Search results for "Nanostructured material"

From Maya Blue to “Maya Yellow”: A Connection between Ancient Nanostructured Materials from the Voltammetry of Microparticles

2011

The yellow hue of a series of samples from wall paintings in several Mayan archaeological sites can be attributed to the presence of indigoid compounds, including isatin and dehydroindigo, attached to palygorskite, a local phyllosilicate clay. SEM/EDX, TEM, UV/Vis spectroscopy, and voltammetry of microparticles show that the ancient Mayas could prepare indigo, Maya Blue, and "Maya Yellow" during successive stages. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Negative pressures in CaWO4 nanocrystals

2009

Tetragonal scheelite-type CaWO4 nanocrystals recently prepared by a hydrothermal method show an enhancement of its structural symmetry with the decrease in nanocrystal size. The analysis of the volume dependence of the structural parameters in CaWO4 nanocrystals with the help of ab initio total-energy calculations shows that the enhancement of the symmetry in the scheelite-type nanocrystals is a consequence of the negative pressure exerted on the nanocrystals; i.e., the nanocrystals are under tension. Besides, the behavior of the structural parameters in CaWO4 nanocrystals for sizes below 10 nm suggests an onset of a scheelite-to-zircon phase transformation in good agreement with the predic…

Photoluminescent hybrid nanomaterials from modified halloysite nanotubes

2018

The synthesis of photoluminescent nanomaterials based on halloysite nanotubes is described. The obtained hybrid was characterized by means of TGA, FT-IR, DLS and XPS measurements; in addition its morphology was imaged by TEM and HR-TEM. The HNT hybrid also exhibited photoluminescent properties, both in solution and in the solid state, and white-light emission (0.24, 0.36; CIE coordinates) was observed. This work could be pioneering as a new strategy for manufacturing both LEDs and fluorescent tags based on HNT nanomaterials. © 2018 The Royal Society of Chemistry.

Pulsed-field studies of the magnetization reversal in molecular nanomagnets

2004

We report experimental studies of crystals of Mn12 molecular magnetic clusters in pulsed magnetic fields with sweep rates up to 4x10^3 T/s. The steps in the magnetization curve are observed at fields that are shifted with respect to the resonant field values. The shift systematically increases as the rate of the field sweep goes up. These data are consistent with the theory of the collective dipolar relaxation in molecular magnets.

Nanostructured Ni-Co Alloy Electrodes Fabrication and Characterization for both Hydrogen and Oxygen Evolution Reaction in Alkaline Electrolyzer

2019

Sun and wind as power sources are becoming more and more relevant owing to the progressive abandoning of the fossil fuels [1,2]. Additionally, worldwide public authorities are encouraging the use of renewable energies by promoting laws and guidelines [3,4]. In this scenario, a fundamental role can play hydrogen that besides being a valuable energy carrier, it can also act as a storage medium to balance the discontinuity affecting the renewable energy sources production [5]. As a consequence, cheap and abundant availability of hydrogen is crucial. Electrochemical water splitting is likely one of the most valuable technique to produce hydrogen because the process is environmentally friendly b…

NANOSTRUCTURED ELECTRODES FOR HYDROGEN PRODUCTION IN ALKALINE ELECTROLYZER

Nanostructured Materials Obtained by Electrochemical Methods: From Fabrication to Application in Sensing, Energy Conversion, and Storage

2020

It is well known that physical and surface properties of nanomaterials are promising to enhance efficiency of nanostructured devices for sensing and for sustainable energy production, conversion, and storage. However, the practical use of nanomaterials is often complicated by the lack of scalable and cost-efficient synthesis procedures and the challenge of integrating into devices 1D nanomaterials saving their structural features. In this field, one of the most severe challenges is to find suitable methods for fabricating nanomaterials. Over the years, numerous preparation methods were proposed in the literature, but not all of them are easily scalable and economically advantageous for indu…

Nanostructured Electrochemical Devices for Sensing, Energy Conversion and Storage

2016

Nanostructured materials are attracting growing interest for improving performance of devices and systems of large technological interest. In this work, the principal results about the use of nanostructured materials in the field of electrochemical energy storage, electrochemical water splitting, and electrochemical sensing are presented. Nanostructures were fabricated with two different techniques. One of these was the electrodeposition of the desired material inside the channels of a porous support acting as template. The other one was based on displacement reaction induced by galvanic contact between metals with different electrochemical nobility. In the present work, a commercial polyca…

Nanostructured binary tin alloy fabrication

2010

The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings

2004

We investigate the effect of a thin alumina coating of nanocrystalline TiO2 films on recombination dynamics of dye-sensitized solar cells. Both coated and uncoated cells were measured by a combination of techniques: transient absorption spectroscopy, electrochemical impedance spectroscopy, and open-circuit voltage decay. It is found that the alumina barrier reduces the recombination of photoinjected electrons to both dye cations and the oxidized redox couple. It is proposed that this observed retardation can be attributed primarily to two effects: almost complete passivation of surface trap states in TiO2 that are able to inject electrons to acceptor species, and slowing down by a factor of…