The electrophoretic transport of ions through single wall carbon nanotubes (SWCNTs) of diameters between 1.2 and 1.8 nm was studied for different monovalent chloride salts using microfluidic devices incorporating either a single or a few CNTs in parallel. The ionic conductance was found to be about one order of magnitude higher than expected from a simple electro-migration behavior without any surface effect. Importantly, the ionic conductance measured for different cations did not scale with their bulk electrophoretic mobility thus indicating a probable selective cation transport through these sub-2 nm SWCNTs. The transport of Na+ was notably found to be favored in comparison to that of Li+ and Cs+ or K+ . These results highlight the influence of steric and surface effects induced by the nano-confinement on the transport of ions through sub-2 nm SWCNTs.

Associations of organic and inorganic molecules involving non covalent and covalent interactions participate to a wide range of structures found in nature. Bridged silsesquioxanes (BS) can be designed with organic units selected to drive self-organization into a solid network. Therefore new hybrids functional materials with controlled morphologies can be synthesized. In particular urea groups, thanks to their ability to self-assemble though H bonds, have been incorporated in BS within the organic subunits (figure 1, UU). Depending on kinetics of the sol gel reaction, hybrid materials bridged by urea groups exhibiting a variety of textures and morphologies were synthetized. Considering the bridging group as a key element for the control of the assembly formed hybrids materials where thiourea groups have also been synthesized (Figure 1, UU or TT). As a matter of fact thiourea groups are also known to link them self via H bonds, but with geometry and strengths that can differ from urea links. Vibrational spectroscopy is used here to explore the self-organization mechanisms involved in the formation of urea bridged and thiourea bridged silsequioxanes. The influence of H-bonding strength and the self-organization properties of the urea and thiourea bridged organic substructures are explored through infra-red spectroscopy coupled with DFT calculations. Some particular vibrations such as amides and thio-amides vibrations are often considered as signatures of H bond strength. The thermal dependence dynamics of such signatures is studied as an indicator of the bond properties. Finally, in-situ high pressure vibrational measurements demonstrate the role of supramolecular interactions on the mechanical response of hybrid materials to high pressure.

Monitoring individual single-walled carbon nanotubes (SWCNTs) during their growth is a highly sought-after goal in view of understanding the processes involved in the nucleation, elongation and termination which ultimately control the diameter and chiral selectivity. Here, we report on the first truly in situ observations of SWCNT growth in an environmental scanning electron microscope (ESEM). The CNT growth from lithographically patterned catalysts was investigated as a function of the catalyst type (Fe, Co or Ni), temperature, type of precursor (ethanol or acetylene), gas phase composition and pressure, and pretreatment conditions, and we report on the most appropriate conditions for SWCNT growth in ESEM conditions. We show that this approach allows the observation at the submicron scale of the different steps of the nanotube synthesis including the catalyst reduction, the growth and percolation of the nanotube network, and the deposition of individual nanotubes grown in the gas phase on the substrate. Despite these obvious advantages, we identified a few limitations which will need to be tackled for fully taking advantage of the approach, for instance for monitoring the growth of individual SWCNTs by ESEM, including the short lifetime of the catalyst nanoparticles, the preference for kite growth (by opposition to surface growth) and the influence of the electron beam on the nanotube growth.