New Low-Temperature Synthetic Routes to Functional Perovskite and Semiconductor Nanocrystals

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。技术概述：该研究项目的目标是开发用于能源应用的功能性无机纳米晶体的低温、固相合成的合理合成方法。低温反应是节能的，并且提供了新的纳米晶体形态、成分和晶体结构的动力学途径的额外好处。在第一种低温方法中，正在探索一种新型的硫源（即二烷基二硫族化合物），用于合成定义良好的半导体纳米晶体。这种方法的关键是二烷基二硫族化合物的热不稳定性，特别是在路易斯酸和伯胺的存在下。这种合成方法被应用于使用二烷基过氧化物和二烷基二硫化物、二硒化物和二碲化物试剂的各种半导体纳米晶体中，并且所得到的纳米晶体的光电和电化学性能正在作为尺寸和组成的函数进行测量。第二种合成方法是基于动力学控制气相将水输送到双金属醇盐溶液中，以促进低温下小钙钛矿纳米晶体的水解、成核和生长。该方法的关键是双金属醇盐前驱体的缓慢水解，它绕过了高温固-固扩散结晶的要求。利用这种合成方法，在极低的温度下合成了一系列钙钛矿纳米晶体，并研究了纳米晶体的介电性能与它们的大小和组成的关系。非技术总结：尽管固体化学领域有了50多年的发展，但合成材料的方法仍然有限。其中大多数需要高温条件。因此，有必要开发在低温条件下合成功能材料的合理方法，就像有机化学家开发了一个非常广泛和多样化的台式反应工具箱一样。由于纳米级（10-9米）材料的功能尺寸和形状依赖特性，设计低温合成方法的动力也适用于纳米晶体的合成。该研究项目的目标是利用这些节能设计原理设计出功能性纳米晶体的新路线，这将对基于这些纳米晶体平台的太阳能转换和储能技术的最终发展具有重要意义。这项研究计划的教育目标是将固态化学的核心概念带给大学、社区学院和高中的学生。在大学阶段，将固态化学整合到课程中，将通过研究生和高级本科生选修的无机结构和键合课程中的固态化学部分来完成。在社区大学和高中阶段，来自洛杉矶县代表性不足和经济弱势群体的学生将成为参加暑期实习的目标。利用太阳能转换和能源储存作为令人信服的工作实例，将开发一个暑期实习，使学生接触到大学环境中发生的前沿和跨学科研究。该课程将包括讨论和实践工作的结合，将说明如何在固态化学和纳米技术的背景下将科学方法应用于实验室研究，并将向学生展示他们在大学及以后的科学和工程领域的机会。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)TECHNICAL SUMMARY:The goal of this research program is to develop rational synthetic methods for the low temperature, solution phase synthesis of functional inorganic nanocrystals for energy applications. Lower temperature reactions are energy efficient and offer the added benefit of providing kinetic pathways to novel nanocrystal morphologies, compositions, and crystal structures. In the first low temperature method, a new type of chalcogen source (i.e., dialkyl dichalcogenides) is being explored for the synthesis of well-defined semiconductor nanocrystals. The key to this method is the thermal instability of dialkyl dichalcogenides, particularly in the presence of Lewis acids and primary amines. This synthetic methodology is being applied to a wide variety of semiconductor nanocrystals using dialkyl peroxides and dialkyl disulfide, diselenide, and ditelluride reagents, and the resulting optoelectronic and electrochemical properties of the nanocrystals are being measured as a function of size and composition. The second synthetic methodology is based on the kinetically controlled vapor phase delivery of water into a bimetallic alkoxide solution to promote the hydrolysis, nucleation and growth of small perovskite nanocrystals at low temperatures. The key to this method is the slow hydrolysis of a bimetallic alkoxide precursor, which circumvents the requirement for high temperature solid-solid diffusion for crystallization. By taking advantage of this synthesis method, a series of perovskite nanocrystals are being synthesized at very low temperatures and the dielectric properties of the nanocrystals are being studied as a function of their size and composition.NON-TECHNICAL SUMMARY:Despite over fifty years of developments in the field of solid-state chemistry, there are still only a limited number of ways to synthesize materials ? the majority of which require high temperature conditions. As such, there is a need to develop rational methodologies for the synthesis of functional materials under low temperature conditions, much in the same way that organic chemists have developed a very extensive and diverse toolbox of bench-top reactions. Because of the functional size and shape dependent properties of nanoscale (10-9 meters) materials, the impetus to design low temperature synthesis methods also applies to the synthesis of nanocrystals. The goal of this research program is to design new routes to functional nanocrystals using these energy-efficient design principles, which will be significant in the ultimate development of solar energy conversion and energy storage technologies based on these nanocrystal platforms. Integrated into this research plan is the educational objective of bringing the core concepts of solid-state chemistry to students at the university, community college, and high school levels. At the university level, integration of solid-state chemistry into the curriculum will be accomplished via a solid-state chemistry component in a course on Inorganic Structure and Bonding, which is taken by graduate students and advanced undergraduates. At the community college and high school levels, students from underrepresented and economically disadvantaged groups in Los Angeles County will be targeted for participation in a summer internship. Using solar energy conversion and energy storage as compelling working examples, a summer internship will be developed that exposes students to cutting edge and interdisciplinary research occurring at the university setting. This program will consist of a combination of discussions and hands-on work, will illustrate how the scientific method is applied to laboratory research in the context of solid-state chemistry and nanotechnology, and will expose the students to opportunities available to them in science and engineering at the university level and beyond.