From cryopreservation to X-ray imaging: finding the right applications for persistent phosphors
From cryopreservation to X-ray imaging: finding the right applications for persistent phosphors lead image
Persistent luminescence, the long afterglow present in a luminescent material after the excitation has stopped, has intrigued researchers for some time. Poelman et al. evaluate proposed applications of persistent phosphors that use materials seemingly unrelated but sharing certain physical principles.
Luminescent materials rely on electronic “traps” to store energy that is subsequently released in the form of light. The deeper the trap, the more difficult it is for the energy to be released, leading to a higher temperature threshold for the energy to escape from the traps.
“Every disadvantage has its advantage,” said author Dirk Poelman. “This means that material with too shallow or too deep traps for one application, is still useful for others.”
State of the art persistent phosphors are already being used in emergency signage, indicators and toys. Tuning the traps used for energy storage could enable future applications. Very shallow traps, for instance, could be used for temperature monitoring in the cryopreservation of biological tissues or viruses. Deeper traps could be useful for medical bio-imaging and personal radiation dosimeters. Minerals with very deep traps could be excellent “clocks” for geological dating, said Poelman.
“I was surprised that the emission of the benchmark green-emitting persistent phosphor can be easily measured for 6 days with an ordinary camera, while it is typically claimed to be visible for only 24 hours,” said Poelman.
In order to utilize these materials for more advanced applications, however, the authors stress that it is necessary to very precisely and quantitatively define the performance of these persistent luminescent materials.
Source: “Persistent phosphors for the future: fit for the right application,” by Dirk Poelman, David Van der Heggen, Jiaren Du, Ewoud Cosaert, and Philippe F. Smet, Journal of Applied Physics (2020). The article can be accessed at https://doi.org/10.1063/5.0032972 .
