The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pressure and a temperature of 160-170 °C. Applicability of infrared (IR) spectroscopy and temperature-programmed desorption mass spectrometry (TPD-MS) for chemical characterization of the derivatized SWNTs was analyzed. It was concluded that IR spectra of oxidized SWNTs treated with amines under different conditions (described here and elsewhere) cannot correspond to amide derivatives on SWNT tips because of the very low concentration of the terminal groups relative to the whole sample mass, which implies a negligible contribution to the IR spectra. The bands detectable in the case of long-chain amines correspond to amine molecules physisorbed because of strong hydrophobic interactions of their hydrocarbon chains with SWNT walls. Energetically preferable adsorption sites are the channels inside SWNTs, according to MM+ molecularmechanics modeling. TPD-MS provided additional information on the chemical state of the amines. Heating of the amine-treated SWNTs at >200 °C causes cleavage of alkenes from the amine residues: nonene and pentene form in the case of nonylamine and dipentylamine, respectively. For the short-chain amine (dipentylamine), only one chemical form was detected, whereas two forms (amide and physisorbed amine) can be distinguished for the SWNTs treated with nonylamine. The content of physisorbed nonylamine is about 1 order of magnitude higher than the amide content. According to the results of two-level ONIOM quantum-chemistry-molecular-mechanics calculations, the direct formation of amides on armchair SWNT tips is more energetically favorable than that on the zigzag tips, although the activation barriers are of approximately equal height.

We performed direct solvent-free amination of multi-walled carbon nanotubes (MWCNTs) with nonylamine, dodecylamine, octadecylamine, 4-phenylbutylamine and 1,8-ocanediamine at a temperature of 150-170 degrees C and reduced pressure. Thermogravimetric analysis and temperature-programmed desorption-mass spectrometry revealed that a major amine fraction decomposes in a temperature interval of 250-500 degrees C, thus existing on multi-walled carbon nanotubes as chemically bonded species; a minor amine fraction was found in physisorbed form. The new derivatization technique combines simplicity in implementation and attractive features of "green" chemistry. It requires no additional chemical activation, but thermal activation instead; it is relatively fast since it can be completed in about 2 h; the high temperature allows one to spontaneously remove excess amine from the nanotube and minimize the possibility of physical adsorption; there is no need to use an (organic) solvent medium. In the case of diamines (represented in this study by 1,8-ocanediamine), the functional groups introduced can be potentially used as chemical linkers for anchoring metal complexes and nanoparticles to multi-walled carbon nanotubes, for adsorption and concentration of trace metal ions.

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The thermal behavior of bone mineral samples was investigated in the range from 600 to 900ºC by X-ray diffraction with line broadening analysis and temperature-programmed desorption mass spectrometry. At least two stages of CO 3 2-release during the thermal evolution were observed, each can be attributed to a different type of carbonate location in the bone mineral. The elimination of CO 3 2-occurring without pronounced variations in the substructural parameters of the biomineral nanocrystals is ascribed to the surface carbonate, while the elimination of CO 3 2-accompanied by the growth of crystals and disappearance of structural distortions is attributed to the lattice carbonate. The sample of affected immature bone with low bioapatite crystallinity was found to have the surface carbonate content greater than the amount of carbonate in the lattice, while for the mature healthy bone the situation is reverse.