M. Bystrzejewski

Dispersion and diameter separation of multi-wall carbon nanotubes in aqueous solutions.

Comparative studies on dispersing of multi-wall carbon nanotubes (CNTs) using two anionic surfactants (sodium dodecyl sulphate, SDS, and sodium dodecyl benzenosulfonate, SDBS) are presented. The studies were conducted on the surfactant concentrations that were close to the critical micelle concentration (CMC). The stability of CNTs suspensions obtained for surfactant solutions at concentrations lower than the CMC was investigated. It was also found that the surfactant structure has an influence on the diameter distribution of dispersed CNTs.

Pulmonary Toxicity of 1‐D Nanocarbon Materials

Abstract 1‐D (one‐dimensional) nanocarbon materials possess unique properties. However, they could become airborne and reach the lungs. In the present study the pulmonary toxicity of nanotubes was investigated. Guinea pigs were intratracheally instilled with different nanotubes and inflammatory response was measured. The results show that both the duration of exposure and material characteristics can affect the respiratory process and induce pathological reaction in lung tissue.

Large scale continuous synthesis of carbon-encapsulated magnetic nanoparticles

Fe, Fe3C and NdC2 nanoparticles, encapsulated within carbon cages, were continuously produced during the induction thermal plasma processing of Fe14Nd2B, in the presence of methane or acetylene. The product morphology was studied by means of SEM. Further structural details were obtained from TEM, HRTEM, Raman spectroscopy and x-ray powder diffraction studies. The so-produced nanostructures have core?shell structure, with inner cavity diameters varying between 10 and 30?nm. The carbon coatings were composed of between 5 and 25 graphene layers. The carbon cages were built from sp2 carbon atoms, which protected the encapsulated nanoparticles from both oxidation and agglomeration. The plasma generated products were ferromagnetic, with maximum values of coercivity field of 600?G?s, and saturation magnetization values of up to 40?emu?g?1.

Catalyst-free synthesis of onion-like carbon nanoparticles

Abstract A one-step process for the synthesis of onion-like carbon nanoparticles is described. The process is based on a thermolysis of a NaN3-C6Cl6 mixture. The effect of buffer gas (Ar or air) on the yield, morphology, and structure of the carbon products was investigated by electron microscopy, X-ray diffraction, and Raman spectroscopy. The products contained carbon-onions, amorphous carbon nanoparticles, and NaCl. The byproducts were completely removed using a simple purification process. The formation of onion-like nanoparticles is likely caused by a shock wave, a rapid increase of pressure, during thermolysis, which induced the coalescence of phenyl radicals.

A novel type of electrochemical sensor based on ferromagnetic carbon-encapsulated iron nanoparticles for direct determination of hemoglobin in blood samples

An effective, fast, facile and direct electrochemical method of determination of hemoglobin (Hb) in blood sample without any sample preparation is described. The method is accomplished by using the ferromagnetic electrode modifier (carbon-encapsulated iron nanoparticles) and an external magnetic field. The successful voltammetric determination of hemoglobin is achieved in PBS buffer as well as in the whole blood sample. The obtained results show the excellent electroactivity of Hb. The measurements are of high sensitivity and good reproducibility. The detection limit is estimated to be 0.7 pM. The electrochemical determination data were compared with the gravimetric data obtained with a quartz crystal microbalance. The agreement between these results is very good. The changes of the electrode surface morphology before and after Hb detection are monitored by electron microscopy. The functionality of the electrochemical sensor is tested with human and rat blood samples. The concentration of hemoglobin in the blood samples determined by using voltammetric/gravimetric detection is in perfect agreement with the data obtained from typical clinical analysis.

A self-assembly SHS approach to form silicon carbide nanofibres

β-SiC nanofibres were efficiently produced using the thermal-explosion mode of self-propagating high-temperature synthesis from elemental Si and poly(tetrafluoroethylene) powder mixtures combusted under different operational parameters. The averaged combustion temperatures were evaluated using emission spectroscopy to be above 2000 K. The solid products were characterized by scanning and transmission electron microscopy, chemical analysis, and x-ray diffraction. Under optimum conditions the conversion of starting elemental Si into products exceeded 90%. To obtain pure (about 90%) SiC nanofibres the solid products were processed by wet chemistry.

Porous graphitic materials obtained from carbonization of organic xerogels doped with transition metal salts

Porous carbons with a well developed graphitic phase were obtained via the pyrolysis of FeCl3-, NiCl2-, and CoCl2-doped organic xerogels. Doping was realized through salt solubilization in a water/methanol solution of resorcinol and furfural. Carbon xerogels with tailored particles, porous morphology and various degrees of graphitization were obtained depending of the water/methanol ratio and the salt content and type in the starting solution of substrates. When obtained via pyrolysis, carbon xerogels retain the overall open-celled structure exhibiting depleted microporosity and a well-developed mesoporic region that expands into macropores. The removal of metal leads to carbon xerogels with specific surface areas between 170 and 585 m2/g and pore volume up to 0·76 cm3/g. The possibility of enhancing the porosity of xerogels via templating with colloidal silica was also investigated. It was assumed that from the three investigated salts, FeCl3 makes the best choice for graphitization catalyst precursor to obtain uniformly graphitized mesoporous carbon xerogels. The obtained carbon samples were characterized by means of SEM, TEM, X-ray diffraction, Raman spectroscopy, N2 physisorption and thermogravimetric analysis.

Carbon Encapsulation of Magnetic Nanoparticles

Abstract Carbon nanoencapsulates with the size between 20 and 50 nm were produced by arc discharge method using graphite anode doped with Fe14Nd2B (27 and 42 wt.%). The obtained products are ferromagnetic, with the maximum coercive force equal to about 413 Oe. X‐ray diffraction (XRD) of the purified products revealed the presence of different Fe, Nd and B phases. Structure and defects of the carbon coating were investigated by XRD and Raman spectroscopy. Optical emission spectroscopy was performed to determine average plasma temperature (5500–6000 K), and total carbon vapor pressure (10–60 kPa) depending on buffer gas pressure (13–60 kPa) and anode composition.

Comparative cytotoxicity studies of carbon-encapsulated iron nanoparticles in murine glioma cells.

Carbon-encapsulated iron nanoparticles (CEINs) have recently emerged as a new class of magnetic nanomaterials with a great potential for an increasing number of biomedical applications. To address the current deficient knowledge of cellular responses due to CEIN exposures, we focused on the investigation of internalization profile and resulting cytotoxic effects of CEINs (0.0001-100 μg/ml) in murine glioma cells (GL261) in vitro. The studied CEIN samples were characterized (TEM, FT-IR, Zeta potential, Boehm titration) and examined as raw and purified nanomaterials with various surface chemistry composition. Of the four type CEINs (the mean diameter 47-56 nm) studied here, the as-synthesized raw nanoparticles (Fe@C/Fe) exhibited high cytotoxic effects on the plasma cell membrane (LDH, Calcein AM/PI) and mitochondria (MTT, JC-1) causing some pro-apoptotic evens (Annexin V/PI) in glioma cells. The effects of the purified (Fe@C) and surface-modified (Fe@C-COOH and Fe@C-(CH2)2COOH) CEINs were found in quite similar patterns; however, most of these cytotoxic events were slightly diminished compared to those induced by Fe@C/Fe. The study showed that the surface-functionalized CEINs affected the cell cycle progression in both S and G2/M phases to a greater extent compared to that of the rest of nanoparticles studied to data. Taken all together, the present results highlight the importance of the rational design of CEINs as their physicochemical features such as morphology, hydrodynamic size, impurity profiles, and especially surface characteristics are critical determinants of different cytotoxic responses.

Synthesis of carbon-encapsulated iron nanoparticles by pyrolysis of iron citrate and poly(vinyl alcohol): a critical evaluation of yield and selectivity

Carbon-encapsulated iron nanoparticles were synthesized by pyrolysis at 1000 °C of two solid precursors: poly(vinyl alcohol) and iron citrate. The weight ratio between the precursors controlled the reaction yield, crystallinity, morphological features and magnetic properties of the products. The encapsulation yield of iron nanoparticles in carbon shells was strongly influenced by the iron-to-carbon ratio and depended on the iron citrate content in the initial reactant mixtures. Despite the inherent simplicity of the process and the use of low cost starting materials the demonstrated route possesses limited selectivity, especially at high iron-to-carbon ratios. At these experimental conditions the as-obtained products contained non-encapsulated Fe particles and graphite in addition to magnetic carbon encapsulates. These by-products were effectively removed by a one-pot purification procedure that included acid treatment.