Nanoparticle-directed synthesis of organic nanorods

来自韦恩州立大学的毛光照（音译）获得了化学系大分子、超分子和纳米化学项目的一项奖励，以研究无机纳米颗粒上的有机纳米棒生长，这种“种子”直径为几纳米（十亿分之一米）。长期目标是学会建造将有机和无机纳米材料的功能联合收割机。具体目标是：1）研究使用金纳米颗粒种子的这些有机结构的生长，2）显示种子大小和形状对纳米棒的影响，以及3）通过在纳米颗粒处使用电流使带电有机分子结晶来制造导电有机纳米棒。这项研究有助于了解纳米尺度下的成核和结晶，这对纳米材料的合成和应用至关重要。由于成核和生长过程的时间和长度尺度及其固有的瞬态性质，所提出的实时测量是具有挑战性的。迄今为止，很少有可靠的测量的微观机制和动力学的分子成核。从有机小分子电化学合成纳米棒和纳米线是变革性的，因为以前合成的大多数纳米棒都是无机材料。种子介导的方法适用于制造廉价和现场准备的电化学传感器。教育计划侧重于三个方面：1）通过利用NSF MRI资源整合研究和教学基础设施，2）通过与韦恩州立大学GO-GIRLS项目合作，指导代表性不足的学生，和3）为本科生提供研究经验。作为成核种子的纳米颗粒在临界种子尺寸以下抑制成核，并促进在尺寸范围内具有与本体不同形态的晶体的成核超过临界尺寸。主要假设是纳米颗粒的小尺寸在成核晶体中施加了不可持续的应变，并导致纳米棒形状。另一种假设是由纳米颗粒晶种的晶面、边缘或拐角施加的晶体学限制。两种不同的系统，羧酸晶体在蒸发结晶和四硫富瓦烯电荷转移盐晶体在电结晶允许一个严格的测试的主要和替代的假设。电结晶提供了对成核和结晶过程的精确控制，这对于理解种子介导的过程至关重要。与其他人使用类似构建块的种子作为核的工作不同，这项工作研究了使用异质和非外延种子介导的成核的纳米颗粒/纳米棒结构的形成。通过实时电化学原子力显微镜实验研究了金纳米颗粒修饰电极上电荷转移盐的结晶过程。拟议的研究探索了一种替代策略，将分子和超分子组件集成到纳米器件中。为了将有机物种用于纳米器件中，必须解决面积或形状限制对分子自组装的影响。拟议的研究是重要的，因为1）该方法结合有机物种，使真正的混合纳米结构; 2）模块化的方法促进发散组合电化学;和3）基于溶液的室温过程是潜在的可扩展的分子导体，连接器，开关和网络的制造。

Guangzhao Mao from Wayne State University is supported by an award from the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry to investigate organic nanorod growth on an inorganic nanoparticle, the "seed" which is several nanometers (billionths of a meter) across. The long-range goal is to learn to build tiny devices that combine the functions of organic and inorganic nanomaterials. The specific objectives are: 1) to investigate growth of these organic structures using gold nanoparticles seeds, 2) to show what effects on the nanorods depend on the seed size and shape, and 3) to make conductive organic nanorods by crystallizing charged organic molecules using electric current at the nanoparticles. The research contributes knowledge of nucleation and crystallization at the nanoscale, which is critical in nanomaterials synthesis and applications. The proposed real-time measurements are challenging because of the time and length scales of nucleation and growth processes and their inherent transient nature. To date, very few reliable measurements of the microscopic mechanisms and kinetics of molecular nucleation have been made. The synthesis of nanorods and nanowires from small organic molecule electrochemistry is transformative because most nanorods synthesized before have been of inorganic materials. The seed-mediated process is applicable to the manufacturing of inexpensive and field-ready electrochemical sensors. The educational plan focuses on three areas: 1) integration of research and teaching infrastructure by utilizing NSF MRI resources, 2) mentoring underrepresented students by working with the Wayne State University GO-GIRLS program, and 3) providing research experiences for undergraduates.Nanoparticles as nucleation seeds inhibit nucleation below a critical seed size and promote nucleation of crystals with different morphology than bulk in a size range above the critical size. The primary hypothesis is that the small size of nanoparticles imposes an unsustainable strain in the nucleated crystal and leads to the nanorod shape. An alternative hypothesis is the crystallographic confinement imposed by crystalline facets, edges, or corners of the nanoparticle seed. Two different systems, carboxylic acid crystals in evaporative crystallization and tetrathiafulvalene charge-transfer salt crystals in electrocrystallization allow a rigorous test of the primary and alternative hypotheses. Electrocrystallization affords a precise control of the nucleation and crystallization process, which is critical for understanding the seed-mediated process. Unlike work by others using seeds of similar building blocks as the nuclei, the work investigates the formation of the nanoparticle/nanorod architecture using heterogeneous and non-epitaxial seed-mediated nucleation. The hypotheses are examined by real-time electrochemical AFM experiments of the charge-transfer salt crystallization on gold nanoparticle-decorated electrodes. The proposed study explores an alternative strategy to integrate molecular and supramolecular components into nanodevices. In order for organic species to be used in nanodevices, the effect of area or shape confinement on molecular self-assembly must be addressed. The proposed research is significant because 1) the method incorporates organic species to make truly hybrid nanostructures; 2) the modular approach facilitates divergent combinatorial electrochemistry; and 3) the solution-based room-temperature process is potentially scalable for the manufacturing of molecular conductors, connectors, switches, and networks.