Janus Nanoparticles by Interfacial Engineering

该奖项授予加州大学圣克莱尔的固态材料化学计划在材料研究部是研究开发一个有效的协议的基础上界面工程制备纳米尺寸的Janus颗粒，并检查这些功能纳米材料作为独特的积木制造更复杂的架构和组件。具体而言，疏水性烷硫醇盐保护的金纳米颗粒将用作初始说明性实例。通过利用在机械压缩时颗粒在空气-水界面处受阻的界面移动性（朗缪尔方法），与注入含水亚相中的亲水性硫醇衍生物的表面交换反应将被限制在颗粒表面的仅一侧，并且因此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有序的集合体，包括接触角测量、扫描探针显微镜（例如，AFM和STM）和光谱学（UV-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。总的来说，为受控组装设计纳米级构建块的结构和性质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，部分活动还将与针对少数民族、女性和弱势大学生的外展计划紧密结合。在本项目中，加州圣克鲁斯大学的陈少伟教授和他的学生将开发一种有效的方法来制备一面具有疏水性另一面具有亲水性的纳米尺寸的颗粒材料。这些粒子类似于双面罗马神Janus，因此是Janus纳米粒子。其动机是通过将疏水配体与颗粒表面上的亲水配体分离，颗粒可以表现得像洗涤剂的表面活性剂分子，导致颗粒定向组装成有组织的结构。金纳米粒子稳定的单层的烷硫醇盐将被用作起始材料。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嵌入，颗粒的移动性将受到阻碍。然后将亲水性配体注入水相中将引发仅限于颗粒的下半部分的配体交换反应，并因此产生Janus纳米颗粒。进一步的工作将扩展到其他纳米粒子材料。然后将所得颗粒用于受控组装成具有独特功能特性的有组织结构。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民族，妇女和弱势本科生的各种外展计划相结合。

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.