Functionalization and solubilization of BN nanotubes by interaction with Lewis bases

By interaction with a trialkylamine or trialkylphosphine, BN nanotubes can be dispersed in a hydrocarbon medium with retention of the nanotube structure

Graphene-based electrochemical supercapacitors

Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H2SO4, the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3.5 V (instead of 1 V in the case of aq. H2SO4), the specific capacitance and energy density being 75 F/g and 31.9 Wh kg−1 respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior to that of single-walled and multi-walled carbon nanotubes

Extraordinary sensitivity of the electronic structure and properties of single-walled carbon nanotubes to molecular charge-transfer

Interaction of single-walled carbon nanotubes with electron donor and acceptor molecules causes significant changes in the electronic and Raman spectra, the relative proportion of the metallic species increasing on electron donation through molecular charge transfer, as also verified by electrical resistivity measurements.Comment: 15 pages, 5 figurre

Electrical properties of inorganic nanowire-polymer composites

Composites of nanowires of ZnO, RuO2 and Ag with polyaniline (PANI) as well as polypyrrole (PPy) have been prepared, for the first time, by an in-situ process, in order to investigate their electrical properties. Characterization by electron microscopy and IR spectroscopy indicates that there is considerable interaction between the oxide nanowires and the polymer. The room-temperature resistivity of the composites prepared in-situ varies in the 0.01-400 Ω cm range depending on the composition. While the resistivities of the PANI-ZnONW and PPy-ZnONW composites prepared by the in-situ process are generally higher than that of PANI/PPy, those of PANI-RuO2NW and PANI-AgNW are lower. Composites of ZnONW with polyaniline prepared by an ex-situ process exhibit a resistivity close to that of polyaniline

Binding of Nucleobases with Single-Walled Carbon Nanotubes

We have calculated the binding energy of various nucleobases (guanine (G), adenine (A), thymine (T) and cytosine (C)) with (5,5) single-walled carbon nanotubes (SWNTs) using ab-initio Hartre-Fock method (HF) together with force field calculations. The gas phase binding energies follow the sequence G $>$ A $>$ T $>$ C. We show that main contribution to binding energy comes from van-der Wall (vdW) interaction between nanotube and nucleobases. We compare these results with the interaction of nucleobases with graphene. We show that the binding energy of bases with SWNTs is much lower than the graphene but the sequence remains same. When we include the effect of solvation energy (Poisson-Boltzman (PB) solver at HF level), the binding energy follow the sequence G $>$ T $>$ A $>$ C $>$, which explains the experiment\cite{zheng} that oligonucleotides made of thymine bases are more effective in dispersing the SWNT in aqueous solution as compared to poly (A) and poly (C). We also demonstrate experimentally that there is differential binding affinity of nucleobases with the single-walled carbon nanotubes (SWNTs) by directly measuring the binding strength using isothermal titration (micro) calorimetry. The binding sequence of the nucleobases varies as thymine (T) $>$ adenine (A) $>$ cytosine (C), in agreement with our calculation.Comment: 7 pages, 6 figure

Penetration of alkali atoms throughout graphene membrane: theoretical modeling

Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout graphene membrane grown on silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate rather low (about 0.8 eV) energy barrier for the formation of temporary defects in carbon layer required for the penetration of Li at high concentration of adatoms, higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100{\deg}C and impenetrability of graphene membrane for Rb and Cs. Differences between epitaxial and free standing graphene for the penetration of alkali ions are also discussed.Comment: 16 pages, 3 figure, accepted to Nanoscal

Monolayer surface chemistry enables 2-colour single molecule localisation microscopy of adhesive ligands and adhesion proteins.

Nanofabricated and nanopatterned surfaces have revealed the sensitivity of cell adhesion to nanoscale variations in the spacing of adhesive ligands such as the tripeptide arginine-glycine-aspartic acid (RGD). To date, surface characterisation and cell adhesion are often examined in two separate experiments so that the localisation of ligands and adhesion proteins cannot be combined in the same image. Here we developed self-assembled monolayer chemistry for indium tin oxide (ITO) surfaces for single molecule localisation microscopy (SMLM). Cell adhesion and spreading were sensitive to average RGD spacing. At low average RGD spacing, a threshold exists of 0.8 RGD peptides per µm2 that tether cells to the substratum but this does not enable formation of focal adhesions. These findings suggest that cells can sense and engage single adhesive ligands but ligand clustering is required for cell spreading. Thus, our data reveal subtle differences in adhesion biology that may be obscured in ensemble measurements

Dielectric function and plasmonic behavior of Ga(II) and Ga(III)

In order to exploit gallium´s (Ga) rich polymorphism in the design of phase-change plasmonic systems, accurate understanding of the dielectric function of the different Ga-phases is crucial. The dielectric dispersion profiles of those phases appearing at atmospheric pressure have been reported in the literature, but there is no information on the dielectric function of the high-pressure Ga-phases. Through first principles calculations we present a comprehensive analysis of the interdependence of the crystal structure, band structure, and dielectric function of two high-pressure Ga phases (Ga(II) and Ga(III)). The plasmonic behavior of these high-pressure Ga-phases is compared to those stable (liquid- and α-Ga) and metastable (β-, γ- and δ-Ga) at atmospherics pressure. This analysis can have important implications in the design of pressure-driven phase-change Ga plasmonic devices and high-pressure SERS substrates.Y.G. and F.M. acknowledges the support by the Army Research Laboratory under Cooperative Agreement Number W911NF-17-2-0023 and by SODERCAN (Sociedad para el Desarrollo de Cantabria) and the Research Vicerrectorate of the University of Cantabria through project 4JU2864661. Y.G. thanks the University of Cantabria for her FPU grant. P.G.-F. and J.J. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant number PGC2018-096955-B-C41

Hall Measurements on Carbon Nanotube Paper Modified With Electroless Deposited Platinum

Carbon nanotube paper, sometimes referred to as bucky paper, is a random arrangement of carbon nanotubes meshed into a single robust structure, which can be manipulated with relative ease. Multi-walled carbon nanotubes were used to make the nanotube paper, and were subsequently modified with platinum using an electroless deposition method based on substrate enhanced electroless deposition. This involves the use of a sacrificial metal substrate that undergoes electro-dissolution while the platinum metal deposits out of solution onto the nanotube paper via a galvanic displacement reaction. The samples were characterized using SEM/EDS, and Hall-effect measurements. The SEM/EDS analysis clearly revealed deposits of platinum (Pt) distributed over the nanotube paper surface, and the qualitative elemental analysis revealed co-deposition of other elements from the metal substrates used. When stainless steel was used as sacrificial metal a large degree of Pt contamination with various other metals was observed. Whereas when pure sacrificial metals were used bimetallic Pt clusters resulted. The co-deposition of a bimetallic system upon carbon nanotubes was a function of the metal type and the time of exposure. Hall-effect measurements revealed some interesting fluctuations in sheet carrier density and the dominant carrier switched from N- to P-type when Pt was deposited onto the nanotube paper. Perspectives on the use of the nanotube paper as a replacement to traditional carbon cloth in water electrolysis systems are also discussed

Rhodium nanoparticles for ultraviolet plasmonics

The nonoxidizing catalytic noble metal rhodium is introduced for ultraviolet plasmonics. Planar tripods of 8 nm Rh nanoparticles, synthesized by a modified polyol reduction method, have a calculated local surface plasmon resonance near 330 nm. By attaching p-aminothiophenol, local field-enhanced Raman spectra and accelerated photodamage were observed under near-resonant ultraviolet illumination, while charge transfer simultaneously increased fluorescence for up to 13 min. The combined local field enhancement and charge transfer demonstrate essential steps toward plasmonically enhanced ultraviolet photocatalysis.This work has been supported by NSF-ECCS-12-32239. This work was partially supported by the Army’s In-house Laboratory Innovative Research program. Financial support from USAITCA (project no. W911NF-13-1-0245) and MICINN (Spanish Ministry of Science and Innovation, project no. FIS2013- 45854-P) is also acknowledged