十二烷基硫酸钠微乳色谱体系中pH值对其电渗流行为与微结构的影响

以十二烷基硫酸钠(SDS)/正己烷/正丁醇/硼砂微乳液为毛细管电色谱运行研究体系,以甲醇峰为微乳体系电渗流峰(EOF),考察不同pH值条件下微乳体系电渗流出峰时间(tEOF)和变化趋势.以微乳液滴粒径和ξ电位考察pH值对SDS缓冲溶液微乳体系微结构的影响,用微乳体系的电导值分析pH值条件下微乳液滴与氢氧根离子之间的相互...     

鼠李糖脂的合成及pH值对其表面活性和微乳微结构的影响

从铜绿假单胞菌发酵液中提取纯化鼠李糖脂生物表面活性剂. 用高效液相色谱-电喷雾质谱法(HPLC-ESI-MS)对鼠李糖脂提取物的组成进行了测定. 用临界胶束浓度(CMC)分析了pH值对其表面活性的影响, 用微乳液滴粒径和灼电位考察了pH值对鼠李糖脂/正庚烷/硼砂缓冲液微乳体系微结构的影响. 结果表明, 在弱碱性条件下(pH7.5-9.5), pH的变化对鼠李糖脂的表面活性和微乳微结构均有显著影响. pH小于9.0时, CMC随着pH的升高而降低, 在pH 9.0处达到最低. pH大于9.0时, CMC随着pH值的升高而逐渐升高. 这是氢键和极性头基间的静电排斥力共同作用的结果. 微乳液滴的粒径及灼电位绝对值都随pH值的升高呈增大趋势, 只在pH 9.0处例外. 少量十二烷基硫酸钠(SDS)或正丁醇的加入都使微乳粒径明显增大.     

溶液性质对微液滴现象的影响

考察了金属表面液滴性质对微液滴形成的影响并探讨了微液滴的来源. 不同pH值液滴附近微液滴形成特征表明, 高电位阴极区氧还原反应是微液滴形成的原因之一. 此外, 研究结果表明, 微液滴是由主液滴挥发的水蒸气经过气相“迁移”至主液滴附近金属表面上重新吸附凝聚形成的.     

模拟混凝土孔隙液中钢筋腐蚀的氯离子临界浓度测试

应用扫描微参比电极法,测量钢筋在模拟混凝土孔隙液中的表面微区电位分布;考察在一定pH值时氯离子浓度对溶液中钢筋腐蚀行为的影响。采用逐步逼近法,测试引起钢筋发生点腐蚀的氯离子临界浓度。当溶液pH为12.0时,可以观察到氯离子浓度变化引起钢筋点腐蚀的变化过程,从而确定氯离子浓度临界值为0.04~0.05 mol/L。     

模拟海洋大气环境中NdFeB(M35)初期腐蚀行为特征

研究模拟海洋大气环境中NdFeB(M35)初期的腐蚀行为.SEM观察表明,该材料初期腐蚀阶段,表面腐蚀过程存在3种代表性类型:Ⅰ)液滴同时覆盖富Nd相和磁性相,富Nd相先发生腐蚀;Ⅱ)液滴覆盖磁性相,磁性相腐蚀沿晶界扩展;Ⅲ)液滴在缺陷附近形成,腐蚀沿缺陷扩展.时间延长,局部腐蚀区相互连接,整体呈现晶界和富Nd相先行腐蚀,磁性相腐蚀相随其后.EDS分析给出腐蚀表面Na、Cl元素的分布,从而明确了腐蚀微电池的形成及腐蚀微电池点位变化是NdFeB(M35)腐蚀的外因.     

体系pH值、乳化温度和电解质离子对异丙甲草胺水乳剂稳定性的影响

通过测定药物液滴的平均粒径和Zeta电位研究了体系pH值、 乳化温度和电解质离子对乳化剂三苯乙烯基苯酚聚氧乙烯醚磷酸酯三乙醇胺盐(SCP)稳定的异丙甲草胺水乳剂稳定性的影响. 结果发现, 体系的pH值影响SCP分子在水中的电离能力, 当pH=9时, SCP完全电离, 能为液滴提供较大的静电稳定作用, 水乳剂稳定性最好; 乳化温度低时, SCP分子向液滴界面扩散慢, 且舒展不完全, 液滴所带负电荷较少, 水乳剂稳定性差; 温度升高后, 水相黏度减小, 布朗运动加剧, 液滴碰撞合并几率增大, 且SCP分子热运动增强, 易从界面逃逸, 液滴间静电斥力减弱, 同时SCP亲水性下降, 水乳剂稳定性变差; 电解质离子会压缩界面双电层, 降低Zeta电位, 液滴带电量减少而聚结, 离子浓度越大, 电荷数越大, 水乳剂稳定性越差. 在相同的离子浓度下, 水合半径小的Ca²⁺压缩双电层能力强于Mg²⁺, 添加Ca²⁺后水乳剂稳定性更差.     

低碳醇氧化电极表面pH值的测量及应用

研究了Ir/IrO₂微平面电极在低碳醇氧化电极表面的pH-E_ocp（pH-开路电位)关系,测量了几种低碳醇在电化学氧化过程中距离电极表面50 μm以内的不同距离处的pH值,对不同低碳醇电化学氧化产生的酸强度进行了比较与分析;Ir/IrO₂微平面电极的pH-E_ocp关系曲线与“醇-羧酸”体系种类有关;乙二醇在电化学氧化过程中产生的pH值最低,甲醇次之,乙醇产生的pH值最高,在500 nm处的稳态pH值分别为0.191、1.13和2.99。通过向电解液中加入NaF,考察了生成的H⁺和F^-结合对金属钛选择性微区刻蚀作用,在乙二醇为前驱体的体系中微孔刻蚀加工速率约为30 nm/min。     

pH/Cl-复合探针技术对钢筋混凝土电化学除氯的原位检测

采用恒电流法电化学除氯处理受氯离子污染的钢筋混凝土试样,并用pH/Cl^-复合探针原位检测电化学除氯过程钢筋混凝土不同位置孔隙液的氯离子含量与pH值分布,同时用线性极化曲线和交流阻抗谱图等电化学技术考察钢筋的腐蚀性能,探讨电化学除氯过程的混凝土微环境和钢筋腐蚀速率. 研究结果表明：在电化学除氯过程,混凝土孔隙液的氯离子浓度逐降,而pH值在初期略有升高,随之其pH值略降;电化学除氯施加的阴极电流,使钢筋处于阴极极化状态而得到保护;除氯停止（即退极化）后钢筋的腐蚀电位明显正移,腐蚀电流降低,极化电阻升高,表明电化学除氯能改善钢筋的腐蚀环境,降低钢筋的腐蚀速率.     

石英晶体微天平研究Zn在薄液膜下的腐蚀动力学

用石英晶体微天平(QCM)测量了在相对湿度RH为85％的薄液膜条件下,金属Zn在不同CO2浓度条件下的腐蚀增质方程.同时结合红外吸收光谱(IR)和X射线能谱(XEDS)研究了Zn在薄液膜下的大气腐蚀机理,并用扫描电子显微镜(SEM)对腐蚀产物形貌做了分析,阐述了腐蚀产物的形成特征及对基体金属的保护特性.     

壳聚糖修饰PLGA阳离子型纳米微球的制备与表征

采用单乳化-溶剂(O/W)挥发技术制备表面带正电荷的壳聚糖(CHS)修饰聚乙/丙交酯(PLGA)纳米微球(PLGA/CHS), 通过正交试验优化了纳米微球的制备条件. 结果表明, 微球粒径可控制在150～200 nm内, 在pH=4时, 纳米微球表面电位最高为55 mV. 影响微球粒径的主要因素是聚合物的浓度, CHS的分子量和浓度以及介质的pH值对微球表面电位也有明显影响. 制备粒径较小而表面电位较高的PLGA/CHS纳米微球条件为: ρ(CHS)=3 mg/mL, ρ(PLGA)=10 mg/mL, Vo/Va=1/4. SEM图像显示经CHS修饰的PLGA的纳米微球形状规整, 荧光显微观察和XPS分析结果证实CHS包覆于微球表面.     

The role of electrochemical polarization in micro-droplets formation

The effects of electrochemical polarization on the micro-droplets formation were investigated using microscope observation method and electrochemical polarization techniques.It is found that cathodic polarization can initiate and accelerate the formation of micro-droplets, whereas anodic polarization can inhibit the micro-droplets formation, independent of metal type, electrolyte species, composition of air, and environmental humidity, indicating that the electrochemical polarization is the key condition for micro-droplets formation on metal surfaces. Based on above results, it is suggested that both the decrease of liquid/metal interface tension and the cooling of temperature of the three-phase-boundary area which are caused by cathodic polarization, may be the main reason for the micro-droplets formation.     

Porous polymer films and honeycomb structures based on amphiphilic dendronized block copolymers

Fabrication of honeycomb patterned films from our synthesized amphiphilic dendronized block copolymer by "on-solid surface spreading" method and "on-water spreading" method was reported for the first time in this paper. The comparison of the two methods indicated honeycomb-patterned films with smaller size, and larger surface density of micropores can be fabricated by spreading on water but with lower regular arrangement. Furthermore, several influencing factors on the formation of the honeycomb structure and the different morphologies, such as the concentration of the copolymer solution and the relative humidity in the atmosphere and the substrates, were investigated. The results showed that comparably high relative humidity from 80% to 95% was needed, and the mica plate as a spreading substrate was suitable to form orderly porous films for such a copolymer. The best ordered pattern could be formed from the copolymer with concentration of 1.00 mg/mL at the relative humidity of 85% using a mica plate. Besides, strong periodicity, regularity, and a large, defect-free area were notable, which made this structure extremely interesting for applications for templated molecular objects formed via intramolecular metal or metal oxide synthesis.     

Spontaneous Synthesis of [FeII(Atrz)3]SO4 and its Analogues Through Accelerated Ageing: New Insights from Small-Scale Reactions

Accelerated ageing reactions that take place between two solid materials on contact in the absence of added solvent have been used to synthesize two spin-crossover-active 1D coordination polymers and one of their Cu(II) analogues. The hygroscopy of the ligands and the relative humidity of the reaction chamber have been shown to be particularly important factors in the rate of reaction. Small-scale reactions between a few individual crystals have allowed observation of deliquescence of the 4-aminotriazole ligand at high humidity. The metal salt does not dissolve, and the ligand diffuses into the crystal of the metal salt during the reaction. In the case of the Cu analogue, the formation of the product causes the crystal of the metal salt to deform with the formation of pseudocrystals, which have a fibrous structure.     

大豆蛋白基茶碱控释片的制备及稳定性研究

以茶碱为模型药物,大豆蛋白和海藻酸钠作为骨架材料,采用混合压片法制备了不同比例的药物片剂。采用紫外比色法测定释放效果,考察了大豆蛋白与海藻酸钠不同比例以及不同pH释放介质和高湿度对茶碱片稳定性的影响。结果表明:大豆蛋白和海藻酸钠作为骨架材料的片剂释药时间都达到了8h以上,在pH6.8PBS中的释药率相对pH1.2盐酸溶液要快,具有良好的定向控释特性。随着湿度的增加,茶碱释放率略有下降,具有较好的湿度稳定性。通过适度调节大豆蛋白和海藻酸钠的比例可实现不同控释效果。实验结果表明大豆蛋白和海藻酸钠共混物是一种良好的天然药物缓控释骨架材料,其释放过程符合一级动力学特征,是药物扩散和骨架溶蚀二者共同作用的结果。     

Ozone oxidation of cysteine in optically trapped aqueous micro-droplets

The ozone (O₃) oxidation kinetics of cysteine in aqueous micro-droplets at different acidities is investigated in this study via aerosol optical tweezers coupled with Raman spectroscopy. This study exploits the O₃ oxidation of cysteine near the interface of micro-droplets as a model system to elucidate the oxidation damage of amino acids in biosurfaces. For each optically trapped micro-droplet, Raman spectroscopy is used to determine its droplet radius, concentrations of solutes, and droplet pH, as well as their time evolutions during the kinetics measurements. The bimolecular rate coefficients of the cysteine + O₃ reaction measured in micro-droplets are around 4 × 10⁵ M⁻¹ s⁻¹ and 2 × 10⁴ M⁻¹ s⁻¹ for pH ≈ 5 and 0.5, respectively. These results agree with the previous bulk measurements, indicating that the observed aerosol kinetics can be solely rationalized via diffusion-limited kinetics. The results also indicate that a high-ionic strength could enhance the cysteine + O₃ reaction, particularly for the zwitterion form of cysteine. The results imply that when surfactant proteins in lung fluids are exposed to ambient O₃, the cysteine residues in proteins will be attacked by O₃ at first due to the high reactivity of the thiol moiety in cysteine.     

聚氧乙烯-粘土-碱金属离子插层复合物作用机理研究

测量了聚氧乙烯(PEO)-粘土-K^＋/Na^＋插层复合物在不同相对湿度环境中的相对吸水量, 研究了相对吸水量与粘土层间距d₀₀₁之间的关系, 并结合X射线光电子能谱的研究结果, 探讨了复合物中PEO、粘土与碱金属离子三者之间的相互作用. 在K-MMT-PEO复合物中, K^＋与PEO和粘土表面都存在配合作用, 形成稳定的三元配合物, 在不同相对湿度下, K-MMT-PEO配合物吸水能力较低, 层间距基本不变. 在Na-MMT-PEO复合物中, Na^＋与PEO形成配合物, 水分子能破坏Na^＋-PEO之间的配合作用, 使PEO和Na^＋各自形成水化层, 因此随着相对湿度的增加Na-MMT-PEO复合物的相对吸水量和层间距都增大.     

Spontaneous transfer of phospholipid-coated oil-in-oil and water-in-oil micro-droplets through an oil/water interface

We studied the evolution of oil-in-oil (O/O) and water-in-oil (W/O) phospholipid-coated micro-droplets at an oil/water interface. We found that, in both cases, micro-droplets spontaneously transferred from the oil phase to the water phase. O/O micro-droplets transformed into oil-in-water micro-droplets, while W/O micro-droplets led to the formation of liposomes.     

Stability of liquid crystal micro-droplets based optical microresonators

Liquid crystal (LC) based tuneable optical microresonators are potential for being used as crucial components in photonic devices. In this article, we report experimental studies on LC micro-droplets dispersed in several dispersing media. We find that the size of the micro-droplets formed in a low refractive index and optically transparent perfluoropolymer are most stable with time than commonly used dispersing media. Using a negative dielectric anisotropy nematic liquid crystal, we show that the whispering gallery mode optical resonance properties such as the quality factor and the free spectral range of stable micro-droplets are independent of the strength of the applied electric field. The optical resonance properties under applied field are significantly different than that of the liquid crystals with positive dielectric anisotropy and are explained based on the elastic deformation of the micro-droplets.     

The effect of humidity on the ozonolysis of unsaturated compounds in aerosol particles

Atmospheric aerosol particles are important in many atmospheric processes such as: light scattering, light absorption, and cloud formation. Oxidation reactions continuously change the chemical composition of aerosol particles, especially the organic mass component, which is often the dominant fraction. These ageing processes are poorly understood but are known to significantly affect the cloud formation potential of aerosol particles. In this study we investigate the effect of humidity and ozone on the chemical composition of two model organic aerosol systems: oleic acid and arachidonic acid. These two acids are also compared to maleic acid an aerosol system we have previously studied using the same techniques. The role of relative humidity in the oxidation scheme of the three carboxylic acids is very compound specific. Relative humidity was observed to have a major influence on the oxidation scheme of maleic acid and arachidonic acid, whereas no dependence was observed for the oxidation of oleic acid. In both, maleic acid and arachidonic acid, an evaporation of volatile oxidation products could only be observed when the particle was exposed to high relative humidities. The particle phase has a strong effect on the particle processing and the effect of water on the oxidation processes. Oleic acid is liquid under all conditions at room temperature (dry or elevated humidity, pure or oxidized particle). Thus ozone can easily diffuse into the bulk of the particle irrespective of the oxidation conditions. In addition, water does not influence the oxidation reactions of oleic acid particles, which is partly explained by the structure of oxidation intermediates. The low water solubility of oleic acid and its ozonolysis products limits the effect of water. This is very different for maleic and arachidonic acid, which change their phase from liquid to solid upon oxidation or upon changes in humidity. In a solid particle the reactions of ozone and water with the organic particle are restricted to the particle surface and hence different regimes of reactivity are dictated by particle phase. The potential relevance of these three model systems to mimic ambient atmospheric processes is discussed.