Avaliação da eficiência de detectores OSL baseados na fluorita natural brasileira com adição de nanopartículas metálicas

Abstract

Optically Stimulated Luminescence (OSL) detectors allow estimating the absorbed dose of ionizing radiation by the detector, after irradiation due to luminescent properties of the detector material. These properties are related to the effects of light absorption and emission, that are intrinsic characteristics in band structure. In order to study the effect of metallic nanoparticles (Nps-M) on the sensitivity and efficiency of OSL detectors based on natural Brazilian fluorite (CaF2), CaF2 detector thin films were produced and added a Nps-M in acetone suspension. The Nps used for this study were: silver (Nps-Ag), gold (Nps-Au), lead (Nps-Pb) and bismuth (Nps-Bi) produced by laser ablation process (LASiS) in acetone. OSL detectors were produced in sheets and cut into circular pellets (about 3 mm) that were distributed into groups with and without CaF2. In order to analyze the efficiency and OSL response of the samples, those were exposed with different types and energies of ionizing radiation. Through this study, it was verified that there is a dependence of the concentration of Nps-M with the efficiency of the CaF2 OSL detector. Furthermore, it was found that the response of the detector with Nps-M, compared to the response of detectors without Nps-M, changes according the dose and type of incident radiation. The influence of the LSPR (Localized Surface Plasmon Resonance) effect of the Nps-M was observed in the study of the efficiency of CaF2 with Nps-M detectors. All detectors with the addition of Nps-M, expose to beta particles, presented an increase in luminescent efficiency. Nps-Pb samples without CaF2 presented an increase in sensitivity for all energies, which may be an indicator of the LSPR effect for stimulation with a blue LED. It was also possible to observe an increase of 26%and 34% in the OSL intensity values of detectors with Nps-Bi and Nps-Pb respectively, for all doses used when compared to detectors without Nps-M. Based on the results, the hypothesis that the LSPR effect occurs due to stimulation in the blue band (Risø stimulation LED) and self-stimulation by luminescent emission from CaF2 crystals can be inferred.