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Laboratoire Interdisciplinaire Carnot de Bourgogne

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Topics

Continuous solvo-thermal synthesis of nano-objets (under and supercritical conditions)

 

supercritique

Contact: Frédéric Demoisson

Flash sintering: autoassembly and nanostructuration

Contacts: Frédéric Bernard, Sophie Le Gallet

Interface reactions: reactive sintering and self-sustained reactions, LiH hydrolysis

Contacts: Florence Baras, Frédéric Bernard

Biomedical applications of oxide nanoparticles and nanotubes

  • SPIONs as nanocarriers and for molecular imaging
  • TiONts as nanocarriers and for healing processes
  • Mesoporous Silica Nanoparticles for anticancer drug nanovectorization

Contacts: Nadine Millot, Frédéric Bouyer, Julien Boudon

 Dielectric properties of insulator solids: phase transitions, relaxation, aging

Study of insulator solids by impedance spectroscopy (organic glasses, semiconductors, oxides)

Contact: Olivier Bidault

Vibrational dynamics of nano-objets

 Lamb

Contact: Lucien Saviot

Presentation

This topic concerns the study of the so-called 'ensemble' or acoustic vibrations of nanoobjets. These vibrations are studied in the lab by low-frequency Raman spectroscopy. The corresponding frequencies are indeed quite small. For example, for a nanoparticle with a diameter of 10 nanometers the most intense Raman signal is approximately at 100 GHz, i.e. close to 3 cm-1 or 0.4 meV. Observation using other vibrational spectroscopies such as inelastic neutron scattering for example is also possible. The optical vibrations of such objects are also investigated.

Main results

Knowing the frequencies of vibrations of nanoobjects enables to measure their size. Indeed, in the framework of continuum elasticity, the frequency varies as the inverse of the dimension of the nanoobjects and the proportionality coefficient can be calculated. From a more fundamental point of view, studying such vibrations give access to the electron-vibration coupling.

Such vibrations are sensitive to various parameters such as the material the nanoobjet is made of, its dimensions, its shape as well as its internal structure. As a result the low-frequency Raman spectra of gold nanoparticles depend on the presence of twins in the cristalline lattice inside the nanoparticle. (doi: 10.1073/pnas.0803748105)

The ensemble vibrations are often modelled using continuum elasticity which is applicable for macrospic objects. Such vibrations can be illustrated in the case of «simple» isotropic spheres by the free oscillations of the Earth. You can also use this javascript calculator to calculate the vibrations of arbitrary isotropic spheres.

terre
A vibration of a free sphere (the Earth)

In the case of nano-objects with a lower symmetry due to a non spherical shape and/or an anisotropic elasticity, the vibrations are calculated using a numerical model and point group theory is used to classify the vibrations according to their irreducible representation. This enables to derive the Raman scattering selection rules for example (doi: 10.1103/PhysRevB.79.214101, 0904.2959).

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