Using Nanoparticles to Confine Molecular Self-Assembly

CBET-0755654Mao该项目处于两个活跃研究领域的交界处：纳米颗粒阵列和有机薄膜。两亲分子的自组装单分子膜与生物过程、润滑、胶体稳定和去污性有关。纳米粒子阵列适用于薄膜器件。这一提议的总体目标是探索在无机纳米颗粒表面成核分子纳米棒的可能性，以探索模板结晶中的纳米限制效应，并产生独特的杂化纳米结构。非外延晶种诱导成核的实验和理论证据表明，一个临界的晶种尺寸和其他限制效应的存在对于选择性地形成附着在纳米颗粒种子上的棒状纳米团簇是必要的。为了验证这一假设，将使用不同大小的金纳米颗粒，并将进行物理化学实验来表征和了解杂化结构潜在的分子自组装机制。这项拟议的研究将以固定在固体衬底上的不同大小的金纳米颗粒为模型，继续进行硒化镉纳米颗粒与二十烷酸共沉积的初步研究。此外，我们还将探索通过控制种子形状来调节杂交种的整体几何形状的能力，以及我们向有机成分传递导电性的能力。通过原位原子力显微镜实验对结晶动力学进行了探讨。除了正在与马克斯·普朗克胶体和界面研究所的Helmuth Mohwald博士合作外，该提案还将寻求通过与剑桥大学的Stuart M.Clarke博士合作，通过中子衍射/散射来表征混合超薄膜结构。智力上的功绩。形状限制形核源于纳米颗粒表面的高曲率，这对切向晶体生长施加了不可持续的应变。我们还将探索纳米颗粒介导的纳米棒成核的其他替代控制措施，包括高过饱和度、种子与核的良好润湿、一维生长习性和种子表面缺陷。晶种介导的成核是纳米颗粒和纳米棒集成的另一种方法。与以前使用相同构建块的种子作为核的工作不同，拟议的工作将使用异质和非外延种子介导的成核来研究纳米颗粒/纳米棒结构的形成，即核由不同的构建块(有机)和种子的构建块(无机)组成。对分子长度为0.11 nm的小分子的限制比对聚合物长度为10100 nm的限制更困难。到目前为止，对早期分子晶体形成的微观机制和动力学的可靠测量还很少。如果成功，基于溶液的室温方法将促进发散的组合和可伸缩的化学，以构建支化的纳米对象。这种混合纳米结构允许每个组件的尺寸依赖属性独立地进行调整。更广泛的影响。仅限于纳米介质的结晶影响了许多新兴技术，包括薄膜和高通量筛选设备。从人力资源的角度来看，美国学生将通过与世界领先的界面材料研究机构合作，获得国际研究经验。代表人数不足的本科生将从密歇根州路易斯·斯托克斯少数族裔参与联盟计划中招募，参加这一全球研究培训。

CBET-0755654MaoThe project is at the interface of two active research areas: nanoparticle arrays and organic thin films. Self assembled monolayers of amphiphiles are relevant to biological processes and in lubrication, colloidal stabilization, and detergency. Nanoparticle arrays are applicable to thin film devices. The overall objective of this proposal is to explore the possibility of nucleating molecular nanorods on inorganic nanoparticle surfaces in order to explore the nanoconfinement effect in templated crystallization and to generate a unique hybrid nano architecture. Experimental and theoretical evidence in non epitaxial seed mediated nucleation suggests that a critical seed size and the presence of other confinement effects are necessary for the selective formation of rod like nanoclusters attached to the nanoparticle seeds. To test this hypothesis, gold nanoparticles of various sizes will be used and physicochemical experiments will be conducted to characterize and understand the underlying molecular self assembly mechanisms of the hybrid architectures. The proposed study will continue a preliminary investigation of co-deposited cadmium selenide nanoparticles with eicosanoic acid, by using gold nanoparticles of varying sizes immobilized on solid substrates as models. Additionally, our ability to regulate the overall geometry of the hybrid by controlling seed shape, and our ability to impart electrical conductivity to the organic component, will be explored. The kinetics of crystallization will be probed by in situ AFM experiments. In addition to ongoing collaboration with Dr. Helmuth Mohwald at the Max Planck Institute of Colloids and Interfaces, the proposal will seek to characterize the hybrid ultrathin film structure by neutron diffraction/scattering through collaboration with Dr. Stuart M. Clarke at the University of Cambridge. Intellectual Merit. Shape restrictive nucleation stems from the high curvature of a nanoparticle surface, which imposes unsustainable strains for tangential crystal growth. Other alternative controls for nanoparticle mediated nucleation of nanorods will be explored, which may include high supersaturation, favorable wetting of seed by nucleus, 1D growth habit, and seed surface defects. The seed mediated nucleation represents an alternative approach to nanoparticle and nanorod integration. Unlike previous work using seeds of the same building blocks as the nuclei, the proposed work will investigate the formation of the nanoparticle/nanorod architecture using heterogeneous and non epitaxial seed mediated nucleation, i.e. the nucleus is made of different building blocks (organic) than those of the seed (inorganic). The confinement control for small molecules at molecular length scales, 0.11 nm, is more difficult than the confinement by polymer length scales, 10100 nm. To date, very few reliable measurements of microscopic mechanisms and kinetics of molecular crystal formation at early stages have been made. If successful, the solutionbased, room temperature approach will facilitate divergent combinatorial and scalable chemistry for the construction of branched nano objects. The hybrid nanostructure allows the size dependent properties of each component to be tuned independently. Broader Impacts. Crystallization confined to nano media impacts a number of emerging technologies including thin film and high throughput screening devices. From a human resources perspective, U.S. students will gain international research experience by working with world leading institutions in interfacial materials research. Underrepresented undergraduate students will be recruited from the Michigan Louis Stokes Alliance for Minority Participation Program to participate in this global research training.