多晶铑表面上碳氧共存体系的研究

用紫外光电子能谱（ＵＰＳ）和俄歇电子能谱（ＡＥＳ）对碳氧共存的多晶铑表面及ＣＯ、Ｏ_２、Ｃ_２Ｈ_４在该表面上的吸附进行了研究，发现铑表面上共存的表面碳和表面氧存在相互作用，由于表面氧的存在，外来吸附物如ＣＯ、Ｏ_２、Ｃ_２Ｈ_４等可以覆盖在表面碳上面，使表面碳占据表面位抑制其它物种吸附的屏蔽效应消失。该表面具有氧化性，可以把吸附的乙烯氧化。     

Simultaneous tuning of chemical composition and topography of copolymer surfaces: micelles as building blocks.

A simple method is described for controlling the surface chemical composition and topography of the diblock copolymer poly(styrene)-b-poly(dimethylsiloxane)(PS-b-PDMS) by casting the copolymer solutions from solvents with different selectivities. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively, and the wetting behavior was studied by water contact angle (CA) and sliding angle (SA) and by CA hysteresis. Chemical composition and morphology of the surface depend on solvent properties, humidity of the air, solution concentration, and block lengths. If the copolymer is cast from a common solvent, the resultant surface is hydrophobic, with a flat morphology, and dominated by PDMS on the air side. From a PDMS-selective solvent, the surface topography depends on the morphology of the micelles. Starlike micelles give rise to a featureless surface nearly completely covered by PDMS, while crew-cut-like micelles lead to a rough surface with a hierarchical structure that consists partly of PDMS. From a PS-selective solvent, however, surface segregation of PDMS was restricted, and the surface morphology can be controlled by vapor-induced phase separation. On the basis of the tunable surface roughness and PDMS concentration on the air side, water repellency of the copolymer surface could be tailored from hydrophobic to superhydrophobic. In addition, reversible switching behavior between hydrophobic and superhydrophobic can be achieved by exposing the surface to solvents with different selectivities.     

聚甲基戊烯膜式氧合器表面碳酸酐酶的固定化及性能研究

聚甲基戊烯(PMP)膜式氧合器表面先用水等离子体改性,以引入羟基官能团;再以溴化氰为偶联剂,将碳酸酐酶(CA)偶联至其表面.改性后用X射线光电子能谱(XPS)、表面接触角及酶活性测定等方法研究PMP表面性能变化.结果表明,等离子体处理后,在PMP表面引入了大量的含氧官能团,与水的表面接触角从103.37°降低至50.01°.再将CA引入PMP表面后,与水的表面接触角进一步降低至39.23°;XPS的C1谱图中出现蛋白质的特征峰;以对硝基苯酚乙酸酯为底物,测得表面接枝CA的活性达到理论单分子层接枝活性的73%.改性后PMP表面物理化学性质的变化证明本文方法确实能成功地将羟基官能团、CA引入其表面.本方法有望应用在膜式氧合器上以提高其清除血液中CO2的能力.     

Phenomenological kinetics of the thermal decomposition of sodium hydrogencarbonate

Aiming to find rigorous understanding and novel features for their potential applications, the physico-geometrical kinetics of the thermal decomposition of sodium hydrogencarbonate (SHC) was investigated by focusing on the phenomenological events taking place on a single crystalline particle during the course of the reaction. The overall kinetics evaluated by systematic measurements of the kinetic rate data by thermogravimetry under carefully controlled conditions were interpreted in association with the morphological studies on the precursory reaction, mechanism of surface reaction, structure of the surface product layer, diffusion path of evolved gases, crystal growth of the solid product, and so on. The precursory reaction was identified as the decomposition of impurity, taking place at the boundary between the surface of the SHC crystal and the adhesive small SHC particles deposited on the surface. In flowing dry N(2), the thermal decomposition of SHC proceeds by two-dimensional shrinkage of the reaction interface controlled by chemical reaction with the apparent activation energy of about 100 kJ mol(-1), after rapid completion of the surface reaction and formation of porous surface product layer. Atmospheric CO(2) and water vapor influence differently on the overall kinetics of the thermal decomposition of SHC. Added gas phase of CO(2) slightly inhibits the overall rate because of the increasing contribution of the surface reaction. Under higher water vapor pressure, the physico-geometrical mechanism of the surface reaction changes drastically, indicating the preliminary reformation of reactant surface and the formation of needle crystals of solid product on the surface. The mechanistic change and extended contribution of the surface reaction result in the deceleration of the surface reaction and acceleration of the established reaction.     

The ion sensitivity of surface conductive single crystalline diamond

Charge build-up at the solid/aqueous interface is a ubiquitous phenomenon that determines the properties of interfacial electrical double layers. Due to its unique properties, the surface of diamond offers an attractive platform to investigate charging mechanisms in aqueous solutions. We investigate the surface charge by studying the ion sensitivity of H-terminated single crystalline diamond surface conductive layers. The effect of monovalent and divalent salts has been probed at different pH values. For a pH above 3.5, increasing the ionic strength results in a decrease of the surface conductivity, in contrast to the results obtained for pH below 3.5. Electrokinetic experiments are in good agreement with the surface conductivity measurements, showing an isoelectric point at pH 3.5 for the H-terminated diamond surface. We discuss the results in terms of the Coulombic screening by electrolyte ions of the surface potential, which is induced by a pH-dependent surface charge. The origin of this surface charge is discussed in terms of charge regulation by amphoteric hydroxyl surface groups and unsymmetrical adsorption of hydroxide and hydronium ions induced by the hydrophobic nature of the H-terminated diamond surface. This surface charge can have important consequences for processes governed by the diamond/aqueous interface, such as electron transfer to charged redox molecules, adsorption of charged molecules and proteins, and ion sensitivity.     

Kinetics of spreading of DOPC liposomes at the air-water interface subjected to phospholipase A2 hydrolisis

The kinetics of surface film formation from DOPC small unilamellar liposomes spread at the air-water interface was studied by recording the surface pressure and the surface potential. The rate constants of the surface transformation of perfectly closed vesicles into open surface active structures was detcrmined.It was found that the surface transformation was accelerated by enzymatid hydrolysis. A theoretical approach, describing the coupling of the surface transformation with the catalytic hydrolysis in the scooting mode of bilayered liposomes is developed.Values of the specific activity of hydrolysis of DOPC bilayered vesicles by phospholipase A₂ fromVipera berus orientalis were obtained by this method and compared with those previously obtained by the classical pH-stat tirration method.     

Numerical computation of surface areas of molecules

For a cubical tesselation of a finite region of space which contains an irregularly shaped surface, a fairly accurate estimate of the surface area is 2/3N a ², whereN is the total number of cubes cut by the surface and a is the length of the edges of the cubes. An estimate of slightly improved accuracy can be obtained by using different increments to the surface area, depending on the number of edges of the corresponding cube cut by the surface and the number of vertices on either side of the surface.     

基于氨基与表面乙烯砜基反应动力学调控配基表面密度

配基表面密度可控为定量研究生物分子相互作用提供了精准的分子基础。然而,经典混合自组装的方法控制配基密度对于不同自组装体系不具有普适性。本文报道了一种基于表面乙烯砜基反应动力学的配基表面密度调控方法。以Nα,Nα-二（羧甲基）-L-赖氨酸（ab-NTA）为生物配基模型,对该表面反应进行了催化剂筛选并利用X射线光电子能谱（XPS）和表面膜电位对该表面反应进行了表征。采用静态水接触角的方法对表面反应的动力学进行了定量表征,计算得到反应速率常数为0.0012 min^-1。采用表面等离子体共振（SPR）分析了该生物功能表面结合组氨酸标签蛋白（SA-6His）的能力,结果表明该表面比传统NHS-NTA表面具有更高的蛋白结合量和结合强度。通过控制反应时间和催化剂种类制备了四种配基密度不同的生物功能表面,并利用SPR对四种表面进行了蛋白质静态吸附实验。实验结果表明通过控制反应时间和催化剂类型均能够实现配基表面密度的调控,并且可以实现表面多价态的调控。     

Photochemical modification and patterning of polymer surfaces by surface adsorption of photoactive block copolymers

We report a simple photolithographic approach for the creation and micropatterning of chemical functionality on polymer surfaces by use of surface-active block copolymers that contain protected photoactive functional groups. The block copolymers self-assemble at the substrate-air interface to generate a surface that is initially hydrophobic with low surface tension but that can be rendered hydrophilic and functional by photodeprotection with UV radiation. The block copolymer employed, poly(styrene-b-tert butyl acrylate), segregates preferentially to the surface of a polystyrene substrate because of the low surface tension of the polyacrylate blocks. The strong adsorption of block copolymers causes a bilayer structure to form presenting a photoactive polyacrylate layer at the surface. In the example described, the tert-butyl ester groups on the polyacrylate blocks are deprotected by exposure to UV radiation in the presence of added photoacid generators to form surface carboxylic acid groups. Surface micropatterns of carboxylic acid groups are generated by UV exposure through a contact mask. The success of surface chemical modification and pattern formation is demonstrated by X-ray photoelectron spectroscopy and contact angle measurements along with imaging by optical and fluorescence microscopy methods. The resultant chemically patterned surfaces are then used to template patterns of various biomolecules by means of selective adsorption, covalent bonding and molecular recognition mechanisms. The surface modification/patterning concept can be applied to virtually any polymeric substrate because protected functional groups have intrinsically low surface tensions, rendering properly designed block copolymers surface active in almost all polymeric substrates.     

Energy and acid-base characteristics of the surfaces of polymeric modifiers for filled cellulose nitrate composites

The energy and acid-base characteristics of the surface of butadiene-nitrile (SKN-18, SKN-26, SKN-40) and urethane (SKU-8A, SKU-8TB) rubbers, and also of polyvinyl nitrate and polyvinyl butyral were determined. Butadiene-nitrile rubbers are characterized by the highest, and vinyl polymers, by the lowest free surface energy. The free surface energy of urethane rubbers has intermediate values. The results obtained show that the surface energy of the polymers is determined both by the chemical nature of functional groups located directly in the surface layer and by the macromolecular packing density. The surface acidity increases in the order polyvinyl butyral < polyvinyl nitrate < SKU < SKN. The nature of the surface of the polymers under consideration is determined by prevalence of certain acid-base sites of adhesion interaction as a result of conformational turns of macromolecular chain segments.     

NC-AFM observation of atomic scale structure of rutile-type TiO2(110) surface prepared by wet chemical process

We succeeded in observing the atomic scale structure of a rutile-type TiO2(110) single-crystal surface prepared by the wet chemical method of chemical etching in an acid solution and surface annealing in air. Ultrahigh vacuum noncontact atomic force microscopy (UHV-NC-AFM) was used for observing the atomic scale structures of the surface. The UHV-NC-AFM measurements at 450 K, which is above a desorption temperature of molecularly adsorbed water on the TiO2(110) surface, enabled us to observe the atomic scale structure of the TiO2(110) surface prepared by the wet chemical method. In the UHV-NC-AFM measurements at room temperature (RT), however, the atomic scale structure of the TiO2(110) surface was not observed. The TiO2(110) surface may be covered with molecularly adsorbed water after the surface was prepared by the wet chemical method. The structure of the TiO2(110) surface that was prepared by the wet chemical method was consistent with the (1 x 1) bulk-terminated model of the TiO2(110) surface.     

激光刻蚀硅表面的形貌及其对浸润性的影响

利用脉冲激光在Si表面刻蚀具有不同宽度和深度的微槽形貌, 通过测量接触角的大小研究其浸润特性, 并分析了形貌与浸润性的关系. 结果表明, 在Si表面刻蚀微槽深度一定的条件下, 刻蚀微槽宽度越宽, 接触角越小; 在Si表面刻蚀微槽宽度一定的条件下, 刻蚀微槽越深, 接触角越大, 最高可达165°. 而且Si表面上刻蚀后产生的细微尖峰结构对其浸润特性有显著的影响. 因此, 利用激光刻蚀表面方法可以在一定程度上调控固体表面的润湿性能.     

Specificity and sensitivity of fluorescence labeling of surface species

FLOSS (fluorescence labeling of surface species) enables one to identify and quantify very low concentrations of surface functional groups. Unlike most surface analytical techniques, FLOSS can provide absolute, as well as relative, surface coverage determination. However, as with any other surface derivatization technique, FLOSS provides a lower limit to surface coverage. The specificity of FLOSS for a particular functional group is the key to this application. In one FLOSS protocol, amine-modified dyes are used to label surface aldehyde groups. However, amine-modified dyes, in principle, can bind to both aldehyde and carboxyl groups, limiting specificity. In this paper, we report that the FLOSS protocol devised results in less than 0.5 % of the carboxyl-modified dyes binding to the surface amine groups. Therefore, the presence of carboxyl groups on the surface should have a limited effect on the detection of aldehyde groups by amine-modified dye. Quenching of fluorescence can potentially affect quantitative measurements. To address this issue, the densities of surface functional groups of CHO-, NH2-, and epoxy-coated glass surfaces were quantified using FLOSS and compared to surface densities estimated by other methods. The FLOSS technique was extended to glass surfaces by using visible absorbing and emitting dyes. The lower detection limit is on the order of 10(9) groups/cm2.     

Influence of hyperbranched polyesters on the surface tension of polyols

The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements.     

Effect of surface hydrophobicity/hydrophilicity of mesoporous supports on the activity of immobilized lipase

Taking advantage of the virtue of hydrophilic surface, lipase was firstly immobilized on SBA-15 as a support. Then the surface of the SBA-15 with enzyme entrapped inside the channels was modified by grafting with organic moieties. It has been found that the silylation with n-decyltrimethoxysilane (DE) and 3-(trimethoxysilyl)propyl methacrylate (MA) following the lipase immobilization increases the surface hydrophobicity. But the surface modified by MA shows more hydrophilicity than that modified by DE. The activity assay indicates that the hydrolytic activity for the hydrolysis of insoluble or partly soluble substrates increases with enhanced surface hydrophobicity.     

Effect of atmospheric-pressure surface discharge on the surface properties of polytetrafluoroethylene films

Alteration of the surface properties of polytetrafluoroethylene thin films by treatment in atmospheric-pressure surface discharge plasma initiated by dc barrier corona in argon has been studied. It has been shown that the plasma treatment of the polymer film surface leads to a substantial reduction of contact angles and an increase in the total surface energy.     

New approach for representation of molecular surface

A new algorithm is proposed for approximation to the molecular surface. It starts with a triangular mesh built on an ellipsoid embracing the whole molecular surface. The triangular mesh is obtained from an icosahedron subdivision sphere with highly uniform vertex distribution, and the embracing surface is deflated stepwise to the best adherence of its triangles onto the surface of the molecule. The deflating direction of each vertex of a triangle is defined by the vector normal at this point to the previous deflated embracing surface. Our results show that the speed of the triangulation embracing ellipsoid method and the quality of the surface obtained by the method are faster and better than the method that starts with a quadrilateral mesh built from meridian and parallel representations on an embracing sphere to get the molecular surface. Furthermore, the surface obtained by the method can be used directly to approximate the molecular surface by spherical harmonic expansions. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1805–1815, 1998     

Surface modification of low-density polyethylene by inductively coupled argon plasma

The surface chemistry and nanotopography of low-density polyethylene (LDPE) were modified by downstream, inductively coupled, radio frequency (rf) Ar plasma without inducing surface damage. The extent of surface modification was controlled by the applied ion energy fluence, determined from the plasma ion density measured with a Langmuir probe. The treated LDPE surfaces were characterized by atomic force microscope (AFM) imaging, contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Analysis of AFM surface images confirmed that topography changes occurred at the nanoscale and that surface damage was insignificant. Contact angle measurements demonstrated an enhancement of the surface hydrophilicity with the increase of the plasma power. XPS results showed surface chemistry changes involving the development of different carbon-oxygen functionalities that increased the surface hydrophilicity. Physical and chemical surface modification was achieved under conditions conducive to high-density inductively coupled rf plasma.     

Studies of Surface Sulfidation and Distribution of Sulfur on Cu-ZnO Catalysts

The changes in the surface areas of copper and zinc oxide have been measured to evaluate the individual rates of sulfur coverage of each of these phases during catalyst exposure to sulfur-containing gas. Zinc oxide surface areas have been measured by CO₂ adsorption and copper surface areas by measurement of the nitrogen formed by exposure to nitrous oxide. The surface areas of both components decreased exponentially with increasing exposure time to the sulfur-containing gas. The zinc oxide component is more sulfur-resistant than copper. This is attributed to either kinetic limitation or the more stable surface sulfides of zinc.