Navegando por Autor "Tranquilin, Ricardo Luis"
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Artigo Cerium molybdate nanocrystals: Microstructural, optical and gas- sensing properties(Elsevier, 2021-03-15) Oliveira, Fernanda Karine Fonseca; Santiago, Anderson de Azevedo Gomes; Catto, Anderson de Azevedo Gomes; Silva, Luís Fernando da; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioMetal molybdate compounds have attracted considerable attention due to their technological applications. Herein, we demonstrate the controllable synthesis of cerium molybdate (Ce2(MoO4)3) nanocrystals via the co-precipitation method followed by microwave-assisted hydrothermal (MAH) treatment at 150 C during different times (15, 30 and 60 min). The effect of MAH treatment time on the microstructural, optical, and ozone gas-sensing properties of these nanocrystals was investigated. X-ray diffraction (XRD) and Raman spectroscopy measurements revealed that the samples presented a single-crystalline phase with scheelite-type tetragonal structure. Field emission gun scanning electron microscopy (FEG-SEM) images showed that the MAH conditions favored changes in the Ce2(MoO4)3 nano crystal morphology. Photoluminescence (PL) measurements indicated a significant enhancement of PL emission with MAH time, suggesting an increase in the intrinsic defects formed during the MAH treatment. The gas-sensing performance of cerium molybdate nanocrystals towards sub-ppm ozone levels was also investigated. The experiments revealed complete recovery and good repeatability as well as good sensor response, which was improved in the sample synthesized at longer MAH timeArtigo Development of ZnO/PDMS nanocomposite with photocatalytic/ hydrophobic multifunction(Chemical Physics Letters, 2020-02) Nascimento, Maria Carolina Burgos Costa do; Santiago, Anderson de Azevedo Gomes; Gondima, Juliane Germano de Souza; Tranquilin, Ricardo Luis; Silva, Fabio S. da; Fernandez, Fernando Ferreira; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioThe polydimethylsiloxane (PDMS)/ZnO nanocomposite coatings were deposited on the borosilicate substrate by spray method. ZnO nanoparticles were synthesized by polyol method and further surface modification by functionalization with [(3-Aminopropyl)triethoxysilane] (APTS) in different concentrations (0.5, 1.0, and 1.5 ml). The results showed that there is an influence in the exposure to UV radiation and a decrease in the temperature, consequently presenting decreases in the contact angle of ZnO/PDMS nanocomposites. The 0.5 ml of APTS was the best design for ZnO/PDMS nanocomposite with photocatalytic and hydrophobic characteristics, showing a contact angle of 117° and 25% of MB discoloration in 90 minArtigo Disclosing the structural, electronic, magnetic, and morphological properties of CuMnO2: a unified experimental and theoretical approach(American Chemical Society, 2020-02-14) Santiago, Anderson de Azevedo Gomes; Tranquilin, Ricardo Luis; Oliveira, Marisa Carvalho de; Ribeiro, Renan Augusto Pontes; Lazaro, Sérgio Ricardo de; Corrêa, Marcio Assolin; Bohn, Felipe; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioPrecise control of the overall performance for solid-state materials is associated with morphological modulations which provide an alternative way to the rational design based on understanding the corresponding electronic structures of the exposed surfaces. Experimental and theoretical efforts were combined herein to elucidate the structural−property relationship of CuMnO2 nanoparticles from different morphologies. The microwave-assisted hydrothermal method was employed to synthesize these crystals with different morphologies, while first-principle quantum mechanical calculations were performed at the DFT level to obtain the structural, electronic, and magnetic properties of CuMnO2 surfaces. Our structural results have confirmed a monoclinic structure for crednerite-type CuMnO2 nanoparticles described by the Jahn−Teller-distorted octahedral [MnO6] clusters, which are connected by linear 2-fold [CuO2]. FE-SEM images combined with Wulff construction analyses indicated that CuMnO2 nanoparticles adopt a hexagonal nanoplate-like morphology which can enclose a major extent of the (100) surface with contributions from (101), (110), and (111) surfaces. Electronic structure and magnetic characterizations were discussed by the role of the corresponding electronic states of exposed surfaces which control the energy-level band diagram and spin density distribution. These results extend our fundamental understanding of the atomic processes which underpin the morphological modulations of the CuMnO2 material, thus creating a new path to obtain selected nanoparticles with desirable properties which optimize their applicationsArtigo Effect of different starting materials on the synthesis of Ba0.8Ca0.2TiO3(SpringerOpen, 2015-01-31) Medeiros, P. N.; Araújo, Vinícius Dantas de; Marques, Ana Paula de Azevedo; Tranquilin, Ricardo Luis; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Varela, José A.; Silva, Elson Longo da; Motta, Fabiana Villela daLiterature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction, co-precipitation and polymer precursors. These compounds are usually obtained using calcium carbonate (CaCO3), barium carbonate (BaCO3) and titanium oxide as starting materials. This study investigated the effect of different starting reagents on the synthesis of Ba0.8Ca0.2TiO3 (BCT) by complex polymerization method (CPM). Two sets of starting precursors were used: titanium citrate, CaCO3 and BaCO3, and titanium citrate and Ba1−x Ca x CO3 solid solution precursor. Samples were crystallized at a temperature range from 400 °C to 700 °C for different time. The obtained powders were characterized by X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), and Raman and infrared spectroscopy. The infrared spectroscopy indicated that the chelation processes of Ba, Ca, Ti and CA ions are very similar. The results showed that the use of CaCO3 and BaCO3 or Ba1−x Ca x CO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPMArtigo Effect of polyvinyl alcohol on the shape, photoluminescence and photocatalytic properties of PbMoO4 microcrystals(Elsevier, 2014-10) Araújo, Vinícius Dantas; Tranquilin, Ricardo Luis; Motta, Fabiana Villela da; Paskocimas, Carlos Alberto; Bernardi, Maria Inês Basso; Cavalcante, L.S.; Andres, Juan; Silva, Elson Longo da; Delmonte, Maurício Roberto BomioFor this study, lead molybdate (PbMoO4) microcrystals were prepared by the co-precipitation method and processed using a conventional hydrothermal method at 100 °C for 10 min with polyvinyl alcohol (PVA) as the capping agent. These microcrystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman spectroscopy, and their morphology was investigated by field-emission gun scanning electron microscopy (FEG-SEM). The optical properties were analyzed by ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectrum indicate that the PbMoO4 microcrystals have a scheelite-type tetragonal structure. FE-SEM images reveal that the PVA promotes the aggregation of several octahedrons and the formation of large porous stake-like PbMoO4 microcrystals which are related to the oriented attachment growth process. Moreover, the effect of the capping agent hinders the growth of a large amount of micro-octahedrons which can be verified with by several nanocrystals on large crystals. Intense green PL emission was observed at room temperature for PbMoO4 microcrystals which are related to structural defects at medium range and intermediary energy levels between the valence band (VB) and the conduction band (CB). Photocatalytic activity was observed for PbMoO4 as a catalyst in the degradation of the rhodamine B (RhB) dye, achieving total degradation after 90 min under UV-lightArtigo 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 BomioZinc 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 sourcesArtigo 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 Experimental and theoretical study to explain the morphology of CaMoO4 crystals(Elsevier, 2018-03) Paskocimas, Carlos Alberto; Silva, Elson Longo da; Oliveira, Fernanda Karine Fonseca de; Oliveira, Marisa Carvalho de; Gracia, Lourdes; Tranquilin, Ricardo Luis; Motta, Fabiana Villela da; Andrés, Juan; Delmonte, Maurício Roberto BomioCaMoO4 crystals were prepared by a controlled co-precipitation method and processed in a domestic microwave-assisted hydrothermal system with two different surfactants (ethyl 4-dimethylaminobenzoate and 1,2,4,5-benzenetetracarboxylic dianhydride). The corresponding structures were characterized by X-ray diffraction and Rietveld refinement techniques, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, and photoluminescence measurements. Field emission scanning electron microscopy was used to investigate the morphology of the as-synthesized aggregates. The structure, the surface stability of the (001), (112), (100), (110), (101), and (111) surfaces of CaMoO4, and their morphological transformations were investigated through systematic first-principles calculations within the density functional theory method at the B3LYP level. Analysis of the surface structures showed that the electronic properties were associated with the presence of undercoordinated [CaOx] (x 1⁄4 5 and 6) and [MoOy] (y 1⁄4 4 and 3) clusters. The relative surfaces energies were tuned to predict a complete map of the morphologies available through a Wulff construction approach. The results reveal that the experimental and theoretical morphologies obtained coincide when the surface energies of the (001) and (101) surfaces increase, while the surface energy of the (100) facet decreases simultaneously. The results provide a comprehensive catalog of the morphologies most likely to be present under realistic conditions, and will serve as a starting point for future studies on the surface chemistry of CaMoO4 crystalsArtigo Influence of Zn1-xCaxWO4 heterostructures synthesized by spray pyrolysis on photoluminescence property(Elsevier, 2019-12-01) Paskocimas, Carlos Alberto; Santiago, Anderson de Azevedo Gomes; Fernandes, Y. L. R. L.; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio; Silva, Elson Longo da; Tranquilin, Ricardo LuisTungstates are inorganic materials with great potential in diverse applications, mainly as a photoluminescent material as a candidate to replace traditional lighting sources. In this study, we report the synthesis and char- acterization of Zn1-xCaxWO4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) powders with white light-emitting properties. Using X-ray diffraction, the formation of the monoclinic ZnWO4 phase was observed for x = 0 and the formation of the tetragonal scheelite phase of CaWO4 was observed for x = 1. The formation of a heterostructure composed of both phases was found for compositions with x = 0.2, 0.4, 0.6 and 0.8. Scanning electron microscopy images showed that the Zn1-xCaxWO4 particles exhibit a spherical morphology. The band-gap energies had variation between 3.79 eV and 3.99 eV, being influenced by the degree of structural disorder. The photoluminescence emission spectra of the samples showed white light emission. Thus, Zn1-xCaxWO4 can be considered as promising white light sources, mainly for the sample synthesized with x = 0.8 for application in LED lamps (6500 K)Artigo Photoluminescent properties of Sm3+ and Tb3+ codoped CaWO4 nanoparticles obtained by a one‐step sonochemical method(Springer Science and Business Media LLC, 2020-07-06) Andrade Neto, Nivaldo Freire de; Silva, J. M. P.; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Domenegueti, J. F. M.; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daLuminescent materials with LED applications can have your emission color controlled by rare earth doping. In this work, Sm3+- and Tb3+-codoped CaWO4 nanoparticles were obtained by a one-step sonochemical method. The nanoparticles were characterized by X-ray difractogram (XRD), Raman scattering (RS) spectroscopy, The Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and visible ultraviolet spectroscopy (UV–Vis). The photoluminescent measurements were taken at room and lower temperatures for analysis of doping in emission color. The difractograms indicate the single-phase CaWO4 with the scheelite structure and it was observed a reduction in the crystallite size as the doping. SEM and TEM images indicate the formation of nanospheres for pure and samarium-doped samples, while terbium doping results in the formation of nanorods. Room temperature photoluminescence spectra indicate a blue emission for the bare and samarium-doped CaWO4, while terbium doping emits at the green color. The codoping mixes the colors blue, green, and orange, indicating a potential material with white color emissionArtigo Photoluminescent properties of the Ba1−xZnxMoO4 heterostructure obtained by ultrasonic spray pyrolysis(Elsevier, 2018-03) Paskocimas, Carlos Alberto; Santiago, Anderson de Azevedo Gomes; Almeida, Cláudio Romero Rodrigues de; Tranquilin, Ricardo Luis; Nascimento, Rubens Maribondo do; Silva, Elson Longo da; Motta, Fabiana Villela da; Bomio, Mauricio Roberto BomioIn this study, Ba1−xZnxMoO4 (x = 0, 0.25, 0.5, 0.75 and 1) microspheres were the first time described in the literature the by ultrasonic spray pyrolysis method. Powders were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM-FEG) and UV–visible and Photoluminescence (PL) spectroscopies. The XRD patterns showed that the samples with x = 0 and x = 1 displayed pure tetragonal and triclinic structures, respectively. On the other hand, samples with x = 0.25, 0.5 and 0.75 revealed the formation of tetragonal/ triclinic heterojunction structure. The SEM-FEG images showed that the Ba1−xZnxMoO4 particles present the spherical morphology with the decrease of particle sizes when the value of “x” increase. The gap energies vary between 4.56 eV and 4.17 eV, being influenced by the degree of structural order-disorder. The PL emission spectra of the samples showed a broad band behavior with emission intensity predominant in the orange-red region and of a lower intensity in the blue-green region. The chromaticity coordinates x and y showed that the samples with x ≤ 0.75 present emission in orange, while the samples with x = 1 showed emission in whiteArtigo Presence of excited electronic states on terbium incorporation in CaMoO4: Insights from experimental synthesis and first-principles calculations(Elsevier, 2021-02) Tranquilin, Ricardo Luis; Oliveira, Marisa Carvalho de; Santiago, Anderson de Azevedo Gomes; Lovisa, Laura Ximena; Ribeiro, Renan Augusto Pontes; Silva, Elson Longo da; Lazaro, Sergio R. de; Almeida, Cláudio Romero Rodrigues de; Paskocimas, Carlos Alberto; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioWe present a combined experimental and theoretical study to understand the structure and electronic and optical properties of CaMoO4:xTb3+ (x = 1 mol%, 2 mol%, and 4 mol%) microspheres. The microspheres were prepared by ultrasonic spray pyrolysis and characterized by X-ray diffraction (XRD), field-emission gun scanning electron microscopy (FEG-SEM), micro Raman spectroscopy, and photoluminescence (PL) spectroscopy. First-principles quantum mechanical calculations were performed at the density functional theory level to obtain the geometry and electronic properties of CaMoO4:xTb3+ microspheres in the ground electronic state and excited electronic states (singlet and triplet). These results, combined with XRD patterns, indicate that these crystals have a scheelite-type tetragonal structure. The morphology of the CaMoO4:xTb3+(x = 1 mol%, 2 mol%, and 4 mol%) samples was investigated by FEG-SEM, and a spherical shape was found. The optical properties were investigated by UV–vis spectroscopy and PL spectroscopy, and the chromaticity coordinates of these compounds were obtained. The relationships between the PL properties and the Raman spectra indicate that Tb3+-doped CaMoO4 microspheres constitute promising photoluminescent materials for use in new lighting devices. This also allowed us to understand the charge transfer process that happens in the singlet (s) ground state and the singlet (s*) and triplet (t*) excited states, which generates the photoluminescent emissions of the Tb3+-doped CaMoO4 microspheresArtigo Spray pyrolysis synthesis and characterization of Mg1-xSrxMoO4 heterostructure with white light emission(Elsevier, 2020-01-15) Paskocimas, Carlos Alberto; Santiago, Anderson de Azevedo Gomes; Tranquilin, Ricardo Luis; Botella, Pablo; Manjon, Francisco Javier; Errandonea, Daniel J.H.; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioMolybdates are inorganic materials with great potential in white phosphors application, being an alternative to traditional lighting sources. In this study, we report the synthesis and characterization of Mg1-xSrxMoO4 (x 1⁄4 0, 0.25, 0.50, 0.75, and 1) powders with white light-emitting properties. Using X-ray diffraction, the formation of the monoclinic b-MgMoO4 phase was observed for x 1⁄4 0 and the formation of the tetragonal scheelite phase of SrMoO4 was observed for x 1⁄4 1. The formation of a heterostructure composed of both phases was found for compositions with x 1⁄4 0.25, 0.50 and 0.75. Scanning and trasmission electron microscopy images showed that the Mg1-xSrxMoO4 particles exhibit a spherical morphology formed by several primary nanoparticles. Raman scattering spectroscopy enabled the accurate identification of the Raman modes for different compositions and their assignment to either the SrMoO4 or b-MgMoO4 modes. The bandgap energies were determined to fluctuate between 4.25 eV and 4.44 eV, being influenced by the degree of structural disorder. The photoluminescence emission spectra of the nanoparticles showed neutral- and cool-white emission with high-quality white light (CRI > 80%). The samples synthesized with x 0.50 are potential materials for the application in LED lamps (6500 K) and pure white-light sources (5500 K)Artigo Stabilization of the γ-Ag2WO4 metastable pure phase by coprecipitation method using polyvinylpyrrolidone as surfactant: photocatalytic property(Elsevier, 2020-07) Andrade Neto, Nivaldo Freire de; Silva, J.M.P.; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daIn this work, the effect of polyvinylpyrrolidone (PVP) concentration as a surfactant was studied in the estabilization of the metastable phase γ-Ag2WO4 by the coprecipitation method at room temperature. The phases obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and spectroscopy in the ultraviolet–visible region (UV–Vis). The pho-tocatalytic activity was estimated by varying the concentration of methylene blue dye. The iffractograms in-dicate that 0.3 g of PVP is ideal for obtaining the single phase of γ-Ag2WO4, as larger or maller amounts favor the appearance of β-Ag2WO4 as a secondary phase while the absence of PVP formed he α-Ag2WO4 phase. UV–Vis spectroscopy showed that both phases have absorption in the ultraviolet region, here the γ-Ag2WO4 phase has a higher absorption at shorter wavelengths. The micrographs indicate that the -g2WO4 morphology is formed by rods, while the γ-Ag2WO4 is formed by octahedrons, both in micrometer cale and with well-defined morphology. The photocatalytic tests indicate that the γ-Ag2WO4 phase has better photocatalytic activity compared to the β-Ag2WO4 phase. The scavenger's methodology indicated that h+ charges are the main mechanism in the photocatalysis of methylene blue dyeArtigo 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 daLead 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 gapArtigo Structure, electronic properties, morphology evolution, and photocatalytic activity in PbMoO4 and Pb12xCaxSrxMoO4 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions(Royal Society of Chemistry, 2020) Gomes, E. O.; Gracia, Lourdes; Santiago, Anderson de Azevedo Gomes; Tranquilin, Ricardo Luis; Motta, Fabiana Villela da; Amoresi, Rafael Aparecido Ciola; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Andres, JuanIn this work PbMoO4 and Pb12xCaxSrxMoO4 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions have been successfully prepared, for the first time, by a simple co-precipitation method and the as-synthesized samples were subjected to a water-based reflux treatment. Structural characterization of these samples was performed using X-ray diffraction with Rietveld refinement analysis and Raman spectroscopy. Their optical properties were investigated by UV-Vis absorption spectroscopy and PL emissions, and the photocatalytic activity of the as-synthesized samples for the degradation process of Rhodamine B has been demonstrated. The surface structure and morphologies were characterized by field emission scanning electron microscopy. To complement and rationalize the experimental results, the geometry, electronic structures, and morphologies of as-synthesized samples were characterized by first-principles quantum-mechanical calculations at the density functional theory level. By using Wulff construction, based on the values of the surface energies for the (001), (100), (110), (111), (011) and (112) surfaces, a complete map of the available morphologies for PbMoO4 was obtained and a good agreement between the experimental and theoretical predicted morphologies was found. The structural and electronic changes induced by the substitution of Pb by Ca and Sr allow us to find a relationship among morphology, the electron-transfer process at the exposed surfaces, optical properties, and photocatalytic activity. We believe that our results offer new insights regarding the local coordination of superficial Pb/Ca/Sr and Mo cations (i.e., clusters) on each exposed surface of the corresponding morphology, which dictate the photocatalytic activities of the as-synthesized samples, a field that has so far remained unexplored. The present study, which combines multiple experimental methods and first-principles calculations, provides a deep understanding of the local structures, bonding, morphologies, band gaps, and electronic and optical properties, and opens the door to exploit the electrical, optical and photocatalytic activity of this very promising family of materialsArtigo 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 daZnMoO4 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 intensityArtigo 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 daZnMoO4 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 intensityArtigo 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 daIn 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 degradationArtigo Toward understanding the photocatalytic activity of PbMoO4 powders with predominant (111), (100), (011), and (110) facets. A combined experimental and theoretical study(American Chemical Society, 2013) Delmonte, Maurício Roberto Bomio; Tranquilin, Ricardo Luis; Motta, Fabiana Villela da; Paskocimas, Carlos Alberto; Nascimento, Rubens Maribondo do; Gracia, Lourdes; Andres, Juan; Silva, Elson Longo daA complementary combination of experimental work and first-principle calculations, based on the density functional theory (DFT) method, has been used to increase our limited understanding of the enhanced photocatalytic activity of PbMoO4 powders with predominant (111), (100), (011), and (110) facets. In this work, PbMoO4 powders were prepared by the coprecipitation method and processed on a hydrothermal reactor at 100 °C/10 min. The variation of different types of modifiers such as acetylacetone (acac) or polyvinylpyrrolidone (PVP) is found to play a crucial role in controlling the particle size and morphology of products and their photocatalytic properties. The structure and morphology of these crystals were characterized by X-ray diffraction (XRD), micro-Raman (MR) spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM), and ultraviolet visible (UV–vis) absorption spectroscopy. Furthermore, the as-synthesized PbMoO4 micro-octahedrons without the presence of the (001) surface exhibit enhanced activity for the photodegradation of rhodamine B (RhB) under ultraviolet–visible light irradiation. On the basis of the theoretical and experimental results, we provide a complete assignment of the micro-Raman spectra of PbMoO4, while a growth mechanism for the formation of PbMoO4 micro-octahedrons was systematically discussed. A schematic illustration of the probable formation of morphologies in the whole of the synthetic process was also proposed, which reveals that the high photocatalytic activity is attributed to the absence of the (001) facet