RODRIGO TEIXEIRA BENTO

RODRIGO TEIXEIRA BENTO

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VIS-active TiO2 films decorated by expanded graphite
2024 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; GASTELOIS, PEDRO L.; PILLIS, MARINA F.
TiO2/C nanocomposite films were applied on water treatment. Expanded graphite nanosheets (EG) were obtained by UVC-assisted liquid-phase exfoliation technique, without the addition of acids, surfactants, or aggressive oxidizing agents, which characterizes the process as an eco-friendly method. The carbon nanosheets were synthesized directly from graphite bulk at different times and deposited on TiO2 films surface by airbrush spray coating method, forming a TiO2/C heterojunction. The increase in the exfoliation time promoted a more efficient photocatalytic dye removal under visible light. Morphological modifications, changes in the electronic structure, and wide range of light absorption were observed from the TiO2/C heterojunction formation. The results showed that hybrid TiO2/C supported photocatalyst is a promise alternative for practical photocatalytic applications under sunlight.
Surface properties enhancement by sulfur-doping TiO2 films
2021 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; ANTUNES, RENATO A.; PILLIS, MARINA F.
TiO2 films were sulfur-doped through an alternative route based on the decomposition of H2S at low temperatures. MOCVD technique was used to grown the films on borosilicate glass substrates at 400 °C. The doping was carried out at 50, 100 and 150 °C under a mixture of H2-2%v.H2S. SO42− groups were observed in the surface revealing the substitution of Ti4+ by S6+. Superficial roughness and wettability were also modified by the formation of these sulfate groups on the surface. Photocatalytic experiments of methyl-orange dye decolorization under visible light indicated that the 8 at.% S-TiO2 film exhibited the highest photocatalytic activity, with 72.1% of dye decolorization. The results suggest that the exposition of TiO2 films to the mixture H2-H2S at low temperatures is an efficient method of doping. These films allow the decolorization of the dye under visible light irradiation, which enable its practical use under sunlight or even indoor.
On the surface chemistry and the reuse of sulfur-doped TiO2 films as photocatalysts
2021 - BENTO, RODRIGO T.; CORREA, OLANDIR V.; PILLIS, MARINA F.
The surface chemistry and recyclability of sulfur-doped titanium dioxide (TiO2) films was evaluated. The photocatalysts were grown by metalorganic chemical vapor deposition (MOCVD) at 400 ◦C. The films were sulfur-doped at 50 ◦C by using hydrogen sulfide (H2S) as sulfur source. The photocatalytic behavior of the films was measure by monitoring the methyl orange dye decolorization under visible light for several cycles. The films are formed only for the anatase crystalline phase. The results demonstrated that no structural modifications or significant differences in the morphology of the films occurred after their use. The sulfur-doped TiO2 films presented good photocatalytic activity, with an efficiency of 72.1% under visible light in its first use. The durability experiments suggest that even with the dye impregnation on the catalyst surface, the photocatalytic activity of the S-doped TiO2 films remained around 70% in the first 3 cycles, which allows their practical application for water treatment and purification under sunlight.
Visible-light photocatalytic activity and recyclability of N-doped TiO2 films grown by MOCVD
2020 - OLIVEIRA, E.C. de; BENTO, R.T.; CORREA, O.V.; PILLIS, M.F.
Nitrogen-doped TiO2 films were grown on borosilicate glass substrates at 400 °C by the metallorganic chemical vapor deposition (MOCVD) for removing dye from water under visible light. The effect of N-doping on the structural, surface, and photocatalytic properties of films was evaluated. X-ray photoelectron spectroscopy (XPS) analyses revealed that 1.56 and 2.44 at% of nitrogen were incorporated into the films by varying the NH3 flux during the growth. Methyl orange dye degradation experiments showed that the N-doped films presented photoactivity under visible light. The film containing 2.44 at% of nitrogen exhibited the best photocatalytic behavior, with 55% of efficiency. Recyclability tests under visible light showed that the film efficiency dropped gradually after each test. N-TiO2 films grown by MOCVD have the potential to be used in environmental applications by removing pollutants using a green method under sunlight or even under internal illumination, although its reuse is limited.
Effect of growth parameters on the photocatalytic performance of TiO2 films prepared by MOCVD
2020 - MARCELLO, BIANCA A.; CORREA, OLANDIR V.; BENTO, RODRIGO T.; PILLIS, MARINA F.
The present study evaluated the main factors that influence the photocatalytic activity of titanium dioxide (TiO2) films grown by metalorganic chemical vapor deposition (MOCVD) at 400 and 500 °C, in different growth times. The photocatalytic behavior was analyzed by measuring the methyl orange dye degradation at different pH values. Structural and morphological characteristics, and the recyclability of the catalysts for several cycles were also investigated. Anatase phase was identified in all films. The higher photodegradation performances were obtained at acidic pH. The results demonstrated that the photocatalyst thickness is an important parameter in heterogenous photocatalysis. The best photocatalytic result occurred for the 395 nm-thick TiO2 film grown at 400 °C, which presented 65.3% of the dye degradation under UV light. The recyclability experiments demonstrated that the TiO2 films grown by MOCVD present a great stability after several photocatalytic cycles, which allows their practical application for water treatment with high efficiency.
Effect of nitrogen-doping on the surface chemistry and corrosion stability of TiO2 films
2020 - SOUZA FILHO, EDVAN A. de; PIERETTI, EURICO F.; BENTO, RODRIGO T.; PILLIS, MARINA F.
TiO2 and N-doped TiO2 films were grown on AISI 316 stainless steel substrates and on Si (100) by metallorganic chemical vapor deposition (MOCVD) at 400 ◦C and 500 ◦C. X-ray photoelectron spectroscopy, scanning electron microscopy, and contact angle techniques were used to characterize de films. The corrosion behavior was assessed by monitoring the open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5 wt% NaCl solution at room temperature. The results show that 6.18 at% of nitrogen was introduced in the films grown at 400 ◦C and 8.23 at% at 500 ◦C, and that besides TiO2, nitrogen phases were identified. All the films are hydrophilic and the contact angles varied from 48◦ to 72◦. The films presented good homogeneity, low porosity and rounded grains in the range of 40–90 nm. The RMS roughness varied between 5.5 and 18.5 nm. Titanium dioxide films grown at 400 ◦C showed better corrosion resistance than those grown at 500 ◦C due to its compact morphology. Nitrogen-doping was not efficient to protect the substrate from corrosion.
Design, development and application of a real‑time capacitive sensor for automatically measuring liquid level
2019 - BENTO, RODRIGO T.; SILVA, ROGER W.O.; DIAS, LUCAS A.; FERRUS FILHO, ANDRE; PITTA, ANTONIO J.C.
In the present study a real-time capacitive sensor based on a capacitance step method is designed, developed and applied on measuring the liquid level by immersion. The capacitive sensor consists of two electrodes from copper plated phenolite plates separated by a gap distance and mounted inside a non-conductive storage tank. Water is used as the dielectric material. The analyzed sensor behavior with liquid level variation is semi-linear and obtained in function of the output voltage variation by using proper signal conditioning circuit. For converting the voltage variation into level variation, a parallel R–C circuit is used instead of conventional bridge circuit. Under suitable parameter settings it provided good reading accuracy. The experimental results demonstrate the high efficiency of the proposed model, which confirm the satisfactory performance of the capacitive sensor for liquid level measurement. The sensor presents an excellent ease of construction and installation, linked to the good measurements precision and high autonomy of system operation. The behavior experiments under different salt concentrations show that the water chemical composition does not interfere on the sensor operation. The proposed model exhibits a promising employment in several applications, such as control equipment for irrigation, biomedical area—in the interaction between antibody–antigen or protein-DNA, aerospace and pharmaceutical industry, gas sensors, and automation solutions.