Symmetry Making and Breaking in the Synthesis and Assembly of Stellated and Bimetallic Nanocrystals

大自然在花朵的美丽、蜂巢的精确和雪花的精致图案中展示了对称性。除了对称形式的吸引力之外，对称还可以赋予功能。例如，圆蛛以螺旋形编织以最大化其网的强度，蜜蜂用密集的六边形建造蜂巢以最大化蜂蜜储存。结构和功能之间的这种相关性也在现代纳米材料设计中得到了体现，其中改变纳米晶体的对称性或由纳米晶体构建的超结构的内部顺序可以提供新的功能。然而，纳米材料的合成和组装一直局限于简单的组成和结构，直到最近。在这项研究中，首席研究员Sara Skrabalak正在开发新的合成方法，以制造具有多种金属和定义形状的金属纳米结构。这些纳米结构也被用作构建块以形成更大的结构，其中构建块的对称性指导更大的上层结构的形状。首席研究员和她的学生还研究了成分和结构如何赋予功能。特别是，对作为对称性函数出现的新的光-物质相互作用的研究正在进行中，以努力实现用于化学传感应用的多功能平台。最终，这项研究通过在多个学科之间建立联系，包括纳米/无机/固态化学，凝聚态物理学，表面科学和材料科学，在该领域产生了更广泛的影响。该项目还包括向非科学家介绍纳米级概念的外联和教育工作。 该项目还让大学生参与研究活动，强调他们与周围社区的联系。印第安纳州大学的Skrabalak小组正在开发种子介导的共还原，作为多金属纳米结构的新合成策略，其中多种金属同时沉积在形状控制的纳米晶体上。 纳米晶种的对称性被转移到最终的纳米结构中。本研究包括晶格失配和沉积动力学对晶粒分布的影响。这项工作是再加上一个研究如何对称性可以减少沿着特定的晶体学方向在种子介导的共同减少，以实现新的星状对称性，反过来又功能多样化。最后，Skrabalak小组正在使用星状金属纳米晶体组装紧密堆积和低密度晶格，以将结晶能力扩展到新的结构类别。 它们还表征了出现的集体光学性质。这三个目标加上推广和教育工作，本科研究人员是科学大使，他们以前的高中，介绍纳米概念的学生，并作为榜样，那些有兴趣在科学，技术，工程和数学领域。研究的进展扩大了纳米晶体和超结构的类别，并确定了种子和积木对称性在金属纳米晶体合成和组装中的作用，以在科学中产生更广泛的影响。

Nature demonstrates symmetry in the beauty of a flower, the precision of a honeycomb, and the elaborate patterns of snowflakes. Beyond the appeal of symmetric forms, symmetry can also impart function. For example, orb spiders weave in a spiral pattern to maximize the strength of their webs and bees construct honeycombs with close packed hexagons to maximize honey storage. This correlation between structure and function is also captured in modern nanomaterial design, where changing the symmetry of a nanocrystal or the internal order of a superstructure built from nanocrystals can give novel function. However, the synthesis and assembly of nanomaterials have been limited to simple compositions and structures until recently. In this research, the principal investigator, Sara Skrabalak, is developing new synthetic methods to make metal nanostructures with multiple metals and defined shapes. These nanostructures are also being used as building blocks to form larger structures, where the symmetries of the building blocks direct the shapes of the larger superstructures. The principal investigator and her students also study how the compositions and structures impart functionality. In particular, studies into the new light-matter interactions that arise as a function of symmetry are underway in an effort to achieve multi-functional platforms for chemical sensing applications. Ultimately, this research has broader impacts in the field by forging links between multiple disciplines, including nano/inorganic/solid-state chemistry, condensed matter physics, surface science, and material science. This project also incorporates outreach and educational efforts that introduce nanoscale concepts to non-scientists. The project also involves undergraduates in research activities in ways that emphasize their connection to the surrounding community.The Skrabalak group at Indiana University is developing seed-mediated co-reduction as a new synthetic strategy to multimetallic nanostructures, where multiple metals are simultaneously deposited onto shape-controlled nanocrystals. The symmetry of the nanocrystal seeds is transferred to the final nanostructures. This research includes studying how lattice mismatch and deposition kinetics contribute to bimetallic distribution. This work is coupled with a study of how symmetry can be reduced along specific crystallographic directions during seed-mediated co-reduction in order to achieve new stellated nanocrystal symmetries and in turn functional diversification. Finally, the Skrabalak group is using the stellated metal nanocrystals to assemble close-packed and low-density lattices to expand crystallization capabilities to new structural classes. They also characterize the collective optical properties that emerge. These three aims are coupled with outreach and educational efforts in which undergraduate researchers are Science Ambassadors to their former high schools, introducing nanoscale concepts to students and serving as role models to those interested in science, technology, engineering and mathematics fields. Advancement in the research expands the classes of nanocrystals and superstructures possible and identifies the roles of seed and building block symmetry in the synthesis and assembly of metal nanocrystals for broader impact in the science.