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

非技术性说明：在诸如医疗保健（成像和传感）、节能管理（固态照明、光电子学和显示器）和国防（固态激光器）等领域中，强烈需要用于生物光子和光子应用的明亮且可调的光学探针。上转换纳米晶体将红外线转换为可见光，具有独特的性质，使其成为非常理想的光学探针。然而，对于这些晶体中的大多数，它们的实现受到其低亮度和降低的颜色可调性的限制。该项目的重点是建立化学成分，原子结构和上转换纳米晶体的发光之间的关系，以期设计明亮和颜色可调的发射器。该项目利用了一系列纳米晶体的多功能性，其成分和原子结构可以精细控制，预计将扩大明亮和闪烁转换器的库，同时还产生了纳米级光-物质相互作用的基础知识。该项目提供了新的机会，有助于在研究生和本科生水平的劳动力发展。研究生在发光纳米材料的合成和高级表征方面进行培训。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：上转换纳米晶体提供了几个潜在的优势，超过了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。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谐性的限制。上转换纳米晶体领域中的持续挑战是通过操纵化学组成和晶体结构来合理设计高效且颜色可调的发射器。该项目利用一系列化学柔性纳米材料，以实现直接参与与光上转换相关的能量转移过程的结构特征的成分控制。我们的目标是建立一系列的晶体化学原理，通过系统分析组成-结构-发光关系，为合理设计具有优化能量传递途径的上转换纳米晶体奠定基础。该项目涉及具有受控化学组成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）组合评估其晶体结构，并使用荧光光谱法（稳态和时间依赖性）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).