SILAS CARDOSO DOS SANTOS

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Synthesis of thulium-yttria nanoparticles with EPR response
2022 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
Approaches to form new materials for radiation dosimetry are essential to enhance quality assurance and quality improvement practices based on radiation protection concept. The present work reports a hydrothermal synthesis based on a relative low temperature and pressure to form thulium-yttria nanoparticles with electron paramagnetic resonance response. Thulium-yttria nanoparticles were prepared and characterized by XRD, SEM, PCS, and EPR. According to results, the hydrothermal method provided thulium-yttria nanoparticles with cubic C-type structure, mean particle size (d50) less than 160nm, and EPR response. The EPR spectra of powders exhibited two resonance peaks p1 and p2 recorded at 350 and 160mT, respectively. The enhancement of the EPR response of yttria by the use of thulium as a dopant provide meaningful parameters to advance in the formation of new rare earth-based materials for radiation dosimetry.
Evaluation of rare-earth sesquioxides nanoparticles as a bottom-up strategy toward the formation of functional structures
2022 - SANTOS, SILAS C. dos; RODRIGUES JUNIOR, ORLANDO; CAMPOS, LETICIA L.
Background: The strategy to form functional structures based on powder technology relies on the concept of nanoparticles characteristics. Rare-earth sesquioxides (RE2O3; RE as Y, Tm, Eu) exhibit remarkable properties, and their fields of application include energy, astronomy, environmental, medical, information technology, industry, and materials science. The purpose of this paper is to evaluate the characteristics of RE2O3 nanoparticles as a bottom-up strategy to form functional materials for radiation dosimetry. Methods: The RE2O3 nanoparticles were characterized by the following techniques: XRD, SEM, PCS, FTIR, ICP, EPR, and zeta potential. Results: All RE2O3 samples exhibited cubic C-type structure in accordance with the sesquioxide diagram, chemical composition over 99.9 %, monomodal mean particle size distribution, in which d50 value was inferior to 130 nm. Among all samples, only yttrium oxide exhibited an EPR signal, in which the most intense peak was recorded at 358mT and g 1.9701. Conclusion: Evaluating nanoparticle characteristics is extremely important by considering a bottom-up strategy to form functional materials. The RE2O3 nanoparticles exhibit promising characteristics for application in radiation dosimetry.
Synthesis of thulium-yttria nanoparticles with EPR response
2021 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
Introduction: High dose dosimetry demands a continuous effort towards the development of new materials with the aim to guarantee assurance of activities in which ionizing radiation is used. The present work reports a hydrothermal synthesis based on a relative low temperature and pressure to form thulium-yttria nanoparticles with electron paramagnetic resonance response. Material and method: Thulium-yttria nanoparticles (Tm:Y2O3) prepared with 0.1at.%Tm (atomic percentage, at.%) were synthesized by an eco-friendly hydrothermal process as reported in previous study[1]. The nanoparticles were characterized by Photon Correlation Spectroscopy (PCS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Electron Paramagnetic Resonance (EPR). Results: According to results, the hydrothermal method provided thulium-yttria nanoparticles with cubic C-type structure, mean particle size (d50) less than 90nm (Fig.1), and EPR response. The EPR spectra of powders exhibited two resonance peaks p1 and p2 recorded at 350 and 160mT, respectively (Fig.2). Conclusions: The enhancement of the EPR response of yttria by the use of thulium as a dopant provide meaningful parameters to advance in the formation of new rare earth based materials for radiation dosimetry.
Dispersion of thulium-yttria nanoparticles to build up smart structures
2021 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
The development of new materials for radiation dosimetry is a challenge to assure quality improvement practices related to radiation protection concept. On this context, colloidal stability provides conditions to build up smart structured materials from bottom-up perspective. The present work reports zeta potential characterization of thulium-yttria nanoparticles in aqueous medium. Thulium-yttria nanoparticles formed by a relative low temperature hydrotermal synthesis were characterized by XRD, PCS, and SEM. The stability of particles in aqueous medium was evaluated by electrophoretic mobility measurements, followed by zeta potential calculation. The results revealed that the isoelectric point of thulium-yttria suspensions shifted in accordance with thulium concentration from pH 8.5 (“pure” yttria) to pH 9.2 (2at.%Tm). Besides, most suspensions could be stabilized at pH 10.5, presenting zeta potential values around 30 mV. These results are substantial parameters to advance toward new materials for radiation dosimetry.
Towards a new promising dosimetric material from formation of thulium-yttria nanoparticles with EPR response
2021 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
Advances toward new materials for dosimetry application is essential to enhance quality assurance and quality improvement practices based on radiation protection concept. Face to this challenge the present work reports an approach to produce thulium-yttria nanoparticles with electron paramagntic resonance response by an alternative hydrothermal synthesis based on a relative low temperature and pressure. Distinct compositions of thulium-yttria nanoparticles with up to 2 at.%Tm (at.%, atomic percentage) were prepared and characterized by XRD, SEM, PCS, and EPR. The proposed synthesis method followed by thermal treatment of the precursor powder at 1100 ◦C for 2 h provided thulium-yttria nanoparticles with rounded shape, cubic C-type structure, and mean particle size (d50) less than 160 nm. Among all compositions formed, thulium-yttria nanoparticles prepared with 0.1%Tm presented the most remarkable EPR response. The production of fine thulium-yttria nanoparticles with EPR response supply meaningful parameters to advance in the formation of new dosimetry materials based on rare earths.