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.
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.
