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

该项目由材料研究部电子与光子材料计划和陶瓷计划联合资助。非技术说明：持久发光，又称余辉和磷光，是指材料在初始光照射结束后，在黑暗中发光数小时的光学现象。长余辉发光现象早在一千多年前就为人类所知。目前，在可见光范围内发射的持久发光材料已广泛应用于日常生活中，如安防标志、紧急路线标志、交通标志、刻度盘和显示器、医疗诊断等。与可见光对应物相比，缺乏近红外(NIR；波长范围在~700至2500纳米)的持久发光材料，这是一个肉眼不可见但对许多重要应用具有影响的光谱区域，如夜视监视、生物医学成像、防伪等。本研究项目研究了一种新型的近红外持久发光材料--三价铬掺杂的没食子酸锂，它在紫外光或太阳光的短时间(秒到分钟)激发后，表现出超过1000小时的超长近红外持久发光。该项目为博士后、研究生、本科生和K-12级学生提供发光材料合成、光谱表征和发光机制研究方面的跨学科培训经验。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：该项目旨在对一系列新的近红外(NIR)永久发光材料：三价铬掺杂的镓酸锂进行全面的材料合成、光学表征和理论研究。这些材料表现出超长的近红外持久发射超过1,000小时和新的光激励持久发光性能。该项目的最终目标是制备高性能的三价铬激活的近红外持久材料，并了解与持久发光过程中的电子捕获、存储和释放相关的潜在机制。采用固相反应法制备了该材料。探索了几个主要的工艺参数，如烧结温度、掺杂和共掺杂的浓度，以确定它们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)被用来获取对于理解电荷捕获和转移过程至关重要的结构特性和光谱数据。几种新的持续发光性质的光学测量技术，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.