Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition. The key concept is to shape metallic clusters that donate or accept a fractional charge upon adsorption of a target molecule, and modify the electron transport in the nanotube. The present work focuses on a simple system, carbon nanotubes with gold clusters. The nature of the gold-nanotube interaction is studied using first-principles techniques. The numerical simulations predict the binding and diffusion energies of gold atoms at the tube surface, including realistic atomic models for defects potentially present at the nanotube surface. The atomic structure of the gold nanoclusters and their effect on the intrinsic electronic quantum transport properties of the nanotube are also predicted. Experimentally, multi-wall CNTs are decorated with gold clusters using (1) vacuum evaporation, after activation with an RF oxygen plasma and (2) colloid solution injected into an RF atmospheric plasma; the hybrid systems are accurately characterized using XPS and TEM techniques. The response of gas sensors based on these nano(2)hybrids is quantified for the detection of toxic species like NO(2), CO, C(2)H(5)OH and C(2)H(4).
This work demonstrates the capabilities of nanoscale secondary-ion mass spectrometry, using the Cameca NanoSIMS50 ion microprobe, to detect and image the copper-ion distribution in microalgal cells exposed to nanomolar and micromolar copper concentrations. In parallel to 63 Cu − secondary-ion maps, images of 12 C −
Interactions between a late Ar-O 2 post-discharge and thin films (*1 -2 lm) of stearic acid (SA), a C 17 aliphatic chain with as end-group a carboxylic acid function, are studied. Thin films grown by evaporation are made of separated droplets and are efficiently etched by the post-discharge to get a clean surface after treatment. The dewetting of the droplets during the first minutes of the treatment leads first to a more homogeneous film in thickness which is etched until isolated islands appear and progressively shrink as a function of time. The etching of the SA occurs via C-C bonds scission when peroxide or hydroperoxide compounds are synthesized from radicals initiated by reaction with atomic oxygen from the post-discharge. A strong functionalization by OH groups grafted on the aliphatic skeleton of the SA is also observed. C = O formation is observed for longer treatment times possibly due to oxidation of OH grafted on the aliphatic chain or to a modification of the branching ratio of the C-C bond scission mechanism due a temperature rise. The acid functional group is likely not modified by the treatment.
Nanodroplets of isotactic polypropylene (iPP) were observed using temperature-controlled AFM
in order to study the polymer's crystallization behavior. The nucleation, growth, and transformation of iPP crystals
on heating have been directly imaged. The strong confinement of the polymer into nanoscale droplets has allowed
the controlled observation of polymer nucleation as well as access to crystal growth at exceptionally high
supercooling in iPP. Different modes of crystal growth were observed depending on the film thickness, including
the formation of multiple independent homogeneous nuclei within single droplets. The temperature at which the
onset of nucleation was observed in individual droplets was found to be dependent on the thickness as well as
the volume of the droplets. For droplets with smaller thicknesses (<5 nm), the thickness of the droplets was
found to be the dominating factor influencing the nucleation temperature. This is the first real-space, real-time
observation of homogeneous nucleation in iPP, almost 125 °C below its melting point, which could signify crystal
growth in the smectic form, and of the subsequent reorganization into the α-form.
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