https://repositorio.ufu.br/handle/123456789/19114 2026-08-09T20:41:16Z https://repositorio.ufu.br/handle/123456789/49359 Title: Caracterização fotofísica dos derivados de Carbazol e Tetrazina para sensoriamento de radiação ultravioleta Abstract: This work investigates the photophysical properties and charge transport mechanisms in donor–acceptor conjugated polymers derived from carbazole and tetrazine. The ma terials analyzed were synthesized at the Paulo Scarpa Polymer Laboratory (LaPPS), Federal University of Paraná (UFPR). The polymer LaPPS80 is based on the carba zole–tetrazine combination (2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2yl)-9-(tridecan 7-yl)-9H-carbazole- alt-3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine), whereas LaPPS81 is derived from condensed carbazole–tetrazine (5,11-bis(2-ethylhexyl)dihydroindolo[3,2 b]-carbazole-alt- 3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine). It is worth noting that LaPPS81 can be obtained through different synthetic routes and is therefore denoted throughout this work as LaPPS81-C and LaPPS81-S. This study proposes a novel application of these materials as selective photodetectors in the ultraviolet–visible region. Spectroscopic characterization by optical absorption, photoluminescence (PL), and photoluminescence excitation (PLE) revealed that the transition from solution to the solid state (thin films) induces strong intermolecular interactions. These interactions are evidenced by Stokes shifts on the order of approximately 59 nm, 101 nm, and 139 nm, as well as by pronounced red-shifts in the emission spectra. These results indicate the formation of molecular aggregates and delocalized excited states, which play a key role in charge transport in these polymeric systems. Photoresistor devices with planar architecture and interdigitated fluorine-doped tin oxide (FTO) electrodes were fabricated and characterized. Morphological and electrical analyses showed that the oligomer LaPPS81-C, due to its low molar mass, does not form efficient percolation networks. In contrast, the polymers LaPPS80 and LaPPS81-S yielded func tional devices with distinct and complementary physical behaviors. LaPPS80 exhibited maximum sensitivity at 450 nm but showed the anomalous phenomenon of negative photoconductivity (NPC) under UV excitation (280–370 nm), attributed to the activation of deep recombination centers by high-energy photons. LaPPS81-S demonstrated positive photoconductivity, with high selectivity at 370 nm, and notable anisotropy in the response to light polarization, indicating a macroscopic molecular alignment that favors directional charge transport. Electrical stability tests (20 voltage sweep cycles) indicated the robustness of the devices, which maintained ohmic behavior without significant degradation or hysteresis. Analysis of the I–V curves suggested the predominance of direct tunneling injection mechanisms at low electric fields, with a transition to regimes consistent with field emission at higher voltages. Impedance spectroscopy corroborated the modulation of bulk resistance under illumination, indicating that LaPPS81 exhibits higher intrinsic conductivity compared to LaPPS80. Taken together, these results suggest that the LaPPS family holds potential for application in selective optical sensors, with responses that can be tuned through molecular engineering and morphological control. 2026-02-23T00:00:00Z https://repositorio.ufu.br/handle/123456789/48507 Title: Análise da deflexão gravitacional da luz em ocultações estelares Abstract: This dissertation investigates the astrometric effects of the gravitational deflection of light during stellar occultations, with emphasis on the simultaneous contribution of multiple bodies in the Solar System. The main objective is to evaluate how these effects contribute to the apparent position of the occulting body under different occultation geometries and to what extent they may affect high-precision astrometric measurements. To this end, the relativistic model of Klioner, with microarcsecond-level accuracy, is employed, from which numerical routines are implemented to compute the deflection vectors associated with different massive bodies. The methodology combines theoretical analysis of the gravitational effect, computational implementation supported by the SORA package, and real case studies. Initially, the fundamental concepts of stellar occultations are presented, including how astrometric positions are determined and which factors constrain their accuracy, such as observation quality, number of chords, and temporal coverage of the event. The Klioner light-deflection model is then described, with emphasis on the specific expressions and approximations used in this work. Based on this, a computational approach is developed to adapt the model to the context of stellar occultations, allowing the evaluation of angular separations, deflection angles, and offsets in right ascension and declination, as well as the combined contribution of each massive body. Validation is carried out through a case study of the stellar occultation by Ganymede on 21 December 2020, which is used as a reference to analyze the behavior of the corrections arising from the proximity of the Sun, Jupiter, and Saturn at that moment. The results show that, although the gravitational deflection due to multiple bodies often remains below the positional uncertainties of many events, its magnitude is comparable to the precision achieved in the best recorded occultations, becoming significant when angular separations are small or when the event has a high signal-to-noise ratio. The analysis demonstrates that the event geometry, the alignment between the star, observer, and deflecting bodies, and the uncertainties in the ephemerides are decisive in determining the final magnitude of the correction. It is concluded that the systematic consideration of gravitational light deflection by multiple bodies improves the astrometric consistency of stellar occultations and may contribute to the refinement of reference frames, especially in future observational scenarios with higher instrumental precision. 2026-02-18T00:00:00Z https://repositorio.ufu.br/handle/123456789/47639 Title: Transições de fase quânticas dinâmicas do modelo de Creutz com hopping de longo alcance Abstract: In this dissertation, we investigate dynamical quantum phase transitions (DQPTs) in the Creutz model with hopping of range D, decaying according to a power-law with exponent ν. We obtain the exact solution of a generic two-band model, of which the Creutz model is a particular case. We derive analytical expressions for dynamical quantities which are relevant to the study of DQPTs, such as the Loschmidt amplitude and the dynamical free energy of the system. This allows us to analytically determine the Yang-Lee-Fisher (YLF) zeros associated with the Loschmidt amplitude. Consequently, we identify the critical times at which non-analyticities in the dynamical free energy occur in the Creutz model with long-range hopping. Our results indicate that the number of YLF zeros increases with increasing D and decreasing ν. In particular, our findings suggest that in the limit D → ∞ e ν → 0, the dynamical free energy becomes non-analytic at almost all times. A similar consequence, when considering these limits, has already been observed in the case of the Su-Schrieffer-Heeger (SSH) model with long-range hopping. 2025-08-01T00:00:00Z https://repositorio.ufu.br/handle/123456789/47519 Title: Uso de espectroscopia de emissão ótica com plasma induzido por laser (LIBS) associada à aprendizagem de máquinas para análise de resíduos de disparos de armas de fogo (GSR) Abstract: In a situation involving an accident or assault with a firearm, it is possible to identify the person responsible for the shots using chemical markers. This is done by identifying elements already catalogued in conventional ammunition, such as Ba - barium, Pb - lead and Sb - antimony. However, ammunition such as NTA (non-toxic ammunition) does not have chemical markers as clear as conventional ammunition, requiring alternative methods to identify a possible shooter. Therefore, this work proposes an experimental protocol capable of providing such chemical markers, while still providing a margin of accuracy in identification and avoiding false positives. To this end, laser-induced breakdown spec- troscopy (LIBS) is used to provide the elemental signature of the samples, which in turn serves as information for training the Random Forest(RF) classification model, which is based on statistical information metrics. With this supervised machine learning method, it is possible to analyze which parameters are used to distinguish a shooter from a non- shooter, making it explainable. The samples were collected at a shooting range, under protocols established by SENASP (National Secretariat for Public Security), consisting of 2, 6 and 8 shots with NTA ammunition, and 1 and 6 shots with conventional ammu- nition. For comparison, samples were taken from 0 shots (samples from the hand of an individual who did not come into contact with the firearm). The results show chemical markers identified from Cu I, Cu II, Ti I and Mo I atomic transitions, the classification model was able to achieve an accuracy of over 90% and has a generalization power high enough to distinguish a shooter from a non-shooter regardless of the type of ammunition, conventional or NTA. 2025-02-25T00:00:00Z