Double-walled carbon nanotubes (DWNTs), consisting of two coaxial and weakly van der Waals coupled single-walled carbon nanotubes (SWNTs), are one of the most ideal and fundamental systems to study the effects of inter-tube coupling on the physical properties in one-dimensional structures.On this poster, we report on the investigations of individual, spatially isolated and suspended double-walled carbon nanotubes (DWNTs) by combination of high-resolution electron microscopy, electron diffraction, Rayleigh spectroscopy and Raman spectroscopy (Figure 1) [1,2]. We first present an overview of the effect of the diameters, inter-tube distance and nature (metallic or semiconducting) on the Raman signature (Radial Breathing Like [1,3,4] and Tangential Modes [4-6]) of DWNTs. We then examine the features of tangential modes and find a clear frequency shift of the inner-layer G modes as a function of the inter-tube distance with respect to the corresponding G modes in equivalent single-walled carbon nanotubes (SWNT).[4-6] These results are understood by considering the effects of the relaxation of the layers and the interaction between the relaxed structures.[7] Finally, we study the experimental excitation dependence of the G modes intensity of the constituent inner and outer SWNTs. In particular, we discuss the effects of the quantum interference between different electronic transitions on the observed behaviors.[8]References[1] D.I. Levshov et al., Carbon, 114, 141 (2017). [2] D.I. Levshov et al., Phys Rev. B 96 (2017), 195410.[3] D.I. Levshov et al., Nano Lett. 11(11) (2011), 4800. [4] H.-N. Tran et al., Adv. Nat. Sci. Nanosci. Nanotechnol. (2017), 8, 15018.[5] D. Levshov et al., J. Phys. Chem. C 119(40) (2015), 23196.[6] D.I. Levshov et al., Phys. Status Solidi B 254(11) (2017), 1700251.[7] V.N. Popov et al., Phys. Rev. B 97 (2018), 165417.[8] H.-N. Tran et al., Phys. Rev. B 95 (2017), 95 (20), 205411

Nowadays, the recovering of both thicknesses and optical properties of nanometric multilayers is still a challenge. We propose a method to recover the effective relative permittivities and the thicknesses of copper/copper oxide layers, from absorbance spectra measured in the visible spectra. The experimental data are fitted with a model of classical light-matter interaction and a combination of two Drude-Lorentz laws to calculate the relative permittivities over the spectrum. The Particle Swarm Optimization and the evolutionary methods are used for the least-square fitting. A two steps study reveals that the relative permittivities of bulk cannot be used to fit adequately the absorbance curves. However, a perturbation of these reference values improves their fitting. The method is applied to the absorption spectra of a set of three copper samples that are progressively oxidized by six successive heat treatments.

Adsorption studies in flexible metal–organic frameworks are challenging and time-consuming. It ismainly because the mechanism of adsorption, defined by structural framework properties, is constantlymodified during the process, as the framework transformation depends on the adsorption uptake. Wepropose here a new approach to investigate adsorption in such complex systems, in which thesimulations of adsorption in a deforming framework are replaced by the analysis of adsorption inintermediate rigid structures. As a proof of concept we analyze carbon dioxide, hexane, and methaneadsorption in MIL-53. 19 intermediate structures were generated using geometrical interpolationbetween the open and the closed MOF forms and optimized with quantum DFT calculations. The grandcanonical Monte Carlo method was applied to calculate adsorption isotherms in all intermediatestructures. The comparison with experimental results enabled the identification of the intermediateadsorption states. The analysis of the microscopic configurations of the adsorbed molecules in thesestructures allowed us to propose a new mechanism of adsorbate evolution over the entire process.

Using an experimental approach that combines high-resolution electron microscopy, electron diffraction and optical spectroscopies, including Raman scattering, Rayleigh spectroscopy and photoluminescence, on individual, spatially isolated and suspended (free-standing) single-walled (SWNTs) and double-walled carbon nanotubes (DWNTs), we have been able to investigate their phonons characteristics and optical properties. In this talk, we present an overview of the most significant results obtained via this approach. Particular attention is paid to the study of DWNTs, a coaxial composite of two SWNTs, which provide a unique model system for studying coupling at the nanoscale. We show how such coupling, originating from the van der Waals interaction between the inner and outer nanotubes, plays a crucial role in determining the characteristics of the collective radial breathing-like modes and G modes in DWNTs (for a review see Ref. 1-2). The effects of quantum interference between different electronic transitions on the experimental behavior of the G-modes intensity are discussed [3]. It must be emphasized that the theoretical predictions of Philippe Lambin and his collaborators have been invaluable in understanding a lot of these experimental data [4].

The goal of this chapter is to review the main information derived from Raman spectroscopy on individual suspended (free-standing) chiralityidentified single-wall carbon nanotubes (SWCNTs) and double-wall carbonnanotubes (DWCNTs) with a special focus on the characteristics of their radial breathing modes and G modes, including their resonance conditions. ForSWCNTs, the different relationships between the radial breathing mode frequency and the inverse of the diameter illustrate the high sensitivity of individual suspended SWCNTs to their environmental conditions. The intrinsicprofiles of the optical longitudinal (LO) and transverse (TO) G modes are unambiguously identified both for metallic and semiconducting chiral and achiral SWCNTs, and the diameter dependence of the LO and TO frequencies are established. In DWCNTs, the intertube coupling, originating from the van der Waals interaction between the inner and outer tubes, plays an important role in determining the features/characteristics of the collectiveradial breathing-like modes and G modes.