Commonly referred to as
phosphorescence
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
, persistent luminescence is the emission of
light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...
by a phosphorescent material after an
excitation by
ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
or
visible light
Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...
.
Mechanism
The mechanism underlying this phenomenon is not fully understood. It is neither
fluorescence
Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ...
nor
phosphorescence
Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
. In fluorescence, the lifetime of the excited state lasts a few nanoseconds. In phosphorescence, even if the emission lives several seconds, this is due to deexcitation between two electronic states of different
spin multiplicity. Persistent luminescence involves energy traps (such as electron or hole traps) in a material, which are filled during the excitation. Afterward, the stored energy is gradually released to light emitter centers, usually by a fluorescence-like mechanism.
Examples of use
Persistent luminescence materials are mainly used in safety signs, watch dials, decorative objects and toys. They have also been used as nanoprobes in small animal optical imaging.
[Q. le Masne de Chermont, C. Chanéac, J. Seguin, F. Pellé, S. Maitrejean, J.P. Jolivet, D. Gourier, M. Bessodes and D. Scherman. Nanoprobes with near-infrared persistent luminescence for in vivo imaging. ''Proc. Natl Acad. Sci. USA'' 104 :9266–9271 2007.]
References
{{Reflist
See also
*
Luminous paint
*
Strontium aluminate
Luminescence