Obtenção e caracterização de uma junção WO3|Cu2O para aplicação em fotoeletrocatálise

Neste trabalho será apresentado a síntese e caracterização de filmes de óxido de tungstênio (WO3) e de óxido de cobre (Cu2O) e a sua aplicação em uma junção WO3|Cu2O. Filmes de WO3 foram obtidos através de deposição de tungstênio por magnetron sputtering, que foi posteriormente convertido a WO3 por duas rotas: i) oxidação térmica e ii) oxidação por anodização. Filmes de Cu2O foram obtidos por duas rotas: i) oxidação térmica e ii) magnetron sputtering reativo. Filmes de WO3 e Cu2O foram submetidos a tratamento térmico em atmosfera de argônio e em ar atmosférico. Os semicondutores foram caracterizados por microscopia eletrônica de varredura, difração de raios X, perfilometria, espectroscopia na região do Uv-vis, medidas de fotoluminescência e foram realizadas medidas fotoeletroquímicas. Análises mostram que tanto por oxidação térmica quanto por anodização é obtido WO3 monoclínico e os filmes apresentam perfil espectral parecido. Análises morfológicas mostram que a maior rugosidade foi obtida por oxidação térmica a 600 oC por 3h. Os maiores valores de fotocorrente foram registrados em filmes obtidos por oxidação térmica a 600 oC por 3 horas. Filmes de Cu2O foram obtidos com sucesso pelo método de sputtering reativo, enquanto o processo de oxidação térmica resultou em um filme de CuO. Análises de XRD mostraram que a fase Cu2O quando submetida a tratamento térmico de 600 ºC só se torna estável quando o processo é conduzido em atmosfera de argônio, portanto a junção WO3|Cu2O foi obtida em atmosfera livre de oxigênio. Análises de perfilometria mostram que filme de CuO apresenta maior rugosidade do que o filme de Cu2O. As medidas de fotocorrente mostram na tensão de 0,6V (vs AgCl), o Cu2O, que é a fase obtida por sputtering reativo, apresentam densidade de fotocorrente aproximadamente 5 vezes maior que a do CuO, que é a fase obtida por oxidação térmica. Na etapa final deste trabalho foi obtida a junção WO3|Cu2O que apresentou valor de fotocorrente inferior ao esperado. Sugerimos que este resultado é devido a degradação da camada de Cu2O observada na junção. A junção obtida por Cu2O sobre WO3 gerado por oxidação térmica produziu maior fotocorrente que a junção obtida por Cu2O sobre WO3 gerado por anodização e este resultado é devido ao maior número de elétrons fotoexcitados na junção sobre WO3 obtido por oxidação.In this work, we will present the synthesis and characterization of tungsten oxide (WO3) and copper oxide (Cu2O) and the application in WO3|Cu2O junction. WO3 films were obtained by deposition of tungsten by magnetron sputtering, which was later converted to WO3 by two routes: i) thermal oxidation and ii) oxidation by anodization. Cu2O films were obtained by two routes: thermal oxidation and ii) reactive magnetron sputtering. WO3 and Cu2O films were subjected to heat treatment in an argon atmosphere and in atmospheric air. The semiconductors were characterized by scanning electron microscopy, X-ray diffraction, profilometry, spectroscopy in the UV-vis region, photoluminescence measurements and photoelectrochemical measurements were performed. Analysis shows that either thermal oxidation or anodization monoclinic WO3 is obtained and the films have a similar spectral profile. The highest roughness was obtained by thermal oxidation followed by heat treatment at 600 oC for 3h. The larger values of photocurrent measurements have been registered for films obtained by thermal oxidation at 600 oC for 3 hours. Cu2O films were successfully obtained by the reactive sputtering method while the thermal oxidation process resulted in a CuO film. XRD analyzes showed that the Cu2O phase when subjected to heat treatment at 600 ºC is only stable when the process is carried out in an argon atmosphere. Therefore, in the assembly of the junction, heating steps must be carried out in an oxygen-free atmosphere. Profilometric analyzes showed that the CuO film presents greater roughness than the Cu2O film. Photocurrent measurements show that at 0.6V voltage (vs AgCl), Cu2O, which is the phase obtained by reactive sputtering, has a photocurrent density approximately 5 times greater than that of CuO, which is the phase obtained by thermal oxidation. In the final step of this work, the WO3|Cu2O junction was obtained, which presented a lower than expected photocurrent value. We suggest that this result is due to the degradation of the Cu2O layer observed at the junction. The junction obtained by Cu2O over WO3 generated by thermal oxidation produced higher photocurrent than the junction obtained by Cu2O over WO3 generated by anodization. This result is due to the higher number of photoexcited electrons at the junction on WO3 obtained by oxidation

Absorbance determination and photocatalytic production of hydrogen using tungsten and TiO2 oxide nanostructures As catalyst

In this paper, we described the production of hydrogen using the water splitting method, in which catalytic reactions activate a photocatalyst in the presence of UVA/vis light. This catalyst breaks the water molecule, from which hydrogen is removed. Currently, the substitution of fossil fuels for alternative energy sources is still insufficient. The great advantage of using an alternative energy source such as hydrogen is that in addition to being clean and renewable, it also does not emit carbon-based gases into the atmosphere. To advance the use of hydrogen, we synthesized TiO2 and TiO2 nanostructures mixed with two tungsten precursors (H2WO4 and Na2WO4.2H2O), aiming to increase the radiation absorption capacity of TiO2. Synthesized nanostructures were used as photocatalysts for hydrogen production by water splitting. The synthesized materials were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and absorbance tests performed with a Konica-Minolta spectrophotometer. The TiO2/Na2WO4.2H2O (800 °C) nanostructures absorbed light in a wider range of wavelengths, and were consequently more efficient in producing H2. The results show that Na2WO4.2H2O plays an important role in the photoactivity of synthesized materials, as it increases the concentration of point defects in TiO2 networks, enhancing hydrogen production and the absorption range. The TiO2, TiO2/WO3, and TiO2/Na2WO4.2H2O catalysts showed the best photocatalytic performance for hydrogen production: 33.5%, 61.6%, and 76.6%, respectively. These samples were synthesized at 800 °C and had specific surface areas of 9.8, 28.5, and 30.9 m2/g, respectively

SARS-CoV-2 introductions and early dynamics of the epidemic in Portugal

Genomic surveillance of SARS-CoV-2 in Portugal was rapidly implemented by the National Institute of Health in the early stages of the COVID-19 epidemic, in collaboration with more than 50 laboratories distributed nationwide. Methods By applying recent phylodynamic models that allow integration of individual-based travel history, we reconstructed and characterized the spatio-temporal dynamics of SARSCoV-2 introductions and early dissemination in Portugal. Results We detected at least 277 independent SARS-CoV-2 introductions, mostly from European countries (namely the United Kingdom, Spain, France, Italy, and Switzerland), which were consistent with the countries with the highest connectivity with Portugal. Although most introductions were estimated to have occurred during early March 2020, it is likely that SARS-CoV-2 was silently circulating in Portugal throughout February, before the first cases were confirmed. Conclusions Here we conclude that the earlier implementation of measures could have minimized the number of introductions and subsequent virus expansion in Portugal. This study lays the foundation for genomic epidemiology of SARS-CoV-2 in Portugal, and highlights the need for systematic and geographically-representative genomic surveillance.We gratefully acknowledge to Sara Hill and Nuno Faria (University of Oxford) and Joshua Quick and Nick Loman (University of Birmingham) for kindly providing us with the initial sets of Artic Network primers for NGS; Rafael Mamede (MRamirez team, IMM, Lisbon) for developing and sharing a bioinformatics script for sequence curation (https://github.com/rfm-targa/BioinfUtils); Philippe Lemey (KU Leuven) for providing guidance on the implementation of the phylodynamic models; Joshua L. Cherry (National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health) for providing guidance with the subsampling strategies; and all authors, originating and submitting laboratories who have contributed genome data on GISAID (https://www.gisaid.org/) on which part of this research is based. The opinions expressed in this article are those of the authors and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government. This study is co-funded by Fundação para a Ciência e Tecnologia and Agência de Investigação Clínica e Inovação Biomédica (234_596874175) on behalf of the Research 4 COVID-19 call. Some infrastructural resources used in this study come from the GenomePT project (POCI-01-0145-FEDER-022184), supported by COMPETE 2020 - Operational Programme for Competitiveness and Internationalisation (POCI), Lisboa Portugal Regional Operational Programme (Lisboa2020), Algarve Portugal Regional Operational Programme (CRESC Algarve2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), and by Fundação para a Ciência e a Tecnologia (FCT).info:eu-repo/semantics/publishedVersio

Educomunicação e suas áreas de intervenção: Novos paradigmas para o diálogo intercultural

oai:omp.abpeducom.org.br:publicationFormat/1O material aqui divulgado representa, em essência, a contribuição do VII Encontro Brasileiro de Educomunicação ao V Global MIL Week, da UNESCO, ocorrido na ECA/USP, entre 3 e 5 de novembro de 2016. Estamos diante de um conjunto de 104 papers executivos, com uma média de entre 7 e 10 páginas, cada um. Com este rico e abundante material, chegamos ao sétimo e-book publicado pela ABPEducom, em seus seis primeiros anos de existência. A especificidade desta obra é a de trazer as “Áreas de Intervenção” do campo da Educomunicação, colocando-as a serviço de uma meta essencial ao agir educomunicativo: o diálogo intercultural, trabalhado na linha do tema geral do evento internacional: Media and Information Literacy: New Paradigms for Intercultural Dialogue

Síntese caracterização de nanotubos de óxidos e oxinitretos de tântalo para geração de hidrogênio através fotólise da água

Os nanotubos de óxido de tântalo (Ta2O5) foram sintetizados pelo método de anodização, utilizando eletrólitos ácidos contendo íons fluoretos (F-). Durante o processo de anodização, foi adotado os tempos de anodização de 5 min, 10 min 15 min e 20 min com taxa de aumento de tensão de 10V/s, temperatura do eletrólito de 40°C e tensão final de 50V e foi variado o tempo de cristalização para o Ta2O5 a temperatura final de 800°C pelo tempo de 1, 2 e 3 horas, em todas as amostras a taxa de crescimento da temperatura foi constante de 5 °C/min durante a cristalização. Esta dissertação de mestrado demonstra a síntese e caracterização do to oxido e oxinitreto de tantalo com as técnicas: microscopia eletrônica de varredura, difração de raio-x, espectrocopia difusa uv-vis, BET, e aplicação do fotocatalisador para a sintetização de hidrogênio. Tendo como material precursor nanotubos de Ta2O5 com as características que maximizam a produção de hidrogênio realizou-se o processo de nitretação dos nanotubos com o objeivo de redução do seu band gap. O procedimento foi realizado pelo método de fluxo de amônia. Para o estudo da geração do nitreto, se realizou o estudo com o processo estatístico delineamento de corpo central rotacional (DCCR), para o procedimento foi variado a temperatura de nitretação, o tempo de nitretação e a taxa de incremento da temperatura. Foi mantida constante durante o estudo a massa do catalisador e também o fluxo de amônia. Os nanotubos de oxinitretos foram caracterizados por difração de raio-x, microscopia eletrônica de varredura, BET, espetroscopia difusa UV-vis, espectroscopia de energia dispersiva. A análise estatística dos dados do planejamento fatorial sugeriram as possibilidades de sínteses mais eficientes dos onixitretos, sendo a maior características a exposição a temperatura mais alta por um tempo menor.The nanotubes tantalum oxide (Ta2O5) were synthesized by the anodization method using acidic electrolyte containing fluoride ions (F-). During the anodizing process it was adopted the anodization time 5 min 10 min 15 min and 20 min with the rate of increase of 10V/s, electrolyte temperature 40 ° C and the final voltage of 50V and it was time varied crystallization Ta2O5 to a final temperature of 800 ° C by the time 1, 2 to 3 hours, in all samples the temperature constant growth rate was 5 ° C / min for crystallization. This dissertation demonstrates the synthesis and characterization to oxide and tantalum oxynitride with the techniques: scanning electron microscopy, X-ray diffraction, UV-vis diffuse spectroscopy, BET, and application of photocatalyst for synthesizing hydrogen. The material precursor was Ta2O5 nanotubes with features that maximize hydrogen production took place the nitriding process of the nanotubes with results in a decreasing the band gap width. The procedure was performed by ammonia flow method. To study the nitride generation, the study was conducted with statistical procedure rotational central body design (CCRD), so the procedure was varied nitriding temperature, the nitridation time and the temperature increase rate. It was kept constant during the study the mass of the catalyst and also the flow of ammonia. The oxynitrides nanotubes were characterized by x-ray diffraction, scanning electron microscopy, BET, UV-vis diffuse spectroscopy, energy dispersive spectroscopy. Statistical analysis of the experimental design data suggest the possibility for more efficient syntheses of onixitretos, with most features exposure to higher temperature for a shorter time

Trabalho de conclusão de curso de licenciatura em física

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