SOLANGE KAZUMI SAKATA

SOLANGE KAZUMI SAKATA

(Fonte: Lattes)

Resumo

Possui graduação em Química bacharelado e licenciatura pela Universidade de São Paulo. Doutorado na área de Química Orgânica, com ênfase em Eletrossintese Orgânica pelo Instituto de Química da Universidade de São Paulo. Pós - doutorados em Biotecnologia no Scripps Institution of Oceanography na University of California - San Diego -USA) e no Instituto de Química da Universidade de São Paulo. Foi pesquisadora visitante no Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB-Stuttgart - Alemanha no estudo do metagenoma na produção de enzimas para fins catalíticos e no Centro Tecnológico da Marinha de São Paulo (CTM-SP) no desenvolvimento e caracterização de polímeros. Atualmente é pesquisadora do Instituto de Pesquisas Energéticas e Nucleares (IPEN- SP / CNEN) no Centro de Tecnologia das Radiações e estuda o efeitos das radiações em nano materiais de carbono. (Texto extraído do Currículo Lattes em 27 dez. 2021).

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ZnO-DSSC
2024 - SERNA, M.M.; GALEGO, E.; FARIA, R.N.; SAKATA, S.K.
In the search for clean energy generation, solar energy has so far occupied the leading role; among the various factors that favor it are the possibility of generating energy on the surface of the planet and in outer space, in addition to the small environmental impact of generation plants and the possibilities of generation in urban environments. Within the different types of solar cells, dye-sensitized solar cells (DSSC) promise to revolutionize energy generation through their application as the external coating of large buildings. In the manufacture of this type of cell, non-toxic and low-cost materials are used; however the maximum conversion efficiency is still low when compared to silicon cells. One of the factors that contribute to the decrease in efficiency is the process of recombination of the photogenerated electron with the electrolyte. In the most common type of DSSC that uses a glass substrate coated with SnO2:F (FTO) to manufacture the photoanode, this surface acts as a recombination site. The objective of this work was to study the addition of a graphene layer between the FTO and the semiconductor oxide film in order to minimize recombination processes through the insertion of a new energy level. The deposition of reduced graphene oxide (rGO) was carried out by dip coating with different numbers of deposition cycles (0, 2, 5, 10 cycles). A ZnO paste was deposited on this film using the doctor blade technique with a green thickness of 50 µm. The assembly was heat treated at 450 °C for 1 h, aiming to reduce rGO to graphene and aggregate ZnO into a porous structure. The set was sensitized with the dye N719 and the solar cells were assembled with an FTO/Pt counter electrode and an electrolyte with the iodide/triodide redox couple. The electrical parameters were obtained from the survey of IV curves in a solar simulator with a power of 100 mW cm-2 and air mass 1.5. The morphology of the photoanode was studied by scanning electron microscopy (SEM). The micrographs obtained by SEM show that a porous ZnO film was formed with an average thickness of 25 µm. The cell efficiency increased with the increase in the number of dip coating cycles from 0.39% without rGO to 0.72% with 10 cycles of rGO deposition. The variation in the fill factor was less than 10%. The series resistance values are of the same order of magnitude, indicating that the rGO did not act to increase the conductivity at the rGO/FTO interface, whereas the series resistance values will increase with the increase in the number of cycles, which allows us to conclude that the rGO acts as a blocking layer preventing the regeneration of the electrolyte with the photogenerated electron.
Study of obtaining ZnO film for application in dye-sensitized solar cells using the doctor blade method
2024 - GALEGO, E.; SAKATA, S.K.; SERNA, M.M.; FARIA, R.N.
The conversion of solar energy into electricity is considered one of the best sustainable technologies for the future replacement of traditional methods of generating electrical energy, such as thermoelectric and nuclear plants. Photovoltaic conversion is the generation system with the greatest potential for growth to meet growing demand, which includes dye-sensitized solar cells (DSSC). DSSC is notorious for mimicking photosynthesis, which mainly focuses on generating electricity under any light intensity. The DSSC is composed by: a semiconductor oxide layer (SO), that functions as a support for the adsorption of a dye; this set is encapsulated between two translucent electrodes and; the space between them is filled with a specific electrolyte. The DSSC, being translucent, acquires the color of the adsorbed dye, which gives it a colorful appearance, a desirable characteristic for applications such as: decorative and architectural objects, among others. The dye is the active element in DSSC and, to have the best possible performance, the dye must be exposed to lighting over the largest area possible. To achieve this, the OS film must have a nanometric porous structure that will guarantee a greater apparent exposure area. This structure is obtained using a mixture of semiconductor oxide with organic products which, after heat treatment, are eliminated. This work aimed to study the influence of organic compounds: polyethylene glycol, ethyl cellulose and glycerin, on the paste viscosity for application by the doctor blade (DB) technique and on the efficiency of DSSC. The pastes were prepared using nanoparticulate ZnO (< 100 nm) in the following compositions: (a) ZnO + ethyl cellulose + terpineol (0.2 g + 0.1 g + 0.5 mL); (b) ZnO + PEG 400 G (0.3 g + 0.3 m?) and; (c) ZnO + liquid glycerin (0.3 g + 0.3 mL). All mixtures were homogenized in an agate mortar and rested for 24 h. Afterwards, they were applied to a glass electrode (FTO) by DB, with a defined area of 8 x 8 mm and subjected to heat treatment: from room temperature to 450 °C with a heating rate of 5 °C min-1 maintained for 1h. Then, the samples were sensitized in the dye N719 for 16h. Next, sealed DSSCs were assembled using an FTO+Pt counter-electrode and filled with electrolyte (I-/I3-). The electrical parameters were obtained from the IV curve obtained under lighting of 100 mW cm-2, air mass: 1.5 G. From the point of view, the applicability by DB, paste (a) presented best result evaluated by ease of application and homogeneity in green. However, electrical parameters revealed that using paste (c) presented the highest short-circuit current value (Isc) however, lowest conversion efficiency n= 0.49%; pastes (a) and (b) showed similar efficiency: n = 0.58% and n = 0.56%. The paste (a) was chosen for future application and studies.
X-ray diffraction evaluation of the average number of layers in thermal reduced graphene powder for supercapacitor nanomaterial
2019 - CARDOSO, QUEZIA de A.; CASINI, JULIO C.S.; BARBOSA, LUZINETE P.; SERNA, MARILENE M.; GALEGO, EGUIBERTO; SOBRINHO, LUIZA F.; SAKATA, SOLANGE K.; FARIA JUNIOR, RUBENS N. de
Graphene oxide (GO) can be partially reduced to graphene-like sheets by removing the oxygen-containing groups and recovering the conjugated structure. In this work, the thermal reduction of GO powder has been carried out using back pumping vacuum pressures and investigated employing X-ray diffraction analysis. The experimental results of estimating the number of graphene layers on the reduced powder at various temperatures (200 – 1000 °C) have been reported. Electrical changes have been produced in a graphene oxide with the vacuum reduction process. This study has shown that the ideal processing temperature for reducing graphene oxide nanomaterial was about 400 oC. It has also been shown that at 600 oC the number of layers in the reduced nanomaterial increased. The internal series equivalent resistance (ESR) has been improved substantially with the vacuum thermal treatment even at temperatures above 400 oC. ESR was reduced from 95.0 to about 13.8 Ω cm2 with this processing. These results showed that the process can be applied to the reduction of graphene oxide to produce supercapacitor nanomaterials. The advantage of employing this method is that the processing is a straightforward and low cost thermal treatment that might be used for large amount of nanocomposite material.