IF - Instituto de Física

URI Permanente desta comunidade

http://200.137.215.59//handle/ri/841

O IF - Instituto de Física, da Universidade Federal de Goiás, oferece Graduação em: Bacharelado em Física; Licenciatura em Física; Física Médica; e, Engenharia Física.

Navegar

Agora exibindo 1 - 10 de 10

Chalcone-based molecules: experimental and theoretical studies on the two-photon absorption and molecular first hyperpolarizability
(2020) Abegão, Luis Miguel Gomes; Santos, Francisco de Assis; Fonseca Rodriguez, Ruben Dario; Barreiros, André Luís Bacelar Silva; Barreiros, Marizeth Libório; Alves, Péricles Barreto; Costa, Emmanoel Vilaça; Souza, Gabriella Barroso; Alencar, Marcio Andre Rodrigues Cavalcanti de; Mendonça, Cleber Renato; Kamada, Kenji; De Boni, Leonardo; Rodrigues Júnior, José Joatan
Five chalcone-based molecules denominated by C-3 ((E)-1-(4-methoxyphenyl)-3-phenylprop-2-en-1-one), C-4 ((E)-1,3-bis(4-methoxyphenyl)prop-2-en-1-one), C-5 ((E)-1-(benzo[d][1,3]dioxol-5-yl)-3-(4-methoxyphenyl)prop-2-en-1-one), C-6 ((E)-3-(naphthalen-1-yl)-1-phenylprop-2-en-1-one) and C-7 ((E)-1-(4-methoxyphenyl)-3-(naphthalen-1-yl)prop-2-en-1-one) were synthesized by Claisen-Schmidt reaction in solution of NaOH in water/ethanol 2:1. The aldehydes used were benzaldehyde, anisaldehyde, and β-naphthaldehyde, while the used ketones were acetophenone, p-methoxyacetophenone, and 3,4-methylenedioxyacetophenone. Z-scan and hyper-Rayleigh scattering techniques were used to study the nonlinear optical properties of these compounds in dichloromethane medium. By using Z-scan technique with femtosecond pulses, two-photon absorption cross-sections (σTPA) were determined, while the first molecular electronic hyperpolarizabilities (βHRS) were evaluated by the hyper-Rayleigh scattering technique, with picosecond pulses. From the recorded two-photon absorption spectra, it was identified that compound C-7 presented the highest σTPA, regarding the HOMO-LUMO transition, with a value of 40 GM, while C-6 achieved the lowest value for the same transition with 13 GM. Concerning the values of the first molecular hyperpolarizability, compound C-4 presented the highest value, 38 × 10−30 cm4 statvolt−1, while C-3 presented the lowest βHRS value of about 16 × 10−30 cm4 statvolt−1. Time-dependent density functional theory calculations were used to simulate the one- and two-photon absorption spectra, as well to predict the theoretical value of βHRS in dichloromethane and vacuum medium.
Dye-doped electrospun fibers for use as random laser generator: the influence of spot size and scatter concentration
(2020) Oliveira, Mário César Albuquerque de; Sousa Junior, Francisco Weldem Silva de; Santos, Francisco de Assis; Abegão, Luis Miguel Gomes; Alencar, Marcio Andre Rodrigues Cavalcanti de; Rodrigues Júnior, José Joatan; Oliveira, Helinando Pequeno de
The development of electrospun polymer fiber networks embedded with metal oxide nanoparticles in organic dye media favors the photons waveguiding and multiple scattering, providing the adequate environment for random laser action. The use of water-soluble polymer solution as support for electrospun matrix introduces relevant application in biomedical applications. Herein, it is explored the use of block copolymers (Eudragit L100) as support for electrospinning of polymer fiber doped with titanium dioxide (scatter centers) and rhodamine B (gain media). The resulting fiber net presented random laser behavior that depends on aggregation degree of gain media (rhodamine B) due to the combination of reabsorption/reemission processes with tunable response (emission peak position). These results open new possibilities for use of low-cost and water soluble electrospun-based random lasers based on organic dyes and random network of polymer matrix.
Effective π-electron number and symmetry perturbation effect on the two-photon absorption of oligofluorenes
(2021) Abegão, Luis Miguel Gomes; Cocca, Leandro Henrique Zucolotto; Mulatier, Jean-Christophe; Pitrat, Delphine; Andraud, Chantal; Misoguti, Lino; Mendonça, Cleber Renato; Vivas, Marcelo Gonçalves; De Boni, Leonardo
Fluorene-based molecules exhibit significant nonlinear optical responses and multiphoton absorption in the visible region, which, combined with the high fluorescence quantum yield in organic solvents, could make this class of materials potentially engaging in diverse photonics applications. Thus, herein, we have determined the two-photon absorption (2PA) of oligofluorenes containing three, five, and seven repetitive units by employing the wavelength-tunable femtosecond Z-scan technique. Our outcomes have shown that the 2PA cross-section in oligofluorenes presents an enhanced value of around 18 GM per Neff, in which Neff is the effective number of π-electrons, for the pure 2PA allowed transition (11Ag-like → 21Ag-like). Furthermore, a weak 2PA transition was observed in the same spectral region strongly allowed by one-photon absorption (11Ag-like → 11Bu-like). This last result suggests a molecular symmetry perturbation, probably induced by the molecular disorder triggered by the increase of moieties in the oligofluorene structure. We have calculated the permanent dipole moment difference related to the lowest-energy transition using the Lippert-Matagaformalism and the 2PA sum-over-states approach to confirm this assumption. Moreover, we have estimated the fundamental limits for the 2PA cross-section in oligofluorenes.
Entrance surface dosimetry with radiophotoluminescent films
(2020) d’Errico, Francesco; Abegão, Luis Miguel Gomes; Souza, S. O.; Chierici, Andrea; Lazzeri, L.; Puccini, Monica; Vitolo, Sandra; Miyamoto, Y.; Nanto, Hidehito; Yamamoto, T.
In a wide international cooperation, thin dosimetric films were developed for radiation protection and clinical dosimetry applications. The goal was providing proof of principle of a novel approach to entrance surface dosimetry, in general, and to extremity dosimetry, in particular. The latter is an extremely challenging task since ring and wrist dosimeters do not allow reliable estimates of the higher doses typically received by the fingertips, while solid-state detector chips worn on the fingertips interfere with the tactile sense of the workers. In our current system, tissue-equivalent polyethylene films are used to embed a variety of luminescent materials, particularly radiophotoluminescent (RPL) glass grains. This work illustrates the results we have achieved so far, proving that polyethylene films loaded with RPL glass grains provide a dosimetric response and have adequate mechanical and wearability properties. Additionally, the signal build-up associated with RPL glass is significantly accelerated when the glass is kept at body temperature, i.e., in contact with the worker's hands. Finally, the use of double gloves further improves the performance of our system.
Influence of electron-withdrawing groups in two-photon absorption of imidazopyridines derivatives
(2021) Pelosi, André Gasparotto; Cocca, Leandro Henrique Zucolotto; Abegão, Luis Miguel Gomes; Sciuti, Lucas Fiocco; Piguel, Sandrine; De Boni, Leonardo; Mendonça, Cleber Renato
This work investigates the influence of different electron-withdrawing groups (Cl, Br, fluorobenzonitrile), on the two-photon absorption cross-section of six imidazo[4,5-b]pyridine derivatives. The two-photon absorption cross-section spectra were obtained by ultra-fast Z-scan technique from 470 nm up to 700 nm. The Sum-Over-States approach was applied to model the two-photon absorption spectra, using a three-level energy system. Photophysical properties, such as transition dipole moment, the difference of permanent dipole moments, and anisotropy coefficient were determined through the analysis of one-photon absorption spectra, solvatochromism, and fluorescence anisotropy, respectively. Besides, the excited state absorption spectra were measured through ultra-fast transient absorption, allowing the excited state lifetime and spectral position determination. Two-photon absorption cross-sections of about 160 GM were observed when two electron-withdrawing groups are linked to the imidazo[4,5-b]pyridine core, elucidating a path to achieve high optical nonlinearities in imidazopyridine derivatives. Furthermore, a increase in the two-photon cross-section was observed when chloride is linked at the C-6 position (90 GM) instead of the C-5 position (50 GM), which is related to the proximity of a higher excited state.
Modeling the first-order molecular hyperpolarizability dispersion from experimentally obtained one- and two-photon absorption
(2022) Sciuti, Lucas Fiocco; Abegão, Luis Miguel Gomes; Santos, Carlos Henrique Domingues dos; Cocca, Leandro Henrique Zucolotto; Costa, Rafaela Gomes Martins da; Limberger, Jones; Misoguti, Lino; Mendonça, Cleber Renato; De Boni, Leonardo
The search for optical materials, particularly organic compounds, is still an attractive and essential field for developing several photonic devices and applications. For example, some applications are based on light scattering with twice the energy of the incoming photon for selected compounds, that is, the nonlinear optical effect related to the second-order susceptibility term from the electronic polarization expression. The microscopic interpretation of this phenomenon is called the first-order molecular hyperpolarizability or incoherent second harmonic generation of light. Understanding such phenomena as a function of the incoming wavelength is crucial to improving the optical response of future materials. Still, the experimental apparatus, hyper-Rayleigh scattering, apparently simple, is indeed a challenging task. Therefore, we proposed a proper alternative to obtain the dispersion of the first-order hyperpolarizability using the well-known one- and two-photon absorption techniques. By the spectral analysis of both the spectra, we gathered spectroscopic parameters and applied them for predicting the first-order hyperpolarizability dispersion. This prediction is based on an n-level energy system, taking into account the position and magnitude of transition dipole moments and the difference between the permanent dipole moment of the n-excited states. Moreover, using the presented method, we can avoid underestimating the first-order hyperpolarizability by not suppressing higher-energy transitions. Quantum chemical calculations and the hyper-Rayleigh scattering technique were used to validate the proposed method.
Nonlinear optical study in a set of dibenzylideneacetone derivatives with potential for optical frequency conversion
(2020) Santos, Francisco de Assis; Abegão, Luis Miguel Gomes; Fonseca, Ruben D.; Alcântara, Aline Moreira de; Mendonça, Cleber Renato; Alencar, Marcio Andre Rodrigues Cavalcanti de; Valle, Marcelo Siqueira; Kamada, Kenji; De Boni, Leonardo; Rodrigues Júnior, José Joatan
The search for advanced optical materials, in particular, materials with nonlinear optical responses, has, in the last years, experienced substantial growth due to their vast applications in the photonics field. One of those applications is ultra-fast optical frequency conversion, in the optics communications field. Organic compounds have emerged as promising candidates for raw materials to develop nonlinear optical devices, such as optical converters, due to their intrinsic ultra-fast electronic responses. Also, the easy tailoring of organic molecular structures makes organic materials much more appealing than the inorganic ones. In this work, we have performed a linear and nonlinear optical characterization of a set of dibenzylideneacetone derivatives. The nonlinear optical responses investigated correspond to second- and third-order nonlinear processes, namely, first electronic molecular hyperpolarizability and two-photon absorption cross-section, respectively. The value of the first electronic molecular hyperpolarizability, up to 52 cm4 ·statvolt−1 , could be considered a robust value when compared to the short-sized π-electron backbone length of the studied compounds. Such results suggest that these compounds exhibit the potential to be used as optical frequency converters. Quantum chemical calculations were used to predict the theoretical value of the first molecular hyperpolarizability, as well as to simulate the one- and two-photon absorption spectra for all compounds.
The ability of 2,5-disubstituted oxazole dyes derivatives to generate two-photon upconversion photoluminescence and its brightness evaluation
(2021) Abegão, Luis Miguel Gomes; Santos, Francisco de Assis; Piguel, Sandrine; Rodrigues Júnior, José Joatan; Mendonça, Cleber Renato; De Boni, Leonardo
The brightness study of emissive compounds is one of the fundamental spectroscopic characterizations. In this work, we assessed the brightness values of eight 2,5-disubstituted oxazole dyes derivatives by combining linear and nonlinear spectroscopic parameters. The range of the brightness values obtained is from 0.26 GM to 15.15 GM. The highest value belongs to compound 14 m, which, compared to previously investigated compounds of similar π-conjugation length, is at least two times higher. Brightness values were determined in the spectral region between 700 nm–720 nm, revealing this class of dyes' potential to be used as photoluminescence bioprobes excited by two-photons.
Tunable random lasing in dye-doped mesoporous silica SBA-15
(2021) Vicente, Fábio Simões de; Moreno, Leandro Xavier; Prado, Marcus Vinícius Alves; Abegão, Luis Miguel Gomes; Melo, Leandro A.; Rodrigues Júnior, José Joatan; Alencar, Marcio Andre Rodrigues Cavalcanti de
Mesoporous silica, known as SBA-15, possesses a hexagonal pore structure, with 8-nm-diameter pores and high surface area (∼700m2/g). The mesoporosity of SBA-15 is excellent to be filled with luminescent chromophores aiming at optical and photonic applications. SBA-15 powder infiltrated with Rhodamine B (RB) was prepared with different RB loads. Using the second harmonic of a pulsed Nd:yttrium aluminum garnet (YAG) laser (8 ns, 10 Hz) as the excitation source, the light emission spectra of the samples were investigated. Typical incoherent feedback random laser behavior was observed. Tunable random laser emissions from 579 to 585 nm were obtained depending on the excitation laser spot diameter and the RB load. The results indicate that mesoporous SBA-15 infiltrated with RB is a promising material for the development of solid-state random lasers.
Two-photon emissive dyes based on push-pull purines derivatives: toward the development of new photoluminescence bioprobes
(2020) Cocca, Leandro Henrique Zucolotto; Abegão, Luis Miguel Gomes; Sciuti, Lucas Fiocco; Vabre, Roxane; Siqueira, Jonathas de Paula; Kamada, Kenji; Mendonça, Cleber Renato; Piguel, Sandrine; De Boni, Leonardo
Fluorescent organic molecules have received great attention due to their largest applications, for example, in DNA and RNA spectroscopies studies, development of new photoluminescence bioprobes, and applications in fluorescence spectroscopy. In specific, purine base analog molecules present high fluorescence quantum yields and significant Stokes shift. Furthermore, the addition of push–pull structures at the purine core could increase the photoluminescence properties, making candidates for photoluminescence bioprobes. To consider this, a complete spectroscopic study was performed on nine push–pull purines, distinguished by different push–pull structures. In specific, for this research, the two-photon absorption (2PA) study showed that the compounds present induced two-photon fluorescence at the therapeutic window, desired for fluorescence microscopy. The brightness property was evaluated, indicating that all chromospheres are fluorescent by a 2PA process. Additionally, ultrafast transient absorption was performed to elucidate contribution of the excited states on the 2PA spectra, and quantum chemistry calculations were performed to corroborate the experimental results.

Navegar

Navegando IF - Instituto de Física por Autor "Abegão, Luis Miguel Gomes"

Resultados por página

Opções de Ordenação