In-Situ, Real Time Transmission Electron Microscope Imaging of Colloidal Crystal Formation

奖：1066573PI：具有复杂分层结构的BAU胶体晶体具有独特的光学、电学、热和机械性能，这些性能与其各自构建块的属性不同。这些超材料在各种新兴技术中发挥着越来越重要的作用，从能源转换(光伏电池)到微电子技术，从医学到国防(隐形技术)。尽管有大量具有不同性质和官能化的纳米晶库可用，但理解胶体晶体的形成和过程动力学仍然是一个挑战。实验者目前可用的工具包括光散射，它提供了关于总体平均的信息，以及？冷冻？的透射电子显微镜。在组装过程中的离散时间(通常在过程结束时)采集的样本，不能揭示过程动态。为了使新工艺和新材料的开发成为可能，随着各种工艺条件的变化，实时观察纳米晶体的自我和可控组装是非常必要的。智力优势：该项目使用一种名为纳米水族馆的新型成像工具来研究胶体晶体的形成。该装置由一个高度从几十纳米到数百纳米的薄反应器组成，夹在两层薄的(电子透明的)氮化硅薄膜之间。纳米水族馆将容纳多种液体和悬浮液，将液体保留在电子显微镜的高真空环境中数小时，没有任何泄漏，并将允许实时跟踪单个粒子、它们的旋转和相互作用。虽然已经成功地完成了证明纳米水族箱用于研究单分散颗粒聚集的初步实验，但仍需改进该装置以允许多种液体的混合，并为该装置配备用于温度测量和控制的嵌入式电阻以及用于感应电场以用于激励和传感的电极。在与化学家和材料科学家的密切合作下，该设备将用于研究二元和三元超晶格的形成。据预测，这种超晶格具有与单个元件显著不同的特性，这可能是光伏电池和微电子学的最佳选择。纳米水族馆提供了一个可编程的？实时研究胶体自身和受控组装的环境作为粒子的函数？几何构型、官能化和浓度；溶剂组成、pH和温度；以及电场。尽管它们具有潜在的重要性，但人们对这些晶体知之甚少？广泛的影响：纳米水族馆广泛适用于液体介质中过程的原位电子显微镜成像，如纳米颗粒自组装和受控组装、纳米颗粒毒理学研究(颗粒在膜上的迁移)、电化学材料沉积、接触线运动、成核过程和生物过程。由于该设备促进了新的实验，它很可能提供新的见解，并使各种学科的发现成为可能。此外，纳米水族馆具有商业化的潜力。许多研究人员都表示有兴趣在他们的研究中使用该设备。拟议的研究结果和利用纳米水族馆获得的视频将被纳入工程、物理和化学专业开设的材料科学、胶体科学、界面现象和纳米技术课程的教学材料中。利用纳米水族馆获得的原位电子显微镜视频片段传达了关于动态纳米级现象的信息，这是生动的、可接触的，对科学家和非科学家都是令人兴奋的。解说视频将被发布在网络上，为高中生和教师、本科生和公众准备，以传达发现的兴奋，并促进对科学和工程的兴趣。该项目将邀请本科生研究人员和高中教师参与设备开发、成像和图像分析。

Award: 1066573PI: Bau Colloidal crystals with complex hierarchical architectures possess unique optical, electrical, thermal, and mechanical properties that differ from the properties of their individual building blocks. These metamaterials are playing an increasingly important role in various emerging technologies ranging from energy conversion (photovoltaic cells) to microelectronics to medicine to defense (stealth technology). While a large library of nanocrystals with various properties and functionalizations is available, understanding colloidal crystal formation and process kinetics remains a challenge. Tools that are currently available to the experimenter include light scattering, which provides information on ensemble averages, and transmission electron microscopy of ?frozen? samples taken at discrete times during the assembly process (typically at the end of the process), which do not reveal process dynamics. To enable the development of new processes and new materials, it is highly desirable to observe the self and controlled assembly of nanocrystals in real time as a function of various process conditions.Intellectual Merit: This project studies colloidal crystal formation with a novel imaging tool dubbed the nanoaquarium. The device consists of a thin reactor, ranging in height from tens to hundreds of nanometers, sandwiched between two thin (electron-transparent) silicon nitride membranes. The nanoaquarium will accommodate multistreams of liquids and suspensions, will retain the liquids for hours in the high vacuum environment of the electron microscope without any leaks, and will allow the tracking of individual particles, their rotation, and interactions in real time. Although preliminary experiments demonstrating the utility of the nanoaquarium for studying the aggregation of monodisperse particles have successfully been completed, it is desirable to improve the device to allow the mixing of multiple liquid streams and equip the device with embedded resistors for temperature measurement and control and with electrodes for the induction of electric fields for actuation and sensing. In close collaboration with chemists and material scientists, the device will be used to study the formation of binary and ternary superlattices. Such superlattices are predicted to have properties that significantly differ from those of the individual components and that may be optimal for photovoltaic cells and microelectronics. The nanoaquarium provides a ?programmable? environment to study colloidal self and controlled assembly in real time as a function of particles? geometries, functionalization, and concentrations; solvent composition, pH, and temperature; and electric fields. Despite their potential importance, little is known about these crystals? nucleation and growth processes.Broader Impact: The nanoaquarium has broad applicability for in-situ electron microscope imaging of processes in liquid media such as nano particle self and controlled assembly, study of nanoparticle toxicology (migration of particles on membranes), electrochemical material deposition, contact line motion, nucleation processes, and biological processes. Since the device facilitates new experiments, it is likely to provide new insights and enable discoveries in a variety of disciplines. Additionally, the nanoaquarium has potential for commercialization. Many researchers have expressed an interest in using the device in their studies. The results of the proposed study and the videos obtained with the nanoaquarium will be incorporated into instructional material in courses on materials science, colloidal science, interfacial phenomena, and nanotechnology offered to engineering, physics, and chemistry majors. In-situ electron microscopy video footage obtained with the nanoaquarium conveys information about dynamical nanoscale phenomena that is vivid, accessible, and exciting to scientists and non-scientists alike. Narrated videos will be posted on the web, prepared for high school students and teachers, undergraduate students, and the public to convey the excitement of discovery and promote interest in science and engineering. The project will engage undergraduate researchers and high school teachers in device development, imaging, and image analysis.