Abstract
In this work we report on the thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of β-Na(Gd,Lu)F4:Tb3+ nanophosphors prepared via a standard high-temperature coprecipitation route. Irradiating this phosphor with X-rays not only produces radioluminescence but also leads to a bright green afterglow that is detectable up to hours after excitation has stopped. The storage capacity of the phosphor was found to be (2.83 ± 0.05) × 1016 photons/gram, which is extraordinarily high for nano-sized particles and comparable to the benchmark bulk phosphor SrAl2O4:Eu2+,Dy3+. By combining TL with OSL, we show that the relatively shallow traps, which dominate the TL glow curves and are responsible for the bright afterglow, can also be emptied optically using 808 or 980 nm infrared light while the deeper traps can only be emptied thermally. This OSL at therapeutically relevant radiation doses is of high interest to the medical dosimetry community, and is demonstrated here in uniform, solution-processable nanocrystals.
Highlights
Luminescent materials, or phosphors, possess the ability to absorb high-energy radiation and convert it into light with a typically lower energy
Some phosphors can store part of the energy that is provided to them during excitation and when this energy is released, it can give rise to emission long after the excitation has stopped, at times that are considerably longer than the photo- or radioluminescence lifetimes [8]. These materials cover a large spectral range, featuring emission from the Ultraviolet C (UVC) range which can be used for sterilization or disinfection [9] up to the red and near-infrared range, enabling the use of persistent phosphors in in vivo medical imaging [10,11,12]
We discuss the thermoluminescence (TL) and optically stimulated luminescence (OSL) of this phosphor and we show that this material differs from conventional persistent phosphors because it possesses an exceptionally high storage capacity which, based on performance, places it among the commercially available afterglow phosphors but with the added advantage that it is nano-sized with a well-defined size distribution
Summary
Luminescent materials, or phosphors, possess the ability to absorb high-energy radiation and convert it into light with a typically lower energy. Some phosphors can store part of the energy that is provided to them during excitation and when this energy is released, it can give rise to emission long after the excitation has stopped, at times that are considerably longer than the photo- or radioluminescence lifetimes [8]. These materials cover a large spectral range, featuring emission from the Ultraviolet C (UVC) range which can be used for sterilization or disinfection [9] up to the red and near-infrared range, enabling the use of persistent phosphors in in vivo medical imaging [10,11,12]. Depending on the envisioned application, the storage or afterglow properties of the materials can be tuned by adding co-dopants [13,14] or by slightly changing the host composition [15]
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