Researchers have described a new material that can emit a long-lasting, near-infrared light even after a minute exposure to sunlight.
This study has been conducted by Zhengwei Pan, associate professor of physics and engineering in the Franklin College of Arts and Sciences and the Faculty of Engineering, and fellow researchers from University of Georgia, and published online in the November 20 issue of the journal Nature Materials.
According to researchers, one minute of exposure of this material to sunlight can create a 360-hour release of near infrared light. In fact, indoor fluorescent lighting can also activate this material.
Researchers used trivalent chromium ion, which is a well-known emitter of near infrared light for a few milliseconds, and hosted it on the matrix of zinc and gallogermanate that worked as a labyrinth of “traps” to capture excitation energy of electrons for an extended period. They found no decrease in the performance of the material even after placing it in freshwater, saltwater or corrosive bleach solution for three months.
This material can be of great use in medical diagnostics, in military and law enforcement agencies as a “secret” source of illumination and solar cells. In the field of medical diagnostics, the material can help in detection of cancer cells after fabrication to nanoparticles. For military and law enforcement agencies, the material can be embedded into ceramic discs that can be visible only to those, in the night, who wear night vision goggles. In the form of powders, the material can be used in paints, whose luminescence will be visible only to selected viewers.
Zhengwei Pan, Yi-Ying Lu & Feng Liu, (2011). Sunlight-activated long-persistent luminescence in the near-infrared from Cr3+-doped zinc gallogermanates. Nature Materials, doi:10.1038/nmat3173