Sorting biological molecules according to their chirality appears a challenge for the parmaceutical industries. Chiral carbon nanotubes formed by rolling up grapheme sheet(s) in a helical arrangement are used in a gigahertz resonator configuration to selectively and reversely detect the right and left handed enantiomers of amino acids. The chiral selectivity is probed through the modification of the resonance frequency of the nanotube, the variations depending on the polarization of the tube and the molecule. The sensitivity of the resonator is optimized when the chiral angle is around 15°. To improve the chiral recognition of molecules by the nanotube and to keep reversibility, the inclusion of peptidic helices inside a single walled nanotube (SWNT) avoids a direct interaction between the peptide and the tube. The polar nature of the helix is responsible for the occurrence of a chiral electric field, which polarizes the tube. Depending on the chiral electric properties of the helix and the nanotube, the sensitivity of the resonator is enhanced from 50 to 100 %. Chirality of carbon nanotubes plays a major influence in the structure stabilization of double-walled nanotubes (DWNTs). The role of chirality in the formation of the inner and outer walls of the DWNTs depending on the radius, chiral angle, length of the tubes has been studied. From an analysis of a large sampling of DWNTs, simple rules connecting RT, θ and LT have been found. The Raman vibrational modes of the DWNT provide information on the chiral arrangement of the two walls. With a larger diameter than the SWNTs, the DWNTs used in resonator configuration could be efficient probes of larger chiral species.
