【作者】 胡凡；

【导师】 郑学仿； 李慎敏；

【作者基本信息】 大连大学 ， 有机化学， 2009， 硕士

【摘要】 纳米尺寸受限溶液广泛存在于溶胶-凝胶玻璃、沸石分子筛以及碳纳米管等纳米材料中。不同于一般的非受限溶液,纳米孔道内受限溶液具有许多特异的物理和化学性质。掌握并利用孔道内流体性质的变化规律不仅具有理论意义,还将对油气的勘探开采以及催化剂应用等许多前沿应用领域产生积极的影响。与此同时,伴随着计算机技术不断的发展,分子模拟技术能够对许多实验中的问题给出合理解释,进而对实验工作者以理论的指导。利用分子动力学模拟方法,本文考察了受限于圆柱形纳米孔道模型内I₂/Ar溶液的振动传能及扩散动力学,计算得到了溶剂径向密度分布、溶质振动弛豫时间以及溶剂轴向扩散系数随孔道半径变化的规律。结果显示:1)溶质振动弛豫时间T₁随着孔道半径的增大而减小;2)溶剂沿孔道轴向扩散系数D_z随着孔道半径的增大而增大;3)随着孔道半径的增大,孔道的限制作用逐渐减小,T₁与D_z趋近于相应的非受限溶液值。另一方面,作为一个原子真实的限制体,受限于碳纳米管内的溶质与周围环境的弱相互作用更为复杂。本文利用量子-经典动力学模拟技术,研究了受限于碳纳米管内I₂分子振动频率的诱导位移及谱分布,并考察受限溶液中诱导位移的主要贡献原子及其空间分布。结果表明:1)相对于体相溶液,受限于碳纳米管内的I₂的诱导位移表现为蓝移,且蓝移大小随碳管半径的增大而增大;2)溶剂Ar原子对I₂分子振动弛豫的诱导作用较大,而碳纳米管对I₂分子振动频率的诱导作用较小;3)仅有少数几个溶剂原子对溶质的振动频率位移发挥着重要的作用,它们主要分布在三个位置:蓝移贡献组主要分布在上述弱红移贡献区域的内侧;强红移贡献组则位于I₂分子键的上方的较小区域内;其余的红移贡献溶剂原子组成较弱的红移贡献组,对称地分布在距I₂分子中心较远的两端区域中,以及强红移贡献组的上方距I₂分子更远的区域。更多还原

【Abstract】 The confinement of micro-porous media,such as sol-gels,zeolites and carbon nanotube can lead to dramatic changes of liquid in their static and dynamic properties from those of the bulk system.To understand the special properties of confined fluids is not only meaningful in theoretical research,but also important in oil exploration,catalyst applications and many other fields.At the same time,with the development of computer science and technology, molecular dynamics sumulation can answer many questions emerged in experiment and becomes a useful guide to researcher now.In this dissertation,molecular dynamics simulations on the vibrational energy transfer and diffusion of I₂/Ar solution confined in a cylindrical nanotube have been presented.The radial density profiles of solvent and solute vibrational energy relaxation time,as well as the solvent diffusion coefficient along the nanotube are calculated as a function of radius of the nanotube.The results show that:1) T₁ decreases as the radius increases;2) D_z increases as the radius increases;3) The confinement effect of the nanotube weakens quickly as the radius becomes larger,and as a result,both T₁ and D_z tend towards the values of the bulk system.On the other hand,as an atomic system,the weak interaction between solute confined in single-walled carbon nanotube and the surrounding environment is more complicated.The quantum-classical dynamics simulation technique has been used to study the solute vibrational line shifts and its distributions as well as the spatial distribution of solvent atoms confined in single-walled carbon nanotube.The results show that:1) The environment-induced vibrational frequency of solute I₂ confined in SWNT is slightly blueshifted compared to the bulk system and increases as the radius increases;2) The solvent contribution to the line shift is bigger than that of SWNT;3) Only a few solvent can determine the frequency shift,which locate in three parts:the atoms with blueshifting are located around the end of I₂ molecule;the redshifting atoms are located in two places:one is near the end of the I₂ molecule in a linear geometry but at a significantly larger distance than the blueshifting argon atoms;the other is at small Ar-I₂ center-of-mass distance with a "T-shape" configuration in which argon atom is located above the center-of-mass of I₂.更多还原