Enhanced thermoluminescence, radioluminescence, and optically stimulated luminescence from lithium fluoride and silver nanoparticles composites

Abstract

Plasmonic properties of metals can increase the sensitivity of ionizing radiation dosimeters. In this work, we study the plasmon resonance of silver nanoparticles (AgNp) to increase the optically stimulated luminescence (OSL) intensity of lithium fluoride (LiF) polycrystals. We produced LiF/Ag nanocomposites with different volumes of a silver nanoparticle dispersion and investigated their OSL response. We also investigated their thermoluminescence (TL) and radioluminescence/scintillation (RL) responses. X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy characterized the synthesized materials. XRD results clearly show the characteristic peaks of LiF and AgNps. TEM images revealed silver nanoparticles with diameters between 80 and 120 nm and LiF crystals with sizes between 1 and 5 μm. Reflectance spectroscopy showed a band around 420 nm, attributed to the plasmon resonance of silver nanoparticles. The responses of the OSL curves to X-ray irradiation were analyzed, showing higher OSL sensitivity with 14 mL AgNp, attributed to the AgNp plasmon resonance. A significant increase in TL and RL intensity could be observed for the LiF/Ag nanocomposites. TL, RL, and OSL results support that addition of AgNps do not lead to the creation of more and new traps or luminescent centers. The increase of TL and RL intensities is therefore related to the coupling of the luminescent centers with the AgNPs plasmons, in an energy-transfer mechanism (plasmon-coupled emission), whereas the enhanced OSL intensity directly correlates with the increased photoionization cross-section of the electronic traps under plasmon resonance conditions (plasmon-coupled excitation). Therefore, these results indicate that AgNp are potential candidates to increase the OSL, TL, and RL intensity from LiF dosimeters.