...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Adsorption of Benzyldimethylhexadecylammonium Chloride at the Hydrophobic Silica-Water Interface Studied by Total Internal Reflection Raman Spectroscopy: Effects of Silica Surface Properties and Metal Salt Addition
【24h】

Adsorption of Benzyldimethylhexadecylammonium Chloride at the Hydrophobic Silica-Water Interface Studied by Total Internal Reflection Raman Spectroscopy: Effects of Silica Surface Properties and Metal Salt Addition

机译：全内反射拉曼光谱研究疏水性二氧化硅-水界面上苄基二甲基十六烷基氯化铵的吸附：二氧化硅表面性质和金属盐添加的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The adsorption of the cationic surfactant benzyldimethylhexadecylammonium (BDMHA~+) chloride was studied at an octadecyltrichlorosilane (OTS)-monolayer-modified silica—water interface by Raman spectroscopy in total internal reflection (TIR) geometry. The present study demonstrates the capabilities of this spectroscopic technique to evaluate thermodynamic and kinetic BDMHA~+Cl~- adsorption properties at the hydrophobic silica surface. The surface coverage of BDMHA~+ decreased by 50% at the hydrophobic OTS-silica surface relative to the surface coverage on bare silica; the dominating driving mechanisms for surfactant adsorption were identified as hydrophobic effects and head group charge screening by the electrolyte counterions. Addition of magnesium metal salt (MgCl2) to the aqueous solution (~ neutral pH) lowered the surface coverage and moderately increased the Langmuir adsorption constants relative to those of the pure surfactant. These trends were previously observed at the hydrophilic, negatively charged silica surface but with a smaller change in the Gibbs free energy of adsorption at the hydrophobic silica surface. The hydrophobic OTS-silica surface properties resulted in shorter times for the surfactant to reach steady-state adsorption conditions compared to the slow adsorption kinetics previously seen with the surfactant at the hydrophilic surface. Adsorption isotherms, based on. Raman signal intensities from spectral analysis, were developed according to the Langmuir adsorption model for the pure surfactant at the OTS-silica—water interface; the modified Langmuir model was applied to the surfactant adsorption in the presence of 5, 10, 50, and 100 mM magnesium chloride. Spectral analysis of the Raman scattering intensities and geometric considerations suggests a hemimicelle-type surface aggregate as the most likely surfactant structure at the OTS-silica surface. The different kinetics observed at the hydrophilic versus the hydrophobic silica surface further indicate that the surface charge and potential influence the surfactant diffusion and kinetic rates of adsorption at the silica—water interface.
机译：通过十八烷基三氯硅烷（OTS）-单层改性的二氧化硅-水界面，通过拉曼光谱法研究了阳离子表面活性剂苄基二甲基十六烷基铵（BDMHA〜+）在全内反射（TIR）几何结构上的吸附。本研究证明了这种光谱技术能够评估疏水性二氧化硅表面的热力学和动力学BDMHA〜+ Cl〜-吸附性能。相对于裸露的二氧化硅，BDMHA〜+在疏水性OTS-二氧化硅表面的表面覆盖率降低了50％。表面活性剂吸附的主要驱动机理被确定为疏水作用和电解质抗衡离子对头部基团电荷的筛选。相对于纯表面活性剂，将镁金属盐（MgCl2）添加到水溶液中（〜中性pH）降低了表面覆盖率并适度增加了Langmuir吸附常数。先前在亲水的，带负电荷的二氧化硅表面观察到了这些趋势，但是疏水二氧化硅表面的吉布斯吸附自由能的变化较小。与先前在亲水性表面处观察到的缓慢吸附动力学相比，疏水性OTS-二氧化硅的表面性质导致表面活性剂达到稳态吸附条件的时间更短。吸附等温线的基础上。根据朗缪尔（Langmuir）吸附模型对OTS-二氧化硅-水界面处的纯表面活性剂进行光谱分析得出拉曼信号强度。在5、10、50和100 mM氯化镁的存在下，将改进的Langmuir模型应用于表面活性剂吸附。拉曼散射强度和几何因素的光谱分析表明，半胶束型表面聚集体是OTS-二氧化硅表面上最可能的表面活性剂结构。在亲水性和疏水性二氧化硅表面观察到的不同动力学进一步表明，表面电荷和电势会影响表面活性剂的扩散和二氧化硅-水界面吸附的动力学速率。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号