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

1133135 PI：Hobbie半导体纳米晶体或量子点独特的光学特性非常适合生物医学成像和传感领域的一系列需求，但迄今为止的工作主要集中在诸如硫化镉等有毒材料上。相比之下，硅是一种丰富的无毒元素，可以在非热等离子体中容易地合成为发光纳米晶体。像所有量子点一样，硅纳米晶体具有有限的光致发光稳定性。出于初步的数据，表明纳米粒子包装和合奏光稳定性之间的明确联系，我们将进行一个结合的实验和计算研究的粒度分布，颗粒包装顺序和局部环境的光稳定性的薄膜和集群组装纯化硅量子点的影响。等离子体合成的纳米晶体将（i）使用不同长度的配体分散在有机溶剂中，（ii）通过密度梯度超离心以可缩放的方式按尺寸分离成高度单分散的部分，以及（iii）通过受控干燥组装成有序的膜和簇。堆积密度，结晶顺序，局部环境，和光稳定性之间的相关性将建立独立测量的微观结构与光学和电子显微镜，同时测量随时间变化的光谱响应。为了解释这些实验，我们将结合联合收割机对干燥胶体悬浮液中非平衡自组装的数值模拟和量子力学模型，该模型解释了粒子间相互作用对紧密堆积的纳米粒子系综的物理学的影响。该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，它将在多个领域产生重大影响。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，我们将利用这一点吸引公众，包括来自北达科他州各地的高中生。我们也有指导本科生，包括妇女和代表性不足的少数民族，通过具有挑战性的项目，最终在高影响力的出版物的良好记录。本提案中的大部分初步数据是由本科生收集和分析的。出于跨学科的研究范围，PI还开发了一个新的研究生课程，专门用于培养博士研究人员在？软硬兼施界面，它代表了纳米技术在21世纪世纪的典范。最后，所获得的知识的潜在技术影响是非常广泛的，从高效的固态照明和溶液处理的光致发光到光纤低温温度计和用于活细胞诊断的稳定无毒荧光团。

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.