首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 152 毫秒
1.
本文研究表明通过膜厚控制和表面等离激元增强方法可有效区分隐藏界面和空气表面的和频振动光谱信号. 以氟化钙基底支撑的PMMA薄膜为模型,观察到隐藏界面和空气表面对和频信号贡献的变化. 通过监控羰基和甲基伸缩振动基团,发现薄PMMA膜的和频信号来自PMMA/空气表面的化学基团-CH2、-CH3、-OCH3和C=O,而厚PMMA膜的和频信号则来自基底/PMMA埋层界面的-OCH3和C=O基团. 随制膜浓度增大,埋层界面C=O基团的取向角从65°下降到43°,且浓度大于或等于0.5 wt%时,取向角等于45°±2°. 相比之下,空气表面C=O的取向角落在21°∽38°之间. 在金纳米棒存在条件下,表面等离激元可以极大地增强和频信号,尤其是来自埋层界面信号.  相似文献   

2.
研究了两种具有两条脂链的羟基卟啉在气液界面上的成膜性能及其LB膜。UV-Vis光谱表明,两种卟啉在LB膜中的聚集态不同,卟啉环上脂链和羟基呈对称了代时形成J-聚体,呈同侧取代时形成氢键聚集体。利用偏振UV-Vis吸收谱测定了LB膜中卟啉环的取向。结果表明,侧链和羟基的相对位置对环的取向没有影响,但影响膜中平均分子截面积的大小和环间的距离,因而影响膜中分子的聚集态。  相似文献   

3.
PET与SAN/PAN复合膜界面的 FTIR-ATR研究   总被引:1,自引:0,他引:1  
应用傅里叶衰减全反射红外光谱(FTIR-ATR)技术对聚对苯二甲酸乙二酯(PET)表面形成不同厚度的超薄苯乙烯-丙烯腈共聚物(SAN)和聚丙烯腈(PAN)的共混物膜及其SAN/PAN共混物膜的厚度、界面层PET亚甲基的构像变化等进行研究,结果表明PET表面共混物膜的厚度随共混物混合液中SAN含量的增加而增加,界面层成膜物质与基材的分子链段间发生了相互渗透和扩散,分子链的极性越相近,越容易成膜.对PET红外光谱吸收峰的A1340/A1410进行定量研究表明,在成膜过程中,PET分子链的亚甲基构像由反式向旁式转变,引起界面层PET的结晶度降低.FTIR-ATR是分析复合膜界面层结构信息的有效方法.  相似文献   

4.
本研究利用红外光谱研究不同压力下离子液体1-Methy1-3-propylimidazolium iodide([MPIM][I])与石墨烯及其氧化物的相互作用.结果表明,[MPIM][I]对压力的变化具有高敏感度,咪唑环与烷基链在0.4 GPa时产生相变化,可明显观察到吸收峰的裂解,且连续加压会导致咪唑环与烷基链的振动频率蓝移.[MPIM][I]与石墨烯作用时加压至2.5 GPa也未观测到相变化的产生,且咪唑环与烷基链的振动频率蓝移趋势也不明显;[MPIM][I]与石墨烯氧化物作用时咪唑环与烷基链的结果与添加石墨烯时几乎相同.石墨烯氧化物具有羟基、羧基、环氧基等共价键结在其表面,这些羟基会扰动[MPIM][I]中的咪唑环与烷基链,导致在常压下振动频率发生蓝移,进而表明石墨烯表面的官能基团会与离子液体产生相互作用.  相似文献   

5.
利用三维朗之万动力学模拟研究了多价态高分子链在受体平面上的吸附行为。其在受体平面上的吸附具有超选择性,随着高分子链上配体浓度的增大,发生超选择性吸附时的平面受体浓度范围变窄;而超选择性吸附最显著时的平面受体浓度,即最佳平面受体浓度随着链上配体浓度的增大而减小。对处于吸附态的多价态高分子链的构象性质进行了系统地研究,发现链的平衡回转半径Rg及其水平分量Rg},随着平面受体浓度的增大都存在极大值。其平衡回转半径Rg与其链长N间的标度指数表明当平面受体浓度的增大时,处于吸附态的链构象介于二维链构象和三维链构象之间;随着平面受体浓度的进一步增大,吸附在平面上的多价态高分子链发生轻微的塌缩  相似文献   

6.
本文使用波长为2.8 μm的分布式反馈激光器来测量水汽辉光放电产生的物种. 使用浓度调制光谱仅观察到OH自由基和瞬态H2O分子的吸收光谱. 吸收峰的强度和方向随解调相位而变化,但是H2O的一个吸收峰的方向始终与其它峰相反. OH和H2O的不同光谱取向反映了能级中粒子数量的增加或减少. 如果在放电过程中可以检测到更多的瞬态物种,则可以更好地研究H2O的激发、电离和分解动力学. 研究表明,浓度调制光谱的解调相位关系可以用来研究分子能级的布居数变化.  相似文献   

7.
和频振动光谱(SFG-VS)研究中由基团在界面上取向所引起的光谱增强或相消的干涉现象为研究分子在界面上的绝对取向提供了一种直接的测量方法. 这一方法比SFG实验中复杂的相位测量方法更为直接和简单可行. 以在空气/水界面取向已知的对羟基苯腈(PCP)分子的氰基(-CN)基团为相位参考来获得3,5-二甲基对羟基苯腈(35DMHBN)和2,6-二甲基对羟基苯腈(26DMHBN)分子在空气/水界面的取向信息. 通过对这三种分子的水溶液和它们两两混合溶液界面上-CN基团和频振动光谱强度的比较,发现在空气/水界面的3  相似文献   

8.
本文利用程序升温脱附技术研究了氧空位浓度对甲基基团和CO在R-TiO2(110)表面吸附的影响. 结果表明,随着氧空位浓度的变化,吸附在桥氧位的甲基基团和吸附在五配位Ti4+位点上的CO分子的脱附温度呈现了不同的趋势,揭示了表面缺陷可能对R-TiO2(110)不同位点上的物质吸附具有重要影响.  相似文献   

9.
利用偏光显微镜及小角X射线散射研究了25 °C下由1-十二烷基-3-甲基咪唑氯化物[C12mim]Cl和水、[C12mim]Cl和不同的醇(正丁醇、正戊醇、正己醇、正辛醇)所形成的二元体系的相行为. 结果表明:[C12mim]Cl和水可以形成六角相,其晶格参数随[C12mim]Cl含量的增多而递减;[C12mim]Cl和不同的醇可以形成层状相,且醇的碳链越长,层状相越易形成. 与水做溶剂相比,在[C12mim]Cl/辛醇体系中,随[C12mim]Cl含量的增加,层状相的层间距反而增大. 通过变温小角X射线散射和差示扫描量热法研究表明:层状相在高于室温的较大温度范围内是稳定的. 由于温度升高使[C12mim]Cl的碳氢链变软并易于缠结,导致层间距随温度的升高而减小. 通过红外光谱可以证明包含咪唑头基、氯离子和辛醇的氢键网络的存在. 疏溶剂力和氢键网络的协同作用是[C12mim]Cl能形成六角相和层状相的关键.  相似文献   

10.
周倩  于淼  张秀玲 《光散射学报》2013,25(2):209-213
采用自行设计的介质阻挡放电反应器,以氩气和离子液体为放电介质,实现大气压下稳定的气(等离子体)-液(离子液体)等离子体放电,并运用光谱法在线诊断氩等离子体光谱。考察了不同咪唑基离子液体以及放电参数对大气压氩气介质阻挡放电光谱的影响。结果表明,离子液体的引入降低了氩气放电光谱的强度,谱峰强度与离子液体阳离子咪唑环上的碳链长度有关,且随碳链长度增加,谱峰强度降低;同时阴离子结构对称性低的离子液体,谱峰强度较低。加入离子液体后氩谱随放电电压及放电频率变化均呈现峰值变化。  相似文献   

11.
The newly prepared ionic liquid, 1-butyl-3-methylimidazolium benzoate, ([bmim][BA]), was found to enhance the fluorescence of Eu3+ and Tb3+. The fluorescence enhancement resulted from a sensitization of the lanthanide fluorescence by the benzoate anion of the ionic liquid, [bmim][BA], and a reduction in the non-radiative channels in the non-aqueous environment provided by the ionic liquid. However, the fluorescence enhancement of the lanthanides in the ionic liquid was limited due to the operation of the inner filter effect, which resulted from the strong absorption of the benzoate. The inner filter effect was minimized by observing the Eu3+ fluorescence using a front face geometry and also by diluting the lanthanide-[bmim][BA] system, using another ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), as a solvent. In the case of Tb3+, the emission from the lanthanide was masked by the strong emission from the ionic liquid in the region 450-580 nm. The long lived Tb3+ emission was therefore observed using delayed gated detection, where an appropriate delay was used to discriminate against the short lived emission from the ionic liquid. The large fluorescence enhancement due to ligand sensitized fluorescence observed with [bmim][BA] diluted in [bmim][Tf2N], leads to nanomolar detection of the lanthanides. This is, to the best of our knowledge, the first report of an ionic liquid being employed for ligand sensitized fluorescence enhancement of lanthanides.  相似文献   

12.
We have investigated the pressure-induced crystallization of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) associated with the conformational changes of [bmim]+ by Raman spectroscopy. [bmim]+ has trans-trans and gauche-trans (GT) conformers of the butyl side chain at ambient pressure. Our result revealed that liquid to solid-phase transition occurs at 0.2–0.4 GPa region, where the GT conformer becomes dominant. We found that the GT dominant state continues up to 4 GPa.  相似文献   

13.
The use of an active nano-interface designed from gold nanoparticles embedded on ionic liquid for DNA damage resulted from formalehyde (HCHO) is reported in this article. The active nano-interface was fabricated by depositing gold nanoparticles on the ionic liquid 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF4]). A glassy carbon electrode modified by this composite film was fabricated to immobilize DNA for probing into the damage resulted from HCHO. The modifying process was characterized by X-ray photoelectron spectroscopy, atomic force microscopy and electrochemistry involving electrochemical impedance spectroscopy. It was found that the modified film performs effectively in studying the DNA damage by electrocatalytic activity toward HCHO oxidation.  相似文献   

14.
In this work, we have used a simple equation of state (EoS) to predict the density and other thermodynamic properties such as isobaric expansion coefficient, αP , isothermal compressibility, κT, and internal pressure, Pi, for nine ionic liquids including trihexyl (tetradecyl) phosphonium chloride ([(C6H13)3P(C14H29)][Cl]), trihexyl (tetradecyl) phosphonium acetate ([(C6H13)3P(C14H29)][Ac]), trihexyl (tetradecyl) phosphonium bis {(trifluoromethyl) sulfonyl} amide ([(C6H13)3P(C14H29)][NTf2]), 1-butyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide ([bmim][NTf2]), 1-hexyl-3-methylimidazolium bis {(trifluoromethyl) sulfonyl} amide ([hmim][NTf2]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-butyl-3-octylimidazolium tetrafluoroborate ([omim][BF4]), 1-butyl-3-octylimidazolium hexafluorophosphate ([omim][PF6]), and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) at different temperatures and pressures. A wide comparison with experimental and literature data has been made. The results show that this EoS can be used to reproduce and predict different thermodynamic properties of ionic liquids within experimental errors.  相似文献   

15.
The high data point density measurements of 1H→11B cross-polarization (CP) kinetics upon magic-angle spinning (MAS) of [bmim][BF4] confined in mesoporous SBA-15 and MCM-41 were carried out. The complex shaped 11B CP MAS signals were observed in both silica and decomposed into two Lorentz components. This points towards the possibility of bimodal distribution of [bmim][BF4] in the studied confinements. The convergence of classical and non-classical spin coupling models was deduced processing CP kinetic curves. A good fit of the theoretical curves to the experimental data was achieved using both models without any non-random deviations between theory and experiment to appear. The convergence of spin coupling models was discussed in terms of relatively high mobility of BF4 ? anion respect to the cation and the dynamics of anions in pores. These factors delete the borders between spin clusters. The spin diffusion along the pore surfaces in MCM-41 is more than twice faster than in SBA-15.  相似文献   

16.
The second‐order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1‐(1‐butyl)‐3‐methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25 °C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi‐parameter correlation of logk2 versus solute–solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen‐bond donor acidity (α) and hydrogen‐bond acceptor basicity (β) of media are the main factors influencing the reaction rate constant. The proposed three‐parameter model shows that the reaction rate constant increases with Sp, α and β parameters. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

17.
The electrical conductances of very dilute solutions of the ionic liquids 1-ethyl-3-methylimidazolium tetrafluoroborate [emim][BF4] and 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] in the low-permittivity solvent dichloromethane have been measured in the temperature range from 278.15 to 303.15 K at 5 K intervals. The data was analyzed assuming the possible presence of contact (CIP) and solvent-separated (SSIP) ion pairs in the solution on the basis of lcCM model to obtain ionic association constants, K A, and the limiting molar conductivities, Λo, of these electrolytes. The examined ionic liquids are strongly associated in dichloromethane over the whole temperature range. From the temperature dependence of the limiting molar conductivities, the Eyring’s activation enthalpy of charge transport was determined. The thermodynamic functions such as Gibbs energy, entropy, and enthalpy of the process of ion pair formation were calculated from the temperature dependence of the association constants.  相似文献   

18.
The binary composite ionic liquid mixtures composed of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) and 1-butyl-3-methylimidazolium acetate ([bmim][Ac]) were studied and used in electroreduction of nitrobenzene for the first time. 1H NMR and Fourier transform infrared (FTIR) spectroscopy were carried out to acquire a deep understanding of the interaction of binary ionic liquids, and UV/Vis spectroscopy was used to study the interaction between the mixture of ionic liquids and nitrobenzene. It was found that chemical shifts of all protons were changed and significant changes in the anion IR bands were induced, and the UV maximum absorption wavelength and absorbance of nitrobenzene in binary ionic liquids were different from those in the neat ionic liquid. The electrochemical reduction behavior of nitrobenzene in binary composite ionic liquids on platinum electrode was studied by cyclic voltammetry, in situ Fourier transform infrared spectroscopy, and constant potential electrolysis. Results indicated that the reduction of nitrobenzene in binary composite ionic liquids demonstrated higher current densities with a more positive potential, and the product (azobenzene) showed higher yield and selectivity in the composite ionic liquids than in the neat ionic liquids; the concentrations of water in the binary mixtures of ionic liquids had great effect on the electrochemical behavior of nitrobenzene. In the end, the mechanism of reduction of nitrobenzene in binary mixtures of ionic liquids was discussed.  相似文献   

19.
Synthesis of tetrasubstituted pyrroles by the three-component condensation reaction of acid chlorides, dialkyl acetylenedicarboxylates, and amino acids in the presence of various room-temperature ionic liquids (RTILs) as catalysts in water is reported. Among the ionic liquids used, the basic functionalized ionic liquid, butyl methyl imidazolium hydroxide [bmim]OH, was the most effective catalyst. The influence of reaction temperature, reaction time, and amount of ionic liquid on the reaction was investigated. The [bmim]OH/H2O catalyst system could be reused for at least five recycles without appreciable loss of efficiency.  相似文献   

20.
Densities and speeds of sound have been measured for the binary mixtures of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] with ethylene glycol monoethyl ether (EGMEE), diethylene glycol monoethyl ether (Di-EGMEE), triethylene glycol monoethyl ether (Tri-EGMEE) over the whole composition range at atmospheric pressure. Experimental densities have been used to estimate excess molar volumes, VE. Changes in isentropic compressibility, Δκs have been estimated by using experimental speed of sound and density values. Excess properties were fitted to the Redlich-Kister polynomial equation to obtain the binary coefficients and the standard errors. The molecular scale interactions between ionic liquid and alkoxyalkanols have been investigated through 1H NMR spectroscopy. NMR chemical shifts for hydroxyl group of alkoxyalkanols and their deviations show hydrogen bonding interactions of varying strengths between ionic liquid and alkoxyalkanol in their binary mixtures.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号