Fluorine-containing block/branched polyamphiphiles forming bioinspired complexes with biopolymers.

Colloidal-chemical characteristics of block/branched cationic and non-ionic polyamphiphiles containing poly(fluorine-alkyl methacrylate) (poly(FMA)) block and their intermolecular complexes with biopolymers were studied. The dependences of their surface activity and micelle size on the length of hydrophobic and hydrophilic blocks, as well as the length of side fluorine-alkyl branches were established. Poly(FMA)-block-poly(DMAEMA) was used for formation of interpolyelectrolyte complexes with plasmid DNA (pDNA) via their electrostatic interaction. Novel non-viral polyplexes were tested as gene delivery systems for mammalian cells. The results of DLS, TEM and MALDI-ToF studies demonstrated disaggregation of lysozyme (LYZ) aggregates in the presence of poly(FMA)-block-poly(NVP) and formation of the polyamphiphile…LYS complex possessing antibacterial action.

Solvent-Free Covalent Functionalization of Fullerene C60 and Pristine Multi-Walled Carbon Nanotubes with Crown Ethers.

The goal of the present work was to test the feasibility of simple, one-step and solvent-free covalent functionalization of pristine multi-walled carbon nanotubes (MWNTs) and fullerene C60 (as a model system) with amino-substituted crown ethers, namely, 4'-aminobenzo-15-crown-5 and 4'-aminobenzo-1 8-crown-6. The attachment technique proposed is based on thermal instead of chemical activation, and can be considered as ecologically friendly. The suggested covalent binding mechanism is the nucleophilic addition of amino functionalities of crown ethers to the 6,6 bonds of pyracylene units in the case of C60, and to pentagonal (and probably other) defects of similar nature in the case of pristine MWNTs. The hybrids of crown ethers with MWNTs were characterized by means of scanning and transmission electron microscopy, Fourier-transform infrared and Raman spectroscopy, as well as thermogravimetric analysis. The functionalized C60 samples were additionally studied by means of 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and laser desorption/ionization time-of-flight mass spectrometry. The approach proposed allows for a facile preparation of crown ether-functionalized pristine MWNTs without contamination with other chemical reagents, detergents and solvents, which is especially important for a vast variety of nanotube applications ranging from nanoelectronics to nanomedicine.

Nanostructured diamine-fullerene derivatives: computational density functional theory study and experimental evidence for their formation via gas-phase functionalization.

Nanostructure derivatives of fullerene C(60) are used in emerging applications of composite matrices, including protective and decorative coating, superadsorbent material, thin films, and lightweight high-strength fiber-reinforced materials, etc. In this study, quantum chemical calculations and experimental studies were performed to analyze the derivatives of diamine-fullerene prepared by the gas-phase solvent-free functionalization technique. In particular, the aliphatic 1,8-diamino-octane and the aromatic 1,5-diaminonaphthalene, which are diamines volatile in vacuum, were studied. We addressed two alternative mechanisms of the amination reaction via polyaddition and cross-linking of C(60) with diamines, using the pure GGA BLYP, PW91, and PBE functionals; further validation calculations were performed using the semiempirical dispersion GGA B97-D functional which contains parameters that have been specially adjusted by a more realistic view on dispersion contributions. In addition, we looked for experimental evidence for the covalent functionalization by using laser desorption/ionization time-of-flight mass spectrometry, thermogravimetric analysis, and atomic force microscopy.

Microwave irradiation of pristine multi-walled carbon nanotubes in vacuum.

The goal of the present paper was to study the behavior of commercially available pristine multi-walled carbon nanotubes (MWNTs) under microwave irradiation (exposures up to 200 s) in vacuum, by means of several experimental techniques. An intense glow and heating of the nanotube samples were observed. Raman spectra, scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) images of the processed nanotubes did not show considerable changes as compared to those for pristine MWNTs. Closer structural investigation by means of conventional and high-resolution transmission electron microscopy (TEM and HRTEM, respectively) revealed an increase in the occurrence of open nanotube ends, whereas the sidewalls remained generally unchanged. The possibility of increase in the number of entry ports for gases was verified by employing temperature programmed desorption experiments with mass spectrometric detection (TPD-MS) with pristine and microwave-irradiated MWNTs exposed to atmosphere. The overall adsorption capacity did not change, whereas the rate of adsorption increased roughly by twice for the nanotubes irradiated for 200 s as compared to pristine MWNTs, which is consistent with selective opening of the nanotube ends.

Fullerene C60 films cross-linked with octane-1,8-dithiol: preparation, characterization and the use as template for chemical deposition of gold nanoparticles.

We report on the preparation of fullerene C60 thin films chemically cross-linked with octane-1,8-dithiol, which are capable of binding gold nanoparticles. The formation of a polymer was directly proved by means of laser desorption/ionization time-of-flight mass spectra, in which we observed the cleavage of fullerene-dithiol polymer at different bonds. Fourier-transform infrared, Raman and UV-visible spectra of the functionalized films exhibited notorious changes due to the formation of new covalent bonds between C60 molecules and bifunctional thiol. We further demonstrated that the dithiol-functionalized fullerene can be employed as a support for stable and homogeneous deposition of gold nanoparticles. Their average size is about 5 nm according to high-resolution transmission electron microscopy observations, and up to 20 nm, as found from scanning tunneling microscopy images. The proposed binding mechanism is through a strong coordination attachment between Au nanoclusters and sulfur donor atoms of the functionalized fullerene, as supported by density functional theory calculations.

Solvent-free derivatization of pristine multi-walled carbon nanotubes with amines.

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.

Interaction of thermally pretreated carbon nanomaterials with water vapor.

We used temperature-programmed desorption-mass spectrometry to verify whether low-molecular-weight products can form by reacting thermally pretreated single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively) with water vapor. The reactivity of MWNTs toward water is similar to the reactivity of graphite, whereas acid-oxidized SWNTs behave like polymerized C60 fullerene. We think the main factors influencing the reactivity are molecular surface curvature and the presence of pyrolyzable defect groups, which create highly strained bonds upon their elimination.