铀酰离子吸附在高岭土基面的分子动力学模拟

为研究铀酰离子在高岭土不同基面上的吸附, 对含有0.01 mol·L^-1碳酸铀酰液相和9×9×3个高岭土单胞的粘土固相的模拟盒子进行了分子动力学模拟. 从模拟的截图中直观地观察到了铀酰离子的吸附位点, 由径向分布函数得到了铀酰离子与水中氧原子的配位情况. 利用原子密度剖面图讨论铀酰离子在两个基面上的吸附倾向, 并从原子密度剖面图和均方位移等角度证实了铀酰离子在硅氧面上形成了外界配合物. 从理论上证明了表面配合模型对于吸附位点所做简化的合理性.     

Molecular Simulation of the Adsorption of Rod/Coil Blends on Nano‐Patterned Surfaces

The adsorption of rod/coil blends onto patterned surfaces with periodic stripes of width w was simulated using Monte‐Carlo methods. The rods and the coils were taken to be fused monomers of diameter σ, interacting with the stripes by a square‐well potential of depth ε and width σ. When the interaction was through excluded‐volume interactions only, we observed segregation of the components in the adsorbed layer. The adsorbed rods are strongly aligned along the stripe for w = σ, but lose their orientational order for larger w. When a repulsive interaction between the rods and the coils was introduced, an increase in the surface coverage of the rods with better recognition of the stripes was observed.

     

Adsorption Properties of Comb-Shaped Polycarboxylate Dispersant onto Different Crystal Pyraclostrobin Particle Surfaces

The stability of the suspension system of the two crystal forms of pyraclostrobin is evaluated using multiple light technology, and the adsorption performance of polycarboxylate dispersant on the surface of two different crystalline pyraclostrobin particles is compared in combination with XRD, FTIR, XPS, and SEM from the microscopic view. The adsorption kinetics and thermodynamics studies of 2700 on the surfaces of different crystalline forms of pyraclostrobin particles show that the adsorption process of 2700 on the surfaces of pyraclostrobin crystal forms II and IV conform to pseudo-second-order kinetic adsorption model. The Ea values for crystal forms II and IV are 12.93 and 14.39 kJ∙mol⁻¹, respectively, which indicates that both adsorption processes are physical adsorption. The adsorption models of 2700 on the surfaces of pyraclostrobin crystal forms II and IV are in accordance with Langmuir adsorption isotherms. The ∆G_ad values of crystal forms II and IV are negative and the ∆S_ad values are positive at different temperatures. Therefore, the adsorption processes are spontaneous and accompanied by entropy increase. The results of this study provide an important theoretical basis for the selection of polycarboxylate dispersants in the suspension of pyraclostrobin. This study also provides a reference for the research of polycrystalline pesticide suspension concentrate.     

BSA在不同形貌氧化锌材料上的吸附热力学

采用高分子模板法合成了4种不同形貌的ZnO,分别为球状颗粒(ZnO NPs)、针状(ZnO NRs)、片状(ZnO NSs)和棒状(ZnO NBs).利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)对产物进行了表征.通过傅里叶变换红外光谱仪(FTIR)和圆二色光谱仪(CD)研究了小牛血清白蛋白(BSA)在不同形貌ZnO上的等温吸附规律、吸附热力学和吸附作用机理.结果表明,4种不同形貌的ZnO对BSA的吸附均较好地符合Langmuir等温吸附模型;吸附量随温度的升高略有增加;从热力学参数(ΔG,ΔH,ΔS)可知,吸附反应为自发进行的吸热反应,作用机理主要为氢键和静电作用.从热力学角度,针状的ZnO更有利于BSA的吸附.     

Fibronectin adsorption onto polyelectrolyte multilayer films

The Layer-by-layer deposition of positively and negatively charged macromolecular species is an ideal method for constructing thin films incorporating biological molecules. We investigate the adsorption of fibronectin onto polyelectrolyte multilayer (PEM) films using optical waveguide lightmode spectroscopy (OWLS) and atomic force microscopy (AFM). PEM films are formed by adsorption onto Si(Ti)O2 from alternately introduced flowing solutions of anionic poly(sodium 4-styrenesulfonate) (PSS) and cationic poly(allylamine hydrochloride) (PAH). Using OWLS, we find the initial rate and overall extent offibronectin adsorption to be greatest on PEM films terminated with a PAH layer. The polarizability density of the adsorbed protein layer, as measured by its refractive index, is virtually identical on both PAH- and PSS-terminated films; the higher adsorbed density on the PAH-terminated film is due to an adsorbed layer of roughly twice the thickness. The binding of monoclonal antibodies specific to the protein's cell binding site is considerably enhanced to fibronectin adsorbed to the PSS layer, indicating a more accessible adsorbed layer. With increased salt concentration, we find thicker PEM films but considerably thinner adsorbed fibronectin layers, owing to increased electrostatic screening. Using AFM, we find adsorbed fibronectin layers to contain clusters; these are more numerous and symmetric on the PSS-terminated film. By considering the electrostatic binding of a segmental model fibronectin molecule, we propose a picture of fibronectin adsorbed primarily in an end-on-oriented monolayer on a PAH-terminated film and as clusters plus side-on-oriented isolated molecules onto a PSS-terminated film.     

甲烷在AFS型分子筛中的吸附模拟

采用巨正则系综蒙特卡罗(GCMC)方法模拟了甲烷分子在AFS型分子筛中的吸附量, 并和Dvren等人(Langmuir, 2004, 20: 2683)设计的金属有机骨架中的甲烷吸附量进行比较, 发现AFS型沸石分子筛对甲烷分子有很好的吸附性能, AFS型分子筛是中低压吸附储存天然气系统中的一种比较理想的吸附剂. 采用Dubinin Asakhov(DA)微孔分析方法, 分析了沸石结构对甲烷储量大小的影响, 总结了影响甲烷储量大小的物理因素.     

多嵌段聚醚氨酯薄膜的表面分析

本文用电子能谱(ESCA)角度外推法得到SPU最表层的组成,并与表面能测定等方法所得结果相对照,结果表明不同本体组成的SPU薄膜的表面成份大致相同。     

Adsorption of Polycation and Anionic Surfactant onto Iron Surfaces and the Inhibition of Carbon Dioxide Corrosion

The adsorption process of two polycations (pDADMAC and C‐PAM) with different charge densities has been investigated using the quartz crystal microbalance technique with dissipation monitoring (QCM‐D). The effect of the charge density of the polycation, the NaCl concentration, and the complexation with an anionic surfactant are addressed in this work. X‐ray photoelectron spectroscopy and atomic force microscopy were utilized to analyze the adsorbate with respect to the film coverage and film structure. The corrosion‐inhibiting performance of the films on high‐purity iron in a CO₂ saturated brine, at 25°C, 1 bar CO₂, and pH 4, was investigated by the linear polarization resistance technique. It was found that the polycations adsorbed onto the iron surface, but the corrosion rate of 1 mm yr^?1 was not lowered. However, the polycations formed a complex with an anionic surfactant, and such films showed excellent inhibition performance. Both films, of pDADMAC/SDS and of C‐PAM/SDS, lowered the corrosion rate of iron below 0.01 mm yr^?1. The SDS concentration was below the cmc. It is believed that the SDS adsorbed into the preadsorbed polycation film, forming a complex structure resulting in a hydrophobic and dense film.     

Infrared Spectroscopic Study on Adsorption of Acetonitrile from Solution onto Several Oxide Surfaces at High Pressure

Adsorption of acetonitrile from toluene solution at a liquid-solid interface under pressures of up to 300 MPa was investigated by IR spectroscopy. The CN stretching vibration bands (v_CN) of adsorbed acetonitrile were observed at higher frequencies than those of the same species in the liquid phase. The shift on alumina-pillared montmorillonite (ALPM) was the largest (ca. 8 cm^-1) for the adsorbents studied. The v_CN intensities of adsorbed acetonitrile on ALPM and on alumina (Al₂O₃) considerably increased with increased pressure, indicating an increase acetonitrile adsorption due to compression. It was concluded that the total volume of the system was reduced by adsorption, and that the reduction was brought about not only by the formation of an adsorption bond but also by the change in the solvation of the adsorbate in the adsorbent pore.     

Adsorption of Dimers at Surfaces

A model for the adsorption of dimers at a surface is presented. The model is based on a generalization of the Ono-Kondo lattice theory. The densities of dimer molecules that are parallel to the surface, x parallel, and perpendicular to the surface, x perpendicular, are calculated. It is shown that symmetric dimer molecules adsorb preferentially parallel to the surface at all densities. The model also predicts that the Gibbs adsorption is negative for small interaction energies between dimers and the surface. Copyright 1999 Academic Press.     

生物金属-有机骨架材料中药物吸附及扩散的分子模拟研究

选用了三种bio-MOFs （bio-MOF-1,bio-MOF-11,bio-MOF-100）材料,采用蒙特卡罗和分子动力学模拟研究了布洛芬分子在bio-MOF材料中的吸附和扩散性质. 结果发现,bio-MOF材料结构对药物分子布洛芬的吸附及扩散有很大影响. 其中,孔径控制着客体分子布洛芬的进入及扩散; 孔隙率大小与布洛芬的吸附量及自扩散系数大小成正比. 静电作用力对布洛芬分子的吸附有较小的促进作用. 另外还研究了布洛芬分子在MOF材料中的最佳吸附位及最优构型,发现布洛芬分子优先吸附在金属角落处,以及不同材料其吸附的布洛芬分子最优构型是不一样的.     

二甲苯在AlPO4-5分子筛中吸附的分子模拟研究

采用巨正则蒙特卡罗法(GCMC)研究了二甲苯异构体在AlPO4-5中的吸附，得到了有关吸附平衡常数、吸附热、吸附等温线及吸附位等信息．结果表明，在303K时，邻二甲苯的吸附量高于其它异构体；而在523和573K时，对二甲苯的吸附量最高．低吸附量时二甲苯的平均势能基本不发生变化，而高吸附量时二甲苯的平均势能随着吸附量增加而降低，尤其邻二甲苯的平均势能变化更加明显．由此对二甲苯各异构体在AlPO4-5中的吸附量差别以及它们在分子筛中的排列方式进行了讨论．     

氧气在聚丙烯内吸附和扩散的分子模拟

采用巨正则Monte Carlo和分子动力学模拟相结合的方法研究了氧气在不同聚合度的聚丙烯内的吸附和扩散. 模拟结果表明, 随聚丙烯聚合度的增加, 聚丙烯对氧气的吸附量逐渐增加, 而氧气在聚丙烯内的扩散系数减小; 当聚合度增大到一定程度时, 吸附量和扩散系数都趋于一稳定值. 随温度的升高, 氧气在聚丙烯内的吸附量减少, 而扩散系数增大. 本文还应用自由体积理论探讨了氧气在聚合物内扩散的机理, 发现氧气在聚丙烯内以空穴形式存在的自由体积之间扩散, 即氧气先在一个空穴内不停振动, 然后通过聚丙烯链段运动形成的通道跳跃到下一个空穴来完成扩散. 结果表明, 较高聚合度的聚合物材料在常温及低温下使用对于其在食品包装材料中的应用是有利的, 这为食品包装材料行业相关产品的应用开发提供了一定的指导和依据.     

Adsorption of polyvinylimidazole onto kaolinite

The adsorption of polyvinylimidazole (PVI) onto kaolinite from aqueous solutions has been investigated systematically as a function of parameters such as calcination temperature of kaolinite, pH, ionic strength, and temperature. According to the experimental results, the adsorption of PVI increases with pH from 8.50 to 11.50, temperature from 25 to 55 degrees C, and ionic strength from 0 to 0.1 mol L(-1). The kaolinite sample calcined at 600 degrees C has a maximum adsorption capacity. Adsorption isotherms of PVI onto kaolinite have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The physical properties of this adsorbent are consistent with the parameters obtained from the isotherm equations. Furthermore, the zeta potentials of kaolinite suspensions have been measured in aqueous solutions of different PVI concentrations and pH. From the experimental results, (i) pH strongly alters the zeta potential of kaolinite; (ii) kaolinite has an isoelectric point at about pH 2.35 in water and about pH 8.75 in 249.9 ppm PVI concentration; (iii) PVI changes the interface charge from negative to positive for kaolinite. The study of temperature effect has been quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (RL) has shown that kaolinite can be used for adsorption of PVI from aqueous solutions.     

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.     

Adsorption on Heterogeneous Regular Surfaces

Quantifying the role of surface shape and physicochemical surface conditions on the interfacial reactivity of particles and substrates is fundamental to a multitude of natural and engineered surface adsorption phenomena. We consider continuum/jump regime adsorption at the gas or liquid interface of arbitrary regular solid surfaces with heterogeneous surface features. In particular, the 3-D boundary value problem (based on Laplace's diffusion equation) is converted into a 2-D integral equation for the adsorbate concentration at the particle surface. This accommodates numerical descretization via the implementation of 2-D Gauss-Legendre quadratures on an arrangement of high- and low-adsorption patch trace sites constructed to completely cover the particle surface. A generalized computer program is developed to solve the resulting linear algebra problem for the unkown local adsorption current densities. We investigate the role of various distributions of high- and low-adsorption sites for a generalized class of spheres which includes the DNA-like shaped twisted spheres. The biological implications of the role of surface curvature on interfacial adsorption/reactivity at particle surfaces are also discussed. Copyright 2001 Academic Press.     

甲烷在中孔分子筛MCM-41中吸附的计算机模拟

采用巨正则系综Monte Carlo方法研究了甲烷在两个不同孔径的MCM-41中不同温度下的吸附等温线和其在孔中的相行为和排列方式.模拟结果显示,在较小孔径的MCM-41中,流体分子达到毛细凝聚所需的化学位较小,并且观察到两个孔径下计算机模拟得到的亚稳态区域都非常宽,使得层状转变（如果有的话）被包含在这个区域.通过比较两种孔径下达到毛细凝聚后的构型,可以看出,在3.5 nm的孔中流体的分子结构出现非常有序的排列,而在5.0 nm的孔中则没有.在常温300 K时甲烷的吸附的计算机模拟表明,孔壁对流体分子的作用仅仅影响较靠近壁面附近的流体分子的排列,而对孔中间的分子几乎没有影响.