的总包反应速率常数[4,5],Taeg和Hershberger用红外二极管激光吸收法研究了该反应[6].他们在实验中只观测到了产物CO和NO,但一些较低能量的产物,如NH+CO2、OH+NCO等却没有被观察到.为了更深一步了解CH与NO2的反应产物及反应通道,我们用时间分辨傅立叶变换红外发射光谱(TR-FTIR)法研究了该反应.     

Classification of Honey Powder Composition by FTIR Spectroscopy Coupled with Chemometric Analysis

Fourier transform infrared spectroscopy (FTIR) in connection with chemometric analysis were used as a fast and direct approach to classify spray dried honey powder compositions in terms of honey content, the type of diluent (water or skim milk), and carrier (maltodextrin or skim milk powder) used for the preparation of feed solutions before spray drying. Eleven variants of honey powders containing different amounts of honey, the type of carrier, and the diluent were investigated and compared to pure honey and carrier materials. Chemometric discrimination of samples was achieved by principal component analysis (PCA), hierarchical clustering analysis (HCA), linear discriminant analysis (LDA), and partial least squares-discriminant analysis (PLS-DA) modelling procedures performed on the FTIR preprocessed spectral data for the fingerprint region (1800–750 cm⁻¹) and the extended region (3600–750 cm⁻¹). As a result, it was noticed that the type of carrier is a significant factor during the classification of different samples of powdered multifloral honey. PCA divided the samples based on the type of carrier, and additionally among maltodextrin-honey powders it was possible to distinguish the type of diluent. The result obtained by PCA-LDA and PLS-DA scores yielded a clear separation between four classes of samples and showed a very good discrimination between the different honey powder with a 100.0% correct overall classification rate of the samples.     

红外光谱法直接鉴别苦丁茶的研究

本文利用傅立叶变换红外光谱(FTIR)法快速、直接地测定了11种苦丁茶,并对所获得的指纹图谱进行特征峰指认和对比分析。结果表明:各种苦丁茶化学成分相同,而由于各成分间的相对含量的不同,使每种样品都有自己独特的红外谱图,不同产地、不同级别苦丁茶的红外吸收频率、吸收峰的相对强度都存在比较大的差异。同时还运用傅立叶变换红外光谱技术对不同产地、不同级别苦丁茶的混合化学体系进行了全组分快速分析,为苦丁茶的鉴别及质量控制提供了可靠的依据。     

多组分烷烃混合气体FTIR光谱定量分析新方法

提出一种核偏最小二乘(KPLS)特征提取耦合支持向量回归机(SVR)的新方法,用于实现气测录井中傅立叶变换红外(FTIR)光谱法对甲烷、乙烷、丙烷、异丁烷、正丁烷、异戊烷以及正戊烷7种组分混合气体的定量分析.采用KPLS方法对光谱数据进行特征提取,将得到的特征组分作为SVR的输入建立7组分气体的定量分析模型.对相同混合气体进行定量分析,结果显示,采用KPLS特征提取后,SVR模型对7种组分气体的预测均方根误差(RMSEP)分别为0.116、0.079、0.104、0.092、0.108、0.029和0.016,均小于线性偏最小二乘法(LPLS)、LPLS-SVR、KPLSR以及SVR模型的RMSEP.结果表明,KPLS-SVR法可以更好地提取隐含在混合气体FTIR光谱数据与其组分浓度之间的非线性特征,并有效地消除光谱数据噪声,大幅度降低数据维数,是一种有效的气测录井烷烃混合气体定量分析方法.     

红外光谱法热分析液晶相变过程

液晶物质在升温过程中会发生多个相转变过程 ,DSC热分析可测量这些相转变的能量变化 ,但却不能提供变化的微观原因和细节 .而温度升高对液晶样品的红外光谱图强度、峰形和吸收频率都有显著影响 .引起这样变化的原因一是热膨胀改变了分子内部化学键的力常数和相互作用 ,从而改变了分子振动偶极矩的性质 ;二是分子中有红外吸收的基团浓度随温度升高而改变 .红外光谱可以给出样品能量变化过程中分子结构变化的细节 ,通过计算还可获得分子结构变化的表观焓变 .前人做过的探索性工作 [1～ 3]都集中在一个或几个功能团的变化上 .在能量变化上仅…     

Probing the Structural Stability of and Enhanced CO2 Storage in MOF MIL‐68(In) under High Pressures by FTIR Spectroscopy

The unique structural topology of metal–organic framework (MOF) MIL‐68, featuring two types of channels with distinct pore sizes, makes it a promising candidate for application in gas storage and separation. In this study, the behavior of as‐made and activated MIL‐68(In) was investigated in a diamond‐anvil cell under high pressure by in situ IR spectroscopy. The framework exhibits high stability under compression up to 9 GPa, whereas the bridging OH groups appear to be very sensitive to compression. Pressure‐induced structural modifications were found to be completely reversible for as‐made MIL‐68(In) but irreversible for the activated framework. Moreover, the addition of Nujol as pressure‐transmitting medium makes the framework more resilient to pressure. Finally, when loaded with CO₂, the framework exhibited interesting differential binding affinities with CO₂ in the hexagonal and triangular pores at different pressures. The pressure‐enhanced CO₂ storage behavior and the guest–host interaction mechanism between CO₂ and the MOF framework were explored with the aid of Monte Carlo simulations. These studies demonstrated great potential for MIL‐68(In) in gas‐storage applications that require extreme loading pressures.     

Quantitative Analysis of Coal by Laser-Induced Breakdown Spectroscopy Using TEA CO2 Laser as the Excitation Source

Plasma Chemistry and Plasma Processing - This work presents a study of the applicability of laser-induced breakdown spectroscopy based on infrared transversally excited atmospheric CO2 pulsed laser...     

Near-critical CO2 in mesoporous silica studied by in situ FTIR spectroscopy

Attenuated total reflection Fourier transform infrared spectroscopy was used to correlate the band shift of the nu2 vibrational band of carbon dioxide with the density of the fluid. Upon adsorption of CO2 on mesoporous silica and a nonporous SiO2 film, additional bands were detected due to interactions of CO2 with SiO2. Near the saturation pressure for the porous samples, the absorbance of the nu2 band increased strongly, which was concluded to be caused by liquidlike CO2 inside the pores. Integration of single-beam-sample-reference spectra between bulk CO2 and CO2 adsorbing on the mesoporous silica coated on one part of the internal reflection element revealed excess adsorption type isotherms with sharp maxima at 21 degrees C. A flatter curve shape could be observed at 25 degrees C, which allowed estimating the pore critical temperature. Moreover, the density of the fluid inside and outside the pores could be compared. Over the investigated ranges of pressure, temperature, and pore size, the results evidenced that the CO2 density was always higher in the silica pores than in the bulk, even under supercritical conditions. This has important consequences on the pressure dependence of dissolution power and diffusivity of fluids in mesoporous solids. An overview is given on the influences of fluid phase behavior in the bulk and in the pores at various conditions on solubility and diffusivity.     

Structure Studies on Ion Coordination in 2,4-Dihydroxy-N-Octadecybenzylideneamine LB Films by UV-Vis Absorption and FTIR Spectroscopy

The coordination reaction of Cu(2+) ions with the Schiff base amphiphile 2,4-dihydroxy-N-octadecylbenzylideneamine in ultrathin organic LB films was probed by Fourier transform infrared (FTIR) transmission spectroscopy and UV-Vis electronic absorption spectroscopy. FTIR spectral changes owing to LB films of 2,4-dihydroxy-N-octadecylbenzylideneamine contacting aqueous Cu(OAC)(2) solution suggest the formation of ion-coordination films, which is corroborated by UV-Vis absorption spectra. The coordination reaction of the annealing film at different temperatures suggests that the microstructure of LB films had an important effect on the reaction rate. Detailed analysis shows that ion-coordination films take an isotropic unaxial orientation and exhibit phase transition behavior, which is determined by the different complex structures of headgroups and of subphase and surface film. Copyright 2000 Academic Press.     

Increasing Complexity in Adamantyl Thioethers Characterized by Rotational Spectroscopy

We report on the synthesis and characterization using high-resolution rotational spectroscopy of three bulky thioethers that feature an adamantyl group connected to a sulfur atom. Detailed experimental and theoretical structures are provided and compared with the 1,1′-diadamantyl ether. In addition, we expand on previous findings concerning microsolvation of adamantyl derivatives by investigating the cluster formation between these thioethers and a water molecule. The investigation of such clusters provides valuable insights into the sulfur-centered hydrogen bonding in thioethers with increasing size and steric repulsion.     

胃和结直肠癌的傅里叶变换红外光谱研究

利用傅里叶变换红外光谱仪及带ATR探头的中红外光纤系统测定了手术切除的胃癌、结直肠癌及相应的正常组织共31对标本粘膜面的反射红外光谱. 结果表明, 与正常组织相比, 癌组织的红外光谱发生明显变化: (1) 与脂类相关的谱带2955, 2920, 2870, 2850和1740 cm-1出现几率明显低于正常组织(P<0.001), I1460/I1400(I为峰强度)明显降低(P<0.001), 表明癌组织的脂类相对含量降低; (2) 与蛋白质相关谱带N—H和O—H明显红移(P=0.025), 表明N—H和O—H的氢键化程度增加, 癌组织的I3375/I1460, I1640/I1460和I1550/I1460明显升高(P<0.01), 表明癌组织的蛋白质相对于脂类的含量增加, 癌组织的HW1550/I1550(HW为半高宽)明显升高(P=0.036), HW1550则明显降低(P=0.05), 表明癌组织中蛋白质的二级结构发生显著变化; (3) 与醣类相关谱带中癌组织的I1160/I1460降低(P=0.002), 结合组织化学染色, 推测可能是癌组织表面的糖蛋白明显减少造成的, 而I1120/I1460升高(P=0.019)则可能是癌组织表面的糖原颗粒增加所致. (4) 与核酸相关谱带中癌组织的PO的反对称伸缩振动蓝移(P=0.033), 表明癌组织中磷酸基团的氢键化程度降低. 研究结果表明, 红外光谱有望成为诊断恶性肿瘤的有力工具.     

Environment Polarity in Proteins Mapped Noninvasively by FTIR Spectroscopy

The polarity pattern of a macromolecule is of utmost importance to its structure and function. For example, one of the main driving forces for protein folding is the burial of hydrophobic residues. Yet polarity remains a difficult property to measure experimentally, due in part to its non-uniformity in the protein interior. Herein, we show that FTIR linewidth analysis of noninvasive 1-(13)C=(18)O labels can be used to obtain a reliable measure of the local polarity, even in a highly multi-phasic system, such as a membrane protein. We show that in the Influenza M2 H(+) channel, residues that line the pore are located in an environment that is as polar as fully solvated residues, while residues that face the lipid acyl chains are located in an apolar environment. Taken together, FTIR linewidth analysis is a powerful, yet chemically non-perturbing approach to examine one of the most important properties in proteins - polarity.     

Conformations and Structures of Ethoxycarbonyl Isothiocyanate Revealed by Rotational Spectroscopy

The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy. Two sets of rotational spectra belonging to conformers TCC (with the backbone of C\begin{document}$ - $\end{document}C\begin{document}$ - $\end{document}O\begin{document}$ - $\end{document}C, C\begin{document}$ - $\end{document}O\begin{document}$ - $\end{document}C=O, and O\begin{document}$ - $\end{document}C(=O)\begin{document}$ - $\end{document}NCS being trans, cis, and cis arranged, respectively) and GCC (\begin{document}$ gauche $\end{document}, cis, and cis arrangement of the C\begin{document}$ - $\end{document}C\begin{document}$ - $\end{document}O\begin{document}$ - $\end{document}C, C\begin{document}$ - $\end{document}O\begin{document}$ - $\end{document}C=O, and O\begin{document}$ - $\end{document}C(=O)\begin{document}$ - $\end{document}NCS) have been measured and assigned. The measurements of \begin{document}$ ^{13} $\end{document}C, \begin{document}$ ^{15} $\end{document}N and \begin{document}$ ^{34} $\end{document}S mono-substituted species of the two conformers have also been performed. The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and \begin{document}$ ^{14} $\end{document}N quadrupole coupling constants, which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate. For conformer TCC, the values of \begin{document}$ P_{ \rm{cc}} $\end{document} keep constant upon isotopic substitution, indicating that the heavy atoms of TCC are effectively located in the \begin{document}$ ab $\end{document} plane.     

Rotational Spectroscopy Probes Water Flipping by Full Fluorination of Benzene

The topology of the interaction of water with benzene changes drastically upon full H→F substitution on the aromatic ring: the weak O−H⋅⋅⋅π hydrogen bond is replaced by a O⋅⋅⋅π linkage, of about the same strength. Hexafluorobenzene–water appears to be the prototype system to investigate this kind of weak bond. The pulsed Fourier transform microwave technique has been used for the detection of the rotational spectra of the normal species and five isotopologues which unambiguously led to the identification of the geometry. Quantum mechanical calculations have been performed to interpret the experimental evidence.     

FTIR study on the formation of TiO2 nanostructures in supercritical CO2

TiO(2) nanospherical and fibered structures were obtained via a one-step sol-gel method in supercritical carbon dioxide (scCO(2)) involving polycondensation of the alkoxide monomers titanium isopropoxide (TIP) and titanium butoxide (TBO) with acetic acid (HAc). The resulting materials were characterized by means of electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermal analysis (TGA), and attenuated total reflection Fourier transmission infrared (ATR-FTIR) analysis. Depending on the experimental conditions, TiO(2) anatase nanospheres with a diameter of 20 nm or TiO(2) anatase/rutile nanofibers with a diameter of 10-100 nm were obtained. Fiber formation was enhanced by a higher HAc/Ti ratio and the use of the titanium isopropoxide (TIP) monomer. The mechanism of the microstructure formation was studied using in situ FTIR analysis in scCO(2). The FTIR results indicated that the formation of nanofibers was favored by a titanium hexamer that leads to one-dimensional condensation, while nanospheres were favored by a hexamer that permits three-dimensional condensation.