Navegando por Autor "Curcio, Sergio Fernando"
Agora exibindo 1 - 9 de 9
Resultados por página
Opções de Ordenação
Item Caracterização de derivados de dimetoxidicinamalacetona, difluroboro flavanonas e quinoxalinas e das interações com Buckminsterfulereno (C60) para aplicação em dispositivos eletrônicos orgânicos.(2022) Curcio, Sergio Fernando; Cazati, Thiago; Valaski, Rogério; Cazati, Thiago; Eccher, Juliana; Soares, Jaqueline dos Santos; Postachini, Bruna Bueno; Merlo, Aloir AntônioCompostos derivados das quinoxalinas (5e, 5g), difluroboro flavanonas (4c, 4e) e dimetoxidicinamalacetona (AGC101), foram estudados em decorrência de suas propriedades fotofísicas. Para executar o estudo, foram preparados soluções e filmes finos desses compostos com diferentes quantidades de C60, com intuito de verificar o potencial desses materiais como doadores de elétrons em dispositivos eletrônicos orgânicos. Os materiais foram caracterizados por espectroscopia de absorção óptica, fluorescência estacionária e fluorescência resolvida no tempo. Para todos os compostos, os decaimentos do estado excitado mostraram redução do tempo de vida no estado sólido em comparação com os tempos de vida das soluções, indicando assim, agregação das moléculas. A aplicação da teoria de Kasha indica agregação tipo H (empilhamento) para a AGC101 e a 5e e tipo J (lado a lado) para 5g, 4c e 4e. Assumindo que estes compostos se comportam como doadores de elétrons e o C60 como aceitador de elétrons, foi analisada a supressão da fluorescência em função da concentração de C60, tanto em solução como em filme. O estudo dos gráficos de Stern-Volmer das soluções dos compostos mostrou predominância de supressões estáticas (do tipo por esfera efetiva). A mesma análise foi realizada para os filmes e, aplicando a teoria de Förster para a transferência de energia ressonante (FRET), foi interpretado o resultado como distância de difusão excitônica LD, obtendo distâncias de 5,3nm a 7,8nm em acordo com os valores encontrados nos artigos de referência. Os coeficientes de difusão D foram também calculados obtendo valores entre 2,8x10-3 cm 2 /s e 5,4x10-3 cm 2 /s na ordem de grandeza dos encontrados na literatura. As estruturas e valores obtidos permitem afirmar que os materiais estudados são de interesse para a fabricação de dispositivos eletrônicos orgânicos.Item Caracterização de filmes de ftalocianina de hidróxido de alumínio com adição de nanotubos de carbono multi-parede funcionalizados para aplicação em dispositivos eletrônicos orgânicos.(2019) Curcio, Sergio Fernando; Cazati, Thiago; Valaski, Rogério; Barbosa Neto, Newton Martins; Soares, Jaqueline dos Santos; Cazati, ThiagoAs propriedades eletrônicas das ftalocianinas as colocam como materiais a serem utilizados na construção de dispositivos eletrônicos orgânicos. Neste trabalho foram utilizadas moléculas orgânicas da família das ftalocianinas, depositadas em filmes finos, como um dos componentes da camada fotoativa de um dispositivo orgânico para conversão de energia. Estas moléculas macrocíclicas conjugadas apresentam absorção de radiação no espectro visível, compatível com o espectro solar sendo caracterizadas como semicondutores orgânicos doadores de cargas. Com a adição de nanomateriais de carbono, caracterizados como semicondutores orgânicos aceitadores de cargas, o sistema doador-aceitador de cargas tem a habilidade de dissociar e transportar cargas elétricas foto-excitadas durante o processo de absorção de radiação para um circuito externo. Neste trabalho a blenda composta pela ftalocianina de hidróxido de alumínio (AlOHPc) juntamente com nanotubos de carbono de paredes múltiplas funcionalizados com ácido carboxílico (MWCNT-COOH) compõem a camada fotoativa do dispositivo fotovoltaico. As propriedades optoeletrônicas, morfológicas e estruturais dos materiais estudados foram caracterizadas através da espectroscopia de absorção, fluorescência estacionária, tempo de vida do estado excitado, voltametria cíclica, microscopia de força atômica, difração de raios X e espectroscopia Raman. A caracterização elétrica em regime de corrente contínua (DC) foi feita através de curvas de densidade de corrente versus tensão (J(V)) em dispositivos de estrutura sanduíche ITO/AlOHPc/Al. A determinação da eficiência de conversão de energia foi feita através da comparação entre as curvas J(V) no escuro e sob iluminação padrão (AM 1.5G, 100 mW/cm2, 300K). A confecção dos dispositivos e as caracterizações elétricas foram realizadas em colaboração com o Laboratório de Dispositivos Orgânicos (LADOR) do INMETRO/RJ.Item Highly luminescent liquid crystals by connecting 1,3,4-oxadiazole with thiazolo[5,4-d]thiazole units.(2021) Santos, Arthur Bernardo de Souza; Manfredi, Alex Molina; Salla, Cristian Andrey Momoli; Farias, Giliandro; Girotto, Edivandro; Eccher, Juliana; Westphal, Eduard; Curcio, Sergio Fernando; Cazati, Thiago; Malvestiti, Ivani; Falcão, Eduardo Henrique Lago; Bechtold, Ivan Helmuth; Gallardo, HugoThe direct bonding between a thiazolo[5,4-d]thiazole and two 1,3,4-oxadiazole units allowed us to create a new and versatile rigid core for luminescent liquid crystal, which showed interesting and variable mesomorphic and photophysical properties. From the 5-bis(5-phenyl-1,3,4-oxadiazol-2-yl)thiazolo[5,4-d]thiazole new core, three molecules with different number of alkoxy chains were synthesized and had their properties correlated with the molecular structure. The molecule with two chains showed a smectic C mesophase, while the mesogens with four and six chains presented hexagonal columnar mesomorphism, which was confirmed by POM and XRD measurements. In addition, the molecule with six chains presented liquid crystalline behavior close to room temperature. In solution, the molecules presented strong photoluminescence ranging from blue to yellow, with quantum yields higher than 0.6. Excited state lifetimes allowed to correlate the fluorescence component associated to the different emitting species to the molecular organization in spin coated films. The molecular energy levels, together with thermal stability and possible charge carrier transport due to molecular packing, suggest that these molecules are promising for optoelectronic applications. Overall, this work contributes to the development of the use of thiazolo[5,4-d]thiazole in liquid crystals, demonstrating its great efficiency and versatility.Item Molecular 5,8-π-extended quinoxaline derivatives as chromophores for photoluminescence applications.(2019) Aguiar, Leonardo de Oliveira; Lima Junior, Adalberto Santana; Bechtold, Ivan Helmuth; Curcio, Sergio Fernando; Cazati, Thiago; Alves, Tiago Vinicius; Vieira, André AlexandreThe 5,8-π-extended quinoxaline derivatives are widely studied due to their wellknown photophysical and electrochemical properties. In order to investigate the structure-property relationship, a novel series of fluorescent calamitic liquid crystals based on the quinoxaline heterocycle was successfully synthesized and characterized. The final molecules presented calamitic mesomorphism with nematic and smectic phases. These compounds displayed intense green photoluminescence under UV light excitation in solution and in the solid state. In chloroform solution, the fluorescence quantum yields (ΦFL= 0.54–0.62) of the quinoxaline-based derivatives were significantly higher than those previously described for similar benzothiadiazoles. The maximum emission peaks were between 511-520 nm with singlet excited-state lifetimes in the nanosecond timescale. The solvatochromism studies showed a significant dependence of the emission on the polarity of the solvent. Doping of the quinoxalines with fullerene C60 suggests a charge transfer process, this being dependent on the π-conjugate core. The energy band gaps predicted with DFT calculations are in excellent agreement with the experimental data.Item New boron(III) blue emitters for all-solution processed OLEDs : molecular design assisted by theoretical modeling.(2019) Salla, Cristian Andrey Momoli; Santos, Jéssica Teixeira dos; Farias, Giliandro; Bortoluzzi, Adailton João; Curcio, Sergio Fernando; Cazati, Thiago; Izsák, Róbert; Neese, Frank; Souza, Bernardo de; Bechtold, Ivan HelmuthLuminescent boron(III) complexes have recently been employed as emitters in organic light-emitting diodes (OLEDs) with reasonable success. They are easy to prepare and sufficiently stable to be used in such devices, being of great interest as a simple molecular emissive layer. Although emitters for this class with all colors have already been reported, highly efficient and stable blue emitters for applications in solution processed devices still pose a challenge. Here, we report the design, synthesis, and characterization of new boron complexes based on the 2-(benzothiazol-2-yl)phenol ligand (HBT), with different donor and acceptor groups responsible for modulating the emission properties, from blue to red. The molecular design was assisted by calculations using our newly developed formalism, where we demonstrate that the absorption and fluorescence spectra can be successfully predicted, which is a powerful technique to evaluate molecular photophysical properties prior to synthesis. In addition, density functional theory (DFT) enables us to understand the molecular and electronic structure of the molecules in greater detail. The molecules studied here presented fluorescence efficiencies as high as Φ = 0.88 and all solution processed OLEDs were prepared and characterized under an ambient atmosphere, after dispersion in the emitting layer. Surprisingly, even considering these rather simple experimental conditions, the blue emitters displayed superior properties compared to those in the present literature, in particular with respect to the stability of the current efficiency.Item Reducing lifetime in Cu(I) complexes with thermally activated delayed fluorescence and phosphorescence promoted by chalcogenolate-diimine ligands.(2020) Farias, Giliandro; Salla, Cristian Andrey Momoli; Heying, Renata da Silva; Bortoluzzi, Adailton João; Curcio, Sergio Fernando; Cazati, Thiago; Santos, Paloma Lays dos; Monkman, Andrew P.; Souza, Bernardo de; Bechtold, Ivan HelmuthLuminescent copper(I) complexes have drawn attention due to their promising performance as alternative optoelectronic materials to the well-known heavy transition metals complexes. Herein, we report the synthesis of six luminescent Cu(I) complexes with phosphines and 1,10-phenanthroline-derived ligands with thiadiazole and selenodiazole groups in order to evaluate the effect of heavy atom on their photophysical properties. Steady-state and time-resolved spectroscopy confirmed delayed fluorescence emission via a thermally activated delayed fluorescence mechanism in all cases. The experimental spectroscopic data was analyzed with detailed quantum-chemical calculations. Interestingly, these complexes did not show the expected “heavy atom effect”, that enhances the spin-orbit coupling matrix elements, but nevertheless the addition of the heavier chalcogens contributed to reduce the photoluminescence lifetime to roughly 800 ns, which is the lowest reported so far for such TADF materialsItem Strongly luminescent and liquid-crystalline π-conjugated 2-methyl[1,2,3]benzotriazoles with a linear donor-acceptor-donor structure.(2020) Silva, Elias Regis da; Hinojosa, Abad Roger Castillo; Eccher, Juliana; Tonet, Michele Duarte; Brondani, Daniela; Zapp, Eduardo; Curcio, Sergio Fernando; Postacchini, Bruna Bueno; Cazati, Thiago; Vieira, André AlexandreSymmetrical 2-methyl[1,2,3]benzotriazole (BZT) derivatives with elongated peripheral units connected via acetylenic triple bonds present calamitic thermotropic mesomorphism with nematic and smectic phases. They show intense photoluminescence with near-unity quantum yields in solution. The peripheral groups significantly influence the excited-state lifetime. Fluorescence quenching is observed in the presence of C60, testifying of charge transfer to the fullerene acceptor. The varying sterical demand of the different substituents considerably influences the efficiency of the charge transfer induced fluorescence quenching. HOMO, LUMO and band gap energies ranged from −5.15 to −5.97 eV (ionization potential), −2.47 to −2.96 eV (electron affinity) and 2.68 to 3.08 eV (optical band gap).Item Synthesis of 2,1,3-Benzoxadiazole derivatives as new fluorophores-combined experimental, optical, electro, and theoretical study.(2020) Frizon, Tiago Elias Allievi; Vieira, André Alexandre; Silva, Fabrícia Nunes da; Saba, Sumbal; Farias, Giliandro; Souza, Bernardo de; Zapp, Eduardo; Lôpo, Michell N.; Braga, Hugo de Campos; Grillo, Felipe Fardin; Curcio, Sergio Fernando; Cazati, Thiago; Rafique, JamalHerein, we report the synthesis and characterization of fluorophores containing a 2,1,3-benzoxadiazole unit associated with a π-conjugated system (D-π-A-π-D). These new fluorophores in solution exhibited an absorption maximum at around ∼419 nm (visible region), as expected for electronic transitions of the π-π ∗ type (ε ∼2.7 × 107 L mol−1 cm−1 ), and strong solvent-dependent fluorescence emission (ΦFL ∼0.5) located in the bluish-green region. The Stokes’ shift of these compounds is ca. 3,779 cm−1 , which was attributed to an intramolecular charge transfer (ICT) state. In CHCl3 solution, the compounds exhibited longer and shorter lifetimes, which was attributed to the emission of monomeric and aggregated molecules, respectively. Density functional theory was used to model the electronic structure of the compounds 9a–d in their excited and ground electronic states. The simulated emission spectra are consistent with the experimental results, with different solvents leading to a shift in the emission peak and the attribution of a π-π ∗ state with the characteristics of a charge transfer excitation. The thermal properties were analyzed by thermogravimetric analysis, and a high maximum degradation rate occurred at around 300◦C. Electrochemical studies were also performed in order to determine the band gaps of the molecules. The electrochemical band gaps (2.48–2.70 eV) showed strong correlations with the optical band gaps (2.64–2.67 eV).Item Synthesis, photophysical and electrochemical properties of novel and highly fluorescent difluoroboron flavanone β-diketonate complexes.(2020) Ariza Paez, Elida Betania; Curcio, Sergio Fernando; Neme, Natália Paz; Matos, Matheus J. S.; Correa, Rodrigo de Souza; Pereira, Fabio Junio; Hilário, Flaviane Francisco; Cazati, Thiago; Taylor, Jason GuyDifluoroboron β-diketonates complexes are highly luminescent with extensive properties such as their fluorescence both in solution and in solid state and their high molar extinction coefficients. Due to their rich optical properties, these compounds have been studied for their applications in organic electronics such as in self-assembly and applications in biosensors, bio-imaging and optoelectronic devices. The easy and fast synthesis of difluoroboron β-diketonate (BF2dbm) complexes makes their applications even more attractive. Although many different types of difluoroboron β-diketonates complexes have been studied, the cyclic flavanone analogues of these compounds have never been reported in the literature. Therefore, the present work aims to synthesize difluouroboron flavanone β-diketonate complexes, study their photophysical and electrochemical properties and assess their suitability for applications in optoelectronic devices. The synthesis was based on a Baker–Venkataraman reaction which initially provided substituted diketones, which were subsequently reacted with aldehydes to afford the proposed flavanones. The complexation was achieved by reacting flavanones and BF3. Et2O and in total 9 novel compounds were obtained. A representative difluoroboron flavanone complex was subjected to single crystal X-ray diffraction to unequivocally confirm the chemical structure. A stability study indicated only partial degradation of these compounds over a few days in a protic solvent at elevated temperatures. Photophysical studies revealed that the substituent groups and the solvent media significantly influence the electrochemical and photophysical properties of the final compounds, especially the molar absorption coefficient, fluorescence quantum yields, and the band gap. Moreover, the compounds exhibited a single excitedstate lifetime in all studied solvent. Computational studies were employed to evaluate ground and excited states properties and carry out DFT and TDDFT level analysis. These studies clarify the role of each state in the experimental absorption spectra as well as the effect of the solvent.