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1. The Role of Zn Ions in the Structural, Surface, and Gas-Sensing Properties of SnO2:Zn Nanocrystals Synthesized via a Microwave-Assisted Route

Author

Luís F. da Silva, Mattia A. Lucchini, Ariadne C. Catto, Waldir Avansi Jr., Sandrine Bernardini, Khalifa Aguir, Markus Niederberger, and Elson Longo

Subjects
SnO2, zinc, non-aqueous synthesis, microwave route, local structure, surface properties, Chemical technology, TP1-1185
Abstract

Although semiconducting metal oxide (SMOx) nanoparticles (NPs) have attracted attention as sensing materials, the methodologies available to synthesize them with desirable properties are quite limited and/or often require relatively high energy consumption. Thus, we report herein the processing of Zn-doped SnO2 NPs via a microwave-assisted nonaqueous route at a relatively low temperature (160 °C) and with a short treatment time (20 min). In addition, the effects of adding Zn in the structural, electronic, and gas-sensing properties of SnO2 NPs were investigated. X-ray diffraction and high-resolution transmission electron microscopy analyses revealed the single-phase of rutile SnO2, with an average crystal size of 7 nm. X-ray absorption near edge spectroscopy measurements revealed the homogenous incorporation of Zn ions into the SnO2 network. Gas sensing tests showed that Zn-doped SnO2 NPs were highly sensitive to sub-ppm levels of NO2 gas at 150 °C, with good recovery and stability even under ambient moisture. We observed an increase in the response of the Zn-doped sample of up to 100 times compared to the pristine one. This enhancement in the gas-sensing performance was linked to the Zn ions that provided more surface oxygen defects acting as active sites for the NO2 adsorption on the sensing material. more...

Published
2023
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2. Light-assisted ozone gas-sensing performance of SnO2 nanoparticles: Experimental and theoretical insights

Author

João V.N. de Palma, Ariadne C. Catto, Marisa C. de Oliveira, Renan A.P. Ribeiro, Marcio D. Teodoro, and Luís F. da Silva

Subjects
SnO2, Nanoparticles, Chemiresistor, Light-assisted, Ozone, DFT calculations, Instruments and machines, QA71-90
Abstract

We report herein an investigation on the ozone gas-sensing performance at room temperature of SnO2 nanoparticles assisted by a light-emitting diode. X-ray diffraction and high-resolution transmission electron microscopy analyses indicated the nanocrystalline characteristics of the SnO2 particles after heat treatment. Besides, optical measurements pointed out that the nanoparticles presented an optical gap of approximately 3.8 eV with a broad photoluminescence emission at around 625 nm, which was linked to the presence of oxygen vacancies, suggested by XPS analysis. With regard to the light-assisted gas-sensing measurements, electrical analysis revealed a clear dependence of the ozone sensing performance on the wavelength of the source of illumination chosen, with the highest ozone response being reached upon excitation in the ultraviolet region. Theoretical calculations showed that the (110) surface could increase the stability of photogenerated carriers and contribute to enhancing the gas-sensing features under ultraviolet excitation due to the presence of [SnO6] and [SnO5] clusters, which are capable of inducing an electron-hole dissociation and a reliable chemical environment for O3 interaction. more...

Published
2022
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3. ZnO/SnO2 Heterojunctions Sensors with UV-Enhanced Gas-Sensing Properties at Room Temperature

Author

Luís F. da Silva, Mattia A. Lucchini, Jean-Claude M’Peko, Sandrine Bernardini, Khalifa Aguir, Caue Ribeiro, Elson Longo, and Markus Niederberger

Subjects
microwave-assisted synthesis, ZnO, SnO2, heterojunction, chemresistors, UV-photoactivated, room-temperature, ozone gas, General Works
Abstract

We report herein the efficiency of microwave-assisted synthesis for obtaining ZnO/SnO2 heterostructures for room-temperature gas-sensing applications. The sensing performances of the traditional oxide materials have been found for applications above 200 °C. However, these temperatures were here reduced to room temperature by considering sensing activity photoactivated by UV light, even for ppb ozone (O3) levels. The heterojunctions exhibited a fast response, total reversibility, and selectivity to oxidizing gases, especially O3 gas. This investigation provides an efficient way to obtain heterostructures exhibiting remarkable properties for practical applications as O3 gas sensor devices. more...

Published
2017
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4. Highly selective ozone gas sensor based on nanocrystalline Zn0.95Co0.05O thin film obtained via spray pyrolysis technique

Author

Elson Longo, Marcio P.F. de Godoy, Valmor Roberto Mastelaro, Ariadne C. Catto, Tomas Fiorido, Luís F. da Silva, Sandrine Bernardini, Y.J. Onofre, Khalifa Aguir, Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (IM2NP), Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU), Universidade Federal de São Carlos [São Carlos] (UFSCar), Grupo Crescimento de Cristais e Materiais Cerâmico (IFSC), Universidade de São Paulo (USP), Federal University of São Carlos [Bresil], FAPESP (Proc. No. 2013/07296-2, 2016/10973-4 and 2017/12437-5), CNPq, and CAPES, Aix Marseille Université (AMU)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), and Universidade de São Paulo = University of São Paulo (USP) more...

Subjects
Materials science, Ozone, FOTOLUMINESCÊNCIA, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, gas sensor, [SPI.MAT]Engineering Sciences [physics]/Materials, Ion, chemistry.chemical_compound, ZnCoO, X-ray photoelectron spectroscopy, Selectivity, Chemiresistor, [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, Thin film, Spray pyrolysis, Surfaces and Interfaces, General Chemistry, Repeatability, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Nanocrystalline material, 0104 chemical sciences, Surfaces, Coatings and Films, Chemical engineering, chemistry, 13. Climate action, 0210 nano-technology
Abstract

International audience; Chemiresistors are highly important for monitoring and detection of harmful gases produced from industrial processes and vehicle emissions. We report herein an experimental investigation of the gas-sensing properties of Zn0.95Co0.05O thin film deposited by spray pyrolysis technique. The X-ray photoelectron spectroscopy indicated the presence of Co2+ ions into de ZnO lattice. The gas-sensing measurements revealed the sensitivity of Zn0.95Co0.05O film towards ozone gas in a wide range of concentrations from 20 to 1040 ppb, exhibiting good repeatability and total reversibility after consecutive exposures. Selectivity towards ozone is observed in comparison to NO2, NH3, and CO gases even at low levels. This manuscript reports the effectiveness of spray-pyrolysis method for obtaining nanostructured Zn1-xCoxO thin films for practical applications as an ozone gas sensor. more...

Published
2019
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5. Improving the ozone gas-sensing properties of CuWO4 nanoparticles

Author

Ariadne C. Catto, Érica L.S. Souza, Juan Andrés, Luís F. da Silva, Waldir Avansi, Khalifa Aguir, Elson Longo, Laécio S. Cavalcante, Tomas Fiorido, Generalitat Valenciana, Ministerio de Economia y Competitividad, and Programa de Cooperación Cientifíca con Iberoamerica (Brazil), Ministerio de Educación, Universidade Estadual Paulista (Unesp), Aix Marseille Univ, Univ Estadual Piaui, Universidade Federal de São Carlos (UFSCar), and Jaume I Univ more...

Subjects
Diffraction, Materials science, Ozone, Annealing (metallurgy), Nanoparticle, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, law.invention, chemistry.chemical_compound, sonochemical, Electrical resistance and conductance, law, Materials Chemistry, surface, Crystallization, chemiresistor, Spectroscopy, Chemiresistor, Mechanical Engineering, Metals and Alloys, 021001 nanoscience & nanotechnology, 0104 chemical sciences, ozone, Chemical engineering, chemistry, Mechanics of Materials, CuWO4, 0210 nano-technology
Abstract

Made available in DSpace on 2018-11-29T12:10:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-06-05 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Brazilian Nanotechnology National Laboratory Brazilian Laboratory of Synchrotron Radiation (LNLS) Generalitat Valenciana, Ministerio de Economia y Competitividad Programa de Cooperacion Cientifica con Iberoamerica (Brazil), Ministerio de Educacion This paper consists of an experimental investigation on the effects of annealing temperature on the structural, surface and ozone gas-sensing properties of CuWO4 nanoparticles prepared via a sono-chemical route. X-ray diffraction patterns and X-ray absorption near-edge structure spectroscopy revealed that both long-and short-order structures increase with the annealing temperature. Electrical resistance measurements indicated that CuWO4 samples were sensitive in the range of 15-1400 ppb, exhibiting a good reversibility and repeatability. The enhancement of the ozone gas-sensing properties was attributed to the reduction of hydroxyl species and the improvement of the crystallization degree. This study provides a versatile strategy for obtaining CuWO4 nanoparticles for practical applications as an ozone gas sensor. (C) 2018 Elsevier B.V. All rights reserved. Sao Paulo State Univ, Inst Chem, POB 355, BR-14801907 Araraquara, SP, Brazil Aix Marseille Univ, CNRS UMR 7334 IM2NP, FS St Jerome S152, F-13397 Marseille, France Univ Estadual Piaui, PPGQ CCN, POB 381, BR-64002150 Teresina, PI, Brazil Univ Fed Sao Carlos, Dept Phys, Lab Nanostruct Multifunct Mat, BR-13565905 Sao Carlos, SP, Brazil Jaume I Univ, Dept Chem & Phys, Castellon De La Plana, Spain Sao Paulo State Univ, Inst Chem, POB 355, BR-14801907 Araraquara, SP, Brazil FAPESP: 2013/07296-2 FAPESP: 2017/10313-7 FAPESP: 2017/12437-5 CNPq: 310863/ 2014-7 CNPq: 434266/2016-7 Brazilian Nanotechnology National Laboratory: LMF-18580 Brazilian Laboratory of Synchrotron Radiation (LNLS): D04B-XAFS111883 more...

Published
2018
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6. Yolk-shelled ZnCo2O4 microspheres: Surface properties and gas sensing application

Author

Valmor Roberto Mastelaro, Jeong Gil Seo, Harsharaj S. Jadhav, Flavio M. Shimizu, Marcelo Ornaghi Orlandi, Luís F. da Silva, Jean-Claude M’Peko, Nirav Joshi, Pedro H. Suman, Osvaldo N. Oliveira, Universidade de São Paulo (USP), Univ Calif Berkeley, Universidade Federal de São Carlos (UFSCar), Myongji Univ, and Universidade Estadual Paulista (Unesp) more...

Subjects
Materials science, Ozone, Annealing (metallurgy), Inorganic chemistry, Impedance spectroscopy, 02 engineering and technology, Conductivity, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, Adsorption, Materials Chemistry, Electrical measurements, Electrical and Electronic Engineering, Instrumentation, business.industry, Metals and Alloys, Parts-per notation, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Yolk-shelled structures, OZÔNIO, Ozone gas sensing, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Semiconductor, Surface-area-to-volume ratio, chemistry, Chemical engineering, Zn-Co glycolate, ZnCo2O4, 0210 nano-technology, business, Co-precipitation
Abstract

Made available in DSpace on 2018-11-26T17:44:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The need to improve the sensitivity, selectivity and stability of ozone gas sensors capable of monitoring the environment to prevent hazard to humans has sparked research on binary metal oxides. Here we report on a novel ozone gas sensor made with ca. 0.5 mu m yolk-shelled ZnCo2O4 microstructures synthesized via an eco-friendly, co-precipitation method and subsequent annealing. With these ZnCo2O4 microspheres, ozone concentrations down to 80 parts per billion (ppb) could be detected with a.c. and d.c. electrical measurements. The sensor worked within a wide range of ozone concentrations, from 80 to 890 ppb, being also selective to ozone compared to CO, NH3 and NO2. The high performance could be attributed to the large surface area to volume ratio inherent in yolk-shell structures. Indeed, ozone molecules adsorbed on the ZnCo2O4 surface create a layer of holes that affect the conductivity, as in a p-type semiconductor. Since this mechanism of detection is generic, ZnCo2O4 microspheres can be further used in other environment monitoring devices. (c) 2017 Elsevier B.V. All rights reserved. Univ Sao Paulo, Sao Carlos Inst Phys, CP 369, BR-13560970 Sao Carlos, SP, Brazil Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA Univ Fed Sao Carlos, Dept Phys, Rodovia Washington Luis Km 235, BR-13565905 Sao Carlos, SP, Brazil Myongji Univ, Dept Energy Sci & Technol, Yongin, South Korea Sao Paulo State Univ, Inst Chem, Dept Phys Chem, POB 355, BR-14800900 Araraquara, SP, Brazil Sao Paulo State Univ, Inst Chem, Dept Phys Chem, POB 355, BR-14800900 Araraquara, SP, Brazil FAPESP: 2012/15543-7 FAPESP: 2013/14262-7 FAPESP: 2013/07296-2 FAPESP: 2014/23546-1 FAPESP: 2016/23474-6 more...

Published
2018
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7. rGO-ZnO nanocomposites for high electrocatalytic effect on water oxidation obtained by microwave-hydrothermal method

Author

Fernanda C. Romeiro, Mônica A. Rodrigues, Luiz A. J. Silva, Renata C. Lima, Luís F. da Silva, Elson Longo, Edson Nossol, Ariadne C. Catto, Universidade Federal de Uberlândia (UFU), Universidade Estadual Paulista (Unesp), and Universidade Federal de São Carlos (UFSCar) more...

Subjects
Materials science, Passivation, Inorganic chemistry, Oxide, General Physics and Astronomy, 02 engineering and technology, Overpotential, 010402 general chemistry, 01 natural sciences, law.invention, chemistry.chemical_compound, law, Zinc oxide, Electrolysis, Nanocomposite, Electrolysis of water, Graphene, Surfaces and Interfaces, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Surfaces, Coatings and Films, Chemical state, chemistry, Nanoparticles, Electrocatalysis O-2 evolution, 0210 nano-technology, Microwave
Abstract

Made available in DSpace on 2018-11-26T15:44:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-11-30 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Financiadora de Estudos e Projetos (FINEP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Reduced graphene oxide-zinc oxide (rGO-ZnO) nanocomposites were successfully synthesized using a facile microwave-hydrothermal method under mild conditions, and their electrocatalytic properties towards O-2 evolution were investigated. The microwave radiation played an important role in obtainment of well dispersed ZnO nanoparticles directly on reduced graphene oxide sheets without any additional reducing reagents or passivation agent. X-ray diffraction (XRD), Raman and infrared spectroscopies indicated the reduction of GO as well as the successful synthesis of rGO-ZnO nanocomposites. The chemical states of the samples were shown by XPS analyses. Due to the synergic effect, the resulting nanocomposites exhibited high electronic interaction between ZnO and rGO sheets, which improved the electrocatalytic oxidation of water with low onset potential of 0.48 V (vs. Ag/AgCl) in neutral pH and long-term stability, with high current density during electrolysis. The overpotential for water oxidation decreased in alkaline pH, suggesting useful insight on the catalytic mechanism for O-2 evolution. (C) 2017 Elsevier B.V. All rights reserved. Univ Fed Uberlandia, Inst Quim, BR-38400902 Uberlandia, MG, Brazil Univ Estadual Paulista, LIEC, Inst Quim, BR-14800900 Araraquara, SP, Brazil Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil Univ Fed Sao Carlos, Dept Quim, LIEC, BR-13565905 Sao Carlos, SP, Brazil Univ Estadual Paulista, LIEC, Inst Quim, BR-14800900 Araraquara, SP, Brazil FAPEMIG: APQ-00988-13 FAPEMIG: CEX-RED-00010-14 FAPEMIG: APQ-00330-14 more...

Published
2017
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8. Plugged Ampullae in a Donkey Stallion ( Equus asinus )

Author

Carolina Tieme Cardoso Okada, Lorenzo G.T.M. Segabinazzi, Luís F. da Silva, Frederico Ozanam Papa, Marco Antonio Alvarenga, Felipe Erison Medrado, and Universidade Estadual Paulista (Unesp)

Subjects
endocrine system, 040301 veterinary sciences, Lumen (anatomy), Semen, urologic and male genital diseases, Semen collection, 0403 veterinary science, Andrology, Obstruction, Donkey, medicine, Ampulla, Plugged, Azoospermia, urogenital system, Equine, business.industry, 0402 animal and dairy science, 04 agricultural and veterinary sciences, Epididymis, medicine.disease, 040201 dairy & animal science, medicine.anatomical_structure, Vagina, Spermiostasis, business
Abstract

Made available in DSpace on 2018-12-11T17:17:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-04-01 The donkey jack sex glands are larger than stallions, responsible for producing most part of seminal plasma and the second fraction of ejaculate, along with epididymis tail. Plugged ampullae occur by sperm accumulation obstructing the lumen, inducing decrease in sperm quality and may cause azoospermia. In this study, a Pêga breed donkey jack, aging 4 years, was evaluated for breeding soundness evaluation due to a sudden decrease in semen parameters and low fertility rates. Palpation, measurements, and ultrasound examinations of testicles were normal; however, rectal palpation revealed increased volume of ampullae and deferent duct, and the transrectal ultrasonography revealed distended ampullae with hyperechogenic material in the ampullae lumen. After ampullae massage, the semen was collected with artificial vagina for evaluation, resulting in high concentrated semen (1.46 × 109 spermatozoa/mL) with low motility (5%), 14% of major defects, and 57% of minor defects. Plugged ampullae were suggested, and the treatment was performed by ampullae massage per rectum and three consecutive semen collections associated with the parenteral use of oxytocin 20 IU iv, aiming to discharge the semen accumulation. Daily regimen of semen collection was recommended during 10 days, and after this time, semen was collected at least three times a week. The semen parameters restored to normal (80% motility) after 30 days. The donkey jack returned to the breeding season with a regimen of 3 days a week of semen collection. Department of Animal Reproduction and Veterinary Radiology College of Veterinary Medicine and Animal Science Univ Estadual Paulista (UNESP) Department of Animal Reproduction and Veterinary Radiology College of Veterinary Medicine and Animal Science Univ Estadual Paulista (UNESP) more...

Published
2018
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9. Unveiling the efficiency of microwave-assisted hydrothermal treatment for the preparation of SrTiO

Author

Luís F, da Silva, Ariadne C, Catto, Waldir, Avansi, Alexandre, Mesquita, Lauro J Q, Maia, Osmando F, Lopes, Máximo Siu, Li, Mário L, Moreira, Elson, Longo, Juan, Andrés, and Valmor R, Mastelaro

Abstract

Material processing has become essential for the proper control, tuning and consequent application of the properties of micro/nanoparticles. In this case, we report herein the capability of the microwave-assisted hydrothermal (MAH) method to prepare the SrTiO3 compound, as a case study of inorganic compounds. Analyses conducted by X-ray diffraction, X-ray photoelectron and X-ray absorption spectroscopies confirmed that the MAH route enables the formation of pristine SrTiO3. The results indicated that the combination of thermal and non-thermal effects during the MAH treatment provides ideal conditions for an efficient and rapid synthesis of pristine SrTiO3 mesocrystals. Scanning electron microscopy images revealed a cube-like morphology (of ca. 1 μm) formed via a self-assembly process, influenced by the MAH time. Additionally, photoluminescence measurements revealed a broad blue emission related to intrinsic defects, which decreased with the MAH synthesis time. more...

Published
2019

10. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

Author

Fernanda C. Romeiro, Luís F. da Silva, Renata C. Lima, Poliana G. Freire, Juliane Z. Marinho, Elson Longo, Ana Paula de Moura, Rodrigo A.A. Munoz, Samantha C.S. Lemos, Universidade Federal de Uberlândia (UFU), and Universidade Estadual Paulista (Unesp) more...

Subjects
Materials science, Photoluminescence, Inorganic chemistry, Doping, Nanoparticle, Carbon nanotube, Condensed Matter Physics, Electrochemistry, Electronic, Optical and Magnetic Materials, law.invention, Electrochemical gas sensor, Inorganic Chemistry, symbols.namesake, Microwave hydrothermal, Electrochemical sensor, law, Zinc oxide, Materials Chemistry, Ceramics and Composites, symbols, Nanoparticles, Hydrothermal synthesis, Physical and Theoretical Chemistry, Raman spectroscopy
Abstract

Made available in DSpace on 2018-11-27T00:47:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Brazilian Nanotechnology National Laboratory, LNNano, Campinas, SP, Brazil We report for the first time a rapid preparation of Zn1-2xCoxNixO nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green-orange-red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. (C) 2015 Elsevier Inc. All rights reserved. Univ Fed Uberlandia, Inst Quim, BR-38400902 Uberlandia, MG, Brazil Univ Estadual Paulista, LIEC, Inst Quim, BR-14800900 Araraquara, SP, Brazil Univ Estadual Paulista, LIEC, Inst Quim, BR-14800900 Araraquara, SP, Brazil FAPEMIG: APQ-00988-13 FAPEMIG: CEX - RED-00010-14 Brazilian Nanotechnology National Laboratory, LNNano, Campinas, SP, Brazil: XPS-18304 more...

Published
2015
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11. Fingerprints of short-range and long-range structure in BaZr1−xHfxO3 solid solutions: an experimental and theoretical study

Author

Rafael Uarth Fassbender, Tatiane Strelow Lilge, Juan Andrés, Mário Lúcio Moreira, Valmor Roberto Mastelaro, Sergio Cava, Luís F. da Silva, and Elson Longo

Subjects
Assisted hydrothermal method, Bazro3, Crystal chemistry, Analytical chemistry, General Physics and Astronomy, NANOPARTÍCULAS, Crystal structure, symbols.namesake, Physical and Theoretical Chemistry, High-resolution transmission electron microscopy, Spectroscopy, Photoluminescence, Decaoctahedron shape, Extended X-ray absorption fine structure, Chemistry, XANES, Chemical physics, symbols, Density of states, Nanoparticles, Raman spectroscopy, Microwave, Electronic-structure, Air batteries
Abstract

A microwave-assisted hydrothermal method was applied to synthesize BaZr1xHfxO3, (BZHO) solid solutions at a low temperature, 140 1C, and relatively short times, 160 min. The detailed features of the crystal structure, at both short and long ranges, as well as the crystal chemistry doping process, are extensively analysed. X-ray diffraction measurements and Raman spectroscopy have been used to confirm that pure and Hf-doped BZO materials present a cubic structure. Extended X-ray absorption fine structure (EXAFS) spectra indicate that Hf4+ ions have replaced the Zr4+ ions on the 6-fold coordination and a subsequent change on the Ba2+ 12-fold coordination can be sensed. X-ray absorption near-edge structure (XANES) spectroscopy measurements reveal a local symmetry breaking process, associated to overlap of the 4d–2p and 5d–2p orbitals of Zr–O and Hf–O bonds, respectively. Field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM) show the mesocrystalline nature of self-assembled BZHO nanoparticles under a dodecahedron shape. In addition first principle calculations were performed to complement the experimental data. The analysis of the band structures and density of states of the undoped BZO and doped BZHO host lattice allow deep insight into the main electronic features. The theoretical results help us to find a correlation between simulated and experimental Raman modes and allow a more substantial interpretation of crystal structure. Brazilian research funding institution FAPESP. 2009/17752-0 FAPERGS. 2031-2551/13-9SIAS CNPq (MCT/CNPq). 458452/2014-9 Generalitat Valenciana. Prometeo/2009/053 Ministerio de Ciencia e Innovacion. CTQ-2012-36253-C03-01 Programa de Cooperacion Cientificacon Iberoamerica (Brazil), Ministerio de Educacion. PHB2009-0065-PC more...

Published
2015
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12. The Role of Nb Addition in TiO2 Nanoparticles: Phase Transition and Photocatalytic Properties (Phys. Status Solidi A 21∕2018)

Author

João Elias Figueiredo Soares Rodrigues, Maria Inês Basso Bernardi, Valmor Roberto Mastelaro, Ariadne C. Catto, Luís F. da Silva, and Waldir Avansi

Subjects
Phase transition, Materials science, 010405 organic chemistry, Tio2 nanoparticles, Surfaces and Interfaces, 010402 general chemistry, Condensed Matter Physics, 01 natural sciences, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Chemical engineering, Materials Chemistry, Photocatalysis, Electrical and Electronic Engineering
Published
2018
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13. El arte rupestre esquemático del Arroyo Barbaón (Parque Nacional de Monfragüe, Cáceres): contextualización arqueológica y caracterización de pigmentos

Author

Hipólito COLLADO GIRALDO, Pierluigi ROSINA, José Julio GARCÍA ARRANZ, Hugo GOMES, Luis F. da SILVA NOBRE, Isabel M. DOMÍNGUEZ GARCÍA, David DUQUE ESPINO, José M.ª FERNÁNDEZ VALDÉS, Emilia BLASCO LAFFÓN, José María TORRADO CÁRDENO, Lázaro RODRÍGUEZ DORADO, Esther RIVERA RUBIO, Magdalena NACARINO DE LOS SANTOS, José Enrique CAPILLA NICOLÁS, and Samuel PÉREZ ROMERO more...

Subjects
pintura esquemática, funcionalidad del arte rupestre, arqueometría, técnicas pictóricas, microfluorescencia-x, espectroscopia raman, microestratigrafía, Archaeology, CC1-960
Abstract

El Parque Nacional de Monfragüe (Cáceres) conserva un importante complejo de arte rupestre formado por más de un centenar de abrigos con pinturas y grabados postpaleolíticos. En el presente trabajo vamos a dar a conocer un avance de las conclusiones obtenidas en las últimas campañas de investigación llevadas a cabo en el sector del cañón del Arroyo Barbaón (Serradilla). En él se ha procedido a la documentación digital de las representaciones pictográficas de sus 29 abrigos. Además, a través de las excavaciones realizadas en el interior de la Cueva del Sapo, que han proporcionado diversos materiales cerámicos y líticos, así como los restos de un hogar, se intenta contextualizar arqueológicamente el conjunto de arte rupestre. Finalmente, el hallazgo en el abrigo Friso del Terror de un fragmento de cuarcita desprendido que conservaba algunos trazos pintados ha permitido realizar análisis para caracterizar el pigmento que fue utilizado en su elaboración. Con estas aportaciones pretendemos una aproximación más precisa a cuestiones como las técnicas de realización, cronología y funcionalidad de la pintura esquemática en este espacio natural cacereño. more...

Published
2015
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14. Discordance Between the Initial Diagnosis of Sarcomas and Subsequent Histopathological Revision and Molecular Analyses in a Sarcoma Reference Center in Brazil

Author

Carlos Diego H. Lopes, Marcello M. Queiroz, Luana A.F. Sampaio, André Perina, Eduardo Akaishi, Frederico Teixeira, Fábio de O. Ferreira, Samir A. Hanna, João Luís F. da Silva, Luiz Guilherme C.A. De Lima, Claudia Regina G.C.M. de Oliveira, and Rodrigo R. Munhoz more...

Subjects
Neoplasms. Tumors. Oncology. Including cancer and carcinogens, RC254-282
Abstract

PURPOSETo investigate the discordance in sarcoma diagnoses between nonspecialized institutions following revision by dedicated sarcoma pathologists at a reference center in Brazil and the relevance of molecular pathology in this context.METHODSWe conducted a retrospective analysis of sarcoma samples initially analyzed at outside laboratories and subsequently reviewed by two specialized pathologists between January 2014 and December 2020. After obtaining demographic and tumor characteristics, pathology results were matched and classified as complete discordance (CD; benign v malignant, sarcoma v other malignancies), partial concordance (similar diagnosis of connective tumor, but different grade/histological subtype/differentiation), and complete concordance (CC). The concordance for histology or grade, and the role of molecular assessments supporting the diagnosis were also independently determined. Statistical analyses were conducted through the kappa coefficient of agreement and adherence by χ2 test, χ2 test by Person, and Fisher exact test.RESULTSIn total, 197 cases were included, with samples obtained predominately from male patients (57.9%) and localized/primary tumors (86.8%). Following revision, the most frequent final diagnoses were undifferentiated pleomorphic sarcoma (17.8%), well-differentiated/dedifferentiated liposarcoma (8.6%), and leiomyosarcoma (7.6%). CD was found in 13.2%, partial discordance in 45.2%, and CC in 41.6% of reviews (P < .001). We found a concordance for histology or grade of 53.5% (P < .001) and 51.8% (P < .001), respectively. Molecular assessments, comprising next-generation sequencing panels (79.5%) and fluorescent in situ hybridization (20.5%), were performed in 44 (22.3%) cases, with findings classified as of diagnostic relevance in 31.8%.CONCLUSIONIn nearly 60% of the cases, the initial sarcoma diagnosis was modified when revised by a reference center and dedicated pathologists, assisted by molecular pathology techniques. These results justify the assembly of referral networks in countries with limited health care resources. more...

Published
2024
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