Functionalization of carbon nanotubes by atomic nitrogen formed in a microwave plasma Ar+N2

peer reviewedMulti-walled carbon nanotubes (MWNTs) are placed under atomic nitrogen flow formed through an Ar + N2 microwave plasma in order to functionalize covalently their side walls with nitrogen-containing groups. The MWNT surface analyzed by X-ray photoelectron spectroscopy shows the presence of amides, oximes and mainly amine and nitrile functions grafted in this way. In order to highlight the actual location of the amine functions grafted on MWNTs, they were considered as initiation species in ring-opening polymerization of £-caprolactone using triethylaluminium as activator. The so-generated poly(e-caprolactone) chains remain grafted on the MWNTs via amide bonds and form polyester islets along the nanotubes surface. TEM images of these MWNT surfaces grafted with poly(e-caprolactone) show a good amino-sidewall distribution. This work demonstrates the side-wall amino-functionalization of carbon nanotubes readily achieved by microwave plasma with the possibility to reach within a short time period very high contents in nitrogen-based functions (~10 at.%)

The Role of TiO2 Doping on RuO2-Coated Electrodes for the Water Oxidation Reaction

Electrochemical water splitting into H2 and O2 presents a significant and challenging energy loss due to the high overpotential required at the anode. Today, in industrially relevant applications, dimensionally stable anodes (DSA) based on the electrocatalytic active RuO2 are conventionally utilized. To enhance the resistance against corrosion, incorporation of TiO2 in the RuO2-coated electrodes is widely employed. In the present work we have used scanning electrochemical microscopy (SECM) to demonstrate that TiO2-doped RuO2-coated electrodes, in addition to being more durable, also show an electrocatalytic activity that is, on average, 13% higher as compared to the pure RuO2-coated electrodes. We also demonstrate that cracks in the pure RuO2 coating are the most active zones, probably because Ti from the Ti support has diffused into the first applied layer of the RuO2 coating. To reveal the nature of this enhanced activity for water oxidation displayed on TiO2-doped RuO2 electrodes, we have employed X-ray photoelectron spectroscopy (XPS) for material characterization. The results show that the electrocatalytic activity enhancement displayed on the mixed (Ru1–x:Tix)O2 coating is promoted through a charge transfer from the RuO2 to the TiO2, which provides new and more reactive sites designated as activated RuO2δ+.This study has partly been carried out in the framework of the European Commission FP7 Initial Training Network “ELCAT”, Grant Agreement No. 214936-2. Portions of this research were performed at SPring-8 with the approval of Japan Synchrotron Radiation Research Institute as Nanotechnology Support Project of the Ministry of Education, Culture, Sports, Science and Technology (Proposal No. 2007A2005 and 2008A1671/BL-47XU)

Preparation and characterisation of gasochromic thin films

peer reviewe

Effect of potassium intercalation on the electronic and vibrational properties of benzylic amide [2]catenane films

The appearance of gap states in benzylic amide catenane thin films following potassium intercalation was investigated by electron energy loss spectroscopy and quantum chemical calculations. Both theory and experience find an excitation energy for transitions into these new states of ~2 eV. The characteristics of these states are discussed.

C60/metal surfaces: adsorption and decomposition

C60 was deposited on Ni(110), Pt(111) and Ag(111) and annealed at different temperatures. The structural properties of the overlayer were investigated by low-energy electron diffraction, the changes induced by adsorption on its electronic properties were studied by valence band and core-level photoemission spectroscopy and inverse photoemission spectroscopy. On all surfaces C60 is chemisorbed and a clear signature for charge transfer is found for C60 on Ni(110) and Ag(111). Decomposition of C60 takes place on Ni(110) and Pt(111) above 690 K and 560 K respectively. The decomposition is a kinetically limited reaction on both surfaces and on Pt(111) we find a very strongly chemisorbed precursor state for decomposition.

Nitrogen profiles in materials implanted via plasma-based ion implantation

International audienc

Photoemission study of pristine and potassium intercalated benzylic amide [2]catenane films

In this paper we report a photoelectron spectroscopy (XPS and UPS) study of films of a benzylic amide [2]catenane on Au(111). We show that this molecule retains its molecular integrity during sublimation and that it chemisorbs on the metal surface. Potassium intercalation modifies the electronic structure of the films. We have observed a reduction of its amide functions and a modification of the charge density of the aromatic rings. The creation of polaron-like states in the gap of the neutral catenane and a decrease in the catenane work function of 0.8 eV have been demonstrated.