Towards nano-sensing using the acoustic vibrations of nano-objects

One of the technological challenges of these last years is the development highly efficient nano-sensing device, to determine for example the size, the mass, or even the presence or not of a given molecule. An interesting... [ view full abstract ]

One of the technological challenges of these last years is the development highly efficient nano-sensing device, to determine for example the size, the mass, or even the presence or not of a given molecule. An interesting route to develop such sensors is to use the mechanical properties of mechanical nano-resonators, whose high frequencies of vibration (GHz to THz) are ideal to develop nano-clocks or nano-balances. The simplest nano-resonator, and maybe the easiest to produce, is the nanoparticle in which the vibration frequency is directly proportional to its reciprocal dimensions (inverse diameter for a sphere, inverse length for a wire, or inverse thickness for a nanoplatelet).

In this paper we show, with two specific cases, that these simple nano-objects have promising potential to develop nano-sensing devices.
The first system studied is a dimer of gold nanoparticles whose ultra low frequency vibration modes (<5GHz~0.15 cm-1) arising from the hybridization of the individual vibration modes of each nanoparticle, is highly sensitive to the elastic properties of the surrounding medium.[1]
The second system consists of nano-platelets of semi-conductor whose thicknesses can be controlled from 2 to 14 monolayers. Detecting the resonant breathing frequency across the thickness of the nano-platelets reveals a significant sensitivity to mass loads attached the free surfaces of the nano-platelets.[2]
Both systems, dimer and nano-platelets, are optically addressed thanks to their specific optical properties (plasmon and exciton), which makes them good candidates to be integrated into high density detectors for sensing applications.


[1].Girard, A. et al. Mechanical coupling in gold nanoparticles super-molecules revealed by plasmon-enhanced ultra low frequency Raman spectroscopy. Nano Lett. 34, acs.nanolett.6b01314 (2016).
[2].Girard, A. et al. Mass load effect on the resonant acoustic frequencies of colloidal semiconductor nanoplatelets. To be published in Nanoscale