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1.
氯铝酸离子液体酸性的红外光谱探针和量子化学研究   总被引:3,自引:0,他引:3  
文章采用吡啶探针红外光谱、吡啶递增吸附实验研究和量子化学理论计算相结合的方法深入研究了氯铝酸离子液体的酸性及氯铝酸离子液体Lewis酸位Al2Cl7-与吡啶吸附之间的相互作用机理。通过实验和理论计算研究发现,Al2Cl7-,AlCl4-阴离子具有吸电性,能够吸引吡啶环上的孤对电子产生吸附作用,具有Lewis酸性,它们分别呈现吡啶探针红外光谱Lewis酸特征峰;通过红外光谱特征峰峰位、键长及电荷分布分析表明Al2Cl7-的酸性强于AlCl4-;氯铝酸离子液体Lewis酸位Al2Cl7-与吡啶吸附的机理为:当吡啶含量小时,仅存在Py-Al2Cl7-吸附;当吡啶量增加到一定程度时,Py-Al2Cl7-配位络合物中的AlCl4-容易与吡啶发生吸附解离为Py-AlCl4-配位络合物和Py-AlCl3配位络合物,导致离子液体吡啶递增吸附红外特征峰发生变化。  相似文献   

2.
用量子化学计算的方法,采用三甲基氧膦(TMPO)、吡啶和三甲基膦(TMP)3种探针分子,研究了工业上常用的3种分子筛H-Y、H-ZSM5、H-MOR的Bronsted酸强度,讨论了这3种探针分子化学位移与Bronsted相对酸强度的相关性,揭示了各种探针分子在表征Bronsted酸性上的适用性.  相似文献   

3.
以蒽醌(AQ)作为探针分子,利用激光光解技术研究了咪唑型离子液体1-丁基-3-甲基咪唑六氟化磷([bmim][PF6])与乙腈(MeCN)混合体系中的光化学反应行为.研究结果表明,离子液体[bmim][PF6]自身可与激发三线态的蒽醌分子(3AQ*)进行反应,且表观反应速率常数随着[bmim][PF6]/MeCN比例的不同呈现特殊规律性的变化.在离子液体的摩尔分数(xRTIL)为0.06处观察到一个明显的临界点.当xRTIL<0.06时,表观速率常数随xRTIL的增大而增大;而当xRTIL>0.06时,表观速率常数随xRTIL的增大而减小.文章给出了[bmim][PF6]/MeCN混合体系中激光诱导化学反应的动力学常数,并初步推测了其反应机理,进一步揭示了离子液体[bmim][PF6]的一些新的光化学特性.  相似文献   

4.
银纳米立方体的合成及其SERS活性研究   总被引:1,自引:0,他引:1  
用乙二醇还原硝酸银,以聚乙烯吡咯烷酮作表面活性剂合成了银纳米立方体晶粒,并以吡啶和SCN-作为探针分子初步研究了银纳米立方体晶粒组装体系的SERS活性。当探针分子吸附于银纳米立方体晶粒上时,吡啶和SCN-的谱峰强度明显增强,表明银纳米立方体晶粒可望作为SERS活性基底。通过研究探针分子的SERS强度与粒子尺度关系,也有望用于表征银纳米立方体晶粒的光学性质。  相似文献   

5.
冠醚铕镧异核配合物的合成表征及荧光性质   总被引:1,自引:0,他引:1  
以 18冠 6为配体 ,分别与高氯酸铕和高氯酸镧在乙腈介质中反应 ,合成冠醚铕和冠醚镧配合物 ;两种冠醚配合物与交联配体———对苯二甲酸反应 ,形成了对苯二甲酸冠醚铕镧异核稀土超分子配合物。由元素分析数据推测 ,超分子配合物的组成式为EuLaL2 L′(ClO4) 4 ·6H2   [L =18 C 6 ,L′ =p C6H4(COO-) 2 ],测定了超分子配合物的红外光谱 ,紫外光谱 ,摩尔电导及荧光光谱。结果表明 ,冠醚和对苯二甲酸根与稀土离子配位 ,而高氯酸根离子处于配合物的外界 ,铕镧异核稀土超分子配合物的荧光强度是冠醚铕的 8倍多。  相似文献   

6.
郑安民  邓风 《波谱学杂志》2006,23(4):543-544
本论文将量化计算和NMR实验方法相结合,研究了有机分子在分子筛孔道中的吸附以及分子筛H-MCM-22和重要烷基化催化剂BF3/γ-Al2O3的酸结构和酸强度, 同时我们成功将组合量子化学ONIOM-GIAO方法用到大体系化学位移的计算.  (1) 将ONIOM-GIAO方法用来预测有机固体化合物和吸附在分子筛孔道中有机小分子的13C化学位移屏蔽张量. 以前该方法仅被用来研究小的体系,我们成功将其用于预测氨基酸分子和一系列被吸附有机分子的13C的化学位移. ONIOM-GIAO方法充分将氨基酸晶体(或分子筛骨架)的空间结构和静电势的影响考虑到活性中心化学位移的计算中,计算得到的13C化学位移与实验值符合得非常好.  (2) 分子筛中铝原子和Brǒnsted酸性质子的分布将直接影响到分子筛的催化反应活性. 我们利用ONIOM方法研究了铝原子在分子筛MCM-22骨架中的分布状态,结合探针分子(丙酮和三甲基膦氧)的固体NMR实验,确定了MCM-22分子筛的酸强度和酸分布,合理地解释该分子筛对某些催化反应所表现出的独特选择性.  (3) 结合固体NMR实验结果,用量化计算方法从原子分子水平揭示了重要烷基化催化剂BF3/γ-Al2O3酸位形成机理,提出来了BF3表面修饰γ-Al2O3后所产生Brǒnsted和Lewis酸性位的结构. 理论计算提出的酸性位的结构和酸强度特征完全符合NMR的实验结果.  (4) 量化计算表明当异丙醇与萘分子共吸附在丝光沸石孔道中,异丙醇呈现被分子筛Brǒnsted酸质子化的趋势. 这是由于萘分子大的共轭体系所表现出的强溶剂诱导效应,分散了异丙醇碳正离子的电荷,这是一种新的非极性溶剂所产生的诱导效应.  相似文献   

7.
Tm3+掺杂SiO2-Al2O3-PbF2-AlF3玻璃的光谱特性   总被引:2,自引:0,他引:2  
用高温熔融法制备了不同Tm3 摩尔分数掺杂的摩尔分数比为0.3(SiO2)…0.1(Al2O3)…0.1(AlF3)…0.5(PbF2)…x(Tm2O3)(摩尔分数x=0.5%,1.0%,2.0%,3.0%)玻璃。从吸收光谱特性出发,应用Judd-Ofelt理论,计算得到了Tm3 的J-O强度参量(Ω2,Ω4,Ω6)及Tm3 各激发能级的自发辐射跃迁概率、荧光分支比以及辐射寿命等光谱参量。在808nm波长的激光二极管激发下,研究了不同Tm3 掺杂摩尔分数下玻璃在约1.47μm与约1.8μm处的荧光特性,在掺杂摩尔分数约达到2.0%时,在1.8μm处的荧光强度达最大,然后随着掺杂摩尔分数的增大,其荧光强度反而降低。作者从Tm3 的交叉弛豫与摩尔分数猝灭效应解释了这一荧光强度变化的规律,同时,根据McCumber理论计算了Tm3 跃迁3H6→3F4的吸收截面和跃迁3F4→3H6的受激发射截面。  相似文献   

8.
离子液体具有熔点低、可忽略的蒸气压、电化学窗口宽、热稳定性高和良好的导电性等独特性能,引起了化学工业和相关领域的广泛关注。离子液体具有低蒸气压,不会造成空气污染,但这并不意味着它们对环境完全无害。大多数离子液体易溶于水,可能会因为意外泄漏或通过污水进入水生环境。常用离子液体[BMIM][PF6]和[BMIM][BF4]的水溶液中,很容易形成氢氟酸,磷酸,具有一定的腐蚀性。将离子液体列为绿色溶剂,也需要提供其关于代谢和降解的毒性、生态毒性研究数据,或者其对环境影响的数据,离子液体在不同溶剂中的检测方法是非常重要的。离子液体的光谱分析法用量较少、方法简单、结果准确。离子液体和许多有机溶剂互溶,可形成均一、稳定的溶液。荧光检测法具有灵敏度高,选择性好,线性范围宽和受外界干扰少等优点。本工作研究了醋酸N-正辛基吡啶(OP-OAc)离子液体在水、乙醇、乙腈、乙酸等4种溶剂中的荧光光谱。研究结果表明,OP-OAc离子液体在不同溶剂中的荧光强度:I乙酸I乙腈I乙醇I;最大发射波长的大小顺序:λem, 水λem, 乙醇λem, 乙腈λem, 乙酸;它们的最大发射波长相对于激发波长发生红移;水中OP-OAc的荧光强度与浓度存在较高的相关性;当加入的甲醇、乙醇、乙腈溶剂不断增加时,OP-OAc离子液体的荧光强度增加,溶剂与水的比例为8∶2时,OP-OAc离子液体的荧光强度最强,溶剂的比例超过80%时,荧光强度突然降低;水中OP-OAc离子液体在pH 10时,荧光强度最高,在pH 14时,荧光强度最低。  相似文献   

9.
银和去合金银-金纳米粒子的SERS活性研究   总被引:4,自引:2,他引:2  
用乙二醇还原硝酸银,聚乙烯吡咯烷酮作表面活性剂合成了大量的银纳米颗粒。银纳米颗粒和HAuCl4发生置换反应后形成去合金银-金纳米粒子。以吡啶和SCN-作为探针分子研究了它们的SERS活性。结果表明,当探针分子吸附于银纳米颗粒和去合金银-金纳米粒子上时,探针分子的特征振动峰强度增强、频率发生位移。SERS可表征纳米粒子物理和化学性质的变化。  相似文献   

10.
Xu CY  Yan L  Liu YW  Li Y  Hua YX  Zhang PX 《光谱学与光谱分析》2010,30(10):2658-2662
离子液体作为一种绿色介质,在电化学领域中的研究正在兴起,引起了研究者的浓厚兴趣。文章运用循环伏安法研究了离子液体(1-丁基-3-甲基咪唑四氟硼酸盐,[bmim]BF4)存在时,酸性硫酸铜溶液中铜在铜电极上的电化学沉积行为。研究表明,[bmim]BF4的加入使铜的沉积峰电位负移,沉积电流增加。采用扫描电镜(SEM)和X射线衍射(XRD)对铜镀层的形貌及结构进行表征,结果显示离子液体的存在可使铜镀层的层状晶粒尺寸减小,镀层出现(220)高择优取向。以甲基橙(MO)为探针分子,研究了所得铜镀层的表面增强拉曼散射(SERS)效应,发现离子液体存在下得到的铜镀层是较好的SERS基底,具有良好的增强效果及稳定性。对MO分子的增强因子可达4.7×105,而且保存了60天后,其检测灵敏度没有显著的降低。  相似文献   

11.
The fixation of carbon dioxide with epoxide catalysed by a series of carboxylic acidic functionalised ionic liquids (ILs) catalysts is investigated by density functional theory method. Except for the catalysts reported by the experiment, the catalytic activity of a new designed catalyst (4c see Scheme 1) is also explored. These ILs are categorised into four groups according to the different cation structures and number of functional groups. The effects of different chain length, anion, and cation structure on the catalytic activity are explored. The elongation of alkyl chain length in cation will increase the product yield, while increasing the chain bulk has almost negligible effect on the enhancement of catalytic activity. Utilisation of imidazole group as the cation is better than pyridine group. And the cation with two functional groups will have a better catalytic activity than that with one functional group.  相似文献   

12.
Novel Lewis acidic ionic liquids containing thionyl cations and chlorozincate anions were obtained by one pot synthesis for the first time. This ionic liquid is used as catalyst for Friedel–Crafts alkylation of benzalazines and acetophenone azines for the synthesis of substituted diaryl alkanes. The products were characterized by elemental and spectral (FT-IR, 1H-NMR and 13C-NMR) analyses.  相似文献   

13.
Ionic liquids, ILs, based on fluorinated pyrrolidinium and piperidinium ammonium cations and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs including melting point, glass transition and degradation temperatures, viscosity, ionic conductivity, and electrochemical stability were determined and compared to alkyl pyrrolidinium and piperidinium ILs. The incorporation of a CF3 group instead of a CH3 induces an increase of the IL viscosity, thus a conductivity decrease. However, good ionic conductivity is obtained with fluorinated pyrrolidinium IL. Cyclic amine ILs with propyl alkyl chain or fluorinated ammonium exhibit very high electrochemical stability toward oxidation. The effect of the addition of LiTFSI on the IL properties was studied with the same methodology.  相似文献   

14.
The surface acidity of mesoporous molecular sieves of aluminum and titanium was evaluated using four different techniques: n-butylamine volumetry, cyclohexylamine thermodesorption, temperature-programmed desorption of ammonia and adsorption of pyridine. The nature, strength and concentration of the acid sites were determined and correlated to the results of a probe reaction of anthracene oxidation to 9,10-anthraquinone (in liquid phase). In general, the surface acidity was highly influenced by the nature, location and coordination of the metal species (Al and Ti) in the mesoporous samples. Moderate to strong Brönsted acid sites were identified for the Al-MCM-41 sample in a large temperature range. For mesoporous materials containing Ti, the acidity was represented by a combination of weak to moderate Brönsted and Lewis acid sites. The Ti-HMS sample exhibits a higher acidity of moderate strength together with a well-balanced concentration of Brönsted and Lewis acid sites, which enhanced both conversion and selectivity in the oxidation reaction of anthracene.  相似文献   

15.
A. Fernicola  B. Scrosati  H. Ohno 《Ionics》2006,12(2):95-102
This paper reviews the various classes of ionic liquids (ILs) in view of their established and expected applications in advanced electrochemical devices, such as lithium batteries, fuel cells, and supercapacitors. In this respect, particular attention is devoted to aprotic and protic ILs, with a related discussion in terms of their thermal and transport properties. In addition, the role in the electrochemical technology of a new class of ILs having cation and anion tethered in an intramolecular form is stressed. Due to their emerging importance, IL-based polymers are finally reported and discussed. A conclusion, where the expected evolution of the ILs research and development is evaluated, is also included.  相似文献   

16.
The redox potentials of ferrocene and decamethylferrocene were determined in a number of molecular and ionic solvents and used as a probe for polarity of room temperature ionic liquids (ILs). No macroscopic solvent property is simply related to redox potentials. Single empirical solvent parameters also are not able to describe the differences in potentials. Instead, Kamlet–Taft multiparameter relationship fits well ferrocenes redox potentials variation, with both molecular solvents and ILs, well describing specific solvent–solute interactions with the two probes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
It is shown that present models of Lewis acidity or basicity and of surface states on ionic solids have substantial overlap, although the former is designed to describe chemical interactions at the surface site, and the latter electron capture. The site requirements for a Lewis acid are compared to the requirements for an acceptor surface state to suggest under what conditions a site should exhibit both strong acidity and a deep surface state: The expected influence of electronic properties of the solid on acid strength, and the influence of adsorbed water, acids or bases on surface state energies are discussed. Experimental measurements are reported where both chemical acidity measurements and electrical surface state measurements are made on a series of Lewis acids. A positive correlation is found. Where there is correlation, it is concluded that chemical interaction measurements should provide a valuable tool to describe the energy distribution of surface states on a semiconductor surface. Also, the use of the surface state models and measurements from semi-conductor physics should help in understanding and classifying acid and basic sites on ionic semiconductors and insulators.  相似文献   

18.
Surface structures of equimolar mixtures of imidazolium-based ionic liquids (ILs) having a common cation (1-butyl-3-methylimidazolium ([C4MIM]) or 1-hexyl-3-methylimidazolium ([C6MIM])) and different anions (bis(trifluoromethanesulfonyl)imide ([TFSI]), hexafluorophosphate ([PF6]) or chlorine) are studied using high-resolution Rutherford backscattering spectroscopy (HRBS). Both cations and anions have the same preferential orientations at the surface as in the pure ILs. In the mixture, the larger anion is located shallower than the smaller anion. The [TFSI] anion is slightly enriched at the surface relative to [PF6] with coverage of ~ 60% for the equimolar mixtures of [C4(6)MIM] [TFSI] and [C4(6)MIM] [PF6]. No surface segregation is observed for [C6MIM] [TFSI]0.5[Cl]0.5 and [C6MIM] [PF6]0.5[Cl]0.5. These results are different from the recent TOF-SIMS measurement where very strong surface segregation of [TFSI] was concluded for the mixture of [C4MIM] [TFSI] and [C4MIM] [PF6].  相似文献   

19.
何建玲 《光谱实验室》2011,28(5):2480-2483
室温离子液体是由特定的阳离子和阴离子构成,具有独特的性质和功能。将路易斯酸型离子液体应用于苯和环己烯的烷基化反应,考察了苯与环己烯摩尔比、反应温度、反应时间对烷基化反应产物收率的影响。结果表明以制备的咪唑盐离子液体为催化剂,在反应温度80℃、反应时间1.0h、苯烯摩尔比8:1的条件下,所得环己基苯的产物收率最高,为86.75%。离子液体可重复使用,活性基本没有降低。  相似文献   

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