Hydrolysis of cephanone in the micelles with different charges

The hydrolysis of cephanone in water and micelles with different charges was studied by UV-vis absorption spectroscopy. The change of pH with the hydrolysis of cephanone was determined. The mechanism of the hydrolysis and the effect of the acidity of the media on the hydrolysis were studied. The results show that the hydrolysis rate of cephanone increases with the acidity. Compared with water, SDS micelles accelerate this hydrolysis, whereas CTAB and Triton X-100 micelles suppress it. The effects of the micelles with different charges on the hydrolysis are explained by the proton concentration of the micro-environment where cephanone exists and by the charge density of the polar group of the cephanone molecules.     

Zeta-potentials of self-assembled surface micelles of ionic surfactants adsorbed at hydrophobic graphite surfaces

The zeta-potentials of the self-assembled surface ionic surfactants (sodium dodecyl sulfate—SDS and hexadecyltrimethyl ammonium bromide—CTAB) on graphite surfaces were determined both from streaming potential and electrophoretic mobility measurements. The adsorption of the surfactants at graphite–liquid interfaces has been studied using atomic force microscopy (AFM) soft-contact imaging which shows the formation of linear, parallel hemicylinders with headgroups oriented towards the solution. The magnitude of the zeta-potential increased with an increase in surfactant concentration, reaching a constant value at a concentration corresponding to the point of surface micelle formation as confirmed from AFM imaging. The streaming potential and electrophoretic mobility measurements showed that the zeta-potentials of SDS and CTAB surface micelles adsorbed at the graphite surface were about −75 and +70 mV, respectively, well in agreement with the values reported for bulk phase micelles in the literature.     

单分散、小粒径金纳米颗粒的形貌控制增长

利用种子生长法合成了形状规则、尺寸单一的形状不同金纳米颗粒. 其中立方体纳米颗粒的边长为33±2 nm, 它是在十六烷基三甲基溴化胺(CTAB)存在的条件下, 在种子的表面上用弱还原剂——抗坏血酸还原而成的. 在这个体系中, 表面活性剂CTAB既作为保护剂又作为颗粒成长的导向剂. 用UV-vis, TEM, XRD对纳米颗粒的光学性质、几何形状、纳米颗粒的单层膜概貌以及纳米颗粒的晶体结构作了表征. 考察了种子生长的时间、种子的量、抗坏血酸的量对生成纳米颗粒形状的影响.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Distinct magnetic properties of one novel type of nanoscale cobalt-iron Prussian blue analogues synthesized in microemulsion

One novel type of nanoscale cobalt-iron Prussian blue analogues (PBA) in the form of mixed nanorods and nanocubes were synthesized using cetyltrimethyl ammonium bromide (CTAB) as the surfactant in microemulsion at low temperature. The generated products were characterized by SQUID, XRD and IR techniques, etc. The effects of potassium contents, cobalt-to-iron ratios, reaction temperatures on the properties of the nanoscale cobalt-iron PBA were systematically explored. The results showed that the novel type of nanomaterials possessed distinct magnetic properties in that their coercivities were intensely dependent on cobalt-to-iron ratios and potassium contents. Furthermore, it was observed that low reaction temperature not only affected the morphologies of the products, but also had influence on their magnetic properties. Additionally, the cobalt-iron Prussian blue analogues were strongly influenced by CTAB around their surface, which led to higher Curie temperatures.     

Interaction of Metal–Dipeptide Complex with Ninhydrin in the Absence and Presence of Conventional CTAB Surfactant

The present work is aimed at studying the interaction between copper-glycyltyrosine [(Cu(II)-Gly-Tyr)]⁺ and ninhydrin in water and in micelles formed by cetyltrimethylammonium bromide (CTAB) using spectrophometric measurements at 80°C and pH 5.0. The order of reaction remains the same in the two systems, that is, first- and fractional-order kinetics with respect to [Cu(II)-Gly-Tyr]⁺ and [ninhydrin], respectively, in the excess of ninhydrin over [Cu(II)-Gly-Tyr]⁺. It was observed that the product formed is same in both the media. The reaction is catalyzed by CTAB, and the maximum rate enhancement is about three fold. Quantitative kinetic analysis of k_ψ–[CTAB] data was explained in terms of pseudo-phase of the micelles (assuming the association/incorporation of both the reactants at the micellar surface).     

Mechanism and Influencing Factors of Wettability Alteration of Water-Wet Sandstone Surface by CTAB

Different experimental methods including ellipsometry, zeta potential measurements, imbibition studies, and contact angle measurements were used to study the mechanism and influencing factors of wettability alteration of water-wet sandstone surface caused by CTAB (hexadecyl trimethyl ammonium bromide). Results show that when the concentration of CTAB reaches a certain level (below CMC), due to the electrostatic attraction between the positively charged head groups of CTAB and the negatively charged sandstone surface, the monolayer of CTAB is formed and hydrophobic chains of CTAB molecules are toward the aqueous phase, making the solid surface oil-wet. When the concentration of CTAB continues to increase (above CMC), due to the hydrophobic interaction, the compact bilayer of CTAB is formed and hydrophilic head groups of CTAB molecules are toward the aqueous phase, rendering the solid surface water-wet. The contact angles between the oil–water interface and the surface treated with CTAB increase with the increase of the concentration of NaCl and CaCl_2. Compared to NaCl, the inorganic salt CaCl₂ has a greater impact on the contact angle. In addition, the contact angles increase with the increase of temperature and decrease with the increase of pH value of the aqueous solution.     

Inhibition of CTAB on the Corrosion of Mild Steel in Hydrochloric Acid

The inhibition effect of cetyl trimethyl ammonium bromide (CTAB) on the corrosion of mild steel in 1.0 mol L^?1 hydrochloric acid (HCl) has been studied at different temperatures (25–60°C) by weight loss and potentiodynamic polarization methods. The results reveal that CTAB behaves as an effective inhibitor in 1.0 mol L^?1 HCl, and the inhibition efficiency increases with the inhibitor concentration. Polarization curves show that CTAB is a mixed-type inhibitor in hydrochloric acid. The results obtained from weight loss and polarizations are in good agreement. The effect of immersion time on corrosion inhibition has also been examined and is discussed. The adsorption of inhibitor on mild steel surface obeys the Langmuir adsorption isotherm equation. Thermodynamic parameters have been obtained by adsorption theory. The inhibition effect is satisfactorily explained by the parameters.     

Kinetics and Mechanism of Cetyltrimethylammonium Bromide Catalyzed N-Bromosuccinimide Oxidation of D-Mannose in Acidic Medium

The kinetics and mechanism of N-bromosuccinimide (NBS) oxidation of D-mannose in the absence and presence of cetyltrimethylammonium bromide (CTAB) in acidic media have been studied under the condition [D-mannose]_T ? [NBS]_T at 40°C. Under the kinetic conditions, both the slower uncatalyzed and faster catalyzed paths go on. Both the paths show the fractional and first order dependence on [D-mannose] and [NBS]_T, respectively. The rate decreased with increase in acidity. Neither succinimide (NHS) nor Hg(II) influenced the reaction rate. Activation parameters of the reactions were determined by studying the reaction at different temperatures (30–50°C). The influence of salts on the reaction rate was also studied. CTAB accelerates the reactions and the observed effects have been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. In the reaction, approximately 1 mole of NBS oxidized one mole of D-mannose. A reaction scheme of the oxidation of D-mannose by NBS was found to be in consistent with the rate law and the reaction stoichiometry.