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4. Intramolecular Energy Transfer in the Terpolymer LaPPS76

Author

dos S. Moraes, Thaís, primary, Uhdre, Quezia P., additional, de J. Santana, Alisson, additional, Turchetti, Denis A., additional, Franchello, Flavio, additional, Fernandes, Ricardo V., additional, Akcelrud, Leni C., additional, Laureto, Edson, additional, and Duarte, José L., additional

Published
2024
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20. Spectroscopic analysis of the structure and stability of two electrochemically synthesized poly(3-alkylthiophene)s

Author

Rodrigues Maia Cristina Elaine, Bento Cristina Danielly, Laureto Edson, Zaia Morozin Augusto Dimas, Therézio Moreira Eralci, Moore Gregory J., and de Santana Henrique

Subjects
conducting polymers, Raman, photoluminescence, poly(alkylthio-phenes), Chemistry, QD1-999
Abstract

In this work, poly (3-methylthiophene) (P3MT) and poly (3-octylthiophene) (P3OT) films were synthesized electrochemically in non-aqueous media through the oxidation of the monomers, (3-methylthiophene and 3-octylthiophene), using a standard three-electrode cell in acetonitrile with 0.100 mol L-1 LiClO4. The polymeric thin films were deposited on platinum plates for optimal quality control of the process. It was observed that the material as-prepared for the anodic electropolymerization undergoes a natural process of de-protonation as a function of time. Moreover, the partial dedoped form, obtained in NH4OH solution, presents a good chemically stabilite form but, when radiated with blue light again becomes unstable. Films obtained by these methods have been characterized by cyclic voltammetry, Raman and photoluminescence spectroscopy. Both Raman and photoluminescence (PL) spectra results led to the characterization of two structures (pristine and non-pristine forms of thiophene rings) which formed the P3MT and P3OT polymer chain. These results were associated with the stabilization of pristine chains and mixed chains (non-pristine structures), radical cation and dication forms, in the polymeric film. Their bands in the Raman and PL spectra are wide and asymmetric and their adjustments by Gaussian functions were necessary, indicating that there are three distinct contributions to the vibration and two to the emission spectra in the formed polymeric material.

Published
2013
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30. Fast and Low-Cost Synthesis of MoS 2 Nanostructures on Paper Substrates for Near-Infrared Photodetectors.

Author

Cordeiro, Neusmar J. A., Gaspar, Cristina, Oliveira, Maria J. de, Nunes, Daniela, Barquinha, Pedro, Pereira, Luís, Fortunato, Elvira, Martins, Rodrigo, Laureto, Edson, Lourenço, Sidney A., and Adeloju, Samuel B.

Subjects
PHOTODETECTORS, NANOSTRUCTURES, ELECTRON microscope techniques, MOLYBDENUM sulfides, MOLYBDENUM disulfide, HYDROTHERMAL synthesis, QUANTUM efficiency, NANOSTRUCTURED materials
Abstract

Featured Application: This work presents an analysis of time and temperature influence of microwave-assisted hydrothermal synthesis on the direct growth of 2D-MoS2 nanostructures on cellulose paper substrates, and the production of MoS2-based low-cost photosensors with high responsivity and detectivity values. Recent advances in the production and development of two-dimensional transition metal dichalcogenides (2D TMDs) allow applications of these materials, with a structure similar to that of graphene, in a series of devices as promising technologies for optoelectronic applications. In this work, molybdenum disulfide (MoS2) nanostructures were grown directly on paper substrates through a microwave-assisted hydrothermal synthesis. The synthesized samples were subjected to morphological, structural, and optical analysis, using techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman. The variation of synthesis parameters, as temperature and synthesis time, allowed the manipulation of these nanostructures during the growth process, with alteration of the metallic (1T) and semiconductor (2H) phases. By using this synthesis method, two-dimensional MoS2 nanostructures were directly grown on paper substrates. The MoS2 nanostructures were used as the active layer, to produce low-cost near-infrared photodetectors. The set of results indicates that the interdigital MoS2 photodetector with the best characteristics (responsivity of 290 mA/W, detectivity of 1.8 × 109 Jones and external quantum efficiency of 37%) was obtained using photoactive MoS2 nanosheets synthesized at 200 °C for 120 min. [ABSTRACT FROM AUTHOR]

Published
2021
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35. Éxcitons em Estruturas Semiconductoras Artificiais de (GaAs)/(AIAs)

Author

Teodoro, Márcio Daldin, González-Borrero, Pedro Pablo, Lenart, Vinícius Mariani, Lupiano Dias, Ivan Frederico, Laureto, Edson, Duarte, José Leonil, and Marega Jr., Euclydes

Subjects
éxcitons, super-redes, fotoluminescência, Física
Abstract

Neste artigo estudamos a influência da direção de crescimento e do número de monocamadas nas propriedades ópticas de super-redes de (GaAs)m/(AlAs)5 com m = 3 ou 5. As direções escolhidas foram a [111]A, [311]A e a [100]. Esta últimafoi utilizada como referência. As configurações das ligações químicas do substrato de arseneto de gálio mudam de acordo com a orientação, o que implica em variações nas propriedades ópticas da heteroestrutura crescida. As super-redes foram caracterizadasatravés da técnica de Fotoluminescência em função da temperatura e da intensidade de excitação. Da análise, verificou-se que os picos principais dos espectros sãoatribuídos a transições indiretas dos éxcitons na direção [100] e [311]A para m=3 ou 5, e [111]A com m=5, assim como as transições com participações de fônons de AlAs na [100] com m=3, e de GaAs para [311]A com m=5. Na [100] com m=5 foiconstatado um aumento na energia de transição excitônica cujo aumento é verificado pela dependência com a temperatura. A superfície [111]A com m=3 apresentou um comportamento anômalo, sendo o pico de maior intensidade deslocado para regiões de menores energias em relação as demais direções.

Published
2009

40. Efeitos da luz em sistemas biológicos.

Author

Dias, Ivan Frederico Lupiano, primary, Siqueira, Cláudia Patrícia Cardoso Martins, additional, Toginho Filho, Dari De Oliveira, additional, Duarte, José Leonil, additional, Laureto, Edson, additional, Lima, Franciele Mendes de, additional, Silva, Francisco Pereira, additional, Castro, Valdênea Aparecida Bordinassi de, additional, Kashimoto, Roberto Kiyoshi, additional, and Durante, Henrique, additional

Published
2009
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50. Spectroscopic analysis of the structure and stability of two electrochemically synthesized poly(3-alkylthiophene)s.

Author

MAIA, ELAINE CRISTINA RODRIGUES, BENTO, DANIELLY CRISTINA, LAURETO, EDSON, ZAIA, DIMAS AUGUSTO MOROZIN, THERÉZIO, ERALCI MOREIRA, MOORE, GREGORY J., and DE SANTANA, HENRIQUE

Subjects
*SPECTROMETRY, *STABILITY (Mechanics), *ELECTROCHEMICAL analysis, *THIOPHENES, *ALKYL group, *PHOTOLUMINESCENCE, *ELECTROPOLYMERIZATION
Abstract

In this work, poly (3-methylthiophene) (P3MT) and poly (3-octylthiophene) (P3OT) films were electrochemically synthesized in non-aqueous media through the oxidation of the monomers, (3-methylthiophene and 3-octyl- thiophene) using a standard three-electrode cell in acetonitrile with 0.100 mol L-1 LiClO4. The polymeric thin films were deposited on platinum plates for optimal quality control of the process. It was observed that the material as- prepared by anodic electropolymerization undergoes a natural process of de- protonation as a function of time. Moreover, the partial de-doped form obtained in NH4OH solution presents a good chemically stable form but becomes un- stable again when radiated with blue light. Films obtained by these methods were characterized by cyclic voltammetry, Raman and photoluminescence spectroscopy. Both Raman and photoluminescence (PL) spectra led to the characterization of two structures (pristine and non-pristine forms of the thio- phene rings), which formed the P3MT and P3OT polymer chains. These results were associated with the stabilization of pristine chains and mixed chains (non- pristine structures), radical cation and dication forms, in the polymeric film. Their bands in the Raman and PL spectra were broad and asymmetric and their adjustments by Gaussian functions indicated that there were three distinct contributions to the vibration and two to the emission spectra in the formed polymeric material. [ABSTRACT FROM AUTHOR]

Published
2013
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