Long-lasting all-weather night-vision material unveiled
A US-based team of scientists claims to have invented a material that releases over two weeks of night-vision light after just one minute's exposure to the sun.
The University of Georgia team says the near-infrared emitting substance could offer the military "secret" illumination at nighttime.
It says the all-weather material could also revolutionise diagnostic medicine.
The details are published in the latest issue of the Nature Materials journal.
The material combines the well-known near infrared-light emitter trivalent chromium ion with zinc gallogermanates - a complex oxide compound.
The chromium ions normally release all of their near infrared-light in the space of a few milliseconds after being exposed to "excitation light", such as sunlight.
However, the zinc and gallogermanates create a "labyrinth of traps" for the energy causing it to be released over an extended period of up to 360-hours.
The scientists tested this material in a variety of conditions and found it could be rapidly and repeatedly charged even if the day was cloudy, overcast or rainy.
The team said the phosphorescent substance did not need to be exposed to direct sunlight. It took on a charge in shadows, underwater or even submerged in a corrosive bleach solution. Fluorescent lights also activated the process.
Lead author, Zhengwei Pan, said the material could be added to ceramic discs or mixed into paints and inks by the army and others.
"The military and security services could use this for identification purposes - either to locate people or equipment in the night so that only people with night vision goggles could see them," Prof Pan told the BBC.
"We are also experimenting with nanoparticles of the substance to see if we can bind them to cancer cells to help researchers and doctors identify them."
Prof Pan said the substance could also help develop next-generation solar energy cells thanks to its efficiency at collecting and storing sunlight.