On the use of cyanine dyes as low-bandgap materials in bulk heterojunction photovoltaic devices

Cyanine dyes with absorption edges of almost 1000 nm were used in combination with MEH-PPV for the fabrication of organic solar cells. For blended thin films, a pronounced phase separation between the two components occurred and resulted in photocurrents with different signs for bilayer and bulk heterojunction devices. Absorption spectra and selective dissolution experiments were used to illustrate the process of vertical phase segregation, with the preferential wetting of the polar anode by the cyanines while maintaining percolating carrier pathways between the electrodes. For a cyanine with long alkyl side chains, the compatibility with the polymer matrix was increased and the development of the effective inverted bilayer configuration was not observed. The generally low oxidative photocurrents were explained with unfavourable shifts of the highest occupied molecular orbital (HOMO) dye energy levels in the solid state

PRODUÇÃO CIENTÍFICA NA FACULDADE DE FILOSOFIA, CIÊNCIAS E LETRAS DE RIBEIRÃO PRETO - USP: APLICAÇÃO DO ÍNDICE DE HIRSCH

 In this work, an analysis of scientific bibliographic productivity was made using the Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRPUSP) as example. It is a special Institution in the Brazilian University system which encompasses four important areas of knowledge (fields of concentration) in natural, biological, humanities, and social areas. It is composed by four departments which offer altogether eight undergraduate courses: 1) Psychology, 2) Pedagogy, 3) Chemistry, 4) Biology, 5) Medical Physics, 6) Biomedical Informatics, 7) Sciences of Information and Documentation and 8) Mathematics Applied to Business and six graduate programs leading to M.S. and Ph.D. degrees. Moreover, when analyzing the different courses of FFCLRP, they represent typical academic organization in Brazil and Latin America and could be taken as a model for analyzing other Brazilian research institutions. This analysis was made using: 1) the total number of papers (indexed in Curriculum Lattes database), 2) the number of papers indexed by Thomson ISI Web of Science database, and 3) the Hirsch (h -index). Bibliometric evaluations of undergraduate courses showed a better performance of the courses of Chemistry (P < 0.05), Biology (P < 0.05) and Medical Physics (P < 0.05) when compared to the Pedagogy, Sciences of Information and Documentation (P < 0.05) and Psychology (P < 0.05). We also analyzed the scientific output of the six graduate programs of FFCLRP-USP: 1) Chemistry, 2) Physics Applied to Medicine and Biology, 3) Entomology, 4) Compared Biology, 5) Psychology, 6) Psychobiology. The graduate programs in Psychobiology, Chemistry, Physics Applied to Medicine and Biology, Compared Biology, and Entomology presented very similar results, concerning the assessment of the three indexes. The graduate program in Psychology presented a lower h -index (P < 0.05) and had fewer papers indexed by the ISI (P < 0.05) when compared to the other graduate programs. The worse performance of the psychology program, pedagogy, sciences of information and documentation, psychology courses may be associated to the limited coverage of ISI database and some particular characteristics of this field of concentration.  O objetivo do presente trabalho foi analisar/quantificar a produtividade cientifica dos docentes pertencentes à Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRP-USP) vinculados aos oito cursos de graduação e seis programas de pós-graduação.  Métodos: Os índices analisados para cada professor foram: 1) número total de artigos (na plataforma Lattes), 2) número de artigos indexados pela Thomson ISI Web of Science, e 3) o índice-h.  Aplicamos os testes ANOVA, Kruskall-Wallis e o Post Hoc (Bonferrroni) para identificar possíveis diferenças entre os cursos de graduação e os programas de pósgraduação. Resultados :  A análise dos oitos cursos de graduação da FFCLRP-USP mostrou que os cursos de Biologia, Química e Física-Médica (FM) apresentaram números elevados para os índices analisados. Entretanto, os cursos de Psicologia, Pedagogia, Matemática Aplicada a Negócios (MAN), Informática Biomédica (IBM) e Ciência da Informação e Documentação (CID) apresentaram médias mais baixas do índice -h  (P < 0,05) e tiveram poucos artigos indexados pelo ISI (P < 0,05) comparado aos outros cursos. Em relação aos programas de pós-graduação, os programas de pós-graduação em Psicobiologia, Química, Física Aplicada à Medicina e Biologia (FAMB), Biologia Comparada, e Entomologia apresentaram resultados muito similares (P < 0,05), em relação à avaliação dos três índices diferentemente do programa de pós-graduação em Psicologia (P < 0,05). Conclusão:  os desempenhos ruins do programa de pós-graduação em Psicologia e dos cursos de graduação em Psicologia, Pedagogia, MAN, IBM e CID podem ser associados às características do campo da concentração e da cobertura limitada do banco de dados ISI. Finalmente, estes resultados indicam que o índice -h  é muito sensível ao campo de concentração e não deve ser usado como o único fator de avaliação da produção científica de pesquisa de um indivíduo.

Produção científica na Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto-USP: Aplicação do índice de hirsch

In this work, an analysis of scientific bibliographic productivity was made using the Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo (FFCLRP-USP) as example. It is a special Institution in the Brazilian University system which encompasses four important areas of knowledge (fields of concentration) in natural, biological, humanities, and social areas. It is composed by four departments which offer altogether eight undergraduate courses: 1) Psychology, 2) Pedagogy, 3) Chemistry, 4) Biology, 5) Medical Physics, 6) Biomedical Informatics, 7) Sciences of Information and Documentation and 8) Mathematics Applied to Business and six graduate programs leading to M.S. and Ph.D. degrees. Moreover, when analyzing the different courses of FFCLRP, they represent typical academic organization in Brazil and Latin America and could be taken as a model for analyzing other Brazilian research institutions. This analysis was made using: 1) the total number of papers (indexed in Curriculum Lattes database), 2) the number of papers indexed by Thomson ISI Web of Science database, and 3) the Hirsch (h-index). Bibliometric evaluations of undergraduate courses showed a better performance of the courses of Chemistry (P < 0.05), Biology (P < 0.05) and Medical Physics (P < 0.05) when compared to the Pedagogy, Sciences of Information and Documentation (P < 0.05) and Psychology (P < 0.05). We also analyzed the scientific output of the six graduate programs of FFCLRP-USP: 1) Chemistry, 2) Physics Applied to Medicine and Biology, 3) Entomology, 4) Compared Biology, 5) Psychology, 6) Psychobiology. The graduate programs in Psychobiology, Chemistry, Physics Applied to Medicine and Biology, Compared Biology, and Entomology presented very similar results, concerning the assessment of the three indexes. The graduate program in Psychology presented a lower h-index (P < 0.05) and had fewer papers indexed by the ISI (P < 0.05) when compared to the other graduate programs. The worse performance of the psychology program, pedagogy, sciences of information and documentation, psychology courses may be associated to the limited coverage of ISI database and some particular characteristics of this field of concentration

Synthesis and characterization of melanin in DMSO

Recently soluble melanin derivatives have been obtained by a synthetic procedure carried out in DMSO (D-melanin). In this work a comparative study of the structural characteristics of synthetic melanin derivatives obtained by oxidation of L-DOPA in H2O and DMSO are presented. To this end, Fourier-transform infrared spectroscopy as well as proton and carbon nuclear magnetic resonance techniques has been employed. In addition, aging effects have been investigated for D-melanin. The results suggest that sulfonate groups (-SO2CH3) from the oxidation of DMSO, are incorporated into melanin, which confers protection to the phenolic hydroxyl group present in its structure. The solubility of D-melanin in DMSO is attributed to the presence of these groups. When D-melanin is left in air for long time periods, the sulfonate groups leave the structure, and an insoluble compound is obtained. NaOH and water have been used, in order to accelerate the release of the sulfonate groups attached to D-melanin, thereby corroborating the proposed structure and the synthesis mechanism. © 2013

Strongly Red-Shifted Photoluminescence Band Induced by Molecular Twisting in Cyanine (Cy3) Dye Films

Cyanine dye molecules, used as monomers or in aggregate form, find interesting applications in optoelectronic devices. Among the various aggregate species incorporating organic dyes, centrosymmetric dimers are known as nonluminescent. They can act as exciton quenchers due to a low-energy optically forbidden excited state. In this study, however, we show that a dimer species in thin films exhibits efficient and strongly red-shifted photoluminescence. When the films were excited, a monomer emission at 590 nm along with a second emission peak at 680 nm was observed. A close relation between the dye concentration and the emission showed that a new emission at 680 nm corresponds to the dimer emission. Circular dichroism (CD) spectroscopy reveals that a fraction of the dimers exist in a twisted dimer configuration. Stable, long-lived, and quenchable fluorescence with high quantum yield is attributed to this dimer emission.ISSN:1932-7455ISSN:1932-744