Navegando por Autor "Tavares, Mara T. S."
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Artigo Enhancement of the photocatalytic activity and white emission of CaIn2O4 nanocrystals(Elsevier, 2016-02-15) Paskocimas, Carlos Alberto; Melo, M. M.; Araújo, Vinícius Dantas; Tranquilin, Ricardo Luis; Almeida, Cláudio Romero Rodrigues de; Delmonte, Maurício Roberto Bomio; Tavares, Mara T. S.; Silva, Elson Longo da; Motta, Fabiana Villela daCaIn2O4 (CIO) nanocrystals (NCs) were prepared by ultrasonic spray pyrolysis at 1223 K without the use of surfactants to investigate the influences of the nanostructure on the photoluminescence and photo-catalytic properties of this white-light emitter. The optical properties were analyzed by ultraviolet evisible (UVevis) absorption spectroscopy, which indicated a band gap energy of 3.83 eV, and photo-luminescence (PL) measurements at room temperature that showed a broad and intense emission band. X-ray diffraction (XRD) analysis confirmed that the CIO NCs adopted the orthorhombic crystalline phase. Field-emission gun scanning electron microscopy (FEG-SEM) micrographs demonstrated the spherical morphology of the CIO NCs, comprising aggregates of several CIO NCs. Furthermore, the as-synthesized CIO NCs exhibited enhanced activity for the photodegradation of methylene blue (MB) under UVevis irradiation. The chromaticity coordinates were calculated for the sample based on the PL spectrum; the CIO NCs had values of x 1⁄4 0.31 and y 1⁄4 0.38, and this point is located on the white region of the CIE diagram. Ultrasonic spray pyrolysis provides a feasible approach for preparing shape- and size-controlled CIO nanocrystals that hold great potential for photocatalytic applications and as photoluminescent white emittersArtigo Photoluminescent and antimicrobial properties of silver doped indium hydroxide synthesized by one-step microwave-assisted hydrothermal method(Wiley, 2018-10-13) Andrade Neto, Nivaldo Freire de; Tavares, Mara T. S.; Ferreira, Erik A. C.; Sales, Ana I. L.; Lima, Lucymara F. A.; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daSilver-doped indium hydroxide In(1-x)(OH)3:xAg (with x = 0, 1, 2, 4 and 8 mol%) of Ag nanoparticles were synthesized by the microwave-assisted hydrothermal (MAH) method at 140oC for 30 min. These nanoparticles were characterized by X-ray diffraction (XRD), fourier transformed infrared (FT-IR) spectroscopy and optical diffuse reflectance. Photoluminescence (PL) spectra were acquired with a 350 nm beam of a krypton ion laser as an excitation source. The antibacterial activities of the samples were evaluated against Gram negative Escherichia coli bacteria and Gram positive Staphylococcus aureus bacteria using the disc diffusion method. The results showed that all diffraction peaks present in XRD patterns could be indexed to the cubic lattice related to the In(OH) 3 phase. Broadband photoluminescence behavior in visible range spectra was observed for all samples with a maximum peak centered in the blue and green regions. The antibacterial activities showed that In(1-x)(OH)3:xAg nanoparticles have a promising bactericide that can be used for deactivating microbes