PATRICIA DE LARA ANTONIO

PATRICIA DE LARA ANTONIO

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Verification of the PTOSL signal from radiation detectors using a 60Co beam and UV light from LEDs
2023 - ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.
Radiation processing techniques induce physical, chemical and biological changes in the structures of materials, instruments and food to reach a certain desired benefit. For this reason, the systematic and periodic radiation dosimetry is so essential to determine the absorbed dose of radiation sources. If the absorbed dose applied to the materials does not correspond to the desired one, the effects in their structures can be adverse. Solid state dosimeters are radiation detectors that are already well established in routine procedures and described in the literature for gamma radiation dosimetry, such as 60Co, with beams employed em radiation processing. This work aims to study the response of commercial dosimeters based in their luminescence phenomenon using the optically stimulated luminescence (OSL) technique. Then, it seeks to verify the phototransfer effect presented by the dosimeters employing the phototransferred OSL technique (PTOSL), for further analysis of the possibility of applying these materials and these techniques for 60Co beam dosimetry. In this work, the OSL/PTOSL responses of LiF:Mg,Ti (TLD-100), CaF2:Dy (TLD-200), CaF2:Mn (TLD-400) and CaSO4:Dy (TLD-900) commercial dosimeters were studied in three steps: 1) OSL after irradiation; 2) OSL after irradiation + thermal treatment post-irradiation (TTPI); 3) PTOSL after irradiation + TTPI + illumination with UV of light-emitting diodes (LEDs). The irradiations were carried out with a 60Co beam from a Gamma-Cell system (383.65 Gy/h - October/2022). All the measurements were taken using the Risø reader system, model TL/OSL-DA-20, and with an illumination time of 100 s. The first phase was to irradiate the dosimeters with the following absorbed doses: 0.7 Gy (TLD-100 and -900), 20 Gy (TLD-200) and 50 Gy (TLD-900), and to measure the OSL signal. The values of the initial decay of the OSL curves were about 3x103 counts (TLD-100), 1x103 counts (TLD-200), 5.4x103 counts (TLD-400) and 9.5.102 counts (TLD-900). For the second phase, the pellets were initially irradiated with the same doses previously given and submitted to the TTPI of 280°C/15 min (TLD-100 e -900), 250°C/15 min (TLD-200) e 350°C/15 min (TLD-400); the first point of the OSL signal was observed at about 400 counts (TLD-100), 460 counts (TLD-200), 530 counts (TLD-400) and 660 counts (TLD-900). In the third phase, the dosimeters were irradiated, treated with TTPI and illuminated with UV of 265 nm/10 min (TLD-100) and 365 nm/10 min (TLD-200, -400 and -900). Comparing these last results with those from the second step, it was possible to observe PTOSL for TLD-100 and -900, because an increase in the signal intensity was observed for both materials. For TLD-200 and -400, the signals were similar for the second and third steps, but more studies are necessary for a final conclusion.
TL and OSL characterization of CaSO4:Tb, CaSO4:Mn AND CaSO4:Mn,Tb phosphors
2023 - SILVA, ANDERSON M.B.; RODRIGUES, DANIEL S.; GUEDES, BEATRIZ D.; SILVEIRA, IURY S.; ANTONIO, PATRÍCIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
The objective of this work was to investigate the luminescence properties of CaSO4:Tb, CaSO4:Mn e CaSO4:Mn,Tb synthesized by slow evaporation route. The crystalline structure, morphology, thermal and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and radioluminescence (RL). Moreover, using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques, the dosimetric properties of the phosphors were comprehensively investigated, such as emission spectra, glow curve reproducibility, dose-response linearity, fading of the luminescent signal, OSL decay curves, correlation between TL and OSL emissions and minimum detectable dose (MDD). For dosimetric analyses the samples were irradiated with doses of between 169 mGy and 10 Gy. TL emission spectra confirmed the presence of Tb3+ and Mn2+ ions in crystalline matrices. The samples showed a typical exponential OSL decay curve with the predominance of a fast decay component, indicating that the traps have a high photoionization cross-section for blue LEDs, and a MDD on the order of mGy. The luminescent signals showed to be linear and reproducible in the studied dose range. The trapping centers located between 0.63 eV and 1.07 eV were revealed. The high TL sensitivity of phosphors was proven when comparing with commercially available dosimeters. It was also observed that co-doping with Mn and Tb contributed to a reduction in fading compared to CaSO4:Mn and CaSO4:Tb.
Phototransferred thermoluminescence in commercial dosimeters after exposure to beta radiation
2023 - ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.
Radiation dosimetry allows the analysis of the energy deposited in a material to evaluate the effect caused on this material; it can be done using different radiation detectors, and there are several dosimetric materials that can be employed, according to the radiation kind and the purpose of its application. A material can only be considered a radiation dosimeter if it presents certain conditions; for dosimeters that present luminescent response, it is necessary to present specific characteristics in this luminescence signal. However, there are ways to study the signal to allow the response obtained to provide these characteristics, for example, studying the phenomenon of phototransfer of the luminescent signal of a material. The main objective of this work was to analyze the occurrence of phototransfer on the thermoluminescence (TL) of different commercial dosimeters, the phenomenon of the phototransferred TL (PTTL). For this, the TL and PTTL responses of LiF:Mg,Ti (TLD-100), CaF2:Dy (TLD-200), CaF2:Mn (TLD-400) and CaSO4:Dy (TLD-900) dosimeters were investigated using the 90Sr+90Y source of the TL/OSL reader system Risø. During the TL/PTTL measurements, performed with the same reader, the maximum temperatures were 350°C (TLD-200), 400°C (TLD-100 e -900) e 450°C (TLD-400), and the heating rate was kept constant at 10°C/s. The first step was to verify the TL response of the materials, by means of the TL emission curves after irradiation (with absorbed doses of 0.7 Gy for TLD-100 and TLD-900, 20 Gy for TLD-200 and 50 Gy for TLD-400). The main peaks were observed at the temperatures of 252°C for TLD-100, 312°C for TLD-200, 398°C for TLD-400 e 226°C for TLD-900. The second step was to analyze the TL response after irradiation and a thermal treatment post-irradiation (TTPI) of 280°C/15 min for TLD-100 e TLD-900, 300°C/15 min for TLD-200 and 400°C/15 min for TLD-400; the highest TL emission occurred at 362°C (TLD-100), 139°C (TLD-200), 398°C (TLD-400) and 397°C (TLD-900). The third step was the verification of the PTTL signal, obtained after irradiation, TTPI and illumination (with UV leds) of the materials at the conditions of 265 nm/5 min for TLD-100 and 365 nm/5 min for TLD-200, TLD-400 e TLD-900. For TLD-100, a PTTL signal was verified, because two new peaks emerged at 133°C and 261°C; for TLD-200 and TLD-400 no PTTL signal was observed; for TLD-900 it was possible to obtain a PTTL response once a peak appeared at 197°C, which did not exist after irradiation and TTPI (second step). In order to continue studying the PTTL signal, this response was verified varying the illumination time for the four materials between 2.5 min and 25 min. The PTTL response maximum was observed for 15 min illumination for all the materials. The PTTL was also studied in function of the wavelength for 265 nm, 310 nm, 365 nm, 400 nm e 420 nm; the results showed that the most intense signal occurred at 265 nm for TLD-100, -400 and -900, and 365 nm for TLD-200.
Thermoluminescence and phototransferred thermoluminescence of radiation dosimeters:
2023 - ANTONIO, PATRICIA L.; SILVEIRA, IURY S.; CALDAS, LINDA V.E.
OSL and PTOSL of dosimetric materials: observation of the luminescence after exposure to 90Sr+90Y source and LEDs in ultraviolet range
2023 - ANTONIO, PATRICIA L.; SILVEIRA, IURY S.; CALDAS, LINDA V.E.
Natural detector irradiated with blue LEDs for measurements in Photodynamic Therapy (PDT) via Spectroscopy (UV-Vis), Design of Experiments (DOE) and Multiple Linear Regression (MLR)
2023 - FRANÇA, MARIA B.A.; ANTONIO, PATRICIA L.; NASCIMENTO, ERIBERTO O.; CALDAS, LINDA V.E.; OLIVEIRA, LUCAS N. de
A new natural detector (Curcuma Longa L.) for photodynamic therapy (PDT) measurements with blue LED irradiations: Application of Convolutional Neural Networks (CNN) and Multilayer Perceptron (MLP)
2023 - OLIVEIRA, LUCAS N. de; NASCIMENTO, ERIBERTO O.; ANTONIO, PATRICIA L.; CALDAS, LINDA V.E.
Investigation of dosimetric properties of CaSO4:Mn phosphor prepared using slow evaporation route
2023 - SILVA, ANDERSON M.B.; RODRIGUES, DANIEL S.; ANTONIO, PATRICIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
The objective of this work was to investigate the luminescent properties of CaSO4:Mn synthesized by slow evaporation route. The crystalline structure, morphology, thermal and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), photoluminescence (PL) and thermogravimetric analysis (TGA). Moreover, using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques, the dosimetric properties of the phosphors, such as emission spectra, glow curve reproducibility, dose-response linearity, fading of the luminescent signal, variation of the TL intensity with the heating rate, OSL decay curves, correlation between TL and OSL emissions and minimum detectable dose (MDD) were comprehensively investigated. For dosimetric analyses, the samples were irradiated with doses from 169 mGy to 10 Gy. The emission band fits with the characteristic line of the Mn2+ emission features, ascribed to 6 A1→4 T1 transition. CaSO4:Mn pellets present a TL glow curve with a single typical peak centered around 494 nm, an OSL decay curve with predominance of a fast decay component, and a MDD on the order of mGy. The luminescent signals showed to be linear and reproducible in the studied dose range. The trapping centers located between 0.83 eV and 1.07 eV were revealed for different heating rates in the TL study. The high TL sensitivity of CaSO4:Mn was proven when comparing with commercially available dosimeters. The luminescent signals exhibit a smaller fading than described in the literature for CaSO4:Mn produced by other methods.
CaSO4 dopado com manganês e térbio (CaSO4:Mn,Tb)
2022 - BEZERRA, ANDERSON M.; RODRIGUES, DANIEL S.; ANTONIO, PATRICIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
Cristais de CaSO4:Mn,Tb foram sintetizados pela rota de evaporação lenta, com dopagens de 0,1 mol% de Mn e Tb. As amostras foram preparadas na forma de pastilhas com adição de Teflon. A estrutura cristalina e as propriedades ópticas dos cristais foram avaliadas por difração de raios X, espectroscopia no infravermelho com transformada de Fourier e fotoluminescência. As propriedades dosimétricas desses cristais foram investigadas pela técnica de termoluminescência (TL) e luminescência opticamente estimulada (OSL). Os cristais irradiados com doses entre 200 mGy e 150 Gy apresentam curva de emissão TL com dois picos em 205°C e 325°C e curva de decaimento de OSL com boa reprodutibilidade e linearidade à dose dos sinais luminescentes. Dois centros de armadilhamento em 0,77 e 1,02 eV foram revelados. A dependência da taxa de aquecimento também foi avaliada. A menor dose detectável foi investigada pelas técnicas TL e OSL, sendo essa da ordem de mGy em ambas as técnicas. Observou-se também que a dopagem e codopagem com Mn e Tb contribuíram para a redução do fading em comparação com resultados sobre CaSO4:Mn e CaSO4:Tb de outros trabalhos.
Investigation of dosimetric properties of CaSO4:Mn phosphor prepared using slow evaporation route
2022 - SILVA, ANDERSON M.B.; RODRIGUES, DANIEL S.; ANTONIO, PATRICIA L.; JUNOT, DANILO O.; CALDAS, LINDA V.E.; SOUZA, DIVANIZIA N.
The objective of this work was to investigate the luminescent properties of CaSO4:Mn synthesized by slow evaporation route. The crystalline structure, morphology, thermal and optical properties of the phosphors were characterized by X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), photoluminescence (PL) and thermogravimetric analysis (TGA). Moreover, using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques, the dosimetric properties of the phosphors, such as emission spectra, glow curve reproducibility, dose-response linearity, fading of the luminescent signal, variation of the TL intensity with the heating rate, OSL decay curves, correlation between TL and OSL emissions and minimum detectable dose (MDD) were comprehensively investigated. For dosimetric analyses, the samples were irradiated with doses from 169 mGy to 10 Gy. The emission band fits with the characteristic line of the Mn2+ emission features, ascribed to 6A1→4T1 transition. CaSO4:Mn pellets present a TL glow curve with a single typical peak centered around 494 nm, an OSL decay curve with predominance of a fast decay component, and a MDD on the order of hundreds of mGy. The luminescent signals showed to be linear and reproducible in the studied dose range. The trapping centers located between 0.83 eV and 1.07 eV were revealed for different heating rates in the TL study. The high TL sensitivity of CaSO4:Mn was proven when comparing with commercially available dosimeters. The luminescent signals exhibit a smaller fading than described in the literature for CaSO4:Mn produced by other methods.