Biological nano-channels expressed in living cells, where they ensure keyphysiological functions, feature outstanding efficiency in terms of both ionselectivity and conductivity. The latter generally exceeds, by 3 to 4 orderof magnitude, the values expected from classical hydrodynamics. This propertyof biological nano-channels may result from their pore width in the rangeof the Debye length (0.3-30 nm) and this currently grounds many researchworks aimed at developing the use of solid-state porous nano-materials for‘‘high-throughput’’ molecular and ion sensing or sorting, with applicationssuch as drug delivery, energy conversion, water desalination and others. Singlewalled carbon nanotubes (SWNTs), which make nano-pores with welldefinedstructural and physical properties, may allow us to overcomingmany limitations of other nano-materials. The possibility of transportingions and molecules through these SWNTs has already been reported by othergroups (Lee et al., 2010, Science 329:1320; Liu et al., 2010, Science 327:64).In this context, we aim at studying the usableness of SWNT-incorporating devicesfor discriminating ions and single small biomolecules, using nucleotidesand amino acids as model compounds. Here, we will present the first part ofthis work, which consists in the fabrication of microfluidic devices incorporatingindividual SWNTs and the study of ion transport inside these devicesusing ionic current measurements, i.e. patch-clamp type. A study of the selectivityof these SWNTs will be also shown using different cations-basedelectrolytes.

We studied the oxygen etching of individual single-walled carbon nanotubes on silicon oxide substrates using atomic force microscopy and high-temperature environmental scanning electron microscopy. Our in situ observations show that carbon nanotubes are not progressively etched from their ends, as frequently assumed, but disappear segment by segment. Atomic force microscopy, before and after oxidation, reveals that the oxidation of carbon nanotubes on substrates proceeds through a local cutting that is followed by a rapid etching of the disconnected nanotube segment. Unexpectedly, semiconducting nanotubes appear more reactive under these conditions than metallic ones. We also show that exposure to electron and laser beams locally increases the chemical reactivity of carbon nanotubes on such substrates. These results are rationalized by considering the effect of substrate-trapped charges on the nanotube density of states close to the Fermi level, which is impacted by the substrate type and the exposure to electron and laser beams.

The rise of efficient extraction techniques triggered a renewal of interest in semiconducting carbon nanotubes (s-SWNT) research. It represents a great interest for optoelectronics, with outstanding properties in field-effect transistor, and s-SWNT ability to efficiently emit light in the near-IR range. In particular, polyfluorene (PFO) wrapped s‑SWNT (s-SWNT@PFO) display strong photoluminescence, and could be coupled with photonic devices such as microring resonators [1,2] to control photoluminescence linewidth and enhance photoluminescence intensity. The main challenge for using s-SWNT@PFO in optoelectronics lies in the difficulty to establish good electrical contact with a PFO embedded carbon nanotube, and existing studies only focused on optical pumping of carbon nanotubes networks, without addressing issues of electrical driving. We propose to investigate these issues using s-SWNT@PFO networks deposited on patterned substrate (Figure). The network formation process allow to control nanotube density, while the amount of remaining metallic nanotube in the network could be adjusted at the extraction phase. A selective annealing process under low pressure is used to tune PFO wrapping around the nanotubes. The resulting s-SWNT@PFO networks are then probed by AFM, Raman spectroscopy, absorption, photoluminescence and electrical experiments.

A double-walled carbon nanotube (DWNT), a coaxial composite of two single walled carbon nanotubes (SWNT), provides a unique model to study interactions between thetwo constituent SWNTs. Combining high resolution transmission electron microscopy (HRTEM), electron diffraction (ED), and resonant Raman scattering (RRS) experiments on the same individual suspended DWNT is the ultimate way to relate unambiguously its atomicstructure, defined by the chiral indices of the coaxial outer/inner SWNTs, and its Raman-active vibration modes. This approach is used to investigate the intertube distance dependence of theG-modes of individual index-identified DWNTs composed of two semiconducting SWNTs.We state the main features of the dependence of the G-mode frequencies on the distance between the inner and outer layers: (i) When the interlayer distance is larger than the nominal van der Waals distance (close to 0.34 nm), a downshift of the inner-layer G-modes with respectto the G-modes in the equivalent SWNTs is measured. (ii) The amplitude of the downshiftdepends on the interlayer distance, or in other words, on the negative pressure felt by the innerlayer in DWNT. (iii) No shift is observed for an intertube distance close to 0.34 nm.

The response of micrometric pseudo-single crystals of β-H2NiO2, deposited on an Au substrate and submitted to high rate charge/discharge cycling under controlled current conditions, is studied by in situ μ-Raman spectroscopy. The intensities of the Raman background and of the hydroxyl stretching band are used to probe in time the single-particle surface and bulk oxidation states respectively. Results, obtained in the absence of electrical binders and chemical dopants, substantiate previous electrochemical investigations suggesting that the occurrence of the nickel electrode activation process is related to the formation of a thin surface limiting layer hindering the active material capacity to store and deliver energy. The feasibility of in situ μ-Raman spectroscopy on nickel hydroxide single particles submitted to electrochemical operation is demonstrated for the first time.

Abstract In this communication, we will illustrate how Raman spectroscopy can be used to study the doping of graphene. We will first report data recorded by in situ Raman experiments on single-layer (SLG) graphene during exposure to rubidium vapor. By this way, we have been able to follow continuously the changes of the G and 2D bands features over a broad doping range (up to about 1014 electrons/cm2). Previous theoretical predictions have shown that the evolution of the G-mode in SLG results from the competition between adiabatic and non-adiabatic effects. We emphasize that a possible substrate pinning effect, which inhibits the charge-induced lattice expansion of graphene layer, can strongly influence the G band position [1]. In the second part, we will show that the charge carrier density of graphene exfoliated on a SiO2/Si substrate can be finely and reversibly tuned between electron and hole doping with visible photons. This photo-induced doping happens under moderate laser power conditions but is significantly affected by the substrate cleaning method. In particular, it requires hydrophilic substrates and vanishes for suspended graphene. These findings also suggest that Raman spectroscopy is not always as non- invasive as generally assumed [2]. References [1] R. Parret, M. Paillet, J.-R. Huntzinger, D. Nakabayashi, T. Michel, A. Tiberj, J.-L. Sauvajol, A.-A. Zahab, ACS Nano, 7 (2013) 165. [2] A. Tiberj, M. Rubio-Roy, M. Paillet, J.-R. Huntzinger, P. Landois, M. Mikolasek, S. Contreras, J.-L. S!auvajol, E. Dujardin, A.-A. Zahab, Scientific Reports, 3 (2013) 2355.

Review on the Raman spectroscopy of nano-carbons