Navegando por Autor "Li, Maximo Siu"

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Effect of Ag clusters doping on the photoluminescence, photocatalysis and magnetic properties of ZnO nanorods prepared by facile microwave-assisted hydrothermal synthesis
(Springer, 2017-04-13) Souza, Renata Priscilla de Araújo; Motta, Fabiana Vilella da; Nascimento, José Heriberto Oliveira do; Delmonte, Maurício Roberto Bomio; Borges, Filipe Martel de Magalhães; Corrêa, Marcio Assolin; Silva, Elson Longo da; Li, Maximo Siu; Bohn, Felipe; Paskocimas, Carlos Alberto
We report a chemical route to synthesize stabilized ZnO:Ag nanoparticles (NPs) combined with nanosized metallic Ag using microwave-assisted hydrothermal synthesis. We employ X-ray diffraction (XRD), field emission guns scanning electron microscopy, transmission electron microscopy, spectrophotometry, photodegradation, photoluminescence and magnetic characterizations to investigate the structural, morphological, photocatalytic and magnetic properties of ZnO:Ag samples with different Ag concentrations. We verify through XRD results the standard wurtzite crystalline phases and face-centered cubic for metallic Ag NPs. Moreover, we confirm through spectrophotometry the photocatalysis in the samples. The Ag clusters doping the pure material causes the shift from green to yellow-red, which are lower energy wavelengths, thus corroborating changes of its electrical properties due to the decreased gap. We interpret the magnetic properties in terms of the nanosizing and similar effects. Under these conditions, we show the improvement of the photocatalytic and magnetic properties of ZnO NPs
Effect of temperature on ultrasonic spray pyrolysis method in zinc tungstate: the relationship between structural and optical properties
(Elsevier, 2021-01-15) Santiago, Anderson de Azevedo Gomes; Tranquilin, Ricardo Luis; Li, Maximo Siu; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
Zinc tungstate is an inorganic material which shows immense potential in diverse areas such as photoluminescence, sodium-ion batteries, and catalysis. Thus, the synthesis and characterization of ZnWO4 by ultrasonic spray pyrolysis using different heat treatments (between 750 °C and 1000 °C) is reported herein. X-ray diffraction and Raman spectroscopy were used to confirm the formation of the ZnWO4 with wolframite-type monoclinic structure. Scanning electron microscopy images revealed that the ZnWO4 particles have a microsphere-like morphology formed by the junction of different nanocrystals and its surface changed by heat treatment. The bandgap energies had a small variation among the samples (3.88 eV–3.98 eV). The photoluminescence emission of the samples showed a broadband spectrum with white light, in which structural alterations occurred with the increase in the heat treatment, which also increased the emission intensity and broadband. The samples synthesized at 950 °C and 1000 °C showed to be promising warm- and neutral-white light emission sources
Effect of the Eu3+ (x = 0, 1, 2 and 3 mol%) doped Zn2−xTiO4 and Zn2Ti1−xO4 obtained by complex polymerization method: photoluminescent and photocatalytic properties
(Springer, 2019-11-08) Paskocimas, Carlos Alberto; Nascimento, G. G.; Andrade Neto, Nivaldo Freire de; Garcia, Laurênia Martins Pereira; Li, Maximo Siu; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In this work, Zn2EuxTi1−xO4 and Zn2−xEuxTiO4 (x=0, 1, 2 and 3 mol%) powders were synthesized by complex polymerization method (CPM) and calcined at 1000 °C for 4 h. The powders were characterized by X-ray difraction (XRD), scanning electron microscopy (SEM), UV–Vis spectroscopy in the visible region and photoluminescence properties (PL). The photocatalytic properties were estimated by degradation of methylene blue (MB) dye when irradiated by UV lamps. X-ray difraction results demonstrated the existence of Zn2TiO4 as primary phase and ZnO with secondary phase. According to difractograms, the crystallite size varied between 49 and 67 nm. The Eu3+ ions introduction provides increased absorption in visible region, but the band-gap remains practically constant. In samples were observed an increased in photocatalysis with the increase in europium concentration, while in the Zn2EuxTi1−xO4 samples, photocatalysis was reduced to europium concentrations greater than 1%. Eu3+ doped Zn2TiO4 provided a photoluminescent intensity increasing. CIE chromaticity coordinates confrm emission in the red region of the phosphor
Evaluation of morphology and photoluminescent properties of PbMoO4 crystals by ultrasonic amplitude
(Springer, 2016-12-30) Paskocimas, Carlos Alberto; Gurgel, G. M.; Lovisa, Laura Ximena; Conceição, O. L. A.; Li, Maximo Siu; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
Lead molybdate (PbMoO4) crystals were synthesized by the facile sonochemical method at 20 kHz frequency with a variable ultrasonic amplitude and synthesis time. These crystals were structurally characterized by X-ray diffraction (XRD). Field emission scanning electron microscopy images were employed to observe the evolution of the crystal growth process. XRD patterns indicate that these crystals have a scheelite-type tetragonal structure. The growth mechanism of PbMoO4 crystal was proposed to explain the development stages starting with precipitates formed by particles with disordered growth to form dendritic structures. The effect of the amplitude processing applied was rather significant for the size range of the particles produced. The optical properties were analyzed by ultraviolet–Visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) measurements. The spectrum shows that the sample has a typical green emission. The origin of the PL emission spectrum of the metal molybdates might be ascribed to the charge-transfer transitions within [MoO4] clusters
Fast and simultaneous doping of Sr0.9−x−y−zCa0.1In2O4:(xEu3+, yTm3+, zTb3+) superstructure by ultrasonic spray pyrolysis
(Elsevier, 2019-09) Paskocimas, Carlos Alberto; Santiago, Anderson de Azevedo Gomes; Lovisa, Laura Ximena; Medeiros, P. N.; Li, Maximo Siu; Carreño, Neftalí Lênin Villarreal; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In the present work, Sr0.9−x−y−zCa0.1In2O4:(xEu3+, yTm3+, zTb3+) particles were synthesized by the ultrasonic spray pyrolysis (USP) method to obtain a single-phase white phosphorus formed by six different cations in solution within the lattice (superstructure). The samples were also structurally and morphologically characterized by X-ray diffraction (XRD) techniques and by field emission scanning electron microscopy (FE-SEM). The photoluminescent behavior and the characteristics of the emitted colors were studied by the variation in the codoping of the rare earth elements. The Sr0.9Ca0.1In2O4 sample showed a near blue color emission, but all codoped samples showed emission in white with very close chromaticity coordinates to the standard white (x = 0.33 and y = 0.33). The Tm3+ → Tb3+ (ET1), Tm3+ → Eu3+ (ET2) and Tb3+ → Eu3+ (ET3) Energy Transfers were proposed and are considered necessary for adjusting and controlling the desired color properties
Fast photocatalytic degradation of an organic dye and photoluminescent properties of Zn doped In(OH)3 obtained by the microwave-assisted hydrothermal method
(Elsevier, 2014-11) Tavares, Marileide L.A.; Lovisa, Laura Ximena; Araújo, Vinícius Dantas; Silva, Elson Longo da; Li, Maximo Siu; Nascimento, Rubens Maribondo do; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Crystalline zinc-doped indium hydroxide structures were prepared by the rapid and efficient microwave-assisted hydrothermal (MAH) method. X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM), photoluminescence (PL) and UV–visible (UV–vis) spectroscopy were used to characterization the materials. FEG-SEM images revealed that pure In(OH)3 samples and Zn-doped samples exhibit nanocubic morphologies with a wide range of particle sizes. Relative intensities of PL emissions decreased as the Zn ion concentration increased from 0 to 4 mol%. UV–vis spectra indicate that Zn ion doping caused a band gap decrease with increased doping of 0% to 4% Zn, respectively, from 5.15 eV for 4.96 eV. Samples with Zn in the crystal lattice showed better photocatalytic activity and degradation of the RhB dye after 16 min of UV exposure
Growth mechanism and vibrational and optical properties of SrMoO4: Tb3+, Sm3+ particles: green– orange tunable color
(Springer, 2020-04-10) Santos, D. F. dos; Lovisa, Laura Ximena; Santiago, Anderson de Azevedo Gomes; Li, Maximo Siu; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
A SrMoO4 series co-doped with Tb3? and Sm3? was successfully prepared by the sonochemical method. The particles were characterized by X-ray diffraction, Raman spectroscopy, field emission gun scanning electron microscopy, UV–Vis spectroscopy and photoluminescence. Changes in SrMoO4: Tb3?, Sm3? morphologies were observed from an orderly growth of the particles. The mechanism of particle growth was proposed, indicating a hierarchical evolution of SrMoO4: Tb3?, Sm3? morphologies. The changes in emissions were evaluated by the effect of the dopants and their concentrations. Emissions were observed in white, green and orange according to the chemical composition of the samples. The SrMoO4 and SrMoO4: 1% Sm samples showed excellent results for CRI (79%) and LE ([ 310 lm/Wopt), thus indicating a material with potential for efficient white light emission
Indium hydroxide nanocubes and microcubes obtained by microwave-assisted hydrothermal method
(Elsevier, 2010) Motta, Fabiana Villela da; Lima, R. C.; Marques, Ana Paula de Azevedo; Li, Maximo Siu; Leite, Edson Roberto; Varela, José A.; Silva, Elson Longo da
Single crystalline indium hydroxide (In(OH)3) architectures were prepared by a rapid and efficient microwave-assisted hydrothermal (MAH) method using indium chloride as the precursor. Nanostructures were obtained at a low temperature (140 °C with a time of 1 min). In(OH)3 samples were prepared at the same temperature for 8 with a time of 64 min. Using this method, In(OH)3 samples were obtained at milder conditions of temperature and time compared to the conventional hydrothermal method. Field emission scanning electron microscopy images confirm that these samples are composed of 3D nanocubic, microcubic and irregular structures of about 70 nm to 5 μm in size. Fourier transform Raman spectroscopy and photoluminescence (PL) measurements were used to characterize the products
Influence Ca-doped SrIn2O4 powders on photoluminescence property prepared one step by ultrasonic spray pyrolysis
(Elsevier, 2018-05-30) Medeiros, P. N.; Santiago, Anderson de Azevedo Gomes; Ferreira, Erik Alexander Cunha; Li, Maximo Siu; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Crystalline Ca-doped SrIn2O4 structures were prepared by a rapid and efficient Ultrasonic Pyrolysis Spray (USP) method. The Sr1-xCaxIn2O4 (x = 0, 0.1, 0.2, 0.3, 0.4 and 1 mol %) samples were obtained by in a single step at a temperature of 1050oC for 1 min for the formation of particles. The powders were characterized by X-ray diffraction (XRD), field emission electron microscopy (SEM-FEG), optical diffuse reflectance and photoluminescence (PL) measurements. All diffraction peaks present in XRD patterns could be indexed to the orthorhombic structure and that with calcium percentage increments indicates the substitution of Ca2+ in the Sr2+ sites promotes a decrease in its lattice parameters of the structure. MEV-FEG images show that the Sr1- xCaxIn2O4 particles have a spherical predominance, with a porous surface in the form of foam for x = 0 and a surface with low roughness and low porosity with an increase in the percentage of Ca2+ ion, especially for the 1 mol % of Ca2+. The gap energy varied between 4.56 eV and 4.86 eV, being influenced by the structural modifications motivated by increase of Ca2+ ion contained in the SrIn2O4 matrix. The PL emission spectrum of the samples presents a broad band behavior with emission intensity predominant in the blue-green region, having the sample with x = 0.1 the highest PL intensity. The chromaticity coordinates were calculated for the sample based on the PL spectrum and coordinates x and y show that the samples have blue emission. Ultrasonic spray pyrolysis was an effective technique for Ca-doped SrInO4 powder production using short production times with hold great potential for photoluminescent emitters
One-step synthesis of CaMoO4: Eu3+ nanospheres by ultrasonic spray pyrolysis
(Springer, 2017-08-02) Paskocimas, Carlos Alberto; Almeida, Cláudio Romero Rodrigues de; Lovisa, Laura Ximena; Santiago, Anderson de Azevedo Gomes; Li, Maximo Siu; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
In this paper, CaMoO4 and of Eu3+-doped CaMoO4 nanospheres were prepared by a spray pyrolysis method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectra and photoluminescence spectroscopy. XRD patterns indicate that these crystals have a scheelite-type tetragonal structure. The morphology of the CaMoO4: Eu3+ nanospheres was investigated from the FESEM results and it was observed the formation of spherical particles peculiar to the synthesis method used. Sample of pure CaMoO4 thermally treated 1000 °C exhibit a photoluminescence behavior broadband type with emission in white light according to the calculated values of the CIE coordinates: x=0.37, y=0.37. The emission intensity in the red for samples doped with Eu3+ (5 D0 → 7 F2 in 615 nm) increases directly with the dopant concentration
Photoluminescence and photocatalytic properties of Ag/AgCl synthesized by sonochemistry: statistical experimental design
(Springer, 2017-05-03) Paskocimas, Carlos Alberto; Andrade Neto, Nivaldo Freire de; Garcia, Laurênia Martins Pereira; Silva, Elson Longo da; Li, Maximo Siu; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Silver chloride (AgCl) particles were produced by sonochemistry synthesis. The effect of the variables such as the time of synthesis, amount of surfactant and reagent in the photocatalytic property of AgCl have were all investigated. AgCl particles became well known for their high photocatalytic activity and their plasmonic properties because of the metallic silver on their surface. In this study, AgCl particles were prepared with sodium chloride (NaCl), polyvinylpyrrolidone and silver nitrate (AgNO3), using a full 23 factorial design and three central points, resulting in 11 experiments. The synthesis was carried out using ultrasonic tip at time intervals of 5, 20 and 35 min. It was used X-ray diffraction, scanning electron microscopy with field emission (SEM-FEG), UV–Vis degradation test and photoluminescence to characterize the particles. The experimental design not only used variables present in the photocatalytic ability of the particles, but also provided a mathematical model. The (ANOVA) analysis of variance was used to confirm this model. Thus the values predicted could be observed. It is provided a response surface that characterizes the optimization zone of the photocatalytic activity of the AgCl particles to better visualize the information about its effects
Photoluminescence properties of (Eu, Tb, Tm) co-doped PbMoO4 obtained by sonochemical synthesis
(Elsevier, 2017-04-05) Gurgel, G. M.; Lovisa, Laura Ximena; Pereira, Laurenice Martins; Motta, Fabiana Villela da; Li, Maximo Siu; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio
The PbMoO4 co-doped with Tm3+, Tb3+ Eu3+ with scheelita structure was synthesized by the sonochemical method. The photoluminescent properties, structural and color coordinates emitted by phosphors were investigated. The structural analysis of the crystal and the changes in lattice parameters confirm that the rare earth ions (RE3+) were successfully introduced into the host of the PbMoO4. The relationship between energy gap (Egap) and the concentration of RE3+ ions was also discussed, the Egap is significantly influenced by the degree of structural order-disorder present in the crystal lattice. The PbMoO4:RE3+ shows light emission in green. Under UV excitation, Photoluminescence (PL) shows a broad band centered at 520 nm and smaller bands belonging to transitions of RE3+: 1G4 → 3 F4 and 1D2 → 3H4 at 480 and 533 nm (Tm3+), 5D4 → 7 Fj (j = 6, 5) at 493 and 550 nm (Tb 3+) 5D0 → 7Fj (j = 1, 2, 4) 593, 615 and 702 nm (Eu3+)
Photoluminescence properties of (Eu, Tb, Tm) co-doped PbMoO4 obtained by sonochemical synthesis
(Elsevier, 2017-04-05) Paskocimas, Carlos Alberto; Lovisa, Laura Ximena; Gurgel, G. M.; Pereira, Laurenice Martins; Motta, Fabiana Villela da; Silva, Elson Longo da; Li, Maximo Siu; Delmonte, Maurício Roberto Bomio
The PbMoO4 co-doped with Tm3+, Tb3+ Eu3+ with scheelita structure was synthesized by the sonochemical method. The photoluminescent properties, structural and color coordinates emitted by phosphors were investigated. The structural analysis of the crystal and the changes in lattice parameters confirm that the rare earth ions (RE3+) were successfully introduced into the host of the PbMoO4. The relationship between energy gap (Egap) and the concentration of RE3+ ions was also discussed, the Egap is significantly influenced by the degree of structural order-disorder present in the crystal lattice. The PbMoO4:RE3+ shows light emission in green. Under UV excitation, Photoluminescence (PL) shows a broad band centered at 520 nm and smaller bands belonging to transitions of RE3+: 1G4 → 3F4 and 1D2 → 3H4 at 480 and 533 nm (Tm3+), 5D4 → 7Fj (j = 6, 5) at 493 and 550 nm (Tb 3+) 5D0 → 7Fj (j = 1, 2, 4) 593, 615 and 702 nm (Eu3+)
Photoluminescent properties of ZrO2: Tm3+, Tb3+, Eu3+ powders — A combined experimental and theoretical study
(Elsevier, 2017-02-25) Paskocimas, Carlos Alberto; Lovisa, Laura Ximena; Andrés, Juan; Gracia, Lourdes; Li, Maximo Siu; Delmonte, Maurício Roberto Bomio; Araújo, Vinícius Dantas; Silva, Elson Longo da; Motta, Fabiana Villela da
Rare-earth (RE) element-based materials for optical applications have received increasing attention owing to the emission properties of RE ions, which render these materials suitable for use in color displays, lasers, and solid-state lighting. In the present work, ZrO2:RE (RE = Tm3+, Tb3+, and Eu3+) powders were obtained via complex polymerization, and characterized by means of X-ray diffraction (XRD), Raman spectroscopy, UV–visible absorption spectroscopy, and photoluminescence measurements. The XRD patterns and Raman spectra revealed the tetragonal phase of ZrO2 co-doped with up to 4 mol.% RE3+ and stabilization of the cubic phase, for up to 8 mol.% RE3+. In addition, the photoluminescence measurements revealed simultaneous emissions in the blue (477 nm), green (496.02 nm and 548.32 nm), and red-orange (597.16 nm and 617.54 nm) regions. These emissions result from the Tm3+, Tb 3+, and Eu3+ ions, respectively. Energy transfers, such as 1G4 levels (Tm3+) → 5D4 (Tb3+) and 5D4 levels (Tb3+) → 5D0 (Eu3+), occurred during the emission process. Calculations based on density functional theory (DFT) were performed, to complement the experimental data. The results revealed that structural order/disorder effects were generated in the cubic and tetragonal ZrO2 phases in the ZrO2:Eu3+ powders, and changes in the electronic structure were manifested as a decrease in the band gap values. The chromaticity coordinates of all the samples were determined from the PL spectrum. The coordinates, x = 0.34 and y = 0.34, of the ZrO2:8%RE sample corresponded to a point located in the white region of the CIE diagram and color correlated temperature (CCT) was found to be 5181 K. More importantly, the present results indicate that ZrO2:RE powders constitute promising photoluminescent materials for use in new lighting devices.
Preparation and photocatalytic properties of hexagonal-shaped ZnO:Sm3+ by microwave-assisted hydrothermal method
(Springer, 2017-02-09) Paskocimas, Carlos Alberto; Carvalho, Raquel Guilherme de; Tavares, Mara Tatiane de Souza; Oliveira, F. K. F.; Nascimento, Rubens Maribondo do; Silva, Elson Longo da; Li, Maximo Siu; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Novel 3D rods ZnO:Sm monophasic microcrystals have been synthesized by the microwave-assisted hydrothermal (MAH) method at 140 °C for 10 min. The experimental results revealed that concentration of samarium have a significant influence on the band gap and photocatalysis. On the other hand, the samarium in the ZnO semiconductor structure increases photodegradation activity. ZnO sample doped with 8% Sm3+ exhibited the best activity in the photodegradation of methylene blue dye when compared to that doped with 0–4 mol%. Enhanced photocatalytic activity was attributed to samarium, which inhibits the recombination of electron–hole pairs
Preparation and photoluminescence characteristics of In(OH)3:xTb3+ obtained by Microwave-Assisted Hydrothermal method
(Elsevier, 2013-03-15) Motta, Fabiana Villela da; Marques, Ana Paula de Azevedo; Li, Maximo Siu; Abreu, Maria Fernanda C.; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Souza, Ricardo Pires de; Varela, José A.; Silva, Elson Longo da
Crystalline terbium-doped indium hydroxide structures were prepared by a rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at a low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of terbium-doped indium hydroxide (In(OH)3:xTb3+) samples under excitation (350.7 nm) presented broad band emission referent to the indium hydroxide matrix and 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3 terbium transitions at 495, 550, 590 and 627 nm, respectively. Relative intensities of the Tb3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol%, of Tb3+, but the luminescence is drastically quenched for the In(OH)3 matrix
Structural refinement, growth mechanism, infrared/Raman spectroscopies and photoluminescence properties of PbMoO4 crystals
(Elsevier, 2013-02-13) Delmonte, Maurício Roberto Bomio; Cavalcante, L. S.; Almeida, Márcio Aurélio Pinheiro; Tranquilin, Ricardo Luis; Batista, Nouga Cardoso; Pizani, Paulo Sérgio; Li, Maximo Siu; Andres, Juan; Silva, Elson Longo da
Lead molybdate (PbMoO4) crystals were synthesized by the co-precipitation method at room temperature and then processed in a conventional hydrothermal (CH) system at low temperature (70 C for different times). These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, micro-Raman (MR) and Fourier transformed infrared (FT-IR) spectroscopies. Field emission scanning electron microscopy images were employed to observe the shape and monitor the crystal growth process. The optical properties were investigated by ultraviolet–visible (UV–Vis) absorption and photoluminescence (PL) measurements. XRD patterns and MR spectra indicate that these crystals have a scheelite-type tetragonal structure. Rietveld refinement data possibilities the evaluation of distortions in the tetrahedral 1⁄2MoO4 clusters. MR and FT-IR spectra exhibited a high mode m1(Ag) ascribed to symmetric stretching vibrations as well as a large absorption band with two modes m3(Eu and Au) related to anti-symmetric stretching vibrations in 1⁄2MoO4 clusters. Growth mechanisms were proposed to explain the stages involved for the formation of octahedron-like PbMoO4 crystals. UV–Vis absorption spectra indicate a reduction in optical band gap with an increase in the CH processing time. PL properties of PbMoO4 crystals have been elucidated using a model based on distortions of tetrahedral 1⁄2MoO4 clusters due to medium-range intrinsic defects and intermediary energy levels (deep and shallow holes) within the band gap
Structure, morphology and photoluminescence emissions of ZnMoO4: RE 3+=Tb3+ - Tm3+ - X Eu3+ (x = 1, 1.5, 2, 2.5 and 3 mol%) particles obtained by the sonochemical method
(Elsevier, 2018-06-25) Paskocimas, Carlos Alberto; Lovisa, Laura Ximena; Oliveira, Marisa Carvalho de; Andres, Juan; Gracia, Lourdes; Li, Maximo Siu; Silva, Elson Longo da; Tranquilin, Ricardo Luis; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
ZnMoO4 and ZnMoO4: RE3+ = 1% Tb3+, 1% Tm3+, x Eu3+ (x = 1, 1.5, 2, 2.5 and 3 mol%) particles were prepared by a sonochemical method. The influence of the dopant content on photoluminescent behavior was investigated. The X-ray diffraction results confirmed the formation of the α-ZnMoO4 phase with a triclinic crystalline structure. The influence of the chemical compositions on photoluminescence emissions has been studied and the results clearly show the specific emissions of Tb3+ and Eu3+, simultaneously, with a strong contribution of the matrix. Band gap values are in the range of 3.55–4.25 eV. From the values calculated for the CIE coordinates, it was observed that this material develops an emission tendency in the orange-red region. It has been demonstrated for the first time that the sample ZnMoO4: 1% Tb3+, 1% Tm3+, 2% molEu3+, presented higher photoluminescence intensity. At higher concentrations of RE3+, the quenching effect was observed. The morphology of samples are interpreted based on a comparative analysis of the calculated and experimental field emission scanning electron microscopy (FE-SEM) images. First-principle calculations at a density functional theory level were performed to obtain the values of surface energies and relative stability of the (120), (001), (011), (201), and (100) surfaces by employing the Wulff construction. A complete map of the available morphologies of ZnMoO4 and ZnMoO4:12.5%molEu3+ is obtained and a possible explanation for the transformation processes is provided in which the experimental and theoretical morphologies can match. The present study offers a fundamental knowledge that is expected to enable the fabrication of ZnMoO4-based phosphor materials with a controllable emission peak shift and intensity
Structure, morphology and photoluminescence emissions of ZnMoO4: RE 3+=Tb3+ -Tm3+ - x Eu3+ (x = 1, 1.5, 2, 2.5 and 3 mol%) particles obtained by the sonochemical method
(Elsevier, 2018-06-25) Lovisa, Laura Ximena; Oliveira, Marisa Carvalho de; Andrés, Juan; Gracia, Lourdes; Li, Maximo Siu; Silva, Elson Longo da; Tranquilin, Ricardo Luis; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
ZnMoO4 and ZnMoO4: RE3+= 1% Tb3+, 1% Tm3+, x Eu3+ (x = 1, 1.5, 2, 2.5 and 3 mol%) particles were prepared by a sonochemical method. The influence of the dopant content on photoluminescent behavior was investigated. The X-ray diffraction results confirmed the formation of the α-ZnMoO4 phase with a triclinic crystalline structure. The influence of the chemical compositions on photoluminescence emissions has been studied and the results clearly show the specific emissions of Tb3+ and Eu3+, simultaneously, with a strong contribution of the matrix. Band gap values are in the range of 3.55 to 4.25 eV. From the values calculated for the CIE coordinates, it was observed that this material develops an emission tendency in the orange-red region. It has been demonstrated for the first time that the sample ZnMoO4: 1% Tb3+, 1% Tm3+, 2% molEu3+, presented higher photoluminescence intensity. At higher concentrations of RE3+, the quenching effect was observed. The morphology of samples are interpreted based on a comparative analysis of the calculated and experimental field emission scanning electron microscopy (FE-SEM) images. First-principle calculations at a density functional theory level were performed to obtain the values of surface energies and relative stability of the (120), (001), (011), (201), and (100) surfaces by employing the Wulff construction.A complete map of the available morphologies of ZnMoO4 and ZnMoO4:12.5%molEu3+ is obtained and a possible explanation for the transformation processes is provided in which the experimental and theoretical morphologies can match. The present study offers a fundamental knowledge that is expected to enable the fabrication of ZnMoO4-based phosphor materials with a controllable emission peak shift and intensity
Synthesis and characterization of Agþ and Zn2þ co-doped CaWO4 nanoparticles by a fast and facile sonochemical method
(Elsevier, 2020-05-15) Andrade Neto, Nivaldo Freire da; Dias, B. P.; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Li, Maximo Siu; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In this work, Agþ and Zn2þ co-doped CaWO4 nanoparticles were obtained by fast and facile sonochemical method. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), visible ultraviolet spectroscopy (UVeVis) and photoluminescence property. The photocatalytic activity was studied against methylene blue (MB) dye under sunlight and CaWO4 powders were tested in 3 reuse cycles. The diffractograms indicate the non-formation of secondary phases and the Rietveld refinement estimated the crystallite sizes, being 27.38, 19.89, 18.70 and 16.39 nm for the pure, Ag, Zn and Ag:Zn samples, respectively. SEM and TEM images showed that the particles are agglomerated and have a mean diameter ranging from 16.76 (Ag:Zn) to 71.76 nm (pure). Defects generated by doping shift the gap band to higher energies and act to prevent electron/hole (e/hþ) pair recombination, reducing photoluminescence and favoring CaWO4 photocatalysis. Scavenger methodology indicated that hþ is the main mechanism acting in photocatalysis, and the reuse tests indicated that the silver-doped sample, even with the better initial response, loses efficiency over the course of the cycle, while the co-doped sample maintains efficiency, and is therefore indicated for reuse photocatalysis applications in methylene blue dye degradation

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Navegando por Autor "Li, Maximo Siu"