The location of the Eu ion in the TiO 2 lattice was investigated as a function of sintering temperature using X-ray photoelectron spectroscopy (XPS), to clarify the role of the Eu ion in TiO 2 nanoparticles synthesized by the simple sol-gel method. The crystalline structure as well as the average crystallite size were evaluated using X-ray diffraction (XRD), and the direct observation of nanoparticles was carried out using atomic force microscopy (AFM). A model was proposed in which, in the as-synthesized gel state, the Eu ion occupies the core part of a nanoparticle, and with increasing sintering temperature, it migrates toward the particle shell to finally reach the surface at high sintering temperatures above 900 C, at which sufficient thermal energy is provided to allow the Eu ion to migrate to the surface of the nanoparticles, resulting in the formation of Eu 2 Ti 2 O 7 with a pyrochlore structure and an abrupt decrease in the photoluminescence (PL) intensity of the Eu ion.
Eu 3þ -and non-doped TiO 2 nanoparticles were synthesized by the sol-gel method at sintering temperatures of 500 or 900 C. The photoluminescence spectra of these nanoparticles have been investigated at various temperatures between 290 and 12 K. Two kinds of Eu 3þ photoluminescence spectra were observed. One spectrum consists of sharp lines; the other consists of broad bands. The former was obtained by indirect excitation into Eu 3þ with light of wavelengths shorter than 330 nm, while the latter was obtained by direct excitation into Eu 3þ with light of wavelengths longer than 380 nm which correspond to the Eu 3þ absorption bands. In the latter case, different spectra were obtained depending on the excitation wavelength even in the same absorption band. It is suggested that the sharp line spectrum is caused by Eu 3þ ions substituted for Ti 4þ but with some distortion around the Eu 3þ ions in the matrix of TiO 2 due to the large difference in ionic radius between the Ti 4þ and Eu 3þ ions, which are mainly present in the interior region of the nanoparticle. The broad band spectrum is caused by the disordered Eu 3þ ions with Eu-O-Ti bonds which are predominantly present in the near surface region.
A UV-photoactive Eu-doped TiO2 nanoparticle activated with its wavelength-matched nanoscintillator is proposed for the effective utilization of spent nuclear fuel. The Eu-doped TiO2 nanoparticles were synthesized by the alkoxide-based sol–gel method at various doping concentrations and sintering temperatures. The X-ray diffraction (XRD) spectra revealed that the existence of the anatase phase of TiO2, which is favorable for photocatalytic application, was extended up to 800 °C by Eu doping. The average crystallite size of 40 nm in the pure TiO2 sintered at 600 °C was decreased by 50% in the case of the 0.5 mol % Eu-doped one. The absorption edge obtained from UV–vis absorbance spectra yielded a slightly blue shift that gave a good agreement with the results of size suppression. The photocatalytic activities of nanoparticles were evaluated from the degradation of methylene blue (MB) solution under UV irradiation, and the optimum activity obtained for the 0.75 mol % Eu-doped TiO2 was three times higher than that of the pure TiO2.
This study aims to determine the strategies of teachers, especially teachers in anticipating violence against students.One of the phenomena that has caught the attention of the world of education today is violence that occurs in the school environment. Violence between students will certainly affect the learning conditions in the classroom. Students who experience physical and verbal abuse will certainly feel psychologically disturbed. Disturbed psychological conditions will also trigger disruption of the enthusiasm and interest of students in learning.The role of the teacher is very necessary to reduce even if it can eliminate the condition. Based on these problems, this study aims to: (1) determine the role of PPKn teachers in anticipating violence against students; (2). Knowing the obstacles of PPKn teachers in anticipating violence against students; (3). know what efforts are made by the PPKn teacher in anticipating violence against students. This research uses a descriptive method with a qualitative approach. Data collection techniques using observations, interviews and documentation conducted in the environment of SMK 17 Serang City. The research results obtained in the field show that the PPKn teacher's strategy in anticipating violence in children is to provide understanding related to norms about diversity, fostering character to care for each other, carrying out positive activities in the school environment such as extracurricular or social activities. others in the classroom environment and broadly in the school, and invites parents to control the activities of children in their environment.the strategy carried out by the teachers is done as an effort to prevent and deal with violence against students.
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