Stéphane Dénommée

Characterization of single-walled carbon nanotubes by scanning transmission X-ray spectromicroscopy: purification, order and dodecyl functionalization.

The C 1s X-ray absorption spectra of several isolated bundles of single-walled carbon nanotubes (SWCNT) have been measured using scanning transmission X-ray microscopy. First the C 1s and O 1s spectra of a purified but unfunctionalized SWCNT were measured. The C 1s --> pi* transition at 285 eV exhibited almost as strong a dichroic effect (spectral dependence on orientation) as that found in multiwalled carbon nanotubes (Najafi; et al. Small 2008, 7, 2279-2285). Second, purified SWCNT were functionalized with dodecyl and then investigated by STXM. Spectral evidence for the dodecyl functionalization is presented and discussed in comparison to the X-ray absorption spectra of aliphatic hydrocarbons. Both orientation and functionalization mapping of an individual SWCNT bundle is demonstrated.

IR multiphoton depletion spectroscopy of metal cluster-ligand complexes

Abstract Free electron laser IR photodepletion spectroscopy of metal cluster–ligand complexes in a molecular beam is demonstrated on Ag n (NH 3 ) m complexes in the range 800–1150 cm −1 . Where direct comparison can be made, our spectra agree with spectra measured by CO 2 laser photodepletion spectroscopy. New vibrational spectroscopic data addressing previously unreachable spectral regions, including results for deuterated ND 3 are reported for complexes of Ag 3 , Ag 4 and Ag 5 .

About the solubility of reduced SWCNT in DMSO

Single-walled carbon nanotubes (SWCNT) have been reduced with sodium naphthalide in THF. The reduced SWCNT are not only soluble in dimethylsulfoxide (DMSO) to form a stable solution/suspension, but also react spontaneously at room temperature with DMSO to evolve hydrocarbon gases and are converted into functionalized SWCNT. The degree of functionalization is about 2C% and the addends are mainly methyl and small oxygen-containing hydrocarbons. The functionalized SWCNT are apparently more soluble and stable in DMSO solution. It may open a new era for further processing and applications.

Polymer nanocomposites from free-standing, macroscopic boron nitride nanotube assemblies†

Here we report the fabrication of free-standing boron nitride nanotube (BNNT) sheets by direct deposition and by vacuum filtration methods, including novel hybrid assemblies with BNNT and carbon nanotubes. Such sheets have enabled production of polymer nanocomposites with high nanotube content. Two example cases, BNNT–epoxy nanocomposites (>30 wt% BNNTs) produced by impregnation of dry sheets and BNNT sheets modified by integration of a thermoplastic polyurethane are described. Related methods have proven advantageous for carbon nanotube composites and, enabled by new technology for large scale BNNT production, such composites have now been realized with BNNTs. This represents an important milestone towards the development of BNNT-based multifunctional composites.

Investigation of some Rydberg states of ketene by two-photon resonance-enhanced multiphoton ionization spectroscopy

Rydberg states of CH2CO and CD2CO in the 54 000–72 000 cm−1 spectral range have been reinvestigated using two-photon resonance-enhanced multiphoton-ionization spectroscopy. Improved resolution and sensitivity has allowed for identifications of more Rydberg states than in previous work. Based on an analysis of rotational structures and quantum defects and a comparison with the results of theoretical calculations, transitions to the 3pz, 4py, 4pz, and 5py, three components of 4d, and two components of 4f Rydberg states with a ground-state ionic core (X 2B1) are identified. Several transitions have been reassigned. Vibrational wave numbers indicate that the geometry of the [X 2B1]3py(1A2) state is almost identical to that of the corresponding cation in its ground electronic state, with C2v symmetry, whereas that of the [X 2B1]3px(1A1) state differs significantly from those of the neutral molecule and the cation in their ground states, consistent with previous quantum chemical calculations that indicated t...

Quantitative EDX Microanalysis On Volatile Alloyed Nanoparticles

Alloyed nanoparticles (NPs) are attracting significant interest as potential catalysts or as probes for biological or chemical events. Some of the relevant properties of these NPs are critically dependent on their composition. In this regard, energy dispersive X-ray (EDX) spectroscopy in a FEG-TEM has become an essential analytical tool for quantifying the components of individual NPs. However, if one or several components of the nanoparticle are beam-sensitive, the EDX results can be misleading, especially if one element is volatile. In this case, the collection of sufficient X-ray signal to carry adequate quantitative analysis is done at the expense of considerable losses of the volatile component resulting in erroneous analysis. It is possible, however to determine the composition of a NP prior to beam-induced damage based on the analysis of the sublimation rate. This paper presents an example of this simple method for alloyed Au-Ag nanoparticles, a system where Ag is lost during electron irradiation.