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

该项目由材料研究部的电子和光子材料计划和陶瓷计划共同资助。非技术描述：持续发光，也称为余辉和磷光，是一种光学现象，材料在初始光照射结束后在黑暗中发光数小时。持续发光现象为人类所知已有1,000多年的历史。目前，在可见光谱范围内发射的持久发光材料已经广泛应用于日常生活中，例如，安全标志、紧急路线标志、交通标志、拨号盘和显示器以及医疗诊断。与其可见光对应物相比，缺乏近红外（NIR;波长在~700至2500纳米范围内）的持久发光材料，这是一个肉眼不可见的光谱区域，但对许多重要应用有影响，如夜视监视，生物医学成像，防伪。本研究项目研究了一系列新型近红外持续发光材料，三价铬掺杂的镓酸锂，在紫外光或太阳光的短时间（秒至分钟）激发后，显示出超过1,000小时的超长近红外持续发光。该项目提供了一个跨学科的培训经验，博士后加上研究生，本科生和K-12学生在发光材料合成，光谱表征和发光机制的调查。K-12教育通过UGA Young Dawgs -科学实验室实习计划为当地K-12学生实施。技术描述：本项目旨在对一系列新型近红外（NIR）持久发光材料：三价铬掺杂没食子酸锂进行全面的材料合成、光学表征和理论研究。这些材料表现出超过1,000小时的超长NIR持续发射和新的光激励持续发光特性。本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，并了解持久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了该材料。 探讨了烧结温度、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。介绍了几种新的持续发光特性的光学测量技术，以及持续发光中两个重要问题的理论模型，电子离域机理和电子转移动力学过程正在研究中。

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.