Janus Nanoparticles by Interfacial Engineering

该奖项由加州大学圣克莱尔分校材料研究部的固态材料化学项目颁发，旨在研究开发一种基于界面工程的有效方案，用于制备纳米级 Janus 颗粒，并检查这些功能性纳米材料作为制造更复杂结构和组件的独特构建块。具体而言，疏水性链烷硫醇保护的金纳米颗粒将用作最初的说明示例。通过利用机械压缩时颗粒在空气-水界面处受阻的界面流动性（朗缪尔法），与注入水性亚相的亲水性硫醇衍生物的表面交换反应将仅限于颗粒表面的一侧，从而形成两亲性纳米颗粒。然后将采用多种分析工具来仔细检查所得颗粒的结构及其组织的整体，包括接触角测量、扫描探针显微镜（例如 AFM 和 STM）和光谱（紫外可见光、FTIR、NMR、动态光散射等）。对 Janus 纳米粒子的进一步操纵将集中在配体和金属核的化学结构的故意变化上。总体而言，为受控组装设计纳米级构建块的结构和特性的能力代表了器件制造和集成的关键的第一步。在这个项目中，学生研究人员将通过学习纳米颗粒合成、表征和组装的最新技术，从工作的跨学科性质中受益。此外，其中一些活动还将与针对少数族裔、女性和弱势本科生的几个外展项目紧密结合。在这个项目中，陈绍伟教授和他在加州大学圣克鲁斯分校的学生将开发一种有效的方法来制备纳米尺寸的颗粒材料，该材料的一面表现出疏水性，另一面表现出亲水性。这些粒子类似于双面罗马神雅努斯，因此也类似于雅努斯纳米粒子。其动机是，通过将颗粒表面的疏水配体与亲水配体分离，颗粒可以表现得像洗涤剂的表面活性剂分子，从而导致颗粒定向组装成有组织的结构。由单层烷硫醇稳定的金纳米粒子将被用作起始材料。实验上，首先在水面上形成单层颗粒；通过机械压缩（朗缪尔法），由于邻近颗粒的有机保护配体的插入，颗粒的移动性将受到阻碍。将亲水配体注入水相中将引发仅限于颗粒下半部分的配体交换反应，从而产生 Janus 纳米颗粒。进一步的工作将扩展到其他纳米颗粒材料。然后，所得颗粒将用于受控组装成具有独特功能特性的有组织的结构。学生研究人员将通过学习纳米颗粒合成、表征和组装的最新技术，从工作的跨学科性质中受益。研究活动还将与针对少数族裔、女性和弱势本科生的各种外展项目相结合。

This award to University of California Santa Clare by the Solid State Materials Chemistry program in the Division of Material Research is study the development of an effective protocol based on interfacial engineering for the preparation of nanometer-sized Janus particles, and examination of these functional nanomaterials as unique building blocks for the fabrication of more complicated architectures and assemblies. Specifically, hydrophobic alkanethiolate-protected gold nanoparticles will be used as the initial illustrating examples. By taking advantage of the impeded interfacial mobility of the particles at the air-water interface upon mechanical compression (the Langmuir method), the surface exchange reactions with hydrophilic thiol derivatives that are injected into the aqueous subphase will be confined to only one side of the particle surface, and hence the formation of amphiphilic nanoparticles. A wide array of analytical tools will then be employed to carefully examine the structures of the resulting particles and their organized ensembles, including contact angle measurements, scanning probe microscopy (e.g., AFM and STM), and spectroscopies (UV-visible, FTIR, NMR, dynamic light scattering, etc). Further manipulation of the Janus nanoparticles will focus on deliberate variation of the chemical structure of ligands and the metal cores. Overall, the capability of engineering the structure and properties of nanoscale building blocks for controlled assembly represents a critical first step towards device fabrication and integration. In this project, student researchers will benefit from the interdisciplinary nature of the work by learning the state of the art of nanoparticle synthesis, characterization, and assembly. Furthermore, some of the activities will also be closely integrated with several outreach programs targeting minority, women, and disadvantaged undergraduate students.In this project Prof. Shaowei Chen and his students at the University of California Santa Cruz, will develop an effective approach to the preparation of nanometer-sized particle materials that exhibit hydrophobic characters on one face and hydrophilic on the other. These particles are analogous to the dual-face Roman god, Janus, and hence Janus nanoparticles. The motivation is that by segregating the hydrophobic ligands from the hydrophilic ones on the particle surface, the particles may behave like the surfactant molecules of detergents, leading to directional assembly of the particles into organized structures. Gold nanoparticles stabilized by a monolayer of alkanethiolates will be used as the starting materials. Experimentally, a monolayer of the particles will be first formed on the water surface; and by mechanical compression (the Langmuir method) the mobility of the particles will be impeded because of intercalation of the organic protecting ligands from neighboring particles. Injection of a hydrophilic ligand into the water phase will then initiate ligand exchange reactions that are limited only to the bottom half of the particles, and hence the production of Janus nanoparticles. Further work will be extended to other nanoparticle materials. The resulting particles will then be used for controlled assembly into organized structures with unique functional characteristics. Student researchers will benefit from the interdisciplinary nature of the work by learning the state of the art of nanoparticle synthesis, characterization, and assembly. The research activities will also be integrated with various outreach programs targeting minority, women, and disadvantaged undergraduate students.