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1.
Langmuir ; 35(49): 16256-16265, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31696717

RESUMO

The design of high-performance energy-converting materials is an essential step for the development of sensors, but the production of the bulk materials currently used remains costly and difficult. Therefore, a different approach based on the self-assembly of nanoparticles has been explored. We report on the preparation by solvothermal synthesis of highly crystalline CeF3 nanodiscs. Their surface modification by bisphosphonate ligands led to stable, highly concentrated, colloidal suspensions in water. Despite the low aspect ratio of the nanodiscs (∼6), a liquid-crystalline nematic phase spontaneously appeared in these colloidal suspensions. Thanks to the paramagnetic character of the nanodiscs, the nematic phase was easily aligned by a weak (0.5 T) magnetic field, which provides a simple and convenient way of orienting all of the nanodiscs in suspension in the same direction. Moreover, the more dilute, isotropic, suspensions displayed strong (electric and magnetic) field-induced orientation of the nanodiscs (Kerr and Cotton-Mouton effects), with fast enough response times to make them suitable for use in electro-optic devices. Furthermore, an emission study showed a direct relation between the luminescence intensity and magnetic-field-induced orientation of the colloids. Finally, with their fast radiative recombination decay rates, the nanodiscs show luminescence properties that compare quite favorably with those of bulk CeF3. Therefore, these CeF3 nanodiscs are very promising building blocks for the development and processing of photosensitive materials for sensor applications.

2.
ACS Appl Mater Interfaces ; 10(38): 32304-32312, 2018 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-30180538

RESUMO

The intrinsic properties of silica aerogels make them well suited for applications requiring high surface area. Therefore, the dispersion of functional nanoparticles (NPs) in these highly porous structures gives access to materials for wide range of applications such as catalysis, energy storage or sensing. The last one is particularly interesting if such composites possess good optical quality. Herein, the synthesis of monolithic and transparent silica aerogels highly loaded with Y3Al5O12:Ce nanocrystals (NCs) (up to 50 wt %) is reported. The developed composite aerogels can be impregnated with liquids, contrary to most of existing aerogels, which crack because of the strong capillary forces. Therefore, this system is designed as a novel concept of 3D porous scintillator, using the efficient photoluminescent and scintillating properties of Y3Al5O12:Ce. The investigated fluid containing low-energetic ionizing radiation emitters impregnates the material, which assures the efficient harvesting of radiation because of highly developed surface area. Such composites prove to be efficient new-type detectors of low-energy beta radiation both in liquids and gases.

3.
Nat Commun ; 8: 15636, 2017 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-28548100

RESUMO

High-performance Li-ion batteries require materials with well-designed and controlled structures on nanometre and micrometre scales. Electrochemical properties can be enhanced by reducing crystallite size and by manipulating structure and morphology. Here we show a method for preparing hierarchically structured Li4Ti5O12 yielding nano- and microstructure well-suited for use in lithium-ion batteries. Scalable glycothermal synthesis yields well-crystallized primary 4-8 nm nanoparticles, assembled into porous secondary particles. X-ray photoelectron spectroscopy reveals presence of Ti+4 only; combined with chemical analysis showing lithium deficiency, this suggests oxygen non-stoichiometry. Electron microscopy confirms hierarchical morphology of the obtained material. Extended cycling tests in half cells demonstrates capacity of 170 mAh g-1 and no sign of capacity fading after 1,000 cycles at 50C rate (charging completed in 72 s). The particular combination of nanostructure, microstructure and non-stoichiometry for the prepared lithium titanate is believed to underlie the observed electrochemical performance of material.

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