Carbon nanotubes (CNTs) possess extraordinary mechanical, thermal, and electrical properties due to their atomically perfect structure and sp2-hybridization. Recently, Single-wall CNTs (SWCNTs) have become an interesting host for the nanoscale confinement of fluids, with a wealth of surprising phenomena appearing: spontaneous filling, frictionless mass transport, unusual phase diagram, etc[1]. Most of these phenomena are still under debate and call for experimental confirmation. But the field is struggling with finding experimental approaches sensitive enough to carry out measurements at the level of individual nanotubes. SWCNT field effect transistors (SWCNT-FETs) showed that the electronic properties of SWCNTs are sensitive to their diameter, defects, doping, adsorbates, and environment [2], [3].In this contribution, we demonstrate that individual carbon nanotube field effect transistors (CNTFET) are excellent tools for this aim, for the first time allowing to precisely identify water confined inside the nanotube. By studying the electrical performances of several unopened and opened CNTFETs submitted to various atmosphere and temperature treatments, i.e. dry air, humidity, secondary vacuum, and current annealing, we show that it is possible to distinguish water being outside and inside the nanotube, just outside, or the nanotube free from water. We thus observed that for opened SWCNT both secondary vacuum and current annealing move threshold gate voltage towards more negative values, while for closed SWCNT secondary vacuum had no effect compared to current annealing. To sum up, the current annealing treatment is essential to distinguish water adsorbed outside from water confined inside. We show that this behavior is universal, as all devices' metallicities behave similarly, provided that the surface of the nanotube is pre-cleaned by current annealing. We will also discuss the mechanisms behind the coupling of electronic transport and the presence of water.Our results open up the possibility to use CNTFET for instance reliable, selective, and sensitive chemical and biological sensors, and also, to resolve the long-standing questions in the nanofluidic community about the behavior of water under nanoscale confinement.Reference:[1] T. A. Pascal, W. A. Goddard, and Y. Jung, “Entropy and the driving force for the filling of carbon nanotubes with water,” Proc. Natl. Acad. Sci., vol. 108, no. 29, pp. 11794–11798, 2011, doi: 10.1073/pnas.1108073108.[2] D. Cao et al., “Electronic sensitivity of carbon nanotubes to internal water wetting,” ACS Nano, vol. 5, no. 4, pp. 3113–3119, 2011, DOI: 10.1021/nn200251z.[3] I. Heller, A. M. Janssens, J. Männik, E. D. Minot, S. G. Lemay, and C. Dekker, “Identifying the mechanism of biosensing with carbon nanotube transistors,” Nano Lett., vol. 8, no. 2, pp. 591–595, 2008, DOI: 10.1021/nl072996i.

The synthesis of multifunctional poly(amidoamine)(PAMAM)-based dendrimers containing a cleavable disulfide linkerwithin each armof the dendrimer, together with condensable triethoxysilyl groups on the periphery of the dendrimer, isdescribed. The dendrimers were mixed with bis(triethoxysilyl)benzene and subsequently transformed into silsesquioxanegels or periodic mesoporous organosilicas (PMOs) to generate materials with dendrimers covalently embedded within theinterior of the silsesquioxane networks. Subsequent treatment of the gels with dithiothreitol enabled the core of thedendrimers to be selectively cleaved at the disulfidesite, thus generating thiol functions localised within the pores.The effect of different dendrimer generations on the reactivity of the pendant thiol functions was probed by impregnationwith gold salts, which were reduced to obtain gold nanoparticleswithin the pore networks of the gels and PMOs. The gelsyielded polydisperse gold nanoparticles (2 to 70 nm) with dimensions modulated by the generation of thedendrimer,together with well-defined gold/thiolate clusters with Au...S distances of 2.3 Å. Suchclusters were also observed in the PMOsystem, together with monodispersed gold nanoparticles with diameters comparable to that of the organised pores in thePMO. The role of surface functionalisation in controlling the formation of gold clusters and/or nanoparticles is discusse

Polarized fluorescence emission of nanoscale emitters has been extensively studied for applications such as bioimaging, display, and optical communication. Extending the polarization properties in large assemblies of compact emitters is, however, challenging because of self-aggregation processes, which can induce depolarization effects, quenching, and cancellations of molecular dipoles. Here we use a-sexithiophene (6T) molecules confined inside boron nitride nanotubes (6T@BNNTs) to induce fluorescence anisotropy in a transparent host. The experiments first indicate that individual 6T@BNNTs exhibit a high polarization extinction ratio, up to 700, at room temperature. Using aberration- corrected HRTEM, we show that the fluorescence anisotropy is consistent with a general alignment of encapsulated 6T molecules along the nanotube axis. The molecular alignment is weakly influenced by the nanotube diameter, a phenomenon ascribed to stronger molecule-to-sidewall interactions compared to intermolecular interactions. By stretching a flexible thin film made of transparent polymers mixed with 6T@BNNTs, we induce a macroscopic fluorescence anisotropy within the film. This work demonstrates that the dyes@BNNT system can be used as an easy-to-handle platform to induce fluorescence anisotropy in photonic materials.

Density functional tight-binding calculations of the adsorption of OH − and other related diatomic anions on carbon nanotubes and graphene show that two adsorption states coexist: a physisorption state caused by Debye interactions, and a chemisorption state at shorter distances dominated by ionic-covalent interactions. For all anions, both adsorption energies scale linearly with the curvature of the carbon surface, and increase with decreasing anion polarizability but also, in metallic nanotubes, with chiral angle. At short distances, charge transfer modifies the attractive Debye forces into repulsive forces of the dipole-dipole type, tuning the strength of the chemisorption state, and may determine its existence and stability.