Metamaterials from Assembly of DNA-functionalized Nanoparticles

0930940 Jayaraman“这个奖项是根据2009年美国复苏和再投资法案（公法111-5）资助。“智力优点：超材料是一种新型的纳米/生物相关材料，其具有独特的光学性质，这些光学性质来自于成分的结构设计，而不是它们各自的化学性质。PI建议使用理论，模拟和实验的综合方法，通过DNA功能化纳米颗粒的组装，从金属纳米团簇产生2D和3D的超材料结构。接枝有单链DNA的纳米粒子是组装的最佳候选者，因为DNA接枝物的互补序列赋予了高度特异性和可调的粒子间相互作用。金属纳米团簇是理想的超材料，因为纳米团簇中的耦合等离子体共振可以同时具有电和磁特征，从而影响宏观光学性质。所提出的工作的新奇在于：1）目标：从DNA功能化纳米颗粒的簇中创建超材料，这是所提出的工作的目标，据PI所知，迄今为止还没有尝试过; 2）所提出的路线：大多数先前用于创建超材料的努力旨在通过自上而下的光刻工艺创建2D有序纳米结构，而PI旨在开发自下而上的方法以形成具有特定形状、尺寸和颗粒间间距的DNA接枝金属纳米颗粒的2D和3D簇，因为光学性质主要取决于簇的尺寸、形状和金属填充分数，而不是簇内纳米颗粒的精确堆叠。以前关于DNA接枝纳米颗粒组装的工作集中在创建晶体结构上，而我们的研究将使用DNA接枝纳米颗粒来创建具有所需空隙率和簇形状的纳米簇; 3）构建块：其他人仅使用在高表面接枝率下各向同性接枝有ssDNA的纳米颗粒，而PI将与具有在低的中等接枝密度下各向同性以及各向异性接枝的ssDNA的纳米颗粒一起工作。低的中等接枝密度和有限数量的ssDNA接枝物的各向异性放置将影响颗粒间相互作用的方向性，从而允许更好地控制簇内的颗粒间距离和填充分数。本项目的具体目标是：1）进行分子水平的理论和模拟研究，以阐明ssDNA接枝长度，碱基序列，各向同性或各向异性放置在不同的接枝密度对组装簇结构的影响。2)利用电磁模拟计算各种奈米团簇结构的有效介电常数、磁导率、阻抗及折射率。3)利用理论和模拟的预测来指导实验，以产生期望尺寸、形状和空隙率的纳米团簇，同时降低光学损耗，增强磁活性和可见频率操作的能力。这项工作是两个PI的新方向。对于PI Jayaraman来说，拟议的工作将提供对生物分子识别的基本理解，并指导未来肽引导纳米颗粒组装的工作。对于PI Park来说，DNA功能化将允许对纳米团簇结构进行更大和更精确的控制，这在他以前的工作中一直是难以捉摸的。更广泛的影响：拟议的工作将通过创造一类新的材料来改变材料工程，这些材料的特性虽然不受麦克斯韦方程的限制，但在自然界中很难找到。传统上，人们把重点放在设计两种材料之间的界面上，以影响它们的光学特性，但是使用超材料，可以通过设计将所需的光学特性构建到材料中。超材料概念提供的前所未有的工程自由度将从根本上改变材料研究的方式。超材料将对隐形防御应用、新型成像设备产生巨大影响，并实现新的通信和计算技术。由于PI来自不同的工程背景，拟议的工作将提供跨学科的研究经验，研究生在这个项目上工作。PI还计划通过功能材料科学与工程的本科生研究经验计划，工程计划中的女性，以及通过促进奇卡诺人和美洲原住民协会（SACNAS），吸引来自代表性不足的少数民族的本科生参加该项目。这项工作的结果将在PI提供的多尺度建模和模拟以及超材料的新选修课程中展示。为了接触到更广泛的社区和年龄组，PI将与布鲁姆菲尔德图书馆馆长合作，通过纳米技术相关的收藏和展览，使这项工作向公众开放。

0930940Jayaraman"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit: Metamaterials are a new class of nano/bio related materials which possess unique optical properties derived from the structural design of the constituents rather than their individual chemistry. The PIs propose to use an integrated approach of theory, simulations and experiments to produce metamaterial structures in both 2D and 3D from metal nanoclusters through assembly of DNA functionalized nanoparticles. Nanoparticles grafted with single stranded (ss) DNA are great candidates for assemblybecause of the highly specific and tunable inter-particle interaction imparted by complementary sequences of DNA grafts. Metal nanoclusters are ideal for metamaterials because the coupled plasmon resonances in a nanocluster can possess both electric and magnetic features, thereby affecting the macroscopic optical properties. The novelty of the proposed work lies in: 1) the goal: Creation of metamaterials from clusters of DNA functionalized nanoparticles, which is the goal of this proposed work, to the best of the PIs' knowledge has not been attempted so far; 2) the proposed route: Most previous efforts for creation of metamaterials have been aimed at creating 2D ordered nanostructures by top down lithographic processes, while the PIs aim to develop bottom up approaches to form 2D and 3D clusters of DNA grafted metal nanoparticles with specific shape, size and inter-particle spacing, since optical properties depend primarily on the size, shape and metal filling fraction of cluster rather than the exact stacking of nanoparticles inside the cluster. Previous work on assembly of DNA grafted nanoparticles has focused on creating crystal structures, while our study will use DNA grafted nanoparticles to create nanoclusters with desired void fractions and cluster shape; 3) the building blocks: Others have only used nanoparticles isotropically grafted with ssDNA at high surface grafting, while the PIs will work with nanoparticles that have ssDNA grafted isotropically as well as anisotropically at low moderate grafting densities. Low moderate grafting densities and anisotropic placement of a finite number of ssDNA grafts will affect the directionality of the inter-particles interactions allowing for better control over the inter-particle distances and packing fraction which within the cluster. The specific aims of this project are: 1) to conduct molecular level theory and simulation studies to elucidate the effect of ssDNA graft length, sequence of bases, isotropic or anisotropic placement at varying grafting density on the structure of assembled cluster. 2) To use electromagnetic simulations to calculate the effective permittivity, permeability, impedance and refractive index for the structure of the various nanoclusters. 3) To utilize the predictions from theory and simulations to guide the experiments for creating nanoclusters of desired sizes, shapes and void fractions with reduced optical loss, enhanced the magnetic activity and ability for visible frequency operation. This work is a new direction for both PIs. For PI Jayaraman the proposed work would provide fundamental understanding of biomolecular recognition and guide future work on peptide guided assembly of nanoparticles. For PI Park, DNA functionalization will allow for greater and more precise control over the nanocluster structures, that has been elusive to him in his previous work.Broader Impacts: The proposed work will transform materials engineering by creating a new class of materials with properties, although not forbidden by Maxwell's equations, are very difficult to find in nature. Traditionally much focus has been placed on designing the interface between two materials to affect their optical properties, but with metamaterials the desired optical properties can be built into the material by design. The unprecedented engineering freedom the metamaterial concept offers will fundamentally change the way materials research is conducted. Metamaterials will have a huge impact on stealth defense applications, novel imaging devices and enable new communications and computing technologies. Since the PIs come from different engineering backgrounds the proposed work will provide interdisciplinary research experiences for graduate students working on this project. The PIs also plan to attract undergraduates from under represented minorities to this project through the Research Experience for Undergraduates program in Functional Materials Science and Engineering, Women in Engineering Program, and through the Society for the Advancement of Chicanos and Native Americans (SACNAS). The results emanating from this work will be demonstrated in new elective courses on Multiscale modeling and simulations and Metamaterials to be offered by the PIs. To reach a much broader community and age groups the PIs will work with the Director of Broomfield library, to make this work available to the general public through nanotechnology related collections and exhibits.