Janus Nanoparticles by Interfacial Engineering

该奖项由加州大学圣克莱尔分校材料研究部固态材料化学项目授予，旨在研究基于界面工程的有效协议的开发，以制备纳米尺寸的Janus颗粒，并检查这些功能纳米材料作为制造更复杂结构和组件的独特构建块。具体地说，疏水烷硫酯保护的金纳米颗粒将被用作最初的举例说明。利用机械压缩时粒子在空气-水界面的界面迁移受阻（Langmuir方法），与注入水亚相的亲水性硫醇衍生物的表面交换反应将被限制在粒子表面的一侧，从而形成两亲性纳米颗粒。然后将使用各种分析工具仔细检查所得颗粒的结构及其组织整体，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，FTIR，核磁共振，动态光散射等）。对Janus纳米颗粒的进一步操作将集中在有意改变配体和金属核的化学结构上。总的来说，为控制装配而设计纳米级构建块的结构和性能的能力是迈向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粒子合成、表征和组装的最新技术，从这项工作的跨学科性质中受益。此外，一些活动还将与几个针对少数民族、妇女和弱势本科生的外展项目密切结合。在这个项目中，加州大学圣克鲁兹分校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疏水一面亲水的纳米级颗粒材料。这些粒子类似于双面的罗马神Janus，因此Janus纳米粒子。其动机是，通过分离颗粒表面的疏水配体和亲水配体，颗粒可能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。由单层烷硫酯稳定的金纳米颗粒将被用作起始材料。实验上，首先在水面上形成一层颗粒；通过机械压缩（Langmuir方法），由于有机保护配体与邻近粒子的嵌入，粒子的迁移性将受到阻碍。将亲水性配体注入水相中，将引发配体交换反应，该反应仅限于颗粒的下半部分，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。由此产生的颗粒将被用于控制组装成具有独特功能特征的有组织结构。通过学习纳米颗粒合成、表征和组装的最新技术，学生研究人员将受益于这项工作的跨学科性质。研究活动还将与针对少数民族、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.