Fe_3O_4纳米粒子在气液界面上与Gemini分子的组装

Assembly of Gemini Surfactant Monolayer with Magnetite Nanoparticles at Air/Liquid Interface

以共沉淀法制得的十二烷基苯磺酸钠（SDBS）改性的纳米Fe3O4溶胶作为亚相，在其气腋界面上与Gemini表面活性剂分子进行了组装，用表面压与单分子面积曲线测定、透射电镜（TEM）和布儒斯特角显微镜（BAM）等手段进行了表征．结果表明：SDBS表面修饰后的Fe3O4纳米粒子表面带负电荷，平均粒径约为10nm；Fe3O4粒子受到Gemaini分子中阳离子头基的吸引进入Gemini单分子层，使得其平均单分子面积从1．00mn^2增加到1．28mn^2，崩溃压从34mN·m^-1升高到40mN·m^-1；通过控制Gemini单分子层的表面压在12～15mN·m^-1范围内，Gemini分子形成聚集并规则地排列形成六边形的区域分布在气／液界面上，Fe3O4纳米粒子受到Gemini分子的静电作用进入Gemini单分子层，在气／液界面上组装成具有六边形形貌的Gemini-Fe3O4复合单分子膜．

Sodium dodecyl benzene sulfonate as surface modified reagent, magnetite nanoparticles were synthesized by controlled chemical co-precipitations method;and as-prepared magnetite hydrosols were used as subphase, Gemini surfactant monolayer with magnetite nanoparticles was assembled at the air/ liquid interface. The surface pressure-area isotherm of Gemini monolayer was measured, and the morphology of Gemini monolayer was investigated via Brewster angle microscope （BAM） and transmission electron microscope （TEM）. The results indicate that magnetite particles with mean diameter of about 10 nm take negative charge. Due to electrostatic attraction by the cationic ammonium groups of Gemini molecules, magnetite nanoparticles move into Gemini monolayer, as a result, the collapse pressure of the monolayer and the area per molecule of Gemini on magnetite hydrosol subphase are increased to 1.28 nm^2 and 40 mN·m^- 1, in contrast to those of pure water subphase which are 1.0 nm^2 and 34 mN·m^- 1 respectively. Extraordinarily when the surface pressure is between 12 mN·m^-1 and 15 mN·m^-1, Gemini molecules have a specific hexagonal configuration at the air/liquid interface which attracts magnetite nanoparticles into it to form a composite monolayer.