The mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets

Adrien Girard (1) , Lucien Saviot (2) , Silvia Pedetti (3) , Mickaël Tessier (3) , Jérémie Margueritat (1) , Hélène Gehan (1) , Benoit Mahler (3) , Benoit Dubertret (3) , Alain Mermet (1)

1 ILM - Institut Lumière Matière [Villeurbanne]
2 ICB - Laboratoire Interdisciplinaire Carnot de Bourgogne
3 LPEM - Laboratoire de Physique et d'Etude des Matériaux (UMR 8213)

Resonant acoustic modes of ultrathin CdS and CdSe colloidal nanoplatelets (NPLs) with varying thicknesses were probed using low frequency Raman scattering. The spectra are dominated by an intense band ascribed to the thickness breathing mode of the 2D nanostructures. The measured Raman frequencies show strong deviations with respect to values expected for simple bare plates, all the more so as the thickness is reduced. The deviation is shown to arise from the additional mass of the organic ligands that are bound to the free surfaces of the nanoplatelets. Calculating the eigenfrequencies of vibrating platelets weighted down by the mass of the organic ligands provides very good agreement with the observed experimental behaviours. This finding opens up a new possibility of nanomechanical sensing such as nanobalances.

Domaines: Optique [physics.optics]; Matériaux

Adrien Girard, Lucien Saviot, Silvia Pedetti, Mickaël Tessier, Jérémie Margueritat, et al.. The mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets. Nanoscale, 2016, 8 (27), pp.13251-13256. ⟨10.1039/C5NR07383A⟩. ⟨hal-02108380⟩