Optical Properties and Physics of Cr3+-Activated Near-Infrared Persistent Luminescent Materials

本项目由材料研究部电子与光子材料项目和陶瓷项目共同资助。非技术描述：持续发光，也称为余辉和磷光，是一种光学现象，材料在最初的光照射结束后在黑暗中发光数小时。人类已经知道持续发光的现象一千多年了。目前，在可见光谱范围内发射的持续发光材料已广泛应用于日常生活中，如安全标志、应急路线标志、交通标志、拨号显示、医疗诊断等。与可见光相比，近红外（NIR；波长在~700到2500纳米范围内）的持续发光材料是缺乏的，这是一个肉眼看不见的光谱区域，但对许多重要的应用有影响，如夜视监控，生物医学成像，防伪。本研究项目研究了一种新型的近红外持续发光材料，三价铬掺杂没食子酸锂，在紫外线或阳光的短时间（秒到分钟）激发后，表现出超过1000小时的超长近红外持续发光。该项目为博士后、研究生、本科生和K-12学生在发光材料合成、光谱表征和发光机理研究方面提供跨学科的培训经验。K-12教育是通过UGA Young Dawgs -科学实验室实习计划为当地K-12学生实施的。技术描述：本项目旨在对一系列新型近红外（NIR）持续发光材料：三价铬掺杂没食子酸锂进行综合材料合成、光学表征和理论研究。这些材料具有超过1000小时的超长近红外持续发射和新的光激发持续发光特性。该项目的最终目标是制造高性能、三价铬活化的近红外持久材料，并了解在持续发光过程中与电子捕获、存储和释放相关的潜在机制。采用固相反应法制备该材料。研究了烧结温度、掺杂剂和共掺杂剂浓度等主要工艺参数对材料结构和光学性能的影响。各种先进的结构和光谱表征工具（包括同步加速器设施）用于获取结构特性和光谱数据，这对于理解电荷捕获和转移过程至关重要。一些新的持续发光性能的光学测量技术，以及持续发光中两个重要问题的理论模型，即电子离域机制和电子转移动力学过程，正在开发中。

This project is jointly funded by the Electronic and Photonic Materials Program and the Ceramics Program, both in the Division of Materials Research.Non-technical Description: Persistent luminescence, also called afterglow and phosphorescence, is an optical phenomenon that materials glow in the dark for hours after the end of the initial light irradiation. The phenomenon of persistent luminescence has been known to mankind for over 1,000 years. Nowadays persistent luminescence materials emitting in the visible spectral range have been widely used in daily life, e.g., security signs, emergency route signs, traffic signage, dials and displays, and medical diagnostics. In contrast to their visible counterparts, persistent luminescence materials in the near-infrared (NIR; with the wavelength in the range of ~700 to 2500 nanometers), a spectral region that is invisible to naked eyes but has implications to many important applications such as night-vision surveillance, biomedical imaging, anti-counterfeiting, are lacking. This research project investigates a novel series of NIR persistent luminescence materials, trivalent chromium doped lithium gallates, which exhibit super-long NIR persistent emission of more than 1,000 hours after short (seconds to minutes) excitation by ultraviolet light or sunlight. The project provides an interdisciplinary training experience to postdocs plus graduate, undergraduate and K-12 students in luminescent material synthesis, spectral characterization, and luminescence mechanism investigations. The K-12 education is implemented through the UGA Young Dawgs - Science Laboratory Internship program for local K-12 students.Technical Description: This project aims to conduct comprehensive material synthesis, optical characterizations and theoretical investigations on a novel series of near infrared (NIR) persistent luminescent materials: trivalent chromium doped lithium gallates. These materials exhibit super-long NIR persistent emission of more than 1,000 hours and new photostimulated persistent luminescence properties. The ultimate goals of this project are to fabricate high performance, trivalent chromium activated NIR persistent materials and to understand the underlying mechanisms associated with electron trapping, storing, and releasing in the persistent luminescence process. A solid-state reaction method is used to fabricate the materials. Several major processing parameters, such as sintering temperature and the concentrations of dopants and co-dopants, are explored to determine their influences on material structures and optical properties. Various advanced structural and spectral characterization tools (including synchrotron facilities) are used to acquire structural properties and spectral data that are essential for understanding the charge trapping and transfer processes. Several new optical measurement techniques for persistent luminescence property, as well as theoretical models for two important issues in persistent luminescence, i.e., the electron delocalization mechanism and electron transfer dynamic process, are under development.