Single-walled carbon nanotubes functionalized with the OH group-terminated moieties (“hydroxyl nanotubes”) have been prepared by fluorine displacement reactions of fluoronanotubes with a series of diols and glycerol in the presence of alkali, LiOH, NaOH, or KOH or with amino alcohols in the presence of Py as a catalyst. The “hydroxyl nanotubes” were characterized by optical spectroscopy (Raman, ATR-FTIR, UV−vis−NIR), electron microscopy (TEM), atomic force microscopy (AFM), and thermal degradation (TGA and VTP-MS) materials characterization methods. The degree of sidewall functionalization in the prepared SWNT derivatives was estimated to be in the range of 1 in 15 to 25 carbons, depending on derivatization method and alcohol reagent used. The hydroxyl nanotubes form stable suspension solutions in polar solvents, such as water, ethanol, and dimethylformamide, which facilitate their improved processing in copolymers and ceramics nanofabrication and provide for compatibility with biomaterials.

A method for direct in situ thickness measurements of ultra-thin soft polymer films is presented in which an atomic force microscope (AFM) tip is used to create a furrow in the film, whereby the thickness is determined by scanning the sample across the furrow with the AFM. The sample does not need to be moved since the scratching and the measurements are performed with the same apparatus. This `furrow method' is applied to layer-by-layer polymer/polyelectrolyte ultra-thin films onto hydrophilic glass and silicon wafer substrates. This procedure is made possible because the polymeric film is less stiff than the substrates and the silicon tip. Results for 10-12-bilayer films are comparable to those obtained from profilometry, whose accuracy is only reasonable for films with more than ten bilayers. Taken together, the AFM and profilometer results show that film thickness increases linearly with the number of bilayers. Furthermore, the film thickness does not seem to depend on the substrate used but only on the number of bilayers deposited.

In this paper we report on complementary measurements on ion-pair formation in collisions between K atoms and CH 3 N0 2 molecules. The experiments were performed in a c.m. energy range from 20 up to 300 eV. Double differential cross sections were obtained by measuring the K + ion yield as a function of the scatter angle and as a function of the post-collision laboratory energy. On the other hand, relative total partial cross sections for the formation of CH 3 N0 2 -, N0 2 -, and 0 -were measured in the same energy range. The experimental results lead to the conclusion that in this energy range electron transfer takes place to three ionic states ofCH 3 NO; , a dominantly repulsive 2AI state and two 2EI states with relatively deep potential wells. 166 J. Chem. Phys. 95 (1).1

Layer-by-layer (LBL) films of a semiconducting polymer (POMA) alternated with a polyelectrolyte (PVS), adsorbed onto silicon oxide, mica, ITO/glass, Au/Cr/glass, hydrophilic and hydrophobic glass were studied by atomic force microscopy (AFM). The samples were characterized LBL with the AFM operating in the contact, friction and tapping modes, which allowed us to determine their morphological surface properties such as roughness, mean grain size, grain boundaries and power spectrum density. Their film thickness was measured by AFM using the tip as a scraping tool. Surface roughness increases with the number of bilayers until a constant value is reached. This is in agreement with the observed increase in the adsorbed amount (per layer) of POMA as the number of bilayers is increased, which also saturates after several bilayers. It is shown that the 3D growth behaviour indicates a similar microscopic mechanism for all systems under study, pointing to a stochastic growth process of the Eden model type, but strongly influenced by initial roughness and water affinity of the virgin substrates. The crystalline or amorphous nature of the substrates does not seem to influence the growth process.

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Among the most efficient techniques for hydrogen desorption monitoring, thermal desorption mass spectrometry is a very sensitive one, but in certain cases can give rise to uptake misleading results due to residual hydrogen partial pressure background variations. In this work one develops a novel thermal desorption variant based on the effusive molecular beam technique that represents a significant improvement in the accurate determination of hydrogen mass absorbed on a solid sample. The enhancement in the signal-to-noise ratio for trace hydrogen is on the order of 20%, and no previous calibration with a chemical standard is required. The kinetic information obtained from the hydrogen desorption mass spectra (at a constant heating rate of 1 degrees C/min) accounts for the consistency of the technique.

Beams of hyperthermal K atoms cross beams of the oriented haloforms CF(3)H, CCl(3)H, and CBr(3)H, and transfer of an electron mainly produces K(+) and the X(-) halide ion which are detected in coincidence. As expected, the steric asymmetry of CCl(3)H and CBr(3)H is very small and the halogen end is more reactive. However, even though there are three potentially reactive centers on each molecule, the F(-) ion yield in CF(3)H is strongly dependent on orientation. At energies close to the threshold for ion-pair formation ( approximately 5.5 eV), H-end attack is more reactive to form F(-). As the energy is increased, the more productive end switches, and F-end attack dominates the reactivity. In CF(3)H near threshold the electron is apparently transferred to the sigma(CH) antibonding orbital, and small signals are observed from electrons and CF(3)(-) ions, indicating "activation" of this orbital. In CCl(3)H and CBr(3)H the steric asymmetry is very small, and signals from free electrons and CX(3)(-) ions are barely detectable, indicating that the sigma(CH) antibonding orbital is not activated. The electron is apparently transferred to the sigma(CX) orbital which is believed to be the LUMO. At very low energies the proximity of the incipient ions probably determines whether salt molecules or ions are formed.