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Thèses |
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1
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LUCIELLY DE SOUZA ALVES
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Light scattering by materials having PT symmetry
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Leader : PAULO CESAR AGUIAR BRANDAO FILHO
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MEMBRES DE LA BANQUE :
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ALEX EMANUEL BARROS COSTA
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ANDRE DE LIMA MOURA
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PAULO CESAR AGUIAR BRANDAO FILHO
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Data: 10 févr. 2023
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Afficher le Résumé
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The objective of this dissertation is to analyze, with a certain level of detail, the scattering of monochromatic electromagnetic radiation by an isotropic and linear dielectric material having $\mathcal{PT}$ symmetry in the Born approximation. Studying the light scattered by a specific material can give us useful information about the nature of the material. Thus, we verify how light scattering behaves in a material that has $\mathcal{PT}$ symmetry and how the presence of gain and loss within the material can affect the spectral density of the scattered field. Spectral density is a quantity that can be measured directly in the laboratory. We verified that, for certain gain and loss distributions, the scattered field direction can be varied without changing the scatterer geometry. The non-Hermitian character of the refractive index of the scatterer is also reflected in the scattered intensity pattern, which now becomes asymmetric with respect to the scattering angle.
We begin in chapter 1 with a brief motivation about the development of the work. Chapter 2 presents the fundamental concepts of $\mathcal{PT}$ symmetry and their respective applications in the field of quantum mechanics, discussing the most important properties that describe this symmetry. We will also make the connection of such symmetry with the research field of optics. Chapter 3 presents the classical theory of scattering and the wave equation satisfied by the electric field in the scalar approximation, starting from the set of Maxwell's equations. The formal theory of scattering for scalar fields and the representation of multiple scattering with the Born series will also be exposed. We will discuss how such approximations are given and their applications of interest to our work. In chapter 4, we will deal with the scattering of light by a $\mathcal{PT}$-symmetric material in the first Born approximation. Our main conclusion is that the scattered field directions can undergo changes depending on the presence of gain and loss in the scattering material. Finally, in chapter 5, we discuss our conclusions and some future perspectives.
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2
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ANA MARIA TORRES DA SILVA
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Immunoagglutination Assays in Acoustofluidic Chips
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Leader : GLAUBER JOSE FERREIRA TOMAZ DA SILVA
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MEMBRES DE LA BANQUE :
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GLAUBER JOSE FERREIRA TOMAZ DA SILVA
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JOSE PEREIRA LEAO NETO
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MAGNA SUZANA ALEXANDRE MOREIRA
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Data: 19 avr. 2023
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Afficher le Résumé
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In this work, we studied the effects of acoustofluidics on immunagglutination assays through the particle agglutination reaction of latex particles coated with anti-PCR gamma globulin. We used an acoustofluidic chip composed of microchannels and an acoustic microcavity, in which the particles are levitated and clustered in the central regions due to radiation force. We performed agglutination tests on the acoustofluidic chip using the BIOLATEX PCR kit to characterize the chip. Initially, we investigated the agglutination patterns formed on a slide by optical microscopy. Then, we analyzed how these patterns behaved within the acoustic microcavity, investigating the reactions between antigens and antibodies and the conditions necessary for this reaction, as well as evaluating the acoustofluidic chip in terms of repeatability, reproducibility, detection limit, and sensitivity. We demonstrated that acoustofluidic systems have great potential for clinical analyses, especially for the reaction between antigens and antibodies, increasing the interaction between these components. A significant decrease in reaction time and greater stability of agglutinates within the microcavity were observed through the agglutination test on the chip. The detection limit was found to be 187,5 pg/μL, which is approximately 32 times higher than that of the conventional test, enabling greater sensitivity of the test. The acoustofluidic chip has unique characteristics that allow its application in life sciences, particularly in the field of clinical diagnostics, offering results with great potential.
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3
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DENISSON GUTEMBERG PEREIRA DA SILVA
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Study of the synergism of nickel-doped titanium dioxide nanocrystals with graphene oxide and its application in sensors for the detection of ascorbic acid.
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Leader : ANIELLE CHRISTINE ALMEIDA SILVA
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MEMBRES DE LA BANQUE :
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ANIELLE CHRISTINE ALMEIDA SILVA
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EDUARDO JORGE DA SILVA FONSECA
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DIOGENES MENESES DOS SANTOS
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Data: 30 juin 2023
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Afficher le Résumé
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Ascorbic acid, known as vitamin C, plays a crucial role in human health, and it is necessary to develop sensitive and selective sensors for its detection in complex samples. In order to enhance electrical responses and interaction with biomolecules, nanomaterials are incorporated into the surface of sensors. Titanium dioxide (TiO2) and graphene oxide (GO) nanocrystals have interesting properties, such as high surface area, catalytic activity and ability to amplify electrical signals, making them excellent candidates for electrochemical sensors. Thus, their synergism can enhance these properties. Therefore, this work investigated the synergism between nanocrystals of TiO2 doped with nickel (Ni) and GO and its application in the detection of ascorbic acid. The optical, structural and vibrational properties of the samples were investigated using optical absorption spectroscopy (AO), X-ray diffraction (XRD), Raman spectroscopy and cyclic voltammetry (VC). In the AO spectra, it confirmed the absorption in the ultraviolet of the TiO2 nanocrystals and that with the doping it altered the band gap. XRD and Raman data confirmed the presence of the anatase phase of the TiO2 nanocrystals, the lattice distortions with doping and the formation of GO. In the results of voltammetry and application in sensors for detection of ascorbic acid, it confirmed that nanocrystals of TiO2 doped with Ni and GO presented a high sensitivity and selectivity in the detection of ascorbic acid, with linear response in the concentration range, enhancing the sensitivity of the sensor . The synergistic effect of the two nanomaterials further enhanced the detection signal. Therefore, these results contribute to the advancement of knowledge in the field of nanomaterials and their application in sensitive and selective detection systems of bioactive compounds, such as ascorbic acid.
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4
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LEONARDO CLEMENTE EMIDIO DE BARROS
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NaYF 4 nanoparticles co- and tri-doped as UV/visible to infrared light converters targeting use in solar cells
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Leader : CARLOS JACINTO DA SILVA
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MEMBRES DE LA BANQUE :
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CARLOS JACINTO DA SILVA
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ANDRE DE LIMA MOURA
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TASSO DE OLIVEIRA SALES
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WAGNER FERREIRA DA SILVA
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ANDRESSA NOVATSKI
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Data: 26 juil. 2023
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Afficher le Résumé
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The urgent need for clean and sustainable energy sources has driven research into the development of technologies that generate energy from renewable sources, as in the case of solar cells (SCs) that convert sunlight into electrical energy. However, the efficiency of these types of devices is still relatively low, as occurs in silicon-based SCs, in which the region where they are most efficient (infrared-IR) the solar emission is lower, when compared to the emissions of the Sun that occur in the UV-visible. Thus, the objective of this study was to investigate combinations of ions, mainly rare earth (REs), capable of converting high energy photons (UV-Visible) into low energy photons (in the IR region, around 980 nm) in order to increase the efficiency of silicon solar cells. Therefore, the main objective was to investigate the luminescent properties of nanoparticles (NPs) doped with REs and other ions and their potential to convert photons from UV-Visible to IR. In this study, the following ions were used: Yb 3+ (Ytterbium), Er 3+ (Erbium), Nd 3+ (Neodymium), Ce 3+ (Cerium), Gd 3+ (Gadolinium), Mn 3+ (Manganese) and Tm 3+ (Thulium). The optical characterizations of the synthesized NPs occurred by obtaining excitation and emission spectra. NPs doped with two and three ions were used. The idea was to find which ions could absorb photons with wavelengths in the UV-visible region and transfer their energy to Yb 3+ ion, thus generating emissions in the IR (~980 nm). As results, in general, it was obtained that the codoped NPs (X 3+ ,Yb 3+ ) presented efficient energy transfers (ETs) between the chosen X 3+ ions and the Yb 3+ . However, in the sample co-doped with Mn 3+ and Yb 3+ , ET was not evidence, although Mn 3+ had shown intense absorption in the desired region. Regarding the tridoped samples doped (X 3+ ,Nd 3+ ,Yb 3+ ), the inclusion of the Nd 3+ ion as an intermediary for the ET between some chosen X 3+ ion and the Yb 3+ , did not prove to be advantageous, since it resulted in a decrease in the Yb 3+ emission. However, when Nd 3+ was combined with Ce 3+ and Yb 3+ ions, the system showed a wide absorption region within the desired spectrum (300 to 600 nm), proving to be an interesting system for future studies. In short, the results obtained here indicate that NPs doped with RE 3+ ions have the potential to improve the efficiency of silicon SCs, however, this possibility still needs to be thoroughly investigated.
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5
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RALINE SILVA DE ARAÚJO
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Dynamical Lorentz symmetry breaking in a derivative four-fermion model
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Leader : TIAGO HOMERO MARIZ DO NASCIMENTO
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MEMBRES DE LA BANQUE :
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ALESANDRO FERREIRA DOS SANTOS
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JOB SARAIVA FURTADO NETO
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TIAGO HOMERO MARIZ DO NASCIMENTO
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Data: 27 juil. 2023
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Afficher le Résumé
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In this dissertation we investigate spontaneous Lorentz symmetry breaking in a 4-fermion derivative model. The essence of the spontaneous Lorentz symmetry breaking mechanism consists in the coupling of tensor fields through potentials in such a way that, in the minima of the potentials, these fields acquire expected values of non-trivial vacuum, thus introducing privileged space-time directions. For this model we calculate the effective potential in the context of zero temperature and finite temperature, we also investigate the conditions for symmetry restoration. Next, we calculate the corresponding effective action and show that the resulting potential is positively defined and has a continuous set of minima, as well as performing the induction of the second order kinetic action in the auxiliary field.
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6
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MAX WENDELL ANDRADE MELO
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Dynamical Lorentz symmetry braeking in a antisymmetric four-fermion model
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Leader : TIAGO HOMERO MARIZ DO NASCIMENTO
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MEMBRES DE LA BANQUE :
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ALBERT PETROV
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PAULO CESAR AGUIAR BRANDAO FILHO
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TIAGO HOMERO MARIZ DO NASCIMENTO
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Data: 28 juil. 2023
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Afficher le Résumé
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In this dissertation we study dynamic Lorentz symmetry breaking, that is, the spontaneous symmetry breaking induced by radiative corrections of a self-interacting fermionic theory. In our study we verified that after introducing an antisymmetric tensor auxiliary field, we obtain a theory with this field minimally coupled to a spinor, in which we calculate the effective potential of a loop, at zero temperature and finite temperature, and also the effective action of a loop. After computing the zero-temperature gap equation of the effective potential, we explicitly demonstrate that the resulting potential is positively defined and has a continuous set of minima. We also investigate the conditions for symmetry restoration when we calculate the gap equation at finite temperature, in which we obtain certain constraints on the antisymmetric components of the tensor field. Furthermore, we get the same second-order kinetic action on fields when we consider the effective action of a loop with the left-right derivative or just one derivative.
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7
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LUCAS DA SILVA FERREIRA
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UV shielding in chitosan films doped with carbon quantum dots measured by wettability
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Leader : ITALO MARCOS NUNES DE OLIVEIRA
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MEMBRES DE LA BANQUE :
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ITALO MARCOS NUNES DE OLIVEIRA
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MARIA SOCORRO SEIXAS PEREIRA
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PEDRO JUVENCIO DE SOUZA JUNIOR
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Data: 14 août 2023
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Afficher le Résumé
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The present study is devoted to characterizing the optical and interfacial properties of chitosan films doped with carbon quantum dots. In particular, carbon nanoparticles are synthesized from the hydrothermal method, using methyl red dye as a precursor. Using UV-Vis spectroscopy and optical tensiometry techniques, the photostability and wettability of polymeric films are analyzed, emphasizing the effects associated with photoexcitation of the samples with a laser in the UV region. The obtained results show that the addition of a small percentage of carbon quantum dots does not modify the wettability of the films but increases the photostability of the samples to UV radiation. Using glycerol as a test liquid during the contact angle measurements, one can observe that the wetting dynamics is not affected by the addition of carbon quantum dots, which act as an absorber center for electromagnetic radiation. Using the kinetic-molecular theory to analyze the wetting dynamics, the physical-chemical parameters that characterize the wetting phenomenon are determined. The results obtained in this work show that the addition of quantum dots can be used to improve the stability of biocompatible polymer films, making them less susceptible to UV radiation from the medium.
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8
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ANTONIO EVANDRO DOS SANTOS
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Study of the Acoustic Scattering Phenomenon using the Finite Element Method (FEM)
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Leader : JOSE PEREIRA LEAO NETO
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MEMBRES DE LA BANQUE :
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JOSE PEREIRA LEAO NETO
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JOSE HENRIQUE ARAUJO LOPES DE ANDRADE
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ALEX EMANUEL BARROS COSTA
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Data: 6 sept. 2023
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Afficher le Résumé
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The propagation of acoustic waves in particles is a complex phenomenon that involves the interaction between waves and particles, resulting in the reflection, transmission, and scattering of acoustic energy. The study of acoustic scattering involves analyzing the solutions of the Helmholtz equation, considering boundary conditions and the expansion into partial waves. This analysis allows us to understand how particles interact with acoustic waves and contribute to the propagation and scattering of acoustic energy. Most theoretical analysis of scattering and acoustic radiation force Frad (the stationary force caused by the linear change of momentum flux during the scattering of an acoustic wave by a particle) in fluids assume that particles have a spherical shape, but this simplification does not represent all real-world situations. The spherical shape is considered an idealized geometric form, where the particle is symmetrical in all directions. This assumption simplifies the problem by allowing simpler mathematical equations to describe the particle’s behavior in response to acoustic radiation. However, when considering particles with non-spherical shapes, exact analytical techniques can become impractical. In such cases, more sophisticated numerical approaches are required, such as finite element methods, finite difference methods, or boundary element methods, to solve the scattering problem and obtain precise and realistic results. Here, we introduce a semi-analytical approach to deal with axially symmetric particles of sub-wavelength size (Rayleigh scattering limit) immersed in an ideal isotropic fluid. The scattering coefficients that reflect the monopole and dipole modes are determined through the numerical resolution of the scattering problem. Our method is compared with the exact result for a rigid sub-wavelength sphere in water, a fluid sphere, and a viscoelastic solid. Additionally, we extend our analysis to an spheroid, a geometry that approximates a sphere but involves analytical complications that make exact solutions more challenging. These studies are fundamental for various biomedical applications, which utilize techniques such as particle trapping, levitation, and acoustic tweezers, among others. Techniques for immobilizing particles and cells in microfluidic systems are often necessary in the concept of Lab-On-Chip technology, where particles with dimensions much smaller than the acoustic wavelength are common, known as the Rayleigh scattering regime, found in Acoustofluidic devices.
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Thèses |
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1
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RENATO FERREIRA DUTRA
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Charge transport and quantum State Transfer in Low Dimensional disordered Geometries
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Leader : FRANCISCO ANACLETO BARROS FIDELIS DE MOURA
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MEMBRES DE LA BANQUE :
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ANDRE MAURICIO CONCEICAO DE SOUZA
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Adauto José Ferreira de Souza
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FRANCISCO ANACLETO BARROS FIDELIS DE MOURA
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GUILHERME MARTINS ALVES DE ALMEIDA
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MARCELO LEITE LYRA
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Data: 10 janv. 2023
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Afficher le Résumé
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In this present work, we study the dynamics of an electron in two-dimensional systems (2D) under the effect of an external electric field. In both cases we investigate the time evolution of an initially localized wave packet, using a Taylor formalism to solve the set of Schrödinger equations. In the first case, we consider a square lattice with the hopping terms distributed aperiodically. The obtained results suggest that fast propagation of electrons (ballistic dynamics) is found for a range of values of the degree of aperiodicity ν of the system. By inserting the effect of a static electric field in the model, it is verified the existence of an oscillatory behavior similar to the electronic dynamics in crystalline systems, or that is, where they exhibit “ Bloch oscillations”. The frequency ω and the size LE of these oscillations are investigated and the results found are compared with the semi-classical approach, resulting in good agreement with default behavior. In the second case, we consider a square lattice with the hopping terms with correlated disorder. Our results indicated that the correlated disorder promotes a fast electronic propagation fast for intermediate times. When we insert an electric field, we also observe behavior similar to “Bloch oscillations”. The frequency obtained for this second case is also in good agreement with those predicted by the semi-classical approach. Despite the absence of extended states and based on the disorder inserted in the model, we discuss the stability of these apparent “Bloch oscillations”. We also investigated the quantum state transfer (QST) in a channel with diagonally uncorrelated disorder, connected to an sender (S) and a receiver (R). We use some measures of the degree of localization in order to evaluate the localization or non-localization properties of the proposed channel for QST. The results revealed that within a certain limit of weak disorder, the transfer of quantum states occurs with good fidelity.
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2
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RAUL LIMA FERREIRA
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Optical properties of organic systems with multifunctional characteristics
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Leader : ITALO MARCOS NUNES DE OLIVEIRA
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MEMBRES DE LA BANQUE :
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MARIO ERNESTO GIROLDO VALERIO
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LUCIMARA STOLZ ROMAN
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ANDRE DE LIMA MOURA
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CARLOS JACINTO DA SILVA
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ITALO MARCOS NUNES DE OLIVEIRA
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MARIA SOCORRO SEIXAS PEREIRA
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Data: 21 mars 2023
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Afficher le Résumé
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The present study is devoted to the investigation of photoluminescent organic materials which are sensitive to environment conditions, envisaging their use in sensing and imaging applications. Four different systems are investigated: a dithienylpyrrole derivative bearing a fluorene substituent (SNSFCA), a carbon quantum dot obtained from dansyl chloride (CD-DsCl), a carbon quantum dot synthetized from an azodye (CDMR), and a polymeric composite of polyvinyl alcohol (PVA) and a carbon dot. Using steady-state and transient UV-vis spectroscopy, we show that SNSFCA diluted in chloroform undegoes a photopolymerization under photoexcitation, which is characterized by changes in the physical parameters of photoluminescent mechanism. Concerning the study of carbon dots derived from dansyl chloride, it is analyzed how the environment conditions affect the photoluminescence of CD-DsCl, with emphasis on temperature and pH effects. Our results reveal that CD-DsCl exhibits a thermally-actived delayed fluorescence, which is associated with a reverse intersystem crossing due to the small energy gap between singlete and triplet excited states. The occurrence of an intersystem crossing in CD-DsCl is exploited to analyze the generation of reactive oxygen species (ROS) of such nanoparticles. Envisaging the use of dye effluents as carbon precursors, we also study the synthesis of carbon dots from the methyl red azodye (CDMR). Using a hydrothermal synthesis method, we have obtained highly nitrogen-doped carbon dots, which present excitation-dependent emission and thermal-quenching fluorescence behavior. Using flurescence confocal microscopy, the possibility of use CDMR in bioimaging application is analyzed, considering HeLa cells as the biological probe. Furthermore, we study the effects of CDMR addition on the optical properties of PVA films. From time-resolved Z-scan measurements, we investigate how the CDMR concentration affects the thermal-optic coefficient and thermal diffusivity of poymeric films. The effects of polymeric matrix on the fluorescence properties of CDMR are also investigated.
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3
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JAMERSON FONSECA DE SOUSA
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Generation of visible light and study of energy-transfer in TeO2:ZnO glass doped and co-doped with Dy3+/Pr3+ and Eu3+/Ho3+
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Leader : ARTUR DA SILVA GOUVEIA NETO
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MEMBRES DE LA BANQUE :
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LUCIANO AVALLONE BUENO
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ERNANDE BARBOSA DA COSTA
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ARTUR DA SILVA GOUVEIA NETO
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FRANCISCO DE ASSIS MARTINS GOMES REGO FILHO
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MARIA TEREZA DE ARAUJO
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Data: 24 mars 2023
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Afficher le Résumé
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In this work, we carried out a spectroscopic study of glass based on Tellurium and Zinc oxides (xTeO2:yZnO) doped and co-doped with Dy3+, Pr3+, Eu3+ and Ho3+ ions under UV and blue excitation. The analysis of this investigation were based on measurements of optical absorption and excitation, luminescence, time-resolved luminescence and energy transfer efficiency parameters. The results show that under UV/blue excitation the co-doped systems generate well-defined emission bands in the visible region, and the behavior of the emission intensity as a function of the co-dopant concentration indicated the presence of energy transfer mechanisms Dy3+ → Pr3+, Pr3+ → Dy3+, Eu3+ → Ho3+ e Ho3+ → Eu3+, which were later confirmed by lifetime measurements. The analysis of energy transfer efficiencies indicated that transfers according to Dy3+ → Pr3+ e Ho3+ → Eu3+ Dy3+ → Pr3+ and Ho3+ → Eu3+ mechanisms are more efficient and, therefore, are more likely to occur. It was also observed that the emissions are sensitive to the excitation wavelengths used, and furthermore, these excitations are responsible for altering the sensitizer/acceptor relationship in the energy transfer process, showing, therefore, that the spectral profile of the emissions is a function not only of the concentration of the ions, but also of the excitation used and consequently of the energy transfer. The results presented here may impact studies that explore the optical properties of devices based on the light emitted by Dy3+/ Pr3+ and Eu3+/ Ho3+ ion pairs
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4
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JONATHAN ALVES REBOUÇAS
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Divergent series, Padé approximants and light scattering
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Leader : PAULO CESAR AGUIAR BRANDAO FILHO
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MEMBRES DE LA BANQUE :
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FELIPE ARRUDA DE ARAUJO PINHEIRO
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DANILO GOMES PIRES
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GUILHERME MARTINS ALVES DE ALMEIDA
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PAULO CESAR AGUIAR BRANDAO FILHO
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SOLANGE BESSA CAVALCANTI
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Data: 31 mars 2023
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Afficher le Résumé
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Light scattering is a very important physical phenomenon when it comes to the study of radiation-matter interaction. This phenomenon can be approached to discover scattering patterns of certain materials, such as determining crystal structures using X-rays, or to produce materials with specific scattering characteristics that result in useful applications, such as metamaterials. From a more formal theoretical perspective, the various equations do not always offer analytical solutions and are, in most cases, quite intractable. Therefore, it is common to resort to approximation methods when seeking to solve scattering problems. Among them, the perturbative methods stands out, which consists of assuming that the scattered field can be written as an infinite power series. The problem is then replaced by several smaller ones, presumably more manageable, which allow finding approximate solutions for a series of physically interesting cases. The Born series is the most commonly used to represent the scattered field in these problems. For scatterings in which light interacts weakly with the material (weak scattering), truncating this infinite series at the first non-zero power term (first Born approximation) already represents a good approximation of the problem solution. However, for scatterings where light interacts strongly with the material (strong scattering), we observe that the first Born approximation fails to describe the result. This fragility of the Born approximation occurs in both Hermitian and non-Hermitian materials, sometimes being more pronounced in the latter. Hence, the need to seek approximate methods that provide good results for both weak and strong scatterings, as well as for any type of material. Padé approximants emerge as a promising tool for this purpose since they usually generate larger convergence regions when compared to the respective Born series. In this work, we apply Padé approximants to a series of physically interesting problems. For certain parameter choices, replacing the analytical solution with the Born series tends to diverge. From the analysis performed, we verify that Padé approximants are an extremely useful tool for describing light scattering in both weak and strong regimes, as well as in non-Hermitian materials.
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5
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LUAN FELIPE SANTOS MARTINS
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Topological order and phase transitions in quantum interacting spin chains.
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Leader : MARCELO LEITE LYRA
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MEMBRES DE LA BANQUE :
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MARCELO LEITE LYRA
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MARIA SOCORRO SEIXAS PEREIRA
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RODRIGO G. PEREIRA
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RENE RODRIGUES MONTENEGRO FILHO
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Adauto José Ferreira de Souza
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Data: 11 avr. 2023
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Afficher le Résumé
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In this work, we investigate topological orders and quantum phase transitions in distinct interacting spin models using numerical methods. We introduce the finite-size tangential scaling method, where we demonstrate its validation in the characterization of topological phase transitions between Haldane and Large-D phases in an anisotropic Heisenberg chain of spin S = 1. Our results were validated by theoretical theories of the critical exponent of the correlation length ν originated from a non-linear effective field theory σ. Next, we investigate the quantum phases and topological phase transitions for a class of tetramer ferrimagnetic models (S1 − S1 − S2 − S2) with isotropic and alternating Heisenberg interactions. We first investigate the case S1 = 1 2 and S2 = 5 2 where we obtain the phase diagram of the model and investigate the quantum phases from different magnetization curves. We characterize a critical point of the phase diagram using the finite-size tangential scaling method, where we have a topological phase transition of critical exponent ν = 2 3 . Next, we investigate the universality of topological phase transitions for a class of ferrimagnetic chains where we demonstrate that the zero-field critical points that arise in this class of models are universal and belong to the universality class SU(2) Wess-Zumino-Witten with ν = 2 3 . Finally, we investigated another tetramer ferrimagnetic chain with S1 = 1 and S2 = 3 2 , obtaining a rich phase diagram of the model showing successive transitions of topological phases at zero field. We investigate these transitions again implementing the finite size tangential scaling method, where we demonstrate that these transitions are also universal and belong to the SU(2) Wess-Zumino-Witten class with ν = 2 3 . Finally, we investigate the role of distinct dissipations in the symmetry-protected topological order given by the Affleck-Kennedy-Lieb-Tasaki model in one dimension using tensor network methods. We show that for asymmetric dissipations with respect to time-reversal symmetry the nontrivial topological ordering is destroyed with increasing dissipation intensity γ. For the case of symmetric dissipation, we saw that the model’s symmetry-protected topological phase is maintained, validated by measurements of the order parameter string, purity Γn, and analyzing the Schmidt spectrum. It is worth mentioning that we identified the degeneracy pattern in the Schmidt spectrum of the model’s density matrix in the steady state, as it is possible to observe in the entanglement spectrum in the case of non-trivial topological phases for pure states. Our results validate the argument that we obtained a dissipative symmetry-protected topological phase and that can be characterized by tools also used for the case of pure states.
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6
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EVERTON BRITO DE LIMA
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Applications of the Finite Element Method in Obtaining the Force and Torque of Acoustic Radiation in Anisotropic Particles
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Leader : JOSE HENRIQUE ARAUJO LOPES DE ANDRADE
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MEMBRES DE LA BANQUE :
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ASKERY ALEXANDRE CANABARRO BARBOSA DA SILVA
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EDIGUER ENRIQUE FRANCO
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FREDERICO SALGUEIRO PASSOS
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GLAUBER JOSE FERREIRA TOMAZ DA SILVA
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JOSE HENRIQUE ARAUJO LOPES DE ANDRADE
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JOSE PEREIRA LEAO NETO
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Data: 13 avr. 2023
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Afficher le Résumé
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The mean acoustic fields of acoustic radiation torque force result from the non-linear interaction of a harmonic acoustic wave in time with a particle. These phenomena are widely used in acustofluidics, in the manipulation of microparticles such as cells and microorganisms. Here we will highlight the contributions of numerical models developed through the finite element method used, firstly, in the validation of an analytical model of the linear interaction with spheroidal particles of sub-wavelength, and later, in the complementation of a semi-analytical model that describes the field means-acoustics on any axisymmetric particle. In the first work, the analytical expressions for the force and torque of acoustic radiation on a sub-wavelength rigid spheroid are obtained in the scattering dipole approximation, where the force has a gradient component of a scattering component, while the torque is given has terms of a contribution due to momentum and another due to acoustic spin. We compared numerical and analytical results, using an acoustic field composed of two raw plane waves. In the following work, a semi-analytical method of remarkable efficiency was proposed in obtaining the means-acoustics radiation force and torque fields exerted on any subwavelength axisymmetric particle, in an ordinary acoustic field. Bypassing both the limitations of analytical methods, restricted to problems with symmetry in relation to a given coordinate system, and the limitations of purely numerical methods, which demand a lot of time and computational power to simulate the behavior of the particle along the acoustic field. In this work, the mean-acoustic fields are given as a function of scattering coefficients referring to the monopole and dipole modes, which are numerically calculated in a given simplistic configuration, and then are used to generalize the results to any incident field. We compare our method with an exact result for a rigid sphere of subwavelength in water, as well as demonstrate the potential of our methodology, presenting a more realistic example of application using a red blood cell immersed in blood plasma under the action of a stationary ultrasonic wave.
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7
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GICLENIO CAVALCANTE DA SILVA
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Fabrication of acoustofluidics lab-on-a-chip devices via additive manufacturing
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Leader : GLAUBER JOSE FERREIRA TOMAZ DA SILVA
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MEMBRES DE LA BANQUE :
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ANTONIO ADILTON OLIVEIRA CARNEIRO
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GLAUBER JOSE FERREIRA TOMAZ DA SILVA
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JOSE HENRIQUE ARAUJO LOPES DE ANDRADE
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RODRIGO PEREIRA BARRETTO DA COSTA FELIX
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UESLEN ROCHA SILVA
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Data: 29 mai 2023
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Afficher le Résumé
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The manipulation of particles or microstructures without contamination, either due to the environment or direct contact is of great interest for studies focused on biotechnology and the development of new drugs and applications aimed at diagnosis. In this context, it is necessary to study techniques that make this process more effective. In recent decades there has been a movement in order to remedy this need. In the present work, we will explore techniques for manufacturing acoustofluidics devices, which combine microfluidics techniques coupled with ultrasonic systems, with this capability, as well as advantages and disadvantages. We will study the physical quantities involved in these devices, and how their behavior affects/implies the aggregated features. We will demonstrate the manufacture of these devices, with project development based on analytical simulation, 3D modeling and manufacturing via additive manufacturing, using a printer with DLP technology based on photopolymerizable resin. This device will be able to levitate and standardize objects or beings of the order of µm, we will evaluate its operation, in addition to indicating pioneering applications for the evaluation of microorganisms such as the causes of leishmaniasis and also Raman spectroscopy, reducing the analysis time, increasing practicality, and amplifying the captured signal through improvements in the focusing system used.
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8
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ANA CAROLINA COSTA SOARES
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Luminescent nanoparticles for sensing in the SWIR region
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Leader : CARLOS JACINTO DA SILVA
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MEMBRES DE LA BANQUE :
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ANDRE DE LIMA MOURA
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CARLOS JACINTO DA SILVA
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ERVING CLAYTON XIMENDES
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NELSON GUILHERME CASTELLI ASTRATH
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TASSO DE OLIVEIRA SALES
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Data: 15 juin 2023
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Research on luminescent nanothermometers (LNTs) is constantly growing due to the need to read and control the temperature of various physiological processes that occur, among others, in biological systems such as tissues, cells and living organisms, enabling the diagnosis and treatment of diseases. In this sense, nanoparticles (NPs) doped with rare earths ions have stood out for presenting several advantages such as having a wide spectral range from ultraviolet to infrared. Thus, they have luminescent properties within the three biological windows (BWs), which are regions where autofluorescence, dispersion and absorption of light by biological tissues are minimized, allowing less influence of the environment under study. In this thesis, we explore emissions and excitations within the BWs, as both are extremely important. The main focus of our study was the short-wave infrared (SWIR) emissions/excitation, which basically operates from 0.7 to 2.5 μm, mainly within the BW-II (1, 0 - 1.35 μm) and BW-III (1.5 - 1.9 μm). However, in an early part of our work, which focused on the effects of core-shell structure engineering, we explored emissions at BW-I (0.65 – 0.94 μm) under excitation at the minimum of the BW-I. In this part we demonstrate that the core-shell engineering, which allows the spatial separation of the emitting elements and, therefore, a control of the energy transfer processes between ions and ions to defects, has a very important role to maintain the spectral form of the NPs emissions in the presence of biological material. Despite the promising applications of LNTs, concerns have arisen about their reliability due to tissue-induced spectral distortions that are present even in BW-II that have been heavily exploited recently. We present an innovative solution to this problem, demonstrating the effectiveness of shifting the operating range of these LNTs to BW-III. Through experimental evidence using CaF2 NPs tri-doped with ytterbium, erbium and thulium, we demonstrate that the luminescence spectra acquired in BW-III are minimally distorted by the presence of tissue, paving the way for reliable LNTs. In addition, advanced analysis (Multiple Linear Regression) of the emission spectra allows obtaining subdegree thermal uncertainties. Aware of the strong absorption of water in the spectral region between BWs II and III (1.4 and 1.5 μm), we explored single-doped LaF3 NPs with Tm3+ as a potential humidity sensor through the use of emissions at 1230 (in JB -II) and 1470 nm. The results showed a reduction greater than 97% in the emission intensity at 1470 nm with the presence of a 2 mm water film, resulting in a relative sensitivity between 0.083 – 0.125 %μm-1
for the smallest water films, demonstrating to be a potential luminescent humidity sensor. Experiments are underway for a comparative study with commercial and other humidity sensors.
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9
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JOSÉ ROBSON DA COSTA VENÂNCIO
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DFT study of electronic, optical and vibrational properties of the dansyl-chloride orthorhombic crystal
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Leader : MARCELO LEITE LYRA
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MEMBRES DE LA BANQUE :
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MARCELO LEITE LYRA
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NILTON FERREIRA FRAZÃO
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RONIEL DE LIMA ARAUJO
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Umberto Laino Fulco
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VINICIUS MANZONI VIEIRA
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WANDEARLEY DA SILVA DIAS
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Data: 27 oct. 2023
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Many researches are related to the use of organic compounds markers by dansyl chloride (DNS-Cl), which can be a flexible and sensitive means for fluorescence detection. Widely used in areas such as pharmacology, toxicology, organic synthesis and biochemistry. There are no reports on the theoretical study of the DNS-Cl molecule in crystalline form. The crystal structure of DNS-Cl was calculated and analyzed to the following structural properties, electronic, optical and normal modes of vibration, infrared and Raman spectra, as well as thermodynamic properties. It is investigated by simulation using first principle calculations in one approach pseudopotential within the formalism of density functional theory (DFT). We consider the generalized gradient approximation with dispersion correction (GGA + TS) and the local density approximation (LDA-CAPZ) implemented in the CASTEP code. In the calculation of the band structure, a direct gap of 1.83 eV for GGA + TS and a direct gap of 1.73 eV for LDA was found. Optical properties were calculated considering the polarization along the 100, 010, 001 direction and for a polycrystalline sample. Infrared spectra and Raman thermodynamic properties were also obtained and analyzed. The crystal has characteristics of a semiconductor material proven by the band structure, if synthesized with great potential in organic crystal applications, or placed in the crystallographic data blank used as a reference for future research on the studied crystal structure.
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