OP: Establishing the Crystallochemical Principles Governing Energy-Transfer Processes in Upconversion Nanocrystals

非技术描述：在医疗保健（成像和传感）、节能管理（固态照明、光伏和显示）和国防（固态激光器）等领域，对生物光子和光子应用的明亮和多色光学探针有强烈的需求。上转换纳米晶体，将红外线转换成可见光，具有独特的特性，使其成为非常理想的光学探针。然而，对于大多数晶体来说，它们的实现受到其低亮度和降低颜色可调性的限制。本项目主要研究上转换纳米晶体的化学成分、原子结构和发光之间的关系，以期设计出明亮、可调色的发光材料。该项目利用了一系列纳米晶体的多功能性，其组成和原子结构可以被很好地控制，并有望扩展明亮和多色上转换器的库，同时也产生纳米尺度上光物质相互作用的基础知识。该项目为研究生和本科生的劳动力发展提供了新的机会。研究生学习发光纳米材料的合成和高级表征。通过韦恩州立大学的纳米工程本科证书课程，开发了将科学研究融入本科教育的教育活动。技术描述：与传统上用于生物光子应用（如光学成像和传感）的分子下转换荧光团相比，上转换纳米晶体具有几个潜在优势。然而，它们作为光学探针的实现受到其低效率和缺乏全光谱颜色可调性的限制。上转换纳米晶体领域的一个持续挑战是通过操纵化学成分和晶体结构来合理设计高效和可调颜色的发射器。该项目利用一系列化学柔性纳米材料来实现与光上转换相关的能量转移过程直接相关的结构特征的成分控制。目标是通过对组成-结构-发光关系的系统分析，建立一系列晶体化学原理，为合理设计具有优化能量转移途径的上转换纳米晶体奠定基础。该项目涉及控制化学成分和尺寸的胶体纳米晶体的溶液相合成，使用多种光谱技术（x射线衍射，x射线全散射和x射线吸收）对其晶体结构进行评估，并使用荧光光谱法（稳态和时间相关）对其光上转换特性进行深入研究。

Non-technical description: There is a strong need for bright and multicolor optical probes for biophotonic and photonic applications in fields such as health care (imaging and sensing), energy efficient management (solid-state lighting, photovoltaics, and displays), and defense (solid-state lasers). Upconversion nanocrystals, which convert infrared into visible light, possess unique properties that make them highly desirable optical probes. However, for most of those crystals their implementation has been limited by their low brightness and reduced color tunability. This project focuses on establishing relationships between the chemical composition, atomic structure, and luminescence of upconversion nanocrystals with a view towards designing bright and color-tunable emitters. The project takes advantage of the versatility of a series of nanocrystals whose composition and atomic structure can be finely controlled, and is expected to expand the library of bright and multicolor upconverters, while also generating fundamental knowledge of light-matter interactions at the nanoscale. The project provides new opportunities to contribute to workforce development at both graduate and undergraduate levels. Graduate students are trained in the synthesis and advanced characterization of luminescent nanomaterials. Educational activities are developed to integrate scientific research into undergraduate education through Wayne State University's Nanoengineering Undergraduate Certificate Program.Technical description: Upconversion nanocrystals offer several potential advantages over molecular downconversion fluorophores traditionally employed in biophotonic applications such as optical imaging and sensing. However, their implementation as optical probes has been limited by their low efficiency and lack of full-spectrum color tunability. An ongoing challenge in the field of upconverting nanocrystals is the rational design of efficient and color-tunable emitters via manipulation of the chemical composition and crystal structure. This project utilizes a series of chemically flexible nanomaterials to enable compositional control of structural features directly involved in energy-transfer processes relevant to light upconversion. The goal is to establish a series of crystallochemical principles that create the basis for the rational design of upconverting nanocrystals with optimized energy-transfer pathways through a systematic analysis of composition-structure-luminescence relationships. This project involves solution-phase synthesis of colloidal nanocrystals with controlled chemical composition and size, evaluation of their crystal structure using a combination of multiple spectroscopic techniques (X-ray diffraction, X-ray total scattering, and X-ray absorption), and thorough study of their light upconversion properties using spectrofluorometry (steady-state and time-dependent).