Akademik Veri Yönetim Sistemi
Karsu E. C., Bos A., Luo H., Dobrowolska A., Dorenbos P.(Yürütücü)
Diğer Uluslararası Fon Programları, 2012 - 2017
Persistent phosphors are phosphors which are continuing emitting light after stopping the excitation.
The phenomenon is also called afterglow and sometime phosphorescence. In those
phosphors electrons liberated by day
light and stored at impurities, are spontaneously released during the night
time to produce luminescence. The most well-known persistent phosphor is SrAl2O4:Eu2+;Dy3+
used as "glow in the dark" pigments in luminescent paints or plastics
that are used for emergency signs in buildings, safety clothing, traffic signs,
road marks etc. Currently methods are available to deliver nano-sized
persistent luminescence particles injected in small animals to specific organs
or tumor cells. The distribution of the particles, even deep inside the animal,
can be imaged from the outside by simply detecting its "glow in the
dark" luminescence.
In spite of many studies the mechanism of the afterglow is still not
understood. The
mechanism of persistent luminescence in Eu2+ doped materials is rather well established,
but some details are still missing and/or contested. It is known that Eu2+ is
the emitting centre and that structural defects act as the trapping sites.
However, the nature of the traps (vacancy, co-dopant, interstitial) is not
clear. Further insight will be
gained by studying the thermoluminescence of some well-known persistent phosphors
in particular Sr4Al14O25:Eu2+;Dy3+
with different Dy concentrations.
The following studies will be performed
1.
Relation
between the afterglow and the decrease of the TL glow peak.
2.
Measurements
of TL emission and excitation spectra;
3.
The
thermoluminescence from low (far below RT) till high temperatures (350 °C). Are
there indications of tunneling effects?)
4.
Thermoluminescence
after various delay times (time between excitation and readout) compared to TL
after thermal cleaning. Determination of Trap Depth Distribution. Comparison
with model calculations
5.
Afterglow
as function of excitation time (charging up effects).