疏水介孔二氧化硅膜的制备与表征

用甲基三乙氧基硅烷(MTES)代替部分正硅酸乙酯(TEOS)作为前驱体，以聚乙烯醚-聚丙烯醚-聚乙烯醚三嵌段共聚物(P123)作有机模板剂，通过共水解缩聚反应制备了甲基修饰的介孔SiO₂膜。利用N₂吸附、FTIR、²⁹Si MAS NMR以及接触角测量仪对膜的孔结构和疏水性进行了表征。结果表明，修饰后的膜材料具有良好的介孔结构，最可几孔径为4.65 nm，孔体积为0.69 cm³·g^-1，比表面积为938.4 m²·g^-1；同时疏水性明显提高，当n_MTES/n_TEOS达到1.0时，其对水的接触角达到109°± 1.1°。气体渗透实验表明气体通过膜孔的扩散由努森机制所控制。     

疏水蛋白在云母表面的吸附

采用分子动力学模拟方法研究了疏水蛋白(HFBI)在亲水云母表面的吸附过程.通过6组平行的分子动力学模拟得到了2种不同的稳定吸附结构,即通过N端和通过亲水的α螺旋与表面吸附,得到了5种吸附残基.进一步用自适应偏置力方法计算了所有吸附残基与表面的结合自由能.结果表明,残基Lys是吸附过程的关键残基,即当HFBI通过含有Lys残基的α螺旋与云母表面作用时,其吸附构象最稳定.静电作用是吸附过程的主要驱动力.在该吸附结构中,HFBI的疏水面暴露在溶液中,有效降低了云母表面的润湿性.     

偏氟乙烯/三氟氯乙烯交替共聚物在TATB表面吸附的分子动力学模拟

采用COMPASS力场和NVT正则系综的动力学模拟方法, 搭建了聚合度分别为10, 50和100的偏氟乙烯(VDF)/三氟氯乙烯(CTFE)交替共聚物, 对交替共聚物在1,3,5-三氨基-2,4,6-三硝基苯(TATB)的(0,0,1)晶面上的吸附和结构进行了分子动力学(MD)模拟. 结果表明, 在300～320 K温区, 聚合度为100的VDF/CTFE交替共聚物链对TATB晶体有理想的表面活性和吸附能力, 以train型构象平铺于TATB表面. 通过对聚合度为10的交替共聚物的多链体系在TATB表面吸附的MD模拟, 表明了VDF/CTFE交替共聚物具有非凝聚吸附的高表面活性特征. 对搭建的乙酸乙酯溶剂化的聚合度为50的VDF/CTFE交替共聚物在TATB晶体表面吸附的模拟, 实验证明了溶剂小分子能够降低共聚物链的吸附能力, 且链以tail型构象吸附于TATB表面.     

疏水改性MCM-41对甲草胺缓释性能的影响

采用浸渍法将甲草胺吸附到纯硅MCM-41(M41)介孔材料中, 以六甲基二硅氮烷(HMDS)为表面改性剂, 通过气-固反应对吸附了甲草胺的M41材料(Ach/M41)进行疏水改性, 得到了既具有高载药性又能有效延缓甲草胺释放的缓释体系Ach/TMS-M41. XRD、低温N₂吸附/脱附、FT-IR和TG等分析结果表明, 甲草胺在M41中的吸附量高达0.381 g·g^-1(质量分数为27.6%), 此时M41仍保持原有的孔道结构, 且甲草胺能完全分散于M41孔道中. 分别对Ach/M41和Ach/TMS-M41在水中的缓释性能进行了测试, 甲草胺释放率分别为62%和38.1%, 表明疏水改性对延缓甲草胺释放有较好的效果. 而且, 介孔材料孔壁对甲草胺具有明显的紫外屏蔽保护作用.     

固体表面特征对脲变α-糜蛋白酶折叠的贡献

以脲变α-糜蛋白酶(α-Chy)为模型蛋白, 用蛋白折叠液相色谱法研究了该蛋白在7种不同固体表面上的折叠及其在折叠过程中形成的中间体, 选用疏水相互作用色谱(HPHIC)固定相为吸附剂, 在动态条件下着重研究了疏水色谱固定相TSK和PEG-600表面对脲变α-Chy复性效率的贡献. 用基质辅助激光解吸附离子化飞行时间质谱对3.0 mol•L^－1脲变α-Chy, 在经 HPHIC柱复性并同时分离的收集组分进行确认后, 仅有一种稳定的脲变α-Chy折叠中间体. 发现PEG-600固定相表面较TSK固定相对α-Chy复性效果好. 证实了疏水性强度及固体表面配基的结构对蛋白折叠起着关键性的作用.     

含氟聚合物修饰碳纳米管及其聚氨酯复合疏水膜的研究

利用羟基碳纳米管上的羟基与2-溴异丁基酰溴之间的简单反应, 在碳纳米管上引入了含溴ATRP引发剂, 并进一步引发含氟丙烯酸酯的ATRP聚合, 从而在碳纳米管表面接枝上了低表面能的含氟聚合物. 红外光谱(FT-IR)、热重分析(TGA)和透射电镜(TEM)的研究结果表明碳纳米管与含氟聚合物之间为化学键连接. 以此低表面能聚合物包裹的碳纳米管作为填充粒子, 采用溶液浇铸方法制备了聚氨酯/碳纳米管复合膜, 并利用溶剂四氢呋喃(THF)刻蚀表面获得了不同碳纳米管裸露程度的复合膜材料. 静态接触角测试结果表明, 无论是羟基碳纳米管还是低表面能修饰的碳纳米管均可提高其复合膜的疏水性能, 且其疏水性能随碳纳米管含量的增加而增加; 相同含量时, 含氟聚合物接枝后的碳纳米管使复合膜具有更佳的疏水性能, 膜表面经溶剂刻蚀后可显著提高其疏水性能. 采用扫描电子显微镜(SEM)研究了加入碳纳米管和溶剂刻蚀对聚合物表面微观结构以及材料表面疏水性能的影响. 上述结果表明: 利用接枝聚合物可改变碳纳米管本身的疏水性能, 并可进一步制备新型的具有表面疏水性能的聚合物纳米复合材料.     

周期性密度泛函理论研究NO在Cu2O(111)表面上的吸附

运用广义梯度密度泛函理论(GGA)的PBE方法结合周期平板模型，在DND基组下，研究了NO以N端和O端两种吸附取向在Cu₂O(111)非极性表面上的吸附。通过对不同吸附位置的吸附能和几何构型参数的计算和比较发现：表面上配位不饱和的铜离子(CuCUS)为活性吸附位；NO的N端吸附比O端吸附更为有利，N端吸附时吸附能可达到113.5 kJ·mol^-1，而O端情况下只有39.7 kJ·mol^-1；NO倾斜吸附在Cu₂O(111)表面上，O端吸附时倾斜度更大。在两种吸附取向情况下，N-O键的伸缩振动频率都发生了较大的红移，N端吸附情况下红移150 cm^-1，O端时红移330 cm^-1。前线轨道分析表明，Cu与NO间的吸附作用主要是Cu的d轨道和NO的π^*轨道间的相互作用。表面弛豫的计算表明，Cu₂O(111)面的弛豫对O端吸附方式产生较大影响，考虑表面弛豫时O端吸附为很弱的化学吸附(吸附能为39.7 kJ·mol^-1)，而没有考虑弛豫时吸附能为60.5 kJ·mol^-1。     

表面活性剂疏水链长对高温下泡沫稳定性的影响

选用不同疏水链长的α-烯烃磺酸盐(AOS)形成泡沫, 分别用泡沫衰减法和泡沫岩芯封堵法测定不同温度下的泡沫稳定性, 并采用动态表面张力、界面流变、分子模拟等方法研究了表面活性剂在气/液界面的吸附行为和界面吸附层的性质, 分析了高温下泡沫的稳定机制. 实验结果表明, 在高温下, 极性头的“锚定作用”减弱, 表面活性剂疏水链难以在气液界面保持以直立状态吸附, 疏水链碳数大于20的表面活性剂分子难以分立吸附, 其疏水链相互交叉缠绕, 增强了泡沫膜的强度, 减缓了气体通过液膜的扩散, 形成的泡沫在高温下具有较好的稳定性.     

十二烷基硫酸钠水溶液的动态表面吸附性质

利用MPTC型气泡压力张仪研究了十二烷基硫酸钠(SDS)溶液在不同NaCl 浓度下的动态表面吸附性质, 分析了离子型表面活性剂在表面吸附层和胶束中形成双电层结构产生表面电荷对动态表面扩散过程和胶束性质的影响. 结果表明, SDS在表面吸附过程中, 表面电荷的存在会产生5.5 kJ·mol^-1的吸附势垒(E_a), 显著降低十二烷基硫酸根离子(DS^-)的有效扩散系数(D_eff). 十二烷基硫酸根离子的有效扩散系数与自扩散系数(D)的比值(D_eff/D)仅为0.013, 这表明SDS与非离子型表面活性剂不同, 在吸附初期为混合动力控制吸附机制. 加入NaCl可以降低吸附势垒. 当加入不小于80 mmol·L^-1 NaCl后, E_a小于0.3 kJ·mol^-1, D_eff/D在0.8-1.2之间, 表现出与非离子型表面活性剂相同的扩散控制吸附机制. 同时, 通过分析SDS胶束溶液的动态表面张力获得了表征胶束解体速度的常数(k₂). 发现随着NaCl 浓度的增大, k₂减小, 表明SDS胶束表面电荷的存在会增加十二烷基硫酸根离子间的排斥力, 促进胶束解体.     

基于疏水滤纸的金纳米花SERS 基底高灵敏检测牛奶中的三聚氰胺

将海胆状金纳米花(gold nanoflowers, GNFs)疏水滤纸基底和表面增强拉曼散射(surface-enhanced Raman scattering, SERS)技术相结合,实现了牛奶中三聚氰胺的高灵敏检测。由左旋多巴还原制备的GNFs拥有许多尖锐突起和尖端可激发强局部电磁场增强(electromagnetic enhancement, EM),产生大量的“热点”,提高SERS检测的灵敏度。采用疏水滤纸作为衬底,改进了纸基衬底上纳米材料分布不均匀的缺点。进而评估了SERS基底的灵敏度、稳定性和重现性。通过对加标牛奶中三聚氰胺的定量检测,在1×10_-3^~1×10_-9 ^mol/L范围内,牛奶中三聚氰胺的浓度对数与SERS强度呈良好的线性关系,检测限低至43 pmol/L,远低于同类检测方法。并且本方法检测实际样品结果与液相色谱法检测结果对比无显著性差异(p>0.05)。GNFs疏水滤纸SERS基底具有高灵敏度、稳定性、重现性和实用性的优点,为牛奶等其他食品中三聚氰胺的定量检测提供了参考价值。     

热处理对憎水硅胶吸附水蒸气的影响

用甲基氯硅烷蒸气或溶液处理硅胶,均可制成憎水硅胶。关于憎水硅胶的吸附性能和热稳定性的研究,文献中时有报道。本文主要探讨以下3个问题:(1)在水蒸气吸附中,硅胶表面自由羟基和缔合羟基究竟哪种起主要作用;(2)从吸附水蒸气等数据讨论硅胶表面有机基团—OSi(CH_3)_3的热稳定性;(3)用二甲基二氯硅烷(DMCS)和三甲基氯硅烷(TMCS)处理的憎水硅胶,哪种硅胶的热稳定性较高。这些基本问题,不仅具有学术意义,对研究氧化物表面改性也有参考价值。     

四苯硼钠在活性炭表面吸附过程的疏水相互作用

In this paper, the adsorption characteristics of sodium tetraphenylborate(NaBPh4) on activated carbon at 298.2,303.2,308.2,313..2 and 323.2 K was studied.The results show that the adsorption isotherm of NaBPh4 on activated carbon at different temperatures could be described using Langrnuir equation. Furthermore, the standard Gibbs energy, enthalpy, entropy and hydrophobic interaction Gibbs energy for the adsorption of NaBPh4 on activated carbon were studied, and the result shows that the hydrophobic interaction of BPh4^- ion plays the most important role for the transfer of NaBPh4 from water to activated carbon surface.     

Mucin Adsorption to Hydrophobic Surfaces

The adsorption isotherm of bovine submaxillary gland mucin (BSM) onto a hydrophobic polystyrene surface was determined by using the solution depletion method, in which mucin concentrations were analyzed by amino acid analysis. Adsorption and desorption kinetics of BSM onto hydrophobic polystyrene surfaces were also studied by the solution depletion method, in which mucin solution concentrations were determined by measuring UV absorbance at a wavelength of 280 nm and by a BCA colorimetric assay with final calibration by amino acid analysis. From the adsorption isotherm, we found that the saturated surface concentration (Gamma(max)) was 2.3 mg/m(2), and the adsorption constant (K) was calculated as 0.099 (ml/mg). By using a Langmuir adsorption model and nonlinear fitting, kinetics parameters, k(on) and k(off), were found to be 8.13x10(-3) cm(3) mg(-1) s(-1) and 5.67x10(-4) s(-1), respectively. The coating was found to be very stable with very limited desorption (less than 2%) from a long-term observation (28 h). The mucin coating layer thickness was investigated by several analytical techniques: flow field-flow-fractionation, photon correlation spectroscopy, scanning electron microscopy, and atomic force microscopy. The thickness was measured as 4-5 nm, from which a monolayer coating was concluded. Finally, the weight average molecular weight of purified bovine submaxillary gland mucin (BSM) was determined as 1.6x10(6) Da by using static light scattering. Copyright 2000 Academic Press.     

Hydrophobic surface modification of chitosan gels by stearyl for improving the activity of immobilized lipase

The hydrophobic surface modification of chitosan gels was carried out using the amidating reaction of amido groups on a gel surface with stearic acid activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC) and N-hydroxysuccinimide (NHS).Lipases from Candida rugosa were adsorbed on the nascent chitosan gels(CS) and stearyl-modified gels(SCS) with different degrees of amidation.The increased surface hydrophobicity of chitosan gels improved the adsorption capacity and activity of the ...     

Adsorption of Bovine Serum Albumin and Lysozyme on Hydrophobic Calcium Hydroxyapatites

The adsorption of bovine serum albumin (BSA) and lysozyme (LSZ) to oleyl phosphate(OP)-grafted calcium hydroxyapatite (OP-CaHAP) with different degrees of hydrophobicity, ranging the number of surface oleyl group per unit nm2 (nO) from 0 to 2.60, was investigated. The pronounced effects of the hydrophobic moiety of adsorbent on protein adsorption were observed. The saturated amount of adsorbed BSA (ns) was increased up to nO = 0.6 by an enlargement of hydrophobic interaction between hydrophobic CaHAP particle and proteins. However, ns decreased at nO >/= 1.3 by increasing the electrostatic repulsive force between negatively charged BSA and OP-CaHAP particles. On the other hand, the ns value of LSZ was continuously increased up to nO = 2.0 and saturated by increasing either the hydrophobic interaction or the electrostatic attraction of positively charged LSZ and negatively charged OP-grafted CaHAPs. The BSA adsorption experiment revealed that the effect of positively charged adsorption sites on the exposed ac or bc crystal faces (C-sites) of the CaHAPs is screened by the OP-groups grafted on their particle surfaces. Copyright 1999 Academic Press.     

Gemini表面活性剂烷烃尾链在吸附和聚集过程中的疏水协同效应(英文)

以表面张力法测定了系列Gemini表面活性剂m-6-m以及对应单体表面活性剂CmTABr的临界胶束浓度(cmc)和降低水表面张力20mN·m-1需要的浓度(pC20).比较这些参数表明m-6-m胶束化和在界面吸附的能力均强于CmTABr,这被归结为Gemini表面活性剂烷烃尾链间的疏水协同效应.与不对称Gemini表面活性剂12-6-m比较,对称的Gemini结构更有利于表面活性剂的聚集和吸附.     

Adsorption of Some Surfactants onto Polyvinyl Alcohol as Hydrophobic Polymer Surface

The adsorption of different types of nonionic and anionic surfactants from aqueous solutions onto polyvinyl alcohol has been studied at different temperatures using surface tension measurements. The nonionic surfactants show Langmuirian L-shape isotherms whereas the adsorption isotherms of the anionic surfactants exhibit segmoidal shape. The experimental adsorption isotherms could be fitted to the Langmuir equation and the values of Γ_max and A_min have been calculated. The effect of temperature on the adsorption process as well as on both efficiency and effectiveness of adsorption has been studied.     

Immobilized Stationary Phases for Hydrophobic Interaction Chromatography of Proteins

Immobilized stationary phases for hydrophobic interaction chromatography (HIC) of proteins are prepared by coating macroporous silica Daisogel of different porosity with hydrophobized cellulose derivatives. The polymer adsorbed on the silica surface afterwards was cross-linked with bifunctional compounds. A uniform polymer nanocoating was indicated using the nitrogen gas adsorption method BET and scanning electron microscopy. The absence of non-specific protein sorption of the synthesized adsorbents shows that the developed polymeric coating isolates silica surface from contact with the sorbate. The retention data of bovine serum albumin (BSA) in the HIC mode on different synthesized adsorbents were evaluated. It was shown that sorption capacity of such phases may vary over a wide range and depends mainly on the substitution degree of the immobilized polymer. The dynamic sorption capacity of BSA was up to 63 mg mL⁻¹. The results proved that the new stationary phases have significant promise for the separation and purification of proteins in the HIC mode.

     

Hydrophobic interaction chromatography of proteins. III. Unfolding of proteins upon adsorption

Hydrophobic interaction chromatography (HIC) exploits the hydrophobic properties of protein surfaces for separation and purification by performing interactions with chromatographic sorbents of hydrophobic nature. In contrast to reversed-phase chromatography, this methodology is less detrimental to the protein and is therefore more commonly used in industrial scale as well as in bench scale when the conformational integrity of the protein is important. Hydrophobic interactions are promoted by salt and thus proteins are retained in presence of a cosmotropic salt. When proteins are injected on HIC columns with increasing salt concentrations under isocratic conditions only, a fraction of the applied amount is eluted. The higher the salt concentration, the lower is the amount of eluted protein. The rest can be desorbed with a buffer of low salt concentration or water. It has been proposed that the stronger retained protein fraction has partially changed the conformation upon adsorption. This has been also corroborated by physicochemical measurements. The retention data of 5 different model proteins and 10 different stationary phases were evaluated. Partial unfolding of proteins upon adsorption on surfaces of HIC media were assumed and a model describing the adsorption of native and partial unfolded fraction was developed. Furthermore, we hypothesize that the surface acts as catalyst for partial unfolding, since the fraction of partial unfolded protein is increasing with length of the alkyl chain.     

Monolith Passive Adsorbers Prepared with Hydrophobic Porous Silica Rods Coated with Hydrogel

This work focuses on the synthesis and characterization of porous silica monolith-based adsorbent materials. Materials with bimodal porosity (macro and meso) were prepared through a sol–gel process. The capacity of adsorption of organic molecules was ensured by grafting of hydrophobic organic coating on the silica surface. Alkylsilane chains or lauryl acrylate polymer were used for this purpose. The adsorption kinetic behavior of the produced materials was assessed through benzophenone adsorption studies in aqueous media. The results have shown that the macropore size of the monoliths had no effect on the adsorption capacity. The thicker organic layer prepared by polymerization of lauryl acrylate has decreased the adsorption kinetics without affecting the total adsorption capacity. The over-coating with additional external layer of hydrogel further slowed the diffusion of benzophenone thus better matches the passive-sampler requirements.