荧光探针法研究胶原蛋白的水溶液聚集状态

利用一种分子内电荷转移化合物３ 甲氧基 ４’ Ｎ，Ｎ 二甲氨基黄酮（ＤＭＭＦ）作为荧光探针，研究了胶原蛋白在水溶液中的聚集状态．研究结果发现，当胶原蛋白浓度增大到０５ｍｇ／ｍＬ以上时，ＤＭＭＦ在４６５ｎｍ处的荧光强度有一突跃；继续增大其浓度，荧光强度越来越大．证明胶原蛋白在水溶液中随浓度增大有明显的聚集行为．利用荧光偏振法测量该体系内ＤＭＭＦ的荧光偏振特性，发现当胶原蛋白浓度增大到０５ｍｇ／ｍＬ以上时，体系具有较高的微粘度，进一步证实了胶原蛋白在水溶液中的聚集特性．     

阳离子荧光敏感器的器件化问题研究

通过对石英玻片表面修饰, 制作了联有多氨基链萘基的超薄膜荧光敏感器件, 研究了它在镍、铜等金属离子水溶液及有机溶剂中的荧光猝灭现象. 发现其荧光光谱无论在水或其他有机溶剂中都存在着单体和激基缔合物(ex-cimer)的发射峰, 当处于镍离子水溶液中时, 其单体峰随离子浓度的增大出现了先增强后减弱的现象, 而激基缔合物的发光峰则仅略有减弱但变化不大. 在铜离子水溶液中其荧光的变化情况和镍离子有所不同, 对单体荧光只能观察到强度减弱的趋势, 而激基缔合物则变化不大. 比较了未联结的敏感器化合物分子在有机溶剂中荧光被铜离子猝灭的行为, 发现与其在器件表面时有很大的差别, 表明其分子结构和构象也有很大的不同.     

离子液体[bmim][PF6]与[moemim][PF6]结构微不均匀性以及微粘度的光谱探测

室温离子液体由于其极低的蒸汽压、比较好的热稳定性和化学稳定性、良好的分子结构与性能的可设计性等优点,作为一种新型的环境友好溶剂在很多领域有着广泛的应用.对于离子液体的微观结构和微观性能的研究是设计新型离子液体以及扩展离子液体应用的关键.本文通过荧光探针分子香豆素153(C153)的转动动力学和对微观环境敏感的荧光探针分子1, 3-二(1-芘基)丙烷(BPP)的稳态荧光光谱,探测和表征了烷基取代的离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bmim][PF₆])和与其具有相似结构的醚键官能化的离子液体1-甲氧基乙基-3-甲基咪唑六氟磷酸盐([moemim][PF₆])的微观结构和微粘度. C153探针分子在离子液体[bmim][PF₆]中的转动过程具有快、慢两个组分表明离子液体[bmim][PF₆]内部存在松散和紧密的两种结构微区;而C153探针分子在离子液体[moemim][PF₆]中的转动动力学只存在一种过程,说明醚键的引入使得[moemim][PF₆]内部趋于一种类型的微环境.通过C153探针分子的转动时间研究发现,醚键官能化的离子液体[moemim][PF₆]的微粘度小于烷基链取代的离子液体[bmim][PF₆],同时通过BPP探针分子的二聚体激基复合物(excimer)与单体(monomer)荧光发射强度的比值(I_E/I_M)研究也证明这一结果.醚键的引入使得离子液体[moemim][PF₆]相对于离子液体[bmim][PF₆],侧链的极性更大、柔顺性更好,同时醚键有可能作为氢键的受体与阳离子形成氢键从而削弱离子液体中阴、阳离子间的相互作用,使得离子液体[moemim][PF₆]的微观环境比离子液体[bmim][PF₆]更为均一,同时具有更小的微粘度.     

荧光探针法研究壳聚糖在水溶液中的聚集态行为

本文用两种结构类似的分子内电荷转移化合物,3-羟基-6甲基-4-N,N-二甲氨基黄酮丙酸酯(PF)和3-甲氧基-4’-N,N-二甲氨基黄酮(DMMF),作为荧光探针,研究了壳聚糖在水溶液中的聚集状态.研究结果发现,当壳聚糖浓度增大到1×10^-3 kg/L或以上时,PF在430 nm处的荧光强度有一突增现象.利用DMMF作为荧光探针,研究了它在不同壳聚糖溶液中的稳态偏振,研究发现,随着壳聚糖浓度的增大,其偏振度也明显增大.这些结果进一步证实了壳聚糖在水溶液中的聚集特性,同时也为分子内电荷转移化合物——黄酮类化合物作为荧光探针研究生物大分子在水溶液中的构象提供了有益的尝试.     

咪唑基离子液体的结构-光谱性能分析及蛋白质传感

考察了对称型卤代咪唑基离子液体咪唑环上的烷基链长度和不同卤素阴离子(Cl-,Br-,I-)对其光谱性能的影响.实验结果表明,随离子液体咪唑环中烷基链长度增加,离子液体的荧光强度增大;随离子液体中卤素阴离子的电负性降低,其荧光强度减弱.加入血红蛋白可导致咪唑型离子液体的荧光强度增强,且在一定范围内与蛋白质浓度成正比,据此可对血红蛋白进行定量检测,线性范围为0.03 ～ 1.0 μmol/L,检出限为8 nmol/L.另外,根据不同蛋白质对咪唑基离子液体荧光性能的影响,建立了阵列传感系统用于8种蛋白质的区分与识别,在蛋白质浓度高于500 nmol/L时,识别正确率达到90％以上.     

功能化苯并咪唑类离子液体的合成及性质

合成了一系列由磺酸基、 羧基修饰的新型功能化苯并咪唑类离子液体, 采用IR, ¹H NMR, ¹³C NMR和ESI-MS对其结构进行了表征, 研究了化合物的热稳定性、 电导率以及室温下在各种溶剂中的溶解性等性质. 结果表明, 该类离子液体在 280 ℃以下基本没有失重, 热稳定性较好; 在水溶液浓度为1×10^-3 mol/L时, 随着温度的升高, 电导率几乎与温度呈正比增大; 能与大多数有机溶剂互溶, 溶解性随着溶剂极性的增加而增大.     

一些染料分子中电子激发态的无辐射转换速率与溶剂粘度的关系

应用10~(-12)s级时间分辨率的荧光光谱,测定了两种碳菁染料和一种荧光素染料(四碘荧光素B)的荧光寿命τ与溶剂粘度η之间的函数关系,发现碳菁染料在二元醇和丙三醇中的τ_(FM)低得反常.在二元醇溶剂中,它们的τ_(FM)与溶剂粘度η~(2/3)呈线性函数关系,但在一元醇溶剂中则并无此线性关系.由此可见,在研究染料分子的寿命与由不同系列醇(例如乙醇和丙三醇)组成的混合溶剂的粘度之间的依赖关系时,必须十分谨慎.对于四碘荧光素B,它在一元醇中的荧光寿命与溶剂粘度的关系符合2/3指数规律.     

疏水化修饰的聚N-异丙基丙烯酰胺高分子的水溶液性质研究

为了研究不同疏水化修饰的聚Ｎ 异丙基丙烯酰胺（ＰＮＩＰＡＭ）高分子的水溶液性质,合成了一系列Ｎ 异丙基丙烯酰胺（ＮＩＰＡＭ）和长链丙烯酸酯及丙烯酸胆固醇酯的共聚物．利用表面张力法证实了该类共聚物在室温下都具有良好的表面活性,在水溶液中能够形成胶束．利用荧光探针法,研究了共聚物的低温临界溶液温度（ＬｏｗｅｒＣｒｉｔｉｃａｌＳｏｌｕｔｉｏｎＴｅｍｐｅｒａｔｕｒｅ,ＬＣＳＴ）,发现,随着丙烯酸酯碳链及其配比（摩尔投料比）的变化,共聚物的ＬＣＳＴ变化不明显,但它们都比均聚的ＰＮＩＰＡＭ要低;利用荧光偏振法研究了共聚物在水溶液中的微粘度,发现其微粘度不随共聚物中丙烯酸酯链长和配比的变化而变化,说明了该类共聚物在室温下能够形成相类同的胶束内核．     

负载型离子液体在C-H键电氧化活化中的应用研究

本文将1-乙基-3-甲基咪唑醋酸盐离子液体修饰在多壁碳纳米管上,制备出离子液体/碳纳米管复合材料,并研究了对甲氧基甲苯（p-MT）在该复合离子液体水溶液体系中的电氧化性能. 同时,通过循环伏安法和计时电流法考查了扫描速率、温度、反应底物浓度等因素对电氧化性能的影响,研究了p-MT在该体系中的动力学过程. 实验结果表明,p-MT在复合离子液体水溶液体系中发生不可逆的电氧化反应,且该过程受扩散控制,扩散系数为7.69×10^-10 cm²·s^-1. 适当地升高温度和增大反应底物浓度都有利于促进p-MT中C-H键选择性电氧化为相应醛基,选择性可达到95%. 通过在不同结构电解槽中进行恒电位电解研究,发现离子液体/MWCNTs复合电解质在一室型电解槽中进行p-MT电氧化的电解效率更高、对目标产物对甲氧基苯甲醛（p-MBA）的选择性也更好.     

Lewis-Br(o)insted复合碱性离子液体的合成及其在催化Knoevenagel缩合反应中溶剂效应的研究

合成了同时含有Lewis碱和Br(o)nsted碱的复合碱性离子液体,研究了其在Knoevenagel缩合反应中的催化性能.结果表明,它们对醛/酮与氰乙酸乙酯的缩合具有很好的催化活性.芳香醛的反应收率可达85%～99%.考察了它们催化Knoevenagel缩合反应的溶剂效应,发现质子溶剂可以促进缩合反应,这一促进作用可能是由于质子溶剂通过氢键活化反应底物的羰基而降低了反应能垒所造成的.该离子液体可以循环使用3次,反应活性没有下降.     

Photoisomerization of cyanine derivatives in 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol: influence of specific interactions

Photoisomerization of two cyanine derivatives, 3,3(')-diethyloxadicarbocyanine iodide (DODCI) and merocyanine 540 (MC 540), has been investigated in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol (93 wt % glycerol +7 wt % water) by measuring fluorescence lifetimes and quantum yields. The aim of this work is to understand how the rates of photoisomerization of DODCI and MC 540 are influenced by specific solute-solvent interactions besides the viscosity of the medium. For DODCI, it has been observed that the nonradiative rate constants, which represent the rates of photoisomerization, are almost identical in the ionic liquid and aqueous glycerol at given temperature, indicating that viscosity is the sole parameter that governs the rate of photoisomerization. In contrast, the photoisomerization rate constants of MC 540 have been found to be a factor of 2 higher in aqueous glycerol compared to the ionic liquid. The observed behavior is due to the zwitterionic character of MC 540, a consequence of which, the twisted state gets stabilized by the solute-solvent hydrogen bonding interactions in aqueous glycerol, thus lowering the barrier for isomerization.     

Solutions of ionic liquids with diverse aliphatic and aromatic solutes – Phase behavior and potentials for applications: A review article

This article principally reviews our research related to liquid–liquid and solid–liquid phase behavior of imidazolium- and phosphonium-based ionic liquids, mainly having bistriflamide ([NTf₂]⁻) or triflate ([OTf]⁻) anions, with several aliphatic and aromatic solutes (target molecules). The latter include: (i) diols and triols: 1,2-propanediol, 1,3-propanediol and glycerol; (ii) polymer poly(ethylene glycol) (PEG): average molecular mass 200, 400 and 2050 – PEG200 (liquid), PEG400 (liquid) and PEG2050 (solid), respectively; (iii) polar aromatic compounds: nicotine, aniline, phenolic acids (vanillic, ferulic and caffeic acid,), thymol and caffeine and (iv) non-polar aromatic compounds (benzene, toluene, p-xylene). In these studies, the effects of the cation and anion, cation alkyl chain and PEG chain lengths on the observed phase behaviors were scrutinized. Thus, one of the major observations is that the anion – bistriflamide/triflate – selection usually had strong, sometimes really remarkable effects on the solvent abilities of the studied ionic liquids. Namely, in the case of the hydrogen-bonding solutes, the ionic liquids with the triflate anion generally exhibited substantially higher solubility than those having the bistriflamide anion. Nevertheless, with the aromatic compounds the situation was the opposite – in most of the cases it was the bistriflamide anion that favoured solubility. Moreover, our other studies confirmed the ability of PEG to dissolve both polar and non-polar aromatic compounds. Therefore, two general possibilities of application of alternative, environmentally acceptable, solvents of tuneable solvent properties appeared. One is to use homogeneous mixtures of two ionic liquids having [NTf₂]⁻ and [OTf]⁻ anions as mixed solvents. The other, however, envisages the application of homogeneous and heterogeneous (PEG + ionic liquid) solutions as tuneable solvents for aromatic solutes.Such mixed solvents have potential applications in separation of the aforesaid target molecules from their aqueous solutions or in extraction from original matrices. From the fundamental point of view the phase equilibrium studies reviewed herein and the diversity of the pure compounds – ionic liquids and target molecules – represent a good base for the discussion of interactions between the molecules that exist in the studied solutions.     

Comparison of photophysical properties of the hemicyanine dyes in ionic and nonionic solvents

The fluorescence properties of 4-[4-(dimethylamino)styryl]-1-n-alkylpyridinium bromide (hemicyanine) dissolved in solvents of different polarities and viscosities (methanol, ethylene glycol, tetra-ethylene glycol, glycerol, benzyl alcohol, pyridine, and two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM]BF4, and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6) were investigated. Significant increase in the fluorescence quantum yield and the fluorescence decay lifetime was observed with the increase in the viscosity of the solvent medium. It is because the intramolecular rotational motion of the molecule becomes more difficult in viscous liquid, which leads to a decrease in the nonradiative decay processes. The fluorescence quantum yields for all of the solutions followed a semiempirical law that depends only on the solvent viscosity. The correlation function C(t) was obtained for each solution by joining fluorescence decay curves measured at different wavelengths. From the fitted results of C(t), we observed the distinctive feature unique to the ionic liquids, in which the correlation functions for ionic liquid solutions are fitted to be biphasic, while they are monophasic for other solvents. The fluorescence maximum of hemicyanine dissolved in these ionic liquids red-shifted following the increase in the excitation wavelength.     

Fluorescence energy transfer efficiency in labeled yeast cytochrome c: a rapid screen for ion biocompatibility in aqueous ionic liquids

A fluorescence energy transfer "de-quenching" assay was implemented to follow the equilibrium unfolding behaviour of site-specific tetramethylrhodamine-labelled yeast cytochrome c in aqueous ionic liquid solutions; additionally, this approach offers the prospect of naked eye screening for biocompatible ion combinations in hydrated ionic liquids.     

Greener synthesis of new ammonium ionic liquids and their potential as extracting agents

New hydrophobic ionic liquids were synthesized from tricaprylmethylammonium chloride (Aliquat 336^©) and selected Bronsted acids by a sustainable, simple and cost-saving deprotonation-metathesis route. Prepared ionic liquids were evaluated as potential extracting agents for cadmium from different aqueous solutions. High efficiency and selectivity were reached for the extraction of cadmium from a natural river matrix with tricaprylmethylammonium thiosalicylate, [A336][TS], a thiol-containing task specific ionic liquid.     

Increased paraoxon detection by acetylcholinesterase inactivation with ionic liquid additives

This is the first study using ionic liquids (ILs) as additive in the aqueous solvent medium for detection of paraoxon by acetylcholinesterase inhibition method. A systematic comparison of various ILs with organic solvents has been made. The aqueous buffer solution containing ionic liquid ethylpyridinium hexafluorophosphate [EtPy]⁺[PF₆]⁻ has been found to give the best results. The inhibition kinetic follows the first order model. Ionic liquids modified aqueous solutions show the potential to provide a promising and effective medium in detection of paraoxon with acetylcholinesterase.     

Side reaction of cellulose with common 1-alkyl-3-methylimidazolium-based ionic liquids

Ionic liquids with 1-alkyl-3-methyl-imidazolium cations react at C-2 with cellulose at its reducing end, forming a carbon-carbon bond. The reaction is strongly catalyzed by bases, such as the commonly present impurities in ILs, imidazole, and 1-methylimidazole. The direct reaction was verified by means of ¹³C-isotopical labeling and with the help of an IL that carried a fluorescence label which was transferred to cellulose upon the reaction. In solutions of cellulose in alkylmethylimidazolium ILs, both the ionic liquid and the cellulose are evidently not inert.     

利用双水相分离回收离子液体的研究进展

研究离子液体的分离与回收对于减少离子液体对环境的影响、提高离子液体的利用效率、降低离子液体的应用成本、促进离子液体的工业应用具有重要的意义.本文重点综述了利用无机盐-离子液体双水相、糖-离子液体双水相、聚合物-离子液体双水相和CO2诱导的离子液体双水相技术分离回收离子液体的研究进展,分析了影响离子液体分离回收的关键因素,评价了不同离子液体双水相体系的优缺点,展望了该领域的发展方向及面临的挑战.     

Thermochemistry of the dissolution and association of ionic liquids in aqueous and acetonitrile solutions

The enthalpies of dissolution for three ionic liquids in water and acetonitrile in the field of dilute solutions at 298.15 K are measured in a hermetic highly sensitive calorimeter equipped with an isothermal shell, along with the enthalpies of dilution for aqueous and acetonitrile solutions of the same compounds in moving from three different concentrations to ones that are approximately the same. The enthalpies and constants of the ionic association of such liquids as electrolytes in solutions are calculated, along with their standard enthalpies of dissolution in water and acetonitrile.     

Evidence of change in the molecular organization of 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions with the addition of water

Physico-chemical properties of ionic liquids like density, viscosity, conductivity, surface tension and excess molar volume are strongly dependent on their concentration in aqueous solutions. 1-n-Butyl-3-methylimidazolium tetrafluoroborate/water solutions, at 25 °C, shows two clearly distinguished behaviors, corresponding to a water-rich and a salt-rich region, with distinct physico-chemical properties. It is shown that [BMIm][BF₄] exhibits surfactant properties. The results obtained are discussed in terms of the interactions between cations and anions of the ionic liquid and the water molecule. IR studies show that the addition of water modifies the organization of the ionic liquid molecules. The data collection reported is helpful for a variety of different technological applications and in particular for electrochemical applications, as capacitors, batteries and fuel cells among others.