液-液界面介导的贵金属纳米粒子自组装：和频振动光谱研究

The assembly of nanoparticles into two- or three-dimensional ordered arrays is crucial for their applications. One of important approches to prepare ordered 2D films of nanoparticles is via liquid-liquid interface mediated self-assembly (LLIMSA). It has been proved that such self-assembly procedure is essentially determined by the contact angle between the nanoparticles and the liquid-liquid interface. However, the key factors affecting the contact angle has not yet been well understood. In this project, we propose to use sum frequency generation vibrational spectroscopy, a spectroscopic tool having high interface selectivity, to study the self-assembly mechanism of noble metal nanoparticles at water-oil interfaces. By investigating the interfacial properties such as chemical composition, molecular configurations and orientations, and how these properties are impacted during nanoparticle assembly, one can gain novel insights into the nature of wetting effect of liquids on nanosurfaces. Based on the gained knowledge, the liquid-liquid interfacial properties will be rationally tunned by selecting proper oil or adding proper reagent into the liquids.This study will broaden the application range of LLIMSA in fabricating well-ordered assemblies of nanoparticles.

将纳米粒子组装成有序的二维或三维阵列对其应用具有重要的意义。液-液界面介导的自组装是制备纳米粒子二维有序薄膜的重要方法。人们已经研究证实此类自组装过程与纳米粒子与液-液界面的接触角密切相关，但对影响该接触角的关键因素还缺乏深入的了解。本项目拟采用具有高界面选择性的和频振动光谱技术研究贵金属纳米粒子在水-油界面上的自组装机制，通过考察液-液界面的分子组成、分子取向与构象等性质以及纳米粒子自组装过程对这些性质造成的影响，在分子水平上揭示液体对纳米粒子表面浸润现象的本质和关键影响因素，进一步通过改变溶剂种类或添加其他试剂，探索有目的性调控液-液界面性质的方法，拓展液-液界面介导纳米粒子自组装方法的应用范围。

自组装是自下而上构筑功能器件的重要手段，而界面特别是液体界面在分子及微纳颗粒的自组装过程中常扮演着关键作用。本项目分别以贵金属纳米粒子、稀土纳米粒子及双亲分子为组装单元，采用和频振动光谱技术研究了其在液体界面上自组装过程的微观机制，特别关注了分子间弱相互作用对自组装过程的影响。具体地，我们通过改变pH值等手段实现了金纳米棒的可逆自组装/解组装，采用和频光谱研究了改变液体环境时金纳米颗粒表面有机配体的构象变化；通过在水-油两相加入不同的配体分子，实现了金纳米粒子的不对称修饰，采用和频光谱原位表征了配体修饰反应动力学；考察了稀土纳米片表面烷基分子取向有序性与纳米片大小、自组装状态之间的关联，揭示了晶面边缘对配体分子有序性的影响，探究了表面配体的种类、修饰密度等因素对自组装过程的影响；研究了一种双亲分子与水分子形成的层状组装结构中原位反应及有序组装（生成金纳米片、聚合物纳米片）的界面分子相互作用机制。在上述基础上，我们还将研究范围扩展到有机光电器件、二次电池等功能体系中界面分子自组装、吸附等过程的研究。这些研究在揭示自组装过程中的分子协同作用机制、设计开辟新的自组装方法和调控手段等方面具有重要的科学价值。在项目支持下，共发表SCI论文8篇。