0000000000461706
AUTHOR
Catherine Pighini
showing 5 related works from this author
Temperature dependent photoluminescence of photocatalytically active titania nanopowders
2007
Abstract Temperature photoluminescence (PL) in the sub-ambient range has been developed as a tool for characterizing photocatalytic materials. The use of well-characterized TiO2 nanoparticles with calibrated particle sizes allowed to face the temperature dependent PL results with the photocatalytic activity and several important physico-chemical parameters. In the relaxation of the photoexcited electron/hole pairs, the transfer towards surface sites is in competition with radiative and non-radiative recombinations. Temperature dependent PL appears thus to be a very sensitive technique to study the efficiency of the electron or the hole trapping at the surface of titania nanoparticles where …
Far infrared absorption by acoustic phonons in titanium dioxide nanopowders
2006
We report spectral features of far infrared electromagnetic radiation absorption in anatase TiO2 nanopowders which we attribute to absorption by acoustic phonon modes of nanoparticles. The frequency of peak excess absorption above the background level corresponds to the predicted frequency of the dipolar acoustic phonon from continuum elastic theory. The intensity of the absorption cannot be accounted for in a continuum elastic dielectric description of the nanoparticle material. Quantum mechanical scale dependent effects must be considered. The absorption cross section is estimated from a simple mechanical phenomenological model. The results are in plausible agreement with the absorption b…
Hydrogen trapping: Synergetic effects of inorganic additives with cobalt Sulfide absorbers and reactivity of cobalt polysulfide
2012
International audience; The biphasic product CoS2 + Co(OH)(2) obtained by oxidation of cobalt sulfide is known to trap hydrogen at room temperature and low pressure according to a balanced reduction equation. Adding various inorganic compounds to this original absorber induces their reduction by hydrogen in the same conditions at a significant rate: (i) excess cobalt hydroxide is reduced to metallic cobalt; (ii) nitrate ions are reduced to ammonia; (iii) sulfur and sodium thiosulfate are reduced to H2S or NaHS and Na2S, respectively. Without a hydrogen absorber these inorganic compounds are not reduced by H-2, suggesting synergetic effects involving H-2 and the hydrogen absorber. Amorphous …
Inelastic neutron scattering due to acoustic vibrations confined in nanoparticles: theory and experiment
2008
The inelastic scattering of neutrons by nanoparticles due to acoustic vibrational modes (energy below 10 meV) confined in nanoparticles is calculated using the Zemach-Glauber formalism. Such vibrational modes are commonly observed by light scattering techniques (Brillouin or low-frequency Raman scattering). We also report high resolution inelastic neutron scattering measurements for anatase TiO2 nanoparticles in a loose powder. Factors enabling the observation of such vibrations are discussed. These include a narrow nanoparticle size distribution which minimizes inhomogeneous broadening of the spectrum and the presence of hydrogen atoms oscillating with the nanoparticle surfaces which enhan…
Hydrothermal synthesis of nanostructured inorganic powders by a continuous process under supercritical conditions
2005
Abstract In this study, using a prototype of hydrothermal synthesis in subcritical and supercritical water working in a continuous way, nanometric ceramic precursors with perfectly defined composition are produced: spinel ferrites such as Fe2CoO4, TiO2 with anatase structure and also perovskite structures such as BaZrO3. The as-prepared powders are fully characterized by complementary experiments: X-ray diffraction, electron microscopies, EDX spectrometry, surface area measurement, etc. Thus, particles size, morphology, aggregation state, crystal structure, composition are investigated. Moreover, magnetic properties of the ferrites products are studied. The powders obtained are pure phases …