Noemi Walsöe de Reca

National Scientific and Technical Research Council | conicet · CINSO-CITEDEF-CONICET

A solution growth approach for zinc oxide (ZnO) nanowires is highly appealing because of the low growth temperature and possibility for large area synthesis. In our work, ZnO nanowires were obtained from thin films prepared on silica glass, Si (100) and Si (111) from a single and five layers spin-coating deposition of a sol–gel prepared with dehydr...

ZnO is a versatile material used in numerous applications, such as antireflective coatings, transparent electrodes for solar cells, gas sensors, varistors and electro and photoluminescent devices. One of the most important properties of ZnO is the photoconductivity in the UV, due to the band-gap energy.

It is known that fats and oils, when submitted to prolonged heat, are subjected to a series of chemical–physical modifications, generating changes in sensory and nutritional characteristics. The aim of the present research was to develop an accurate and repeatable method to predict appearance of undesired odour when extra‐virgin olive oils from Arb...

From my early childhood I wanted to imitate my parents: my mother for her femininity and aptness to teach and my father for his will power and ability as a chemist. My goal was to be as accomplished as my parents. At the state secondary school, I received the diploma to be a teacher for primary education; afterwards, I studied Chemistry at the Facu...

The aim of the present research was to evaluate bovine muscles to be subjected to freeze-drying for an instant meal. Physicochemical and senescence parameters were evaluated. The experimental part was divided into two steps. In the first step, the Semitendinosus muscle was chosen to establish methodology and experimental conditions. Physicochemical...

Nanocrystalline pure and doped SnO2 have been intensively studied for a long time to build resistive gas sensors. However, it is still useful to synthesize nanopowders with the smallest crystallite size to build devices. A modified gel-combustion method and a novel reactive oxidation process are proposed for nanopowders synthesis and results are co...

Response of metal-oxide sensors based on tin dioxide ${rm SnO}_{2}$ (P and T) and chromium titanium oxide, and on tungsten oxide (LY) were used to analyze different cultivars of garlic scapes. Temperature and time for sample incubation were set at two temperatures (40 $^{circ}{rm C}$ and 50 $^{circ}{rm C}$ ) and at two incubation times (6 and 10 mi...

Pure ZnO have been prepared on amorphous SiO2 substrates from a precursor solution of dihydrated zinc acetate and absolute alcohol. The sol was deposited on the substrates by the spin-coating technique. After de deposit of each layer, a drying treatment was performed at 200 °C for10 min, to solidify the deposited material. Finally, all the specimen...

An assay based on an electronic olfactory system was set to evaluate tomato fruits by sensing the aromatic volatiles during postharvest storage of 21 days at 19 ± 0.5 ∘ C in darkness. Olfactory system measurements were coupled with colour values. Odour profile and senescence parameters were carried out at 7-day intervals. Discriminant function anal...

The aim of this paper was to describe the methods of nanocrystalline SnO 2 preparation and to show the improvement of the behaviour of a hydrogen sensor built with the grown SnO 2 nanoparticles since particular properties of the nanomaterial are related to the sensor response. Nanocrystalline SnO 2 was synthesized by gel-combustion and by reactive...

In previous works, the authors improved the characteristics of resistive gas sensors using SnO 2 nanoparticles to build them. Upon the convenience to increase the surface dimension to enhance the gas absorption area, well aligned SnO 2 nanotubes were prepared by sol-gel method within the pores of a polycarbonate template to increase the sensing sur...

The synthesis of ZnO nanoparticles by a modified gel-combustion method and the preparation of ZnO nanomorphologies using a combination of sol-gel and membrane template method are reported. Optimization of the synthesis parameters and characterization of the materials by X-Ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM) an...

The electronic nose emerged in the mid 80's due that the food industry needed quicker instruments to be applied in food control for the characterization of smell, in order to complement the work done by human panels. But scientific researchers noticed that electronic nose could also be used in other fields, such as environmental contamination, heal...

The aim of the performed work was to evaluate with an electronic nose changes in odor profile of Arauco and Arbequina varieties of extra‐virgin olive oil during deep‐frying. Changes in odor were analyzed using an electronic nose composed of 16 sensors. Volatile compounds were analyzed by SPME‐GC‐FID. Principal Component Analysis was applied for ele...

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Two applications of nanostructured ceramic materials developed at CINSO in recent years are reviewed, including the synthesis and properties of these materials:(i)Application of nanostructured SnO2-based semiconductors for gas sensors, showing the increase of their sensitivity and the decrease of their operating temperature if the sensor is built w...

Olives are one of the main cultivation crops across the Mediterranean region and have been occupying an essential part in the diet of people in addition to their economy and culture for years. Besides food, olive oil has been used in various parts of daily life, such as medicines, fuel source, cosmetics, soap and even religious rituals. Olive oil i...

ZnS is a useful II-VI compound for optical devices. Due to its strong fluorescence and high resistance to electric fields, it is a material with interesting applications for solar cells, IR windows, lasers and sensors. ZnS has a low excitonic Bohr radius (2.5 nm) so their nanoparticles are appropriate to produce small bio-molecular probes for fluor...

Iron–cobalt-based perovskite oxides with general formula Ln0.7Sr0.3Fe0.8Co0.2O3−δ (where Ln=La, Pr and Gd) have been investigated for their application as intermediate-temperature cathodes in solid oxide fuel cells (SOFCs). Powdered samples of these materials were synthesized by a novel gel combustion process and then characterized by X-ray powder...

In this work, an original route for ZnO nanostructured spherical colloids and their assembly into colloidal crystals are presented. The temporal evolution of crystal size and shape was followed by X-ray diffraction and the colloids size distribution by scanning electron microscopy. These spherical colloids showed a change in their size dispersion w...

Start Nano-scaled ZnO with 1% Er doping was prepared by soft chemistry methods. The synthesis was carried out in anhydrous polar solvent to achieve a crystal size of a few nanometers. Resulting particles were processed as precipitates or multi layer films. Structural characterization was evaluated by X-Ray diffraction and transmission and scanning...

In this research work, changes in odour and degradation of tocopherols (α and γ) were evaluated in extra-virgin olive oil of Arauco and Arbequina varieties. Oils were exposed to light and darkness during 120 days. Odour changes were monitored using an electronic nose and volatile compounds by Solid Phase Microextraction-Gas Chromatography (SPME). T...

Bees use signals from plants to identify worthwhile visits. They learn quickly to differentiate mainly their floral odor than their colour. In some species the flowers remain open, intact and turgid until they are pollinated (anthesis) after which they are no longer attractive to pollinators (post‐anthesis). Pollinators use fragrance for distance o...

Changes in odour of Arauco (ARA) and Arbequina (ARB) extra-virgin olive oil (OO) were monitored during frying by electronic nose (EN) and solid-phase microextraction–gas chromatography methodologies. Degradation of α- and γ-tocopherols was monitored by HPLC. Electronic nose data and volatile compounds were analysed at intervals of 15 min (t15) duri...

PdONiOSDC composites (SDC: Sm2 O3 -doped Ce O2) have been proposed to be excellent anodes for single-chamber, intermediate-temperature solid oxide fuel cells (SC-IT-SOFCs) operated under mixtures of C H4 and air, reaching high power densities at relatively low working temperatures. In this work we evaluated the catalytic activity of these composite...

The ionic transport properties of dense nanocomposites of yttria-doped ceria (YDC) and yttria-stabilized zirconia (YSZ), in a volume ratio of 1 : 1, have been investigated by electrochemical impedance spectroscopy. These materials were prepared by means of a fast-firing process starting from nanopowders with high specific surface area, avoiding the...

The crystal structure and the local atomic order of a series of nanocrystalline ZrO 2 –CaO solid solutions with varying CaO content were studied by synchrotron radiation X-ray powder diffraction and extended X-ray absorption fine structure (EXAFS) spectroscopy. These samples were synthesized by a pH-controlled nitrate–glycine gel-combustion process...

The development of active and selective catalysts for methane partial oxidation is one of today's challenges, because these catalysts could be used either for hydrogen production purposes or as anode materials in single-chamber solid oxide fuel cells (SOFCs).In this work, the synthesis of ceria–zirconia solid solutions of nominal composition Ce0.9Z...

Crystal and local structures (long- and short-range order, respectively) of four nanocrystalline zirconia-based solid solutions—ZrO2-6 and 16 mol % CaO and ZrO2-2.8 and 12 mol % Y2O3—synthesized by a pH-controlled nitrate-glycine gel-combustion process were studied. These materials were characterized by synchrotron X-ray diffraction (XRD) and exten...

Crystal structure of compositionally homogeneous, nanocrystalline ZrO2–CeO2 solutions was investigated by X-ray powder diffraction as a function of temperature for compositions between 50 and 65 mol % CeO2. ZrO2-50 and 60 mol % CeO2 solid solutions, which exhibit the t′-form of the tetragonal phase at room temperature, transform into the cubic phas...

The transition between tetragonal and cubic phases in nanostructured ZrO2-Sc2O3 solid solutions by high-temperature X-ray powder diffraction using synchrotron radiation is presented. ZrO2-8 and 11 mol% Sc2O3 nanopowders that exhibit the t′- and t″-forms of the tetragonal phase, respectively, were synthesized by a stoichiometric nitrate-lysine gel-c...

Single-chamber SOFCs have received much attention in recent years due to their simple design and low cost. In this work, we evaluated single-chamber SOFCs that operate in methane/air mixtures at high temperatures (900-1000{degree sign}C). YSZ was used as electrolyte, La0.8Sr0.2MnO3 as cathode, and NiO and NiO/ZrO2-50; 70 or 90 mol% CeO2 composites...

In recent years, new concepts have been explored in order to find anodes adequate for operation with hydrocarbon fuels with high catalytic activity at intermediate temperatures, since the usual internal reforming of methane requires very high temperatures. In this sense, single-chamber SOFCs have attracted great attention because they take advantag...

Iron-cobalt-based perovskite materials with different A-site cations Ln0.7Sr0.3Fe0.8Co0.2O3-δ (Ln = La, Pr and Gd) were investigated for SOFC application as intermediate temperature cathodes. These samples were synthesized by a novel gel combustion process and characterized by X-ray diffraction. The diffraction patterns of the samples were indexed...

We investigated the performance of Ag/La0.6Sr0.4Co1-xFexO3 (x = 0;0.8) nanotube composite cathodes using samaria-doped ceria as electrolyte. These composites were prepared by mixing a commercial Ag paste and La0.6Sr0.4Co1-xFexO3 (x = 0;0.8) nanotubes synthesized by the pore wetting technique using plastic templates. Electrochemical impedance spectr...

A new generation of nanostructured cathodes for intermediate temperature solid-oxide fuel cells, with very low polarization resistance, is presented. They were prepared from cobaltite nanotubes using a fast and simple method that allows the retention of the original nanostructure.

The enhancement of the total ionic conductivity in nanostructured heavily doped dense ceria pellets was investigated. The physical mechanism behind the remarkable enhancement of the ionic conductivity in nanostructured oxide-ion solid electrolytes was proposed. The transport properties of heavily doped CeO2-based nanoceramics were studied by EIs me...

The crystal structure of pure (undoped) zirconia nanopowders synthesized by different wet-chemical routes has been investigated by synchrotron X-ray diffraction. Whereas some previous authors reported the retention of the cubic phase in similar materials, we demonstrate here that pure zirconia nanopowders with average crystallite sizes ranging from...

Compositionally homogeneous ZrO2–CeO2 nanopowders have been characterized by Raman and extended x-ray absorption fine structure (EXAFS) spectroscopies. These techniques revealed a tetragonal-to-cubic phase transition as a function of CeO2 content, as observed in a previous synchrotron x-ray diffraction study. The tetragonal–cubic phase boundary was...

The electrical properties of nanostructured, heavily yttria- or samaria-doped ceria ceramics are studied as a function of grain size using electrochemical impedance spectroscopy (EIS). A remarkable enhancement in the total ionic conductivity of about one order of magnitude is found in nanostructured samples, compared with the intrinsic bulk conduct...

Zr{sub 0.85}Ce{sub 0.15}O{sub 2} nanopowders synthesised by gel-combustion and spray-pyrolysis methods were comparatively studied by means of X-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, specific surface area measurements, scanning and transmission electron microscopies and chemical analysis. Fully tet...

The crystal structures of a number of nanocrystalline ZrO2–CeO2 solid solutions, synthesized by a pH-controlled nitrate-glycine gel-combustion process, were studied. By using a synchrotron X-ray diffractometer, small peaks of the tetragonal phase, which correspond to forbidden reflections in the case of a perfect cubic fluorite structure, were clea...

Solid oxide fuel cells have a promissory future in the direct combustion of fuels but, their main drawbacks are the high operation temperature and the rapid performance degradation due to carbon deposition in the anode. The development of ceria-based anodes with good electronic conductivity at lower temperatures seems to be a promising way to solve...

A nanocrystalline ZrO2–10 mol% Y2O3 powder synthesized by a nitrate–citrate gel-combustion process and stabilized in the metastable t′′-form of the tetragonal phase has been characterized using mainly the Perturbed Angular Correlations technique. The determined hyperfine interaction allows a clear distinction between the zirconium surroundings in t...

In the last decades, a new interest in active components of phytodrugs as well as in the control of their quality has pointed out new ways to identify and characterize natural plants which, till present, did not fulfill the claimed specifications—Valerians among them. Valerians exhibit numerous and traditional medical uses. In this paper, the use o...

Samples of piles from the Biosolids Composting Plant of Bariloche city (Rı́o Negro, Argentina) have been analyzed with an electronic nose to detect differences in the evolution of the thermophilic period. Gas chromatography followed by mass spectroscopy, enabled to identify organic compounds present in each stage.The aim of this work was (I) to ass...

materials. Particularly, in case of nanostructured ceramics, the presence of a large fraction of grain boundaries (GB) can lead to unusual or better properties. One growing area of investigation is the ionic transport in nanostructured solid electrolytes (nanoionics) with important applications, solid oxide fuel cells (SOFCs), among them, since an...

The synthesis of nanocrystalline ZrO2–15 mol% CeO2 powders by a pH-controlled nitrate–glycine gel-combustion process was investigated. It was found that the metastable tetragonal phase could be fully retained probably due to the small crystallite size of the powders (5–8 nm). The effect of the glycine content and calcination temperature on powder m...

En las últimas décadas, ha surgido un renovado interés en los componentes activos de las fitodrogas así como la necesidad de un mayor control de calidad, exigiendo nuevas formas de caracterizar las plantas naturales para que llenen las especificaciones terapéuticas requeridas. Entre las plantas medicinales se encuentran las valerianas las que exhib...

Ordered structures, CuPt and CuAu I types in HgCdTe are reported for the first time. Hg1−xCdxTe thin crystals were grown by isothermal vapour phase epitaxy (ISOVPE) method on a CdTe substrate and they were observed by transmission electron microscopy (TEM) in planar view and cross-sectional geometries. Two variants of CuPt-type ordered structure we...

The crystal structure of compositionally homogeneous, nanocrystalline ZrO2–10, 30, 50, 70 and 90 mol% CeO2 powders synthesised by a pH-controlled nitrate–glycine gel-combustion process has been studied by X-ray diffraction and Raman spectroscopy. All the powders with a CeO2 content up to 70 mol% exhibited the tetragonal phase (P42/nmc space group),...

The aim of this work was to study the stability of the tetragonal phase in nanocrystalline ZrO2 - 2 to 15 mol% CeO2 powders, synthesized by a nitrate-glycine gel-combustion process. Phases present in these materials were analyzed by X-ray diffraction and Roman spectroscopy. The average crystallite sizes of all the powders were in the range 8-14 nm....

The characterization of a ceremonial bronze axe is described. The axe is assigned to the Santamarian culture of north-west Argentina, c. 1000–1470 ad, and was selected to increase presently limited knowledge of prehistoric metallurgy in the Andean region of Argentina. The characterization methods used were electron probe microanalysis, gamma radiog...

HgCdTe (MCT) is an important semiconductor material used for infrared photovoltaic detectors. Although ion implantation is a widely used technique in the manufacture of devices based on MCT to obtain n/p junctions, a detailed understanding of the n-type behavior of the unannealed damage region has not yet been established. In this work, n/p junctio...

In this work, the synthesis of CeO2–10 mol% Y2O3 powders by a nitrate–glycine gel-combustion route was investigated. Special attention was given to the influence of the glycine/metal ratio and calcination temperature on powder morphology. In contrast to the usual reported behavior, the best powder properties (crystallite size, 4.5–7 nm; specific su...

Two nitrate–citrate gel combustion routes for the synthesis of nanocrystalline SnO2 powders were compared. Metallic tin and tin dichloride were used as raw materials. The combustion process was more intense for the metallic tin route, resulting in smaller crystallite size (10.5 nm) and higher specific surface area (49.4 m2/g). The presence of chlor...

Compositionally homogeneous, nanocrystalline ZrO2-35 mol% CeO2 powders were synthesized by gel-combustion synthesis. As a result, highly reactive, compositionally homogeneous powders were produced.

The crystal structure of compositionally homogeneous, nanocrystalline ZrO2 - X mol% Y2O3 (X = 2.8, 4, 5, 6, 7, 8, 9, 10, 11, and 12) powders synthesized by a nitrate-citrate gel-combustion process has been studied by X-ray diffraction. By applying the Rietveld method, it was found that all the powders presented the tetragonal phase (P4 2/nmc space...

The advances in the technology of multisensor arrays and neural computation have allowed the development of “electronic noses”, which has enabled the discrimination of compounds by their odours and consequently, has played a fundamental role in the environmental monitoring. An electronic nose MOSES II (MOdular SEnsor System) with two arrays of eigh...

An X-ray study of the solid solution CsxCu(1−x)Cl was carried out to determine the powder diffraction peaks (hkl indices) pertaining to the intermediate compound CsCu2Cl3. This phase forms at 623 K and can be retained at room temperature as a single phase.

A nitrate–citrate combustion route to synthesise nanocrystalline yttria-doped zirconia powders for tetragonal zirconia polycrystal (TZP) ceramics is presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction b...

The synthesis and structural properties of zirconia-based nanocrystalline powders and fine-grained ceramics are reviewed, emphasizing the conditions required for the retention of the high temperature tetragonal and cubic phases, which are the most important ones for applications. Different methods for the synthesis of powders (coprecipitation, amor...

The crystal structure of compositionally homogeneous, nanocrystalline ZrO2–12 mol% Y2O3 powders was studied by X-ray diffraction. By applying the Rietveld method, it was found that these powders present a tetragonal phase with an axial ratio of unity, but with the oxygen ions displaced from their ideal fluorite positions along the c-axis (t″-form o...

A novel synthesis method for preparing nanocrystalline SnO2 powders by means of a nitrate-citrate gel-combustion process is presented. SnO2 powders with an average crystallite size of 10nm were obtained. The influence of ignition temperature, fuel content in the precursor mixture and calcination temperature on the characteristics of the powders was...

A novel method to obtain nanocrystalline SnO2 powders based on a gel-combustion process is presented. It consists of a rapid combustion of a gel formed by a salt of the desired metal and an organic fuel. Two fuels, citric acid and glycine, with different molar ratios of tin/fuel ranging were studied. Average crystallite sizes were in the range 6-30...

Diffusion processes and their importance on the properties of II-VI (binary and ternary) semiconductors are reported taking in mind that their control is a main problem in the characterization of the different stages of optoelectronic devices manufacture. References are given on the II-VI compounds crystalline structure, crystallographic polarity a...

In this work, wet-chemical methods to obtain yttria or calcia-doped zirconia powders for partially stabilized zirconia ceramics are presented. They are based on pyrolisis of nitrate solutions with the addition of citric acid or glycine as a fuel. Powders were characterized by X-ray diffraction and scanning electron microscopy, finding that tetragon...

Single crystalline epitaxial films of Hg 1-xCd xTe (MCT) with x ≃ 0.2 were grown on CdTe, CdZnTe and CdTeSe (100) substrates by ISOV-PE technique (isothermal vapor phase epitaxy) without Hg overpressure. Substrates and films were structural and electrical characterized, the latter by Hall effect measurements. The grown material has good electrical...

The preparation of tetragonal zirconia polycrystal (TZP) ceramics stabilized by the addition of calcia is presented. These novel ceramics were obtained by means of a fast-firing treatment applied to compacts of nanocrystalline powders with a composition of ZrO2 — 4 mol% CaO. Powders were synthesized by a nitrate-citrate gel-combustion process and t...

MCT epitaxial films have been obtained on CdTe substrates with (111)Cd, (111)Te, (100) and (110) crystalline orientations and on Cd0.96Zn0.04Te and CdTe0.96Se0.04 substrates with (111)Cd and (110) crystalline orientations by the ISOVPE technique without Hg overpressure. The misfit dislocation distribution in the MCT films interface has been obtaine...

MCT epitaxial films have been grown on CdTe, Cd0.96Zn0.4Te and CdTe0 96Se0 04 substrates with (111)Cd, (111)Te, (100) and (110) crystalline orientations by the ISOVPE technique without Hg overpressure. The misfit dislocation distribution in the MCT films interface has been obtained on the cleaved preferential surfaces of the {110} by chemical etchi...