Navegando por Orientadores "DEL NERO, Jordan"

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Análise da potencialidade a condução do BDT através da densidade eletrônica de estados via tight binding e desenvolvimento de software (B3J)
(Universidade Federal do Pará, 2007) GUIMARÃES, Jeconias Rocha; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work we studied the potentiality of the polymer BDT (1,3-benzodithiole 4Hciclopenta[2,1-b:3,4b’]) to become a conducting polymer. Ground state conformations and the electronic structure have been calculated through quantum chemical methods in order to obtain the density of electronic states. The presence of several types of conformational defects and the variation of doping level has been considered. One of the most used theories to study the doping effects on conjugated polymers is the Huckel method. It is based on the separability of the sigma and pi bonds of planar molecules. BDT oligomers are not planar molecules and an extended Huckel method that includes all the atomic valence functions has been used. An original computation code, the B3J program, has been developed for this purpose. Simulations of the absorption spectrum in the UV-visible-near IR region have seen performed as well. Program B3J calculates the density of states of polymeric systems. The band structure of BDT was obtained with this software. We calculated the density of states of the neutral system and doped systems including several doping levels and both random and uniform distribution of defects. The square of the coefficients expansion of the wave function was obtained for polymers including up to 20 monomers. For these calculations we used geometries calculated by AM1 and PM3 quantum chemical methods. Finally, we studied the asymmetry of the charge separation induced by the presence of an external static electrical field in BDT oligomers suitably substituted by electron acceptor/donor species. The results are consistent with a transistor-like behavior of neutral and charged molecules.
Acesso aberto (Open Access)
Análise do enxofre corrosivo em óleo mineral isolante e remoção do dibenzil dissulfeto com nanotubos de carbono baseados em matriz metálica
(Universidade Federal do Pará, 2012-05-07) SARAIVA, Augusto Cesar Fonseca; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
Unexpected failures in transformers led to the identification of copper sulphide formation, deposited on the conductors. The qualitative presence evaluation of corrosive sulfur in insulating mineral oil, led to a change in the Brazilian standards ABNT NBR 10505, which assesses the presence of corrosive sulfur in mineral oil, change in the time and test temperature to 150 °C / 48 hours. Performing the chemical speciation of organosulfur compounds (by gas chromatography coupled to mass spectrometry), were found 13 compounds in the Nynas oil and 9 compounds in the Petrobras oil. DBDS, which was found only in the Nynas oil, and it was the compound with the highest concentration. To perform the determination of the presence of DBDS in insulating mineral oil, a method by gas chromatography coupled to mass spectrometry was developed, and it was possible to quantify the amount of DBDS in insulating mineral oil samples derived from the power transformer. The passivation process by tolutriazol and benzotriazol, used as anticorrosive additives in the core of electrical equipament, was evaluated; after a while the effect of the addition of passivating agent becomes ineffective with time. The solution for the remotionl of DBDS from mineral oil was realized by using carbon nanotube reinforced by metallic matrix as agent to remove the DBDS. It was found that the adsorption agent was able to realize the complete DBDS remotion from insulating mineral oil up to a volume of 4000 mL (oil contaminated with DBD).
Acesso aberto (Open Access)
Aplicação de métodos teóricos na investigação da transferência auto-consistente de elétrons em nano-retificador orgânico
(Universidade Federal do Pará, 2009-02-11) ALEIXO, Vicente Ferrer Pureza; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work we present a theoretical study on the electronic structure of a molecule of the type Donor- dinitrobenzene and a group Acceptor- dihydrophenazine (D-A) with polienic bridges varying of π = 0 to the π = 10. It’s a promising system for construct molecular rectifiers that under chemical to dope can come to acquire electric properties of conductive material. It is still, under action of external electric field it presents equivalent behavior to the of usual devices, with countless advantages, for instance, extremely reduced size and intense optical response in a non-linear regime. To study this class of system, we optimize the geometry systematically, performing ZINDO/S-CI (Zerner´s Intermediate Neglect of Differential Orbital/Spectroscopic – Configuration Interaction Single) calculations and using 220 configurations as average. We observe the electronic transfer calculated by Hartree-Fock. Our results show a well defined localization of the Boundary Molecular Orbitals (BMOs) HOMO [LUMO] at the D [A] groups for large polienic bridges. The opposite is verified for small bridges and uniformity is observed for the BMOs in the DA terminals. This would indicate that only large polienic bridges work for devices using the LUMO as conduction channel. A detailed analysis of the molecular charge rearrangement due to an external electric field shows that the charge transport at the D [A] group is bridge size independent. An applied voltage suffices to create a saturation potential for this system with too close DA groups (presenting a saturation and an operation region to systems with small bridges), usually present in systems with relatively large molecular bridge and in macroscopic semiconductors devices. We believe that the LUMO play an important role in the charge transfer at relatively large structures, in addition to fails in molecular structures where the D group is too closer to A. Our results show that we have a Molecular rectifier that works as a macroscopic rectifier.
Acesso aberto (Open Access)
Caracterização de polímeros unidimensionais (Poliacetileno, Poliazina e Poliazoeteno) através de cálculos espectroscópicos e transporte eletrônico
(Universidade Federal do Pará, 2010) LEAL, José Fernando Pereira; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work is presented a theoretical investigation of the neutral and bipolarononlike ground and excited states of molecules and polymers isoelectronic composed by Polyacetylene, Polyazine and Polyazoethene. The results obtained, utilizing DFT and ab initio methodologies, reveal that a very good defects description can be important in the investigation of insulator-metal transition of quasi-unidimensional polymers indicating metallic behavior around the Fermi level as mechanism of conductivity of polymers. This result is consistent with experimental data and do not anticipate by Su-Schrieffer-Heeger (SSH) methodology. These results are consistent with significant features as a nanodevice and can be summarized as: (i) it could be used as single directional molecular rectiffer with a conformational geometry with small lead coupling; (ii) our non-equilibrium green function simulation present that Polyacetylene, Polyazine and Polyazoethene could rectifield without gate current; (iii) based on properties of bonds type, it can be utilized to design devices with applications in molecular electronics.
Acesso aberto (Open Access)
Desevolvimento de dispositivos eletrônicos orgânicos nano e micro-estruturados: memória volátil, sesores e fotocélulas
(Universidade Federal do Pará, 2011-02-14) REIS, Marcos Allan Leite dos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work, several nano and microstructured organic devices were developed based on molecules of 4-dimethyl amino azobenzene-2-carboxylic acid (Methyl Red – VM), C60 Fullerene, nanocomposite of Aluminum/Carbon Nanotubes (Al/NC) and polymers: Poly(3, 4- dioxithiophene ethylene)-poly(sulfonate stireno) – PEDOT-PSS and poly(3-hexiltiofeno) – P3HT. These devices are volatile memory, fuel sensors, thermal-piezoresisitive sensor and photocells, which were manufactured by spin-coating, drop casting and chemical vapor deposition, resulting in devices with planar or layer by layer geometry. Morphological, optical, electrical and thermal characterizations were performed on devices, resulting: (a) volatile memory with a bit retention time of 4.5 s, the characteristic curves of current vs. voltage with peak-valley ratios of 8: under a 10:1 voltage positive and negative electrical energized with electrical conductivity of 10-4 S / m (OFF state) to 3.10 S / m (ON) at room temperature, (b) fuel sensors like chemiresistor sensors characteristics with sensitivity to ethanol and gasohol in concentrations of 26.25 ppm, (c) thermal-piezoresistive sensor with polynomial relationship between temperature and electrical resistance, linear relationship between pressure and electrical resistance, more accurate than a K type thermocouple when compared to a mercury thermometer at room temperature, (d) photocells with better performance when doped by Methyl Red showed quantum efficiencies up to 0.04%, real power at 0.27 and power conversion efficiency of 2.0%. These results indicate that electronic devices developed showed a better performance in comparison to similar organics.
Acesso aberto (Open Access)
Design de nano-antenas dendriméricas
(Universidade Federal do Pará, 2015-02-23) SOUSA, Gleida Tayanna Conde de; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
Structures named derivatives dendrimers (DD) have fascinating electronics proprieties. From the technological point of view, they are completely different from those ones obtained only by their basics constituents and with discrete states of conductivity, which emerges from the points of Fermi's surroundings. One preponderant factor of the engineering of the DD is its dimensionality. Experiments using molecular spectroscopy (Raman) and high resolution microscopy (TEM, AFM and STM) confirmed the nature n-D of their electrons. They concluded that the dimensionality of one DD has a deep influence on its physics properties. This peculiar characteristic of electronics properties adjusts according to the geometry, along with the reduced dimensions, created a huge technological race, aiming to develop electronic devices (diodes, transistors, logical doors, displays,…) from DD. Some interesting applications refers to the usage of the DD as: antennas, by the DD’s impedance properties modifications in the presence of chemical species, clamps and the microscope probe, basis for lithium batteries, waves of nanoguides, and others. The study’s proposal is based on investigate the behavior’s changes of function of this classes of antennas DD pure and doped, in the presence of an extern electric field. For that, the terminals regions, which are associated with the parameters the defined the DD, will be modified.In this study, will be shown the DD’s electronics structures pure and doped, in the presence of an extern electric field, using the derived approaches from Hartree-Fork’s method. Therefore, using this method, the DD is obtained from the precursor structure, optimized by the molecular mechanical method.The DD’s investigation aims to calculate its electronic structure via Hartree-Fock semi empirical (AM1 and Zinco/S-CI) and ab initio, when convenient for little oligomers. This is important for the knowledge and analysis of which structural properties are related with the molecular electronic transport’s mechanism. The empirical analysis of Millikan-Laurtisen (ML) and Fowler-Nordheim (FN), it's also presented for better detailing of the electronic transport , in order to demonstrate the DD’s electronic signature, for the usage in dendrimers antennas.
Acesso aberto (Open Access)
Design de nanodispositivos eletroluminescentes baseados no ALQ3
(Universidade Federal do Pará, 2013-04-29) SILVA, Alessandre Sampaio da; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this study we investigated theoretically the electronic structure of [tris-(8-hidroxiquinolinolato) aluminum (III) - Alq3, solvation properties of the electroluminescent Alq3 organic liquids such as methanol, ethanol, dimethylformamide (DMF) and acetonitrile in order to understand the dependence the variation of system environments, improving the operation of conveyors films in electroluminescent devices of the type OLED (Organic Light-Emitting Diodes), and finally investigated the mechanism of Alq3 in the electron transport applying a low electrical current in the molecule and current curves showing the –voltage characteristic of the device. The simulation method consists of applying the sequential Monte Carlo / Quantum Mechanics (S-MC/MQ), that part of an initial treatment for separation of stochastic structures most likely to lower energy and subsequently with a quantum treatment to plot the electronic spectra of the layers solvation separated by the ZINDOS/S method. In the electrical properties of transport we use the Green function method coupled nonequilibrium density functional theory (DFT) inferring that the ramifications outer rings corresponding to the Alq3 would terminals for electronic transfer. Our results showed that the average absorption spectra of Alq3 for solvation in solutions undergoes a minimum deviation with changing environment, being in good agreement with the experimental results from the literature, and the IV curves confirmed the behavior of the diode device, corroborating the senses as more relevant to the terminals in Alq3 to have a satisfactory transport electronics.
Acesso aberto (Open Access)
Efeito de interferência quântica no transporte eletrônico de dispositivos "quasi"-unidimensionais
(Universidade Federal do Pará, 2018-05-03) OLIVEIRA, Alexandre de Souza; SILVA, Shirsley Joany dos Santos da; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The study of electronic transport in nano devices has been of great relevance in the last years, since the work of Aviran and Ratner, based on the properties of electrical conductivity in individual rectifying molecules under the action of an external electric field. The organic conjugated polymers in the pure state have low conductivity, but when doped, treated with reducing agents or connected to gold electrodes (Au) and subjected to an external electric field, they have a metallic behavior, that is, with high conductivity in line with experimental work. In this research we used devices composed of organic polymers conjugated in the pure state and also doped with chains containing simple (σ) and double (σ-π) type bonds, alternating between the carbons and these bound only to hydrogen atoms with gold electrodes (Au) connected at the ends of the individual molecules. This study was proposed for two types of electrodes: pyramid and plane. The model devices were optimized through the Extended Hückel Theory (EHT) and the computation of the electronic transport was performed using EHT combined with the Non-Equilibrium Green Function (NEGF). These devices are either quasi-1D or approximately linear structures and have been divided into two groups: the first, with odd numbers of carbon atoms from five (5) to nineteen (19) carbon atoms in their individual molecule (Group 1) and the second, with even numbers starting at six (6) going up to twenty (20) carbon atoms in its individual molecule (Group 2). The devices were subjected to two conditions: at low voltage, ranging from 0 to 0.1 Volt and then to high voltage, from 0 to 1.0 Volt. In order to compare the current and voltage (I - V) curves and the differential - voltage conductance (G - V) between low and high voltage results, the same voltage range was used, that is, from 0 to 0.1 Volt. For this work, the effects of destructive quantum interference (DQI) as well as constructive quantum interference (CQI) were analyzed. The effects of DQI are produced due to anti-resonance in the transmittance evidenced by unaccessed states observed in the transmission peaks, not allowing the transport to occur without presenting oscillations in the conductivity curve.
Acesso aberto (Open Access)
Eletrônica molecular via método híbrido DFT/FGNE em anéis fenilas acoplados a eletrodos metálicos de nanotubos de carbono: a regra de conformação e quiralidade molecular
(Universidade Federal do Pará, 2011-11-11) SILVA JÚNIOR, Carlos Alberto Brito da; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this thesis, we investigate in detail the electronic transport properties, conformation and symmetry of zz9 SWCN structures attached to phenyl rings (2, 3, 4 and 5) under the influence of external electric field (voltage) via hybrid method DFT type B3LYP 6-311G (d, p) combined with NEGF and Group Theory. We found a good relationship between: 1 - the chiral index () by Group Theory and the law of cos2 (, dihedral angle) for the geometry under the influence of external electric field because  only depends on the atomic positions () of conformations, and is also strongly correlated with current passing through the system; 2 - normalized conductance (G / Go) is proportional to cos2 in the region of the gap (EHOMO-ELUMO), ie, in regions where the resonance occurs negative differential resistance (NDR) and 3 - the Fowler-Northeim (FN) plot Vmin displays that occurs when the tail of a resonant transmission peak voltage enters the window, that is, when these structures is an NDR, NDR as the number of the IV plot is associated with the number Vmin of the FN plot and can be explained by the model of molecular transport line 4 - the barrier height (EF - EHOMO and ELUMO - EF) as a function of molecular length, 5 - Vmin as a function of barrier height (EF - EHOMO ) and the molecular length. Thus, one implies that the molecular conformation plays a major role in determining the transport properties of the junction, suggests that the second law of cos2 is a more general applicability regardless of the nature of the electrodes; 3 serves as a spectroscopic tool and also to identify the molecule at the junction, 4 and 5 as the molecular length reaches a certain value (1.3 nm) the Vmin remains virtually unchanged. The results showed that the structural properties (geometric) undergo significant changes with increasing external electric field that are in good agreement with the values found in literature. The behavior of I-V curves and G/Go-V lose their linear dependence to give rise to a nonlinear behavior with the appearance of NDR. This point reveals the structural modifications suffered by the system. The I-V plot confirmed the statements that were made through the structural analysis for the system considered and showed how it gives the load flow analysis systems.
Acesso aberto (Open Access)
Estados ligados de Majorana em nanodispositivo com ponto quântico acoplado à cadeia de átomos em zigue zague sobre supercondutor topológico.
(Universidade Federal do Pará, 2018-10-11) BEIRÃO, Antonio Thiago Madeira; SILVA, Shirsley Joany dos Santos da; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The research in condensed matter physics with insulators and superconductors topological has contributed greatly to the characterization of the surface properties and modes zero in nanowires. We investigate theoretically, through the recursive Green’s function approach, the electron transport through the T-shaped quantum dot (PQ) with a single level and spinless, connected to a zigue zague chain and coupled to a p-wave superconductor. This model is an extension of the Kitaev chain for a network triangular of finite-size with for three, four, and five sites. We find that the Majorana zero modes can be tuned through the coupling parameters of the device and the linear conductance show both the Majorana Bound States (MBS) in topological phase and in the general topological phase maximally robust. This more realistic model allows the detection of MBS through of the control of the parameters governing the electronic tunneling and can be helpful for relevant experiments. Keywords: Majorana Fermions, recursive Green’s function approach, Kitaev chain, class of electronic nanodevices, Quantum Dot, T-shaped, Qubit, Majorana Bound States (MBS).
Acesso aberto (Open Access)
Estudo de solvatocromismo em líquidos moleculares orgânicos via método seqüencial Monte Carlo/Mecânica Quântica
(Universidade Federal do Pará, 2007-03) MARTINS, Hardiney dos Santos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The Sequential Monte Carlo / Quantum Mechanical method was applied to study the solvatochromic shifts and the dipole moments for organic molecules: Uracil in water, - carotene in oleic acid, ricinoleic acid in methanol and in ethanol and oleic acid in methanol and in ethanol. The optimizations and charges distributions had found by Density Functional Theory through the B3LYP functional and sets basis functions 6-31G(d) to all molecules except water and Uracil, whose was applied the sets basis functions 6-311++G(d,p). In the classical approach, Monte Carlo, was applied the algorithm Metropólis through the DICE program. The sampling of statistically relevant configurations to averaged calculations of the properties was used with auto-correlation function performed to each system. The Radial Distribution Function of the molecular liquids was applied to separate the first shell solvation for each system, which gives the main interaction between solute-solvent. The statistically relevant configurations of the first shell of solvation of the each system were subject a quantum mechanical calculations at the semi-empiric level with the method ZINDO/S-CI. The absorptions spectrum had found to solutes in gas phase and to the systems of molecular liquids spoken. The electric dipole moments of these were also found. All the bands of spectrum absorptions had a blue shift, except the second band of the -carotene in oleic acid that was a red shift. The results found have a very good agreement with the values found in the literature. All the system had increase in the electric dipole moments because the solvents molecules are polar molecules. The system of fatty acids in alcohols had results very similar, in other words, the fatty acids mentioned had characteristics spectroscopic similar submitted to same solvents. The simulations whose with Sequential Monte Carlo / Quantum Mechanical method were studied show the methodology is effective to find the spectroscopic proprieties of molecular liquids analyzed.
Acesso aberto (Open Access)
Estudo do transporte eletrônico em nanoestruturas baseadas em carotenoides e tétrades com fulereno C60
(Universidade Federal do Pará, 2013-04-09) ALEIXO, Vicente Ferrer Pureza; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work it is presented a theoretical study on the electronic structure of a fullerene molecule (C60) with junctions in four terminals based on groups electron donors. tetrathiafulvalene (TTF) – and groups acceptors of electrons – fenilpropanodinilla (FPP) and molecular devices based on Carotenoid derivatives. The transport mechanism investigated for the carotenoids derivatives were utilized for better understanding of Fowler-Nordheim (FN) and Millikan-Lauritsen (ML) plots for the systems based in fullerene C60. In all cases it was possible to confirm that the Millikan- Lauritsen (ML) analysis empirical is also sufficient to describe all aspects the transition voltage spectroscopy (TVS). To study this class of systems, optimize the geometry systematically and observe the electronic transfer calculated by Hartree-Fock and Density Functional Theory (DFT). The results show through a detailed analysis of the molecular charge rearrangement due to an external electric field shows that the charge transport is directly on to the type of junction that this system is submitted of form that the applied voltage suffices to create a saturation potential in the systems in study: fullerene C60 with three terminals of tetrathiafulvalene and one terminal of fenilpropanodinilla (C60-(TTF)3-FPP); fullerene C60 with four terminals of fenilpropanodinilla (C60-(FPP)4). The particularity observed in C60-(FPP)4 is the disposal of the structure to operate with rectifying character for the electronic transport in the presence of orthogonal electric field to terminal data. The results show that we have a Molecular rectifier that works as a macroscopic rectifier.
Acesso aberto (Open Access)
Implementação do phagrafeno no patch de uma antena de microfita
(Universidade Federal do Pará, 2023-08-25) CARDOSO, Darlan Holanda; SILVA, Shirsley Joany dos Santos; http://lattes.cnpq.br/6060351208361634; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
This research corresponds to the implementation of Phagraphene in the Patch of a microstrip antenna, from the perspectives analyzed of a graphene microstrip antenna. Phagraphene is a new allotrope of carbon and its structure distorts the Dirac cones, having binding characteristics and packing density compatible with that of graphene. In this work, the simulator used is the COMSOL multifiphsysics software, where it performs multiphysics modeling, in which to implement Phagraphene in the program library, it is necessary to have the optical properties, such as: electrical conductivity, relative permittivity and relative permeability. The SIESTA package was used to optimize the geometry and determine the optical properties from the Phagraphene unit cell. The results obtained from Phagraphene, compared with graphene, show that electronic and magnetic properties become useful for the microstrip antenna designer. In this way, two microstrip antennas were simulated: one with the patch made of Phagraphene and the other of graphene. In this way, two microstrip antennas were simulated: one with patch made of Phagraphene and another of graphene. The aim was to make a comparative term between them and ensure that Phagraphene is more stable in a THz band width. As the results obtained (of Return Loss, Impedance, VSWR and gain radiation diagram) of the Phagraphene antenna were satisfactory, three more simulations were carried out, varying their designer: (i) one with periodic structures, one with air holes (PBG Antenna), (ii) another with the addition of two Phagraphene Nanoribbons on the edges of the antenna patch (Nano Antenna), and finally, the last projected antenna (iii), the junction of the antennas (i) and (ii) called (PBG+Nano Antenna). Therefore, the use of these variations proved to be interesting for applications in this frequency range, as they obtained good results, opening up a range of applicabilit
Acesso aberto (Open Access)
Investigação da dinâmica sequêncial Monte Carlo/Mecânica Quântica para sitemas moleculares orgânicos
(Universidade Federal do Pará, 2007-03) GESTER, Rodrigo do Monte; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
The main objective of this work is to investigate theoretically the electronic and optical properties of organic compounds on liquid enviroment. The understanding of interactions on liquid systems is very important for the description of phenomena in many parts of the Science, like Physics, Chemistry, Biology and Materials. Also as in the development of optical materials. The thermal fluctuations make that lots of configurations can be generated. This is the reason of the statistical behavior realized in liquid systems. Considering these difficulties, to describe liquid systems, the sequential Monte Carlo / quantum mechanics (S-MC/QM) treatment is used in this work. On this procedure, first the liquid structure is generated by MC simulation and later, only the most important part of the system is treated as quantum mechanics.Using the above procedure, the quantum properties of the Methyl Orange (MO) and O 2,3-dimethyl thiene[3,4-b]pirazine (DTP) were investigated. MO is a well known pH indicator and can be found under basic and acidic conditions. Its minimal energy geometries were obtained by Density Functional Theory by the B3LYP functional, being the system described by Pople basis with one polarization function (6-31G*). To obtain the average properties of the quantum observables of these systems quantum chemistry calculations were performed within semi-empirical INDO/S-CI approach. About the absorption spectra of the MO, the experimental data presented in scientific literature reports a broad band placed on the lowest energies, more precisely between 400 and 600 nm. Our theoretical results for the alcaline form show an intense π → π* transition at about 432.4±0.03 nm and under acidic conditions, considering the MO acidic form, this transition appears at about 507.4±0.12, 496.4±0.28 or 545.3±0.10 nm, showing good agreement with experimental results. The DTP is a particular system used in the production of low band gap polimers. Its electrical and optical properties were obtained by the novel Average Solvent Electrostatic Configuration (ASEC) methodology. The ASEC procedure include a solvent molecules point charges and permits obtaining quantum mechanical quantities performing only few quantum calculations. For DTP, using the Mφller- Plesset second order perturbation thoery (MP2) and the aug-cc-pVDZ, the electric dipole moment 1.16 D was reached performing only four quantum calculations on representative configurations, presenting an increase of 42% when compared to the isolated dipole. The polarizability also was apparised considering the same level of dipole calculation, the average value 132.7 a30 was observed. The lowest energy region of the absorption spectra was also investigated by ASEC procedure and using both, semi-empirical and DFT quantum approaches. This absorption region is the reason of contraditory conclusions about of the n → π* and π → π* transitions. Our results show these excitations are observed and they can overlap themselves. As example, our DFT results using the B3LYP functional show that these transitions are placed at about 360.63 and 351.15 nm, respectively, being in good agreement with experimental predictions.
Acesso aberto (Open Access)
Investigação da transição isolante-metal do CDM via algoritmos computacionais e estudo de nano-dispositivos orgânicos
(Universidade Federal do Pará, 2007) AMAZONAS, Járlesson Gama; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
We present in this work a theoretical study on conjugated organic polymers. These systems, in general semiconductors or insulators, when doped, show an increase in electrical conductivity. Under action of electric field, small oligomers can present a similar behavior to of usual devices, but with innumerable advantages as, for example, size extremely reduced (some nanometers). In the first chapter we will make a brief introduction on organic polymers conjugated showing some experimental results for 4-dicianometileno-4,4-ciclopenta polymer [2,1-b: 3,4b'] ditiofeno - CDM, that is the central object of study. Chapter 2 deals with the used quantum methods. We will cite the Hartre-Fock (HF) approximation and its semiempirical derivations. The Configuration Interaction (CI) method and the Density Functional Theory (DFT) also will be treated in this chapter. Chapter 3 is dedicated to describe the characteristics of some usual devices as diodes and transistors. We will still cite some extremely small electronic devices. Chapter 4 describes our results and quarrels about the possibility the of the transistion insulator-metal in CDM when doped. We got the characterization optics of oligomers of CDM with null charge and in the presence of defects of the type bipolaron. From the Hartree-Fock level we calculate the Structure of Bands and the Density of States (DOS) for the PCDM in the neutral and doped state. The calculation of the DOS and the Dispersion had been carried through computational programs developed here in the Group GFMA. We still present in this chapter the theoretical absorption spectra for oligomers of CDM with geometry fully optimized by DFT. In chapter 5 we have the relative results to the analysis of nanodevice based on tetramers of CDM with and without charge. The curves of the charge displacement versus voltage present characteristics of curves of usual devices. We also analyze the theoretical absorption spectra of the nanodevice for values of null tension and in points of current saturation.
Acesso aberto (Open Access)
Investigação das características I x V e C x V de NCPS puro, com nitrogênio substitucional carregado (-1 e +1) e com grupos doador (NO2)-aceitador (NH2) através de métodos derivados de hartree-fock
(Universidade Federal do Pará, 2006-06-15) SILVA JÚNIOR, Carlos Alberto Brito da; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work, we relate an investigation on the theoretical study of the I x V and C x V characteristics os SWCN pure, with substitutional Nitrogen charged with charge -1 (n-type material) and +1 (p-type material) and in the presence of donor (NO2)-aceptor (NH2) grups, through of the computational simulation of the SWCN ground states as well as your electronic structure and optics properties utilizing quantum chemical approaches: AM1 (Austin Model 1) and ZINDO/S-CIS (Zerner’s Intermediate Neglect of Differential Orbital/Spectroscopic – Configuration Interaction Simple) semi-empirical parametrization, Hartree-Fock based theory. By mean of this theoretical model, we analyse the electrons and optics properties, of more interest for that materials, the end understand the best shape of interation of this materials in the fabrication of electronic devices such as FETs (Field-Effect Transistors) or in optoelectronic applications such as LEDs (Light-Emitting Devices). We observate that SWCN with substitutional Nitrogen presents conformational defects of the polaron type. We made the curves of the UV-visivel Absorpion Spectra for armchair and zigzag SWCN pure, with substitutional Nitrogen charged with charge -1 (n-type material) and +1 (p-type material) and in the presence of donor (NO2)-aceptor (NH2) grups, when they are perturbed by different intensity of electric field. We examine in zigzag SWCN when it has na increase in the intensity of the electric field, yours curves suffer large perturbations. We get the curves p x E, I x V and C x V for this SWCN, we conclude that armchair armchair possess resistor behavior, therefore yours curves are linears and zigzag possess similar behavior at the importants electronic devices for the tecnologics advance. Our results are good agreement with the experimentals and theoretical results of the SWCN pure and with Nitrogen found in the literature.
Acesso aberto (Open Access)
Métodos teóricos na investigação da estrutura eletrônica do resveratrol e derivados
(Universidade Federal do Pará, 2004-09) COSTA, Sheila Cristina dos Santos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work we report na ab initio, density functional and a semiempirical investigation of the ground and vertical excited states and of the spectroscopic properties of resveratrol, a phytoalexin with known antioxidative properties, and of structurally related derivatives as piceatannol, paravinylphenylphenol and resveratrol-dihydroxyl_N (N=1,2 and 3). The results of the simulation of bond length resulting from the photoexcitation and of the corresponding theoretical spectra gives us new insight of how chemical modifications of these molecules could affect the possible physiological properties of resveratrol. Also we report new molecules (piceatannol and resveratrol-dihydroxyl_3) as antioxidative properties by the analysis of molecular parameters and electronic properties.
Acesso aberto (Open Access)
Modelamento do transporte eletrônico em dispositivos moleculares
(Universidade Federal do Pará, 2013-08-29) GRANHEN, Ewerton Ramos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In the present work we simulate the transport properties and absorption spectra of the organic compound ethyl red. This is the first theoretical study of a specific pH indicator utilized as nano-device, based on quantum theory and a non-diffusive transport model. The charge distribution along the molecule is calculated via Ab initio technique as a function of an external electric field. Based on a resonant multilevel model we also calculate the current against bias voltage. Both the charge accumulation and the current present similar behavior, like resonant type conduction and asymmetric charge–voltage and current–voltage curves. Our main results suggest that the present system could operate as a bidirectional molecular transistor. We spread this methodology to another molecular device however, with three-terminal. For this system, our main finding is a negative differential resistance (NDR) in the charge Q as a function of an external electric field. To explain this NDR effect we apply a phenomenological capacitive model based on a quite general system composed of many localized levels (that can be LUMOs of a molecule). The capacitance accounts for charging effects that can result in Coulomb blockade (CB) in the transport. We show that this CB effect gives rise to a NDR for a suitable set of phenomenological parameters, like tunneling rates and charging energies. The NDR profile obtained in both Ab initio and phenomenological methodologies are in close agreement.
Acesso aberto (Open Access)
Nanofabricação, caracterização e modelagem de dispositivos optoeletrônicos nanoestruturados de corantes orgânicos
(Universidade Federal do Pará, 2008-07-28) COSTA, Sheila Cristina dos Santos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
To better understand the process of miniaturization and the behavior of molecular structures under this effect we appeal to the calculations based in Quantum Mechanics (QM) with the purpose to corroborate theoretical and experimental data as electronic structure as well as electric properties. Another method sufficiently known consists simulate solute-solvent effect through the probabilistic Monte Carlo (MC) method. Of ownership of these computational tools we develop simulations QM/MC that translate the behavior of organic composites Methyl Red (MR) and 1,4-bis (5-phenyl-2-oxazolyl) benzene (POPOP), when suffer structural changes, modification in the optic answers, etc., due miniaturization processes, environment variations, external actions. The Methyl Red composite is known as a sensible dye of pH variation and meets in the basic and acid (isoeletrônico, zwitteriônico) forms is classified as azo-composite for the presence of (– N = N –) bonding in its structure. The POPOP is a luminescent dye of intense fluorescence in the blue region of the UV-Visible spectrum; we stand out that to investigate the functional and mannering principles of this structure we consider two conformational structures protonated derivatives of POPOP: C1 (N+) and C2 (N+). Initially all organic composites structures of MR and POPOP had been optimized through of the quantum methods: semiempirical PM3 (Parametric Method 3) and ab initio HF (Hartree-Fock) and DFT (Density Functional Theory), getting the geometric parameters and the conformations of lowest energy of each system, for the study of the electronic structure. Sequentially, two distinct stages of simulation had been used for the study of composites: 1st) The MR and POPOP structures had been optimized through the method PM3 + External Electric Field (the EEC), getting the geometric parameters and charge parameters. We use this method with the purpose to simulate the electronic transport properties of organic composites as the electric reply characterized by the charge transport (e) curve in function of the variation of the tension (V) in the structures. By means of the electric reply [(e) × V] we characterize this function to use them in nanostructured devices, as photodiodes, photodetector, solar cells, etc. The 2nd stage consists of simulate organic composites through the Monte Carlo method, to investigate its behaviors in liquid. The systems distinct consist of the addition of VM (basic, acid: isoelectronic and zwitterionic) and POPOP [C1 (N+) and C2 (N+)] in 1000 water molecules to analyze the solute-solvent interactions for development of interchange systems optoelectronic systems as sensory. In MC simulation had been carried 1×1010 steps MC for both thermalization and equilibrium stages in NVT ensemble. Generate a set of 105 configurations, from these we select a set reduced of 103 descorrelantion configurations of which we obtain the convergence average of the electronic transitions π→π*. The convergence average of the electronic transitions π→π* for MR: basic s of 434.33 ± 1,0 [436,34 ± 2,0 nm], isoelectronic 485,80 nm ± 2,0 nm [480,66 nm ± 3,0 nm], and zwitterionic [502.13 nm ± 3.0 nm]; for POPOP C1 [361,25 nm ± 2,0 nm], C1(NP+P) [485.0 ± 26.0 nm], C2 [355,39 nm ± 3,0 nm] and C2(NP+P) [472.0 ± 24.0 nm]. The averages of the electronic transitions π→π* had been obtained through semiempirical ZINDO/S-CIS (Zerner Intermediate Neglect of Orbital Diffential Spectroscopic - Configurations Interaction, Single excitation) method that better translates the spectroscopic parameters of the organic molecules in the UV-visible region. Experimentally we develop two distinct types of systems through of the techniques: Sol-Gel that consists in the incorporation of composites in host matrix of APP (Aluminum Polyphosphate), and Blendes that consist in the manufacture of volume devices within active monolayer. The MR and POPOP composites had been diluted in hybrid solution (10% etanol + 90% water), aliquots of these solutions had been incorporated in the synthesis of APP/Gel. The samples obtain for the Sol-Gel process had been submitted to the variation pH and characterized by spectroscopy of absorption in the UV-Visible region, whose bands of maximum absorption are of [431 nm, 513 nm, 511 nm] for MR and [358 nm, 511 nm and 472 nm] for POPOP and values of [355 nm, 361 nm] for POPOP in solution, that corroborate the theoretical results from the averages of the electronic transitions π→π*. The monolayer devices of MR and POPOP had been manufactured by overlapped of thin films in vitreous substrate/FTO (1st electrode)/PEDOT/P3HT/ active monolayer -Aluminum (2nd electrode) and characterized electrically for charge density (J) in function of applied voltage (V), under dark current and under 550 nm monochromatic light. The MR devices present curve (J×V) characteristic of a rectifier junction p-n of higher electric current signal under reverse polarization for dark current, being this signal intensified under light 550 nm; under forward bias the device presents the same behavior how much to the current signal, this is intensified when measured on monochromatic light (550 nm) in comparison with dark current, however under reverse polarization and forward bias the device presents curve characteristic (J×V) analogous of the conventional photodetector and diode tunnel. For POPOP intensification of the electric chain signal is observed under forward bias and reverses when the devices are under monochromatic light in comparison with measures made under dark current, in way that the characteristic curve (J×V) has similar behavior of the conventional photodiodes. The theoretical-experimental results of the electric (J×V) properties of composites had presented similar behaviors in the voltage range [- 2.0 V – 2.97 V] for MR and [- 2.86 V - 2.86V] for POPOP. We development a complete study with polymers of low bandgap (gap 1 eV) based in monomers bridges composition for carbon forming polymeric chains had been investigated by the methods AM1 (Austin Model 1), PM3 and DFT [B3LYP/6-31G] to corroborated the results of the oligomers of CDM (4-dicyano methyllene-4H-cyclopente [2.1 - 3: 4-b'] dithiophene) and BDT (1,3-benzodithiole-4H-cyclopenta [2,1-b: 3,4-b'] dithiophene), derived from the ditiophene. The results show that the growth of the polymeric chain formed by monomers of CDM and BDT provokes the reduction bandgap of the oligomers, analogous behavior to the polymers based on (3-alkylthiophenes) whose electronic transition π→π* energy is of 1.67 eV, the maximum absorption of the CDM and BDT are of 1.28 eV and 1,73 eV, respectively The theoretical methods used in this study to describe satisfactorily this behavior, whose maximum absorption is of approximately 1,28 eV for CDM and 1,74 eV for BDT, these results had been obtain from the polymeric chains formed by 5 monomers units, demonstrating that the geometric conformations of the polymeric chains simulated are equiprobability, proving the trustworthiness of the methods used in our investigation. In general lines, the results presents to demonstrate that the organic composites investigated are good candidates for employ in nanostructured organic devices applied in the molecular electronics and new technology of materials.
Acesso aberto (Open Access)
Nanotecnologia: a revolução silenciosa na segurança do trabalho
(Universidade Federal do Pará, 2023-09-28) ALMEIDA, Patrícia do Socorro Pereira Macêdo; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
A pesquisa exploratória tem como objetivo analisar a regulamentação existente em relação à nanotecnologia e seu impacto na segurança dos trabalhadores. O estudo se concentrará em examinar os desafios específicos associados à nanotecnologia, incluindo a falta de dados toxicológicos adequados para avaliar os riscos, a complexidade da caracterização dos nanomateriais e as limitações das técnicas de monitoramento existentes. Um dos principais desafios enfrentados é a falta de dados suficientes sobre os efeitos à saúde dos trabalhadores expostos a nanomateriais. A nanotecnologia é uma área relativamente nova, e ainda há muito a ser aprendido sobre os possíveis efeitos adversos à saúde que esses materiais podem causar. A falta de dados toxicológicos adequados dificulta a avaliação precisa dos riscos e a implementação de medidas de proteção eficazes. Além disso, a caracterização dos nanomateriais também é uma tarefa complexa. Suas propriedades físicas e químicas únicas exigem métodos de análise especializados e técnicas avançadas. A falta de padronização nesse campo dificulta a compreensão completa dos nanomateriais e sua relação com os efeitos à saúde. Outro desafio é a limitação das técnicas de monitoramento disponíveis para avaliar a exposição dos trabalhadores a nanomateriais. Os métodos tradicionais de monitoramento podem não ser adequados para detectar e quantificar a presença de nanomateriais no ambiente de trabalho, devido ao seu tamanho diminuto e às suas propriedades únicas. Isso dificulta a avaliação precisa da exposição dos trabalhadores e a implementação de medidas de controle apropriadas. O estudo também se propõe a examinar as estratégias e abordagens adotadas por diferentes países e organizações internacionais para enfrentar esses desafios e garantir a segurança dos trabalhadores expostos à nanotecnologia. Isso pode incluir o desenvolvimento de regulamentações específicas, a promoção de pesquisas e estudos toxicológicos, a criação de diretrizes de boas práticas e a implementação de medidas de controle de engenharia e proteção individual. Em resumo, a pesquisa exploratória visa analisar a regulamentação existente e os desafios relacionados à segurança dos trabalhadores na área da nanotecnologia. Compreender e abordar esses desafios é essencial para garantir a proteção dos trabalhadores e promover o uso seguro e responsável da nanotecnologia na indústria.