Maria A. Gomes

Particle size control of Y 2 O 3 : Eu 3+ prepared via a coconut water-assisted sol-gel method

Eu3+-doped Y2O3 nanoparticles were produced through proteic sol-gel technique, and the adjustment of pH was tested in order to control the particle size of the powders. A strong correlation between the initial pH and the temperature of crystallization was observed, allowing the production of particles with controlled diameter from 4nm to 50 nm. The samples were characterized by X-ray diffraction, high-resolution transmission electron microscopy, optical microscopy and photoluminescence spectroscopy in both absorption and emission modes. A blue shift of the excitation peak corresponding to energy transfer from Y2O3:Eu3+ host to Eu3+ ions was observed, as the particle size was reduced from 50 to 4 nm. The suppression of a charge transfer band also resulted from the reduction of the particle size. The emission spectrum of the Y2O3: with particles of 50nm was found to be similar to that of bulk material whereas 4 nm particles presented broadened emission peaks with lower intensities.

Wet chemical synthesis of rare earth-doped barium titanate nanoparticles

Barium titanate (BaTiO3) is a common ferroelectric material with perovskite structure widely used for the production of a variety of electro-optical devices. When doping with rare earth elements, very interesting characteristics can be attributed to BaTiO3. Among the methods used to synthesize BaTiO3, wet chemical approaches are the most suitable for preparing homogenous and pure nanostructured materials. In this sense, the present article aims to summarize the state-of-the-art of the most relevant wet chemical routes for the synthesis of nanocrystalline BaTiO3 doped with rare earth (RE) ions (BaTiO3:RE), which include the following: sol–gel, sol–emulsion–gel, Pechini, solvothermal/hydrothermal, and co-precipitation methods. The influence of each method on morphology and particle size, as well as on the dielectric and/or luminescent properties of the powders is discussed.

A Comparative Study of Er3+, Er3+-Eu3+, Er3+-Tb3+, and Er3+-Eu3+-Tb3+Codoped Y2O3Nanoparticles as Optical Heaters

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.

An Eco-Friendly Method of BaTiO3 Nanoparticle Synthesis Using Coconut Water

BaTiO3 nanoparticles were successfully synthesized by a new coconut water-based sol–gel method using Ba(CH3COO)2 and TiCl3 as the starting salts. The influence of the amount of coconut water and calcination conditions on the barium titanate crystallization was investigated. The resulting nanoparticles were characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, and Raman and Fourier transform infrared (FTIR) spectroscopies. The ferroelectric tetragonal single phase of BaTiO3 was obtained in samples prepared with a ratio of coconut water volume (mL)/BaTiO3 mass (g) of 25 : 2 and 30 : 2, calcined at 1100°C, which was confirmed by XRD measurements. Crystallites with an average size of about 31 nm for both samples were obtained, and microscopy images revealed the presence of particles in the range of 40 to 60 nm. Raman and FTIR spectra confirmed the dominant tetragonal phase of BaTiO3, meanwhile traces of BaCO3 were identified in FTIR spectra.

A comparative study of Er 3+ , Er 3+ -Eu 3+ , Er 3+ -Tb 3+ , and Er 3+ -Eu 3+ -Tb 3+ codoped Y 2 O 3 nanoparticles as optical heaters

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.

A Comparative Study of Er3

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.