RESUMO
A forward-directed high-efficiency stimulated inelastic light scattering was detected in an aqueous suspension of spherical nanoparticles (nanoballs) of amorphous SiO2 of similar sizes (0.25 µm) with a concentration of 1013 cm-3. In the stimulated scattering spectrum, there was an intense forward directed Stokes component with a frequency shift of 0.54 cm-1, corresponding to the boson peak mode of spherical nanoparticles. The results obtained are of interest for non-equilibrium excitation of spherical particles of similar sizes of different nature present in liquids (clusters, fullerenes, spherical macromolecules, viruses, etc.).
RESUMO
In our recent work [Bunkin et al. Water 2013, 4, 129-154] it was first obtained that the water layer, having a size of several tens of micrometers and being adjacent to the swollen Nafion interface, is characterized by enhanced optical density; the refractive index of water at the interface is 1.46. Furthermore, the birefringence effect was observed in this layer. To explain these results, it has been hypothesized that because of "disentangling" of charged polymer chains from the Nafion surface toward the bulk of water, a photonic crystal close to the surface is formed [Bunkin et al. Water 2013, 4, 129-154]. In this paper, we describe experiments with laser-stimulated luminescence from dry and swollen Nafion. It was shown in the experiment with dry Nafion that the apparatus function of our experimental setup (Green's function) is well-described by a Gaussian profile. It was obtained that a highly concentrated colloidal suspension of Nafion particles with a steep spatial boundary is formed in the water layer adjacent to the interface. The volume density of the Nafion particles as a function of the distance from the Nafion interface was found. These findings can be considered indirect confirmation of the previously formulated photonic crystal hypothesis [Bunkin et al. Water 2013, 4, 129-154].