Photostable Luminescent Coatings Assembled from Flow-Purified Silicon Nanocrystals: Effects of Size, Packing Order, and Environment

1133135PI：Hobbie半导体纳米晶体或量子点的独特光学性质非常适合生物医学成像和传感的一系列需求，但到目前为止，工作主要集中在硒镉等有毒材料上。相比之下，硅是一种丰富的无毒元素，可以很容易地在非热等离子体中合成发光纳米晶体。像所有的量子点一样，硅纳米晶体的光致发光稳定性有限。在初步数据显示纳米粒子堆积与系综光稳定性之间存在明显联系的基础上，我们将对粒子尺寸分布、粒子堆积顺序和局域环境对由纯化的硅量子点组装的薄膜和团簇的光稳定性的影响进行实验和计算相结合的研究。等离子体合成的纳米晶将(I)使用不同长度的配体分散在有机溶剂中，(Ii)通过密度梯度超速离心法以可伸缩的方式分离成高度单分散的组分，以及(Iii)通过控制干燥组装成有序的薄膜和团簇。通过用光学显微镜和电子显微镜独立地测量微结构，同时测量随时间变化的光谱响应，将建立堆积密度、晶序、局域环境和光稳定性之间的关联。为了解释这些实验，我们将结合胶体悬浮液干燥过程中非平衡自组装的数值模拟和考虑粒子间相互作用对紧密堆积的纳米粒子系综的光物理影响的量子力学模型。这个项目代表了第一个关于粒子相互作用对硅量子点光稳定性影响的全面科学研究，它将在许多不同的前沿产生重大影响。光致发光的惊人视觉信号是纳米技术在宏观尺度上特别容易获得的表现形式，我们将利用这一点来吸引公众，包括来自北达科他州的高中生。我们也有良好的记录，通过具有挑战性的项目指导本科生，包括妇女和代表性不足的少数群体，这些项目最终形成了影响很大的出版物。这项提案中很大一部分初步数据是由本科生收集和分析的。在跨学科研究范围的推动下，国际和平研究所还开发了一门新的研究生课程，专门为培养软硬专业的博士研究人员而设计。界面，它代表了21世纪纳米技术的范例。最后，所获得的知识的潜在技术影响非常广泛，从高效的固态照明和溶液处理的光伏，到用于活细胞诊断的光纤低温温度计和稳定的无毒荧光团。

1133135PI: HobbieThe unique optical properties of semiconductor nanocrystals, or quantum dots, are well suited to a range of needs in biomedical imaging and sensing, but work so far has focused on toxic materials like cadmium selenide. Silicon, in contrast, is an abundant nontoxic element that can be readily synthesized into luminescent nanocrystals in nonthermal plasmas. Like all quantum dots, silicon nanocrystals have limited photoluminescent stability. Motivated by preliminary data that demonstrate a clear link between nanoparticle packing and ensemble photostability, we will perform a combined experimental and computational study of the influence of particle size distribution, particle packing order, and local environment on the photostability of films and clusters assembled from purified silicon quantum dots. The plasma-synthesized nanocrystals will be (i) dispersed in organic solvents using ligands of varied length, (ii) separated by size in a scalable fashion through density-gradient ultracentrifugation into highly monodisperse fractions, and (iii) assembled into ordered films and clusters through controlled drying. Correlations between packing density, crystalline order, local environment, and photostability will be established by independently measuring the microstructure with optical and electron microscopy while simultaneously measuring the time-dependent spectral response. To interpret these experiments, we will combine numerical simulations of non-equilibrium self-assembly in drying colloidal suspensions with a quantum-mechanical model that accounts for the influence of inter-particle interactions on the photophysics of closely packed nanoparticle ensembles.This project represents the first comprehensive scientific study of the influence of particle interactions on the photostability of silicon quantum dots, and it will have significant impact on a number of diverse fronts. The striking visual signal of photoluminescence is a particularly accessible manifestation of nanotechnology at macroscopic scales, and we will exploit this to engage the public, including high school students from across the state of North Dakota. We also have a strong record of mentoring undergraduates, including women and underrepresented minorities, through challenging projects that culminate in high-impact publications. A significant portion of the preliminary data in this proposal were collected and analyzed by undergraduates. Motivated by the interdisciplinary scope of the research, the PI is also developing a new graduate course specifically designed to train doctoral researchers at the ?soft-hard? interface, which represents a paradigm for nanotechnology in the 21st century. Finally, the potential technological impact of the knowledge gained is tremendously broad, ranging from efficient solid-state lighting and solution-processed photovoltaics to fiber-optic cryothermometers and stable non-toxic fluorophores for live cell diagnostics.