Inductive coupled rf-plasma at 13.56 MHz was used to modify multiwalled carbon nanotubes (MWCNTs). This technique can be easily used to tailor the chemical composition of carbon nanotubes by attaching a wide variety of functional groups at their surface: oxygen-, nitrogen-, and fluorine-containing groups have been grafted. The influence of various plasma conditions (power, type of gas, treatment time, pressure, position of the CNT sample inside the chamber) on the functionalization of the MWCNT surface was analyzed by x-ray photoelectron spectroscopy. The results show that for too high oxygen plasma power, chemical etching occurs at the surface of the CNT, thus destroying its structure. On the other hand, for optimal values of the plasma parameters, functional groups (hydroxide, carbonyl, carboxyl, amine, fluorine, etc.) were found to bond to the CNT surface, suggesting that both the concentration and type of the functional groups are in close connection with the plasma conditions. These results were compared to interaction energies predicted by ab initio calculations for different functional groups under consideration, showing that functionalization by oxygen plasma produces mainly functional groups with lower interaction energy.

A new method of synthesising nanoparticle-functionalised nanostructured materials via Aerosol Assisted Chemical Vapour Deposition (AACVD) has been developed. Co-deposition of Au nanoparticles with WO(3) nanoneedles has been used to deposit a sensing layer directly onto gas sensor substrates providing devices with a six-fold increase in response to low concentrations of a test analyte (ethanol).

Chlorosulfonic acid assisted the exfoliation of MoS2 and WS2 resulting in retaining their semiconducting 2H-phase, sharply contrasting the semiconducting-to-metallic phase-transition observed with the currently available exfoliation techniques.

Tungsten oxide nanostructures functionalized with gold or platinum NPs are synthesized and integrated, using a single‐step method via aerosol‐assisted chemical vapour deposition, onto micro‐electromechanical system (MEMS)‐based gas‐sensor platforms. This co‐deposition method is demonstrated to be an effective route to incorporate metal nanoparticles (NP) or combinations of metal NPs into nanostructured materials, resulting in an attractive way of tuning functionality in metal oxides (MOX). The results show variations in electronic and sensing properties of tungsten oxide according to the metal NPs introduced, which are used to discriminate effectively analytes (C2H5OH, H2, and CO) that are present in proton‐exchange fuel cells. Improved sensing characteristics, in particular to H2, are observed at 250 °C with Pt‐functionalized tungsten oxide films, whereas non‐functionalized tungsten oxide films show responses to low concentrations of CO at low temperatures. Differences in the sensing characteristics of these films are attributed to the different reactivities of metal NPs (Au and Pt), and to the degree of electronic interaction at the MOX/metal NP interface. The method presented in this work has advantages over other methods of integrating nanomaterials and devices, of having fewer processing steps, relatively low processing temperature, and no requirement for substrate pre‐treatment.

Primary amine‐based plasma polymer films (NH2‐PPF) were synthesized using plasma polymerization of allylamine in continuous wave (CW) and pulsed radio‐frequency (RF) modes. Plasma chemistry, studied by residual gas analysis mass spectrometry, revealed that the precursor fragmentation is a function of the equivalent power (Peq) dissipated in the discharge, independently of the plasma mode used. X‐ray photoelectron spectroscopy combined with time‐of‐flight secondary ion mass spectrometry suggests as the precursor fragmentation in the plasma increases: (i) a decrease of the primary amine concentration in the NH2‐PPF (%NH2) and (ii) an increase of the cross‐linking degree. For a given Peq, similar to the precursor fragmentation in the plasma, the NH2‐PPF characteristics were found to be independent of the plasma mode used. Therefore, the main advantage of using pulsed RF processes over CW ones is the possibility to work at very low Peq which enables low precursor fragmentation, optimization of %NH2, and reduction of the film cross‐linking degree. The chemical composition and the cross‐linking degree of the NH2‐PPF synthesized by allylamine plasma polymerization can thus be tailored by adjusting the equivalent RF power injected in the plasma.

The covalent functionalization of exfoliated semiconducting MoS 2 by 1,2-dithiolanes bearing an ethylene glycol alkyl chain terminated to a butoxycarbonyl-protected amine and a photoactive pyrene moiety is accomplished. The MoS 2 -based nanohybrids were fully characterized by complementary spectroscopic, thermal, and microscopy techniques. Markedly, density functional theoretical studies combined with X-ray photoelectron spectroscopy analysis demonstrate preferential edge functionalization, primarily via sulfur addition along partially sulfur saturated zig-zag MoS 2 molybdenum-edges, preserving intact the 2D basal structure of functionalized MoS 2 -based nanohybrids as confirmed by high-resolution transmission electron microscopy and electron energy loss spectroscopy. Furthermore, in the MoS 2 -pyrene hybrid, appreciable electronic interactions at the excited state between the photoactive pyrene and the semiconducting MoS 2 were revealed as inferred by steady-state and time-resolved photoluminescence spectroscopy, implying its high potentiality to function in energy conversion schemes.

International audienceNear-edge X-ray absorption spectroscopy (NEXAFS)1 is an essential analytical tool in material science. Combining NEXAFS with scanning transmission X-ray microscopy (STXM) adds spatial resolution and the possibility to study individual nanostructures2, 3. Here, we describe a full-field transmission X-ray microscope (TXM) that generates high-resolution, large-area NEXAFS data with a collection rate two orders of magnitude faster than is possible with STXM. The TXM optical design combines a spectral resolution of E/ΔE = 1 × 104 with a spatial resolution of 25 nm in a field of view of 15-20 µm and a data acquisition time of ~1 s. As an example, we present image stacks and polarization-dependent NEXAFS spectra from individual anisotropic sodium and protonated titanate nanoribbons. Our NEXAFS-TXM technique has the advantage that one image stack visualizes a large number of nanostructures and therefore already contains statistical information. This new high-resolution NEXAFS-TXM technique opens the way to advanced nanoscale science studies

The effect of ultrasonication parameters, such as time and power applied, to exfoliate graphite in o-dichlorobenzene (o-DCB) and N-methyl-1,2-pyrrolidone (NMP) was examined. It was found that the concentration of graphene was higher in o-DCB, while its dispersibility was increased when sonication was applied for a longer period and/or at higher power. However, spectroscopic examination by X-ray photoelectron spectroscopy (XPS) revealed that ultrasonication causes defects and induces oxygen functional groups in the form of carboxylic acids and ethers/epoxides onto the graphene lattice. Additional proof for the latter arose from Raman, IR, and thermogravimetry studies. The carboxylic acids and ethers/epoxides onto exfoliated graphene were derived from air during ultrasonication and found independent of the solvent used for the exfoliation and the power and/or time ultrasonication applied. Quantitative evaluation of the amount of oxygenated species present on exfoliated graphene as performed by high-resolution XPS revealed that the relative oxygen percentage was higher when exfoliation was performed in NMP. Finally, the sonication time and/or power affected the oxygen content on exfoliated graphene, since extended ultrasonication resulted in a decrease in the oxygen content on exfoliated graphene, with a simultaneous increase of defected sp3 carbon atoms.