Europium-doped calcium titanate: Optical and structural evaluations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photoluminescence properties of CaTiO3:Eu3+ nanophosphor obtained by the polymeric precursor method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural and electronic analysis of the atomic scale nucleation of Ag on alpha-Ag2WO4 induced by electron irradiation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Toward an Understanding of the Growth of Ag Filaments on alpha-Ag2WO4 and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Very Intense Distinct Blue and Red Photoluminescence Emission in MgTiO 3 Thin Films Prepared by the Polymeric Precursor Method: An Experimental and Theoretical Approach

MgTiO3 (MTO) thin films were prepared by the polymeric precursor method with posterior spin-coating deposition. The films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates and heat treated at 350 °C for 2 h and then heat treated at 400, 450, 500, 550, 600, 650 and 700 °C for 2 h. The degree of structural order−disorder, optical properties, and morphology of the MTO thin films were investigated by X-ray diffraction (XRD), micro-Raman spectroscopy (MR), ultraviolet− visible (UV−vis) absorption spectroscopy, photoluminescence (PL) measurements, and field-emission gun scanning electron microscopy (FEG-SEM) to investigate the morphology. XRD revealed that an increase in the annealing temperature resulted in a structural organization of MTO thin films. First-principles quantum mechanical calculations based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and disordered asymmetric models. The electronic properties were analyzed, and the relevance of the present theoretical and experimental results was discussed in the light of PL behavior. The presence of localized electronic levels and a charge gradient in the band gap due to a break in the symmetry are responsible for the PL in disordered MTO lattice.

Freezing Distortions and Photoluminescence Property in PbMoO4 Micro Octahedrons: An Experimental and Theoretical Study

In this paper, we report a detailed structural and electronic characterization of PbMoO4 crystals by using a conventional hydrothermal (CH) method. The samples were characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman), field-emission gun scanning electron microscopy (FEG-SEM) and photoluminescence (PL) measurements. In addition, first-principles quantum mechanical calculations based on the density functional theory were employed in order to understand the band structure and density of states for the PbMoO4. Analysis of both theoretical and experimental results allows to rationalize the role of order-disorder effects in the observed green PL emissions in these ordered powders.

Parameters optimization of heat treatment for obtaining luminescent PZT powders

Low crystalline PZT powder samples were successfully synthesized using polymeric precursor method and slow decomposition steps. The polymeric resin precursor was thermal treated in a muffle type oven varying the temperature from 250 °C to 700 °C and the time from 3 to 24 hours in order to investigate the order/disorder mechanism toward the amorphous powders. Powder samples with low crystalline phases were obtained at lower temperatures and long time of thermal treatment, demonstrating a kinetic dependence for organic removal and a thermodynamic barrier for crystallization processes. Through XRD and FTIR spectroscopy characterizations the long time thermal treated samples showed to be composed of the solid solution of metal oxides in absent of organic matter, originating broad XRD peaks profiles and no carbonaceous bands in FTIR spectra. A Photoluminescence characterization showed that the peak emission is higher for disordered and homogeneous phases, which only can be reached through the long time of thermal treatment.

Um estudo teórico e experimental de nanoestruturas de 'ZnS': propriedades físicas e químicas

Pós-graduação em Química - IQ

A new approach to the electronic structure of two dimensional disordered alloys

We propose a novel method to calculate the electronic Density of States (DOS) of a two dimensional disordered binary alloy. The method is highly reliable and numerically efficient, and Short Range Order (SRO) correlations can be included with no extra computational cost. The approach devised rests on one dimensional calculations and is applied to very long stripes of finite width, the bulk regime being achieved with a relatively small number of chains in the disordered case. Our approach is exact for the pure case and predicts the correct DOS structure in important limits, such as the segregated, random, and ordered alloy regimes. We also suggest important extensions of the present work. © 1995.

Ordered phases in the extended Hubbard model

A novel method to probe the diverse phases for the extended Hubbard model (EHM), including the correlated hopping term, is presented. We extend an effective medium approach [1] to a bipartite lattice, allowing for charge- and/or spin-ordered phases. We calculate the necessary correlation functions to build the EHM phase diagram.

Evolution of photoluminescence as a function of the structural order or disorder in CaMoO4 nanopowders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

First order reversal curve analysis of nanocrystalline Pd80Co20 alloy films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

An exploratory dimensional approach to premenstrual manifestation of obsessive-compulsive disorder symptoms: A multicentre study

Objective: In women with obsessive-compulsive disorder (OCD), symptom severity appears to fluctuate over the course of the menstrual cycle. The objective of this paper was to compare female OCD patients with and without premenstrual worsening of obsessive-compulsive symptoms (OCS), in terms of the clinical characteristics of OCD. Methods: This was a cross-sectional study involving 455 women with OCD, of whom 226 (49.7%) had experienced premenstrual OCS worsening and 229 (50.3%) had not (PMOCS-worse and PMOCS-same groups, respectively). Data were collected with the original and dimensional versions of the Yale-Brown Obsessive-Compulsive Scale, as well as with the Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). Results: We found significant differences between the PMOCS-same and PMOCS-worse groups, the latter showing a higher frequency of suicidal ideation (P<.001), suicide attempts (P=.027), current use of selective serotonin reuptake inhibitors (P=.022), lifetime use of mood stabilisers (P=.015), and sexual/religious obsessions (P<.001; OR. =1.90), as well as higher scores on the BDI (P<.001) and BAI (P<.001). Conclusion: Underscoring the fact that OCD is a heterogeneous disorder, there appears to be a subgroup of female OCD patients in whom the premenstrual period is associated with a higher frequency of sexual/religious obsessions, depression, anxiety, and suicidality. This might be attributable to hormonal fluctuations. Further studies are warranted in order to investigate this hypothesis by evaluating such patients at different phases of the menstrual cycle, as well as measuring hormonal levels. © 2012 Elsevier Inc.

Local order of Pb1-xLaxZr0.40Ti 0.60O3 ferroelectric ceramic materials probed by X-ray absorption and Raman spectroscopies

This paper reports on the structural characterization of Pb 1-xLaxZr0.40Ti0.60O3 (PLZT) ferroelectric ceramic compositions prepared by the conventional solid state reaction method. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used to probe the local structure of PLZT samples that exhibits a normal and relaxor ferroelectric behavior. From the Zr K-edge and Pb LIII-edge EXAFS spectra, a considerable dissymmetry of Zr and Pb sites was observed in all samples, including those showing a long-range order cubic symmetry and a relaxor behavior. The Raman spectroscopy results confirmed the existence of a local disorder in all PLZT samples through the observation of Raman active vibrational modes. The variation in the intensity of the E(TO 3) mode in the PLZT relaxor samples indicates that the process of correlation between nanodomains stabilizes at temperatures lower than T m. © 2013 Elsevier B.V. All rights reserved.

Exaggerating, mislabeling or simulating obsessive-compulsive symptoms: Case reports of patients claiming to have obsessive-compulsive disorder

Background: There are no reported cases of factitious or simulated obsessive compulsive disorder (OCD). However, over the last years, our clinic has come across a number of individuals that seem to exaggerate, mislabel or even intentionally produce obsessive and/or compulsive symptoms in order to be diagnosed with OCD.Methods: In this study, experienced clinicians working on a university-based OCD clinic were requested to provide clinical vignettes of patients who, despite having a formal diagnosis of OCD, were felt to display non-genuine forms of this condition.Results: Ten non-consecutive patients with a self-proclaimed diagnosis of OCD were identified and described. Although patients were diagnosed with OCD according to various structured interviews, they exhibited diverse combinations of the following features: (i) overly technical and/or doctrinaire description of their symptoms, (ii) mounting irritability, as the interviewer attempts to unveil the underlying nature of these descriptions; (iii) marked shifts in symptom patterns and disease course; (iv) an affirmative yes pattern of response to interview questions; (v) multiple Axis I psychiatric disorders; (vi) cluster B features; (vii) an erratic pattern of treatment response; and (viii) excessive or contradictory drug-related side effects.Conclusions: In sum, reliance on overly structured assessments conducted by insufficiently trained or naive personnel may result in invalid OCD diagnoses, particularly those that leave no room for clinical judgment. (C) 2014 Elsevier Inc. All rights reserved.