CAREER: Tuning optical responses in artificial molecules of monovalent gold nanocrystals

明湖加州大学滨江分校的Tang在职业奖中获得了大分子、超分子和纳米化学项目的支持，以独特的明确方式将纳米颗粒连接在一起。由金和其他贵金属制成的纳米颗粒可以表现出表面等离子体模式，其在吸收或散射可见光谱的特定区域中的光方面特别有效。 这项研究是以选择性的方式将它们连接在一起，目标是扩大我们在纳米级控制光与物质相互作用的能力。该方法是通过化学手段，使得人们可以容易地放大这些组装体的合成。这个CAREER项目的教育部分是向更多的公众提供等离子体纳米粒子的迷人特性的兴奋。它包括创建一个纳米材料为重点，发现为基础的实验室课程，“与等离子体和聚合物绘画”，为一年级的本科生。这代表了加州大学滨江分校（UCR）学习社区计划的新成员，该计划已被证明可以提高STEM专业的保留率，并将4年毕业率从24%提高到40%。这门课的一年级学生领袖预计将与当地的初中和高中学生进行科学演示，并用他们个人通往STEM学位的故事激励他们。PI通过为这些学校的学生和教师提供与研究生和本科生沿着在她的研究实验室工作的机会来指导他们。控制纳米粒子组装中纳米级光物质相互作用的目标是通过诱导强电磁跃迁来实现的，特别是后者，这在可见光频率下特别弱。超分子化学和固相合成被用于产生“单价金”结构单元，即，金纳米粒子，每个都有一个单一的结合位点，作为一个强大的替代目前的最先进的DNA为基础的自组装。自组装方法的目的是控制颗粒的尺寸为5-100 nm，并将颗粒间距离设计为1-20 nm。首先，精确控制不同组成的两个纳米颗粒之间的距离，产生异二聚体，用于识别对称参数不允许的模式。第二，凭借由分子支架决定的粒子间几何形状，在人造分子内的循环电流中感应出电偶极子和磁偶极子。强的、可调谐的磁偶极子允许引入具有高品质因数的Fano共振，这对于感测是有用的。第三，正在研究具有核壳纳米颗粒的三维四面体结构，这些纳米颗粒预计具有重叠的电偶极子和磁偶极子。

Ming L. Tang of the University of California Riverside is supported by the Macromolecular, Supramolecular and Nanochemistry program in a CAREER award to link nanoparticles together in uniquely well-defined ways. Nanoparticles made of gold and other noble metals can exhibit surface plasmon modes that are particularly effective at absorbing or scattering light in specific regions of the visible spectrum. This research is to hook them together in selective ways, the goal being to expand our ability to control interactions of light with matter at the nanoscale level. The approach is by chemical means, so that one can readily scale up the synthesis of these assemblies. The education component of this CAREER project is to deliver to the greater public the excitement of the fascinating properties of plasmonic nanoparticles. It includes the creation of a nanomaterials-focused, discovery-based laboratory course, "Painting with Plasmons and Polymers," for first year undergraduate students. This represents a new addition to the University of California Riverside's (UCR's) Learning Community program, which has been shown to increase retention rates of STEM majors and push 4-year graduation rates from 24% to 40%. First year student leaders from this class are expected to engage local middle and high school students with scientific demonstrations and to inspire them with stories about their personal path towards a STEM degree. The PI mentors students and teachers from these schools by providing them an opportunity to work in her research laboratory along with graduate students and undergraduates.The goal of controlling nanoscale light-matter interactions in nanoparticle assemblies is achieved by inducing strong electric and magnetic transitions, particularly the latter, which are especially weak in the visible frequencies. Supra-molecular chemistry and solid phase synthesis is being used to create "monovalent gold" building blocks, i.e., gold nanoparticles each with a single binding site, as a powerful alternative to the current state of the art DNA-based self-assembly. The self-assembly method aims to control particles from 5-100 nm in size and to engineer inter-particle distances on the order of 1-20 nm. First, precise control over the distance between two nanoparticles of different composition creates heterodimers employed to identify modes disallowed by symmetry arguments. Second, by virtue of an inter-particle geometry dictated by a molecular scaffold, both electric and magnetic dipoles are induced in the circulating currents within the artificial molecule. Strong, tunable magnetic dipoles allow introduction of Fano resonances with high quality factors that are useful for sensing. And third, 3-D tetrahedral constructs with core-shell nanoparticles predicted to have overlapping electric and magnetic dipoles are being investigated.