Particulate multilayers prepared from surfactant-stabilized SnO2 nanoparticles

Surfactant-stabilized SnO2 nanoparticulate organosol was prepared. The organosol mixed with arachidic acid was spread on water surfaces in a Langmuir-Blodgett (LB) balance. Surface pressure versus surface area isotherms were determined. The surfactant-stabilized SnO2 nanoparticulate monolayers were transferred, layer-by-layer by the LB technique, to solid substrates. Then the multilayers were characterized by Fourier transform IR spectroscopy, UV-visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The results indicate that the multilayer is composed of SnO2 nanoparticles and arachidic acid. It forms a Z-type periodic structure with a long spacing of 7.48 nm, i.e. a kind of three-dimensional superlattice. (C) 1999 Elsevier Science S.A. All rights reserved.

ORDERED ARRAYS OF MYOGLOBIN ADSORBED ON THE SURFACTANT MODIFIED SURFACE BY SCANNING-TUNNELING-MICROSCOPY

Myoglobin molecules were deposited on a surfactant sodium dodecyl sulfate modified HOPG surface and imaged in air with a high resolution scanning tunneling microscope (STM) for the first time. STM images exhibit not only ordered arrays of the surfactant m

Capillary electrochromatography using a strong cation-exchange column with a dynamically modified cationic surfactant

A novel mode of capillary electrochromatography (CEC), called dynamically modified strong cation-exchange CEC (DMSCX-CEC), is described in this paper. A column packed with a strong cation-exchange (SCX) packing material was dynamically modified with a long-chain quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), which was added to the mobile phase. CTAB ions were adsorbed onto the surface of the SCX packing material, and the resulting hydrophobic layer on this packing was used as the stationary phase. Using the dynamically modified SCX column, neutral solutes were separated with the CEC mode. The highest number of theoretical plates obtained was about 190 000/m, and the relative standard deviations (RSD's) for migration times and capacity factors of alkylbenzenes were less than 1.0% and 2.0% for five consecutive runs, respectively. The effects of CTAB and methanol concentrations and the pH value of the mobile phase on the electroosmotic flow and the separation mechanism were investigated. Excellent simultaneous separation of the basic and neutral solutes in DMSCX-CEC with a high-pH mobile phase was obtained, A mixture containing the acidic, basic, and neutral compounds was well separated in this mode with a low-pH mobile phase; however, peak tailing for basic compounds was observed in this mobile phase.

Capillary electrochromatography with a silica column with a dynamically modified cationic surfactant

A novel mode of capillary electrochromatography (CEC), called dynamically modified silica-capillary electrochromatography, is described in this paper. The column packed with bare silica was dynamically modified with long chain quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), which was added into the mobile phase. CTAB ions were adsorbed onto the surface of bare silica, and the resulted hydrophobic layer on the silica gel was used as the stationary phase; Using the dynamically modified silica column, neutral solutes were separated by CEC. The highest number of theoretical plates obtained was about 71 500/m and the relative standard deviations for t(0) and capacity factor of toluene were 4.7% and 4.9% for 20 consecutive runs, respectively. The separation mechanism of neutral solutes and the influence of mobile phase composition on the separation was investigated. The separation of nitrogen-containing solutes was carried out with this mode and the peak tailing of basic solute was effectively eliminated because the adsorption of basic solute on silica was blocked by the preferred adsorption of CTAB. (C) 1999 Elsevier Science B.V. All rights reserved.

Acid catalyzed synthesis of ordered bifunctionalized mesoporous organosilicas with large pore

Thiol-functionalized mesoporous ethane-silicas with large pore were synthesized by co-condensation of 1,2-bis(trimethoxy-sily)ethane (BTME) with 3-mercaptopropyltrimethoxysilane (MPTMS) using nonionic oligomeric polymer C1H (OCH(2)-CH(2))(10)OH (Brij-76) or poly(alkylene oxide) block copolymer (P123) as surfactant in acidic medium. The results of powder X-ray diffraction (XRD), nitrogen gas adsorption, and transmission electron microscopy (TEM) show that the resultant materials have well-ordered hexagonal mesoscopic structure with uniform pore size distributions. (29)Si MAS NNR, (13)C CP-MAS NMR. FT-IR, and UV Raman spectroscopies confirm the attachment of thiol functionalities in the mesoporous ethane-sificas. The maximum content of the attached thiol group (-SH) in the mesoporous framework is 2.48mmol/g. The ordered mesoporous materials are efficient Hg(2+) adsorbents with almost every -SH site accessible to Hg(2+). In the presence of various kinds of heavy metal ions such as Hg(2+), Cd(2+), Zn(2+), Cu(2+) and Cr(3+), the materials synthesized using poly(alkylene oxide) block cooollxmier (Pluronic 123) g(2+), as surfactant show almost similar affinity to Hg(2+), Cd(2+), and Cr(3+), while the materials synthesized using ofigomeric polymer C(18)H(37)(OCH(2)CH(2))(10)OH (Brij-76) as surfactant exhibit high selectivity to Hg(2+). (C) 2004 Elsevier Inc. All rights reserved.

Hydrothermal synthesis of alumina nanotubes templated by anionic surfactant

The alumina nanotubes were prepared by using the anionic surfactant, sodium dodecyl sulfonate (SDS), as structure-directing template for the first time with Al(NO3)(3)center dot 9H(2)O as precursor via a hydrothermal method. Structure and morphology of the nanotubes were characterized by XRD, TEM, FT-IR, TG and N-2 adsorption-desorption. The obtained nanotubes were found having outer diameters from 6 to 8 nm with length up to 200 nm. (C) 2005 Elsevier B.V. All rights reserved.

Comparative studies of AOT and NaDEHP by fluorescence technique and z-potential (ζ) measurements

The aggregation behaviors of two surfactants with the same hydrophobic tail, sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium bis(2-ethylhexyl)phosphate (NaDEHP), have been investigated by the fluorescence technique and z-potential (ζ) measurements. Five fine peaks of the pyrene molecule fluorescence spectroscopy appear in the surfactant solution, and the micropolarity at which pyrene locates is monitored from the intensity ratio of the first (I1) and the third peak (I3). A wide peak around 475 nm, the emission spectra of the excimer of pyrene molecules, is observed in the NaDEHP solution, while this is not found for the AOT system. The value of I1/I3 decreases in a more limited concentration range for the AOT system than for NaDEHP, indicating that small aggregates can be more easily formed by NaDEHP molecules. The z-potential results for the aggregates formed by the two surfactants show that the interaction between AOT and PVP is stronger than that between NaDEHP and PVP.

The interaction between poly(vinylpyrrolidone) and reversed micelles of water/AOT/n-heptane

The interactions between poly(vinylpyrrolidone) (PVP) and the reversed micelles composed of water, AOT, and n-heptane are investigated with the aid of phase diagram, measurements of conductivity and viscosity, Fourier transform infrared (FTIR) spectrum, and dynamic light scattering (DLS). The phase diagrams of water/AOT/heptane in the presence of and absence of PVP are given. The conductivity of the water/AOT/heptane reversed micelle without PVP initially increases and then decreases with the increase of water content, ω0 (the molar ratio of water to AOT), while the plots of conductivity (K) versus ω0 of the reversed micelle in the presence of PVP depend on the PVP concentrations. The plot of K versus ω0 with 2.0%wt PVP is similar to that without PVP. Only the ω0,max (the water content that the maximum conductivity corresponds to) is larger than that without PVP. Nevertheless, the conductivity of the reversed micelle containing more than 4%wt PVP always rises with the increase of the water content in the measured range. The DLS results indicate that the hydrodynamic radius (Rh) in the presence and absence of PVP rises with the increase of ω0. The plots with PVP and without PVP have almost the same value when ω0<17; and after that, it quickly increases with the increase of ω0. It is interesting to find that there is almost no effect of the PVP concentration on the viscosity and Rh of the reversed micelle at ω0 = 15. The FTIR results suggest that the contents of SO3--bound water and Na+-bound water both decrease with PVP added, while the content of the bulky-like water increases. However, the trapped water in the hydrophobic chain of the surfactant is nearly unaffected by PVP. It is also found from the FTIR that the carbonyl group stretching vibration of AOT is fitted into two sub-peaks, which center at 1740 and 1729 cm-1, corresponding to the trans and cis conformations of AOT, respectively.

Immunosensor Interface Based on Physical and Chemical Immunogylobulin G Adsorption onto Mixed Self-Assembled Monolayers

An immunosensor interface based on mixed hydrophobic self-assembled monolayers (SAMs) of methyl and carboxylic acid terminated thiols with covalently attached human Immunoglobulin G (hIgG), is investigated. The densely packed and organised SAMs were characterised by contact angle measurements and cyclic voltammetry. The effect of the non-ionic surfactant, Tween 20, in preventing nonspecific adsorption is addressed by ellipsometry during physical and covalent hIgG immobilization on pure and mixed SAMs, respectively. It is clearly demonstrated that nonspecific adsorption due to hydrophobic interactions of hIgG on methyl ended groups is totally inhibited, whereas electrostatic/hydrogen bonding interactions with the exposed carboxylic groups prevail in the presence of surfactant. Results of ellipsometry and Atomic Force Microscopy, reveal that the surface concentration of covalently immobilized hIgG is determined by the ratio of COOH/CH3-terminated thiols in SAM forming solution. Moreover, the ellipsometric data demonstrates that the ratio of bound anti-hIgG/hIgG depends on the density of hIgG on the surface and that the highest ratio is close to three. We also report the selectivity and high sensitivity achieved by chronoamperometry in the detection of adsorbed hIgG and the reaction with its antibody.

Microscopic Model Of Nano-Scale Particles Removal In High Pressure Co2-Based Solvents

A physical model is presented to describe the kinds of static forces responsible for adhesion of nano-scale copper metal particles to silicon surface with a fluid layer. To demonstrate the extent of particle cleaning, Received in revised form equilibrium separation distance (ESD) and net adhesion force (NAF) of a regulated metal particle with different radii (10-300 nm) on the silicon surface in CO2-based cleaning systems under different pressures were simulated. Generally, increasing the pressure of the cleaning system decreased the net adhesion force between spherical copper particle and silicon surface entrapped with medium. For CO2 + isopropanol cleaning system, the equilibrium separation distance exhibited a maximum at temperature 313.15 K in the Equilibrium separation distance regions of pressure space (1.84-8.02 MPa). When the dimension of copper particle was given, for example, High pressure 50 nm radius particles, the net adhesion force decreased and equilibrium separation distance increased with increased pressure in the CO2 + H2O cleaning system at temperature 348.15 K under 2.50-12.67 MPa pressure range. However, the net adhesion force and equilibrium separation distance both decreased with an increase in surfactant concentration at given pressure (27.6 or 27.5 MPa) and temperature (318 or 298 K) for CO2 + H2O with surfactant PFPE COO-NH4+ or DiF(8)-PO4-Na+. (C) 2008 Elsevier B.V. All rights reserved.

Dissipative particle dynamics simulation of wettability alternation phenomena in the chemical flooding process

Wettability alternation phenomena is considered one of the most important enhanced oil recovery (EOR) mechanisms in the chemical flooding process and induced by the adsorption of surfactant on the rock surface. These phenomena are studied by a mesoscopic method named as dissipative particle dynamics (DPD). Both the alteration phenomena of water-wet to oil-wet and that of oil-wet to water-wet are simulated based on reasonable definition of interaction parameters between beads. The wetting hysteresis phenomenon and the process of oil-drops detachment from rock surfaces with different wettability are simulated by adding long-range external forces on the fluid particles. The simulation results show that, the oil drop is liable to spread on the oil-wetting surface and move in the form of liquid film flow, whereas it is likely to move as a whole on the water-wetting surface. There are the same phenomena occuring in wettability-alternated cases. The results also show that DPD method provides a feasible approach to the problems of seepage flow with physicochemical phenomena and can be used to study the mechanism of EOR of chemical flooding.

Synthesis and formation mechanism of silver nanowires by a templateless and seedless method

Silver nanowires in large quantities can be obtained through a simple method in the absence of a surfactant or polymer and without addition of external seeding nanocrystallites. A plausible mechanism was proposed to elucidate the formation mechanism of silver nanowires based on TEM studies.

小麦光系统I的分离纯化及其光合特性的研究

从不同基因型的小麦京411和小偃54中分离纯化了PSI颗粒并研究了PSI颗粒的一些光合特性： 1. 测定了两种基因型小麦PSI颗粒的室温吸收光谱、低温荧光光谱，并进行了SDS-PAGE多肽分析。吸收光谱显示了红区680nm和蓝区439nm的两个最大吸收峰，低温荧光光谱显示了PSI特征的位于735nm左右的发射峰，同时SDS-PAGE也显示我们的制备物包括PsaA、PsaB、LHCI以及一些其它小分子量蛋白亚基。这些都表明我们从不同基因型小麦中获得了比较理想的PSI颗粒制备物。 2. 测定了京411类囊体膜和PSI颗粒的脂类组成和脂肪酸成分，发现PSI颗粒中也存在着类囊体膜中的五种膜脂，即：MGDG、DGDG、PG、SQDG、PC，但PSI颗粒的MGDG含量比类囊体膜高，而DGDG含量较类囊体低。PSI颗粒和类囊体膜的脂肪酸组成也有差异。 3. 运用光谱学手段，研究两种基因型小麦PSI颗粒光破坏过程的异同。发现在经过强光破坏后，两种小麦PSI颗粒都发生叶绿素漂白现象，在各种状态叶绿素中，683nm状态的Chl a对强光最为敏感，受到光破坏的程度最大，而649nm Chl b和667nm Chl a分子变化较小。结合吸收光谱和低温荧光光谱我们提出了PSI中可能存在的能量传递途径。比较两种小麦PSI颗粒光破坏在低温荧光光谱上的不同，我们初步认为，小偃54可能通过将能量较多地分配给予长波长Chl而一定程度的避免过多能量向P700反应中心传递，从而起到对P700的保护作用。 4. 研究了不同表面活性剂SDS和Triton X-100对PSI颗粒色素结合状态和能量传递的影响。发现表面活性剂对色素状态和PSI中的能量传递都有很大的影响。并且Triton X-100的作用较SDS强烈。紫外荧光显示PSI蛋白结构也发生了显著变化。

表面活性剂存在下的光系统I的光合特性

本文主要研究了在非离子表面活性剂－辛基硫代葡萄糖苷（OTG）处理条件下菠菜叶绿体中光系统I（PSI）颗粒的光合特性，主要的研究结果如下： 1. 在所研究的OTG浓度范围内（0.01～13%，w/v），OTG对PSI的电子传递活性有显著的促进作用。而与此相对照，阴离子表面活性剂－十二烷基硫酸钠（SDS）对PSI的活性具有抑制作用。 2. OTG对PSI在SDS和高温（70℃）处理后失去的电子传递活性具有恢复作用。 3. OTG对PSI的色素结合状态和能量传递都有很大的影响，影响程度和影响方式与OTG的浓度有关。在其临界胶束浓度（cmc）以上的一定浓度范围内，OTG处理会导致PSI捕光天线色素蛋白复合体（LHCI）的解离;而更大浓度的OTG会使PSI中产生自由色素。

Vertical variation in dissolved alkaline phosphatase activity in a shallow eutrophic lake determined in reverse micelles

We evaluated the feasibility of microencapsulating dissolved alkaline phosphatase of a water body into reverse micelle systems prepared by hexadecyltrimethylammonium bromide as a surfactant in cyclohexane and 1-butanol as co-surfactant. The dissolved alkaline phosphatase activity within the micelle was described, including its kinetic parameters and the effects of pH and temperature on catalytic activity in surface, overlying and interstitial water of Lake Donghu. We found the similarities on the behavior of dissolved alkaline phosphatase of surface and interstitial water in reverse micelles, which was distinctly different from its behavior in the overlying water. This difference likely reflected the different origins of the dissolved alkaline phosphatase in the vertical profile of the lake. This system provides a novel tool with which to study the diversity and ecological significance of extracellular enzymes in aquatic environments.