While materials that emit visible light after being exposed to sunlight are quire common, scientists have had little success creating materials that emit light in the near-infrared (NIR) range.
Now, however,University of Georgia (Athens, GA) scientists have done just that -- producing a material that emits a long-lasting, NIR glow after a single minute of exposure to sunlight.
Zhengwei Pan, an associate professor of physics and engineering in the Franklin College of Arts and Sciences and the Faculty of Engineering, says that formilitary and law enforcement use, the material could be fashioned into ceramic discs that serve as a source of illumination that only those wearing night vision goggles can see. Similarly, it could be turned into a powder and mixed into a paint whose luminescence was only visible to a select few.
Pan's material uses a matrix of zinc and gallogermanate to host trivalent chromium ions, creating a chemical structure that captures excitation energy from light. As the stored energy is released, the compound persistently emits NIR light over period of up to two weeks.
Pan and postdoctoral researcher Feng Liu and doctoral student Yi-Ying Lu spent three years developing the material. Initial versions emitted light for minutes, but through modifications to the chemical ingredients and material preparation techniques, they were able to increase the afterglow from minutes to days and, ultimately, weeks.
The US Office of Naval Research, the National Science Foundation, the American Chemical Society Petroleum Research Fund, and the UGA Research Foundation supported the research.
-- By Dave Wilson, Senior Editor,Vision Systems Design
