We report for the first time the production of single wall carbon nanotubes (SWCNTs) by KrF excimer laser ablation method under the krypton gas atmosphere. For the ablation experiment 450 mJ energy and 30 Hz repetition rate KrF excimer laser was used, and the target was prepared with the following composition: 0.6% Ni, 0.6% Co, and 98.8% C (atomic percentage). The ablation product was characterized by confocal Raman microspectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The SWCNTs obtained are a mixture of semiconducting and metallic types with narrow diameters distribution of 1.26 to 1.49 nm, are micrometers long, and contain low amount of graphite and amorphous carbon.

The recent development of the using the magnetic nanoparticles for hyperthermia treatments emphasizes the needed of smart materials to become a safety for heat therapy. Self-regulate magnetic nanoparticles of MnZnFe2O4 may be proper for thermal treatments. Structure and magnetic properties of the synthesis Mn1-xZnx Fe2O4 with x=0- 0.5 by step 0.1were studied. Superparamagnetic nanoparticles of MnZnFe2O4 were prepared by co-precipitation method, followed that heat treatment in the autoclave reactor. XRD results showed that is difficult to prepare MnZnFe2O4 directly using the co-precipitation method. Preparation method yield nanoparticles with spherical shape and there is a slight change in the particle size distribution, also observed shrinkage occurs in the particle size after heat treatments, the average particle size was estimated about 20nm as confirmed by FESEM images. FTIR spectra of samples showed two distinct absorption peaks in the range ~ 617 – 426 (cm-1) related to stretching vibrations of the (Fe-O) in the tetrahedral and octahedral side respectively. Magnetic measurements were carried out using (VSM), M-H curves indicate typical soft magnetic materials and particles so small to be identical superparamagnetic nanoparticles. Heating ability of water based colloidal dispersions of samples were studied under magnetic field strength 6.5kA/m and the frequency 190 kHz, and the results showed when increasing Zn2+ to x=0.3 or more the samples not heated up. Depending on the heating curve susceptibility, effective relaxation time and Néel relaxation time , were determined.

Abstract:The single-wall carbon nanotubes (SWCNTs) were synthesized using the equipment, method and experimental conditions described in [1]. Starting from the results shown in [2] and [3] we studied the influence of inert carrier gas over ablated mass, collected material, conducting character of SWCNTs and diameter distribution of SWCNTs. In our study KrF 248nm excimer laser was used instead of Nd:YAG (532nm) in [2] and four ablation gases: argon, nitrogen, neon and helium were involved. This kind of study, performed in our experimental conditions, was not reported so far. The ablated products were characterized using Raman spectroscopy and thermogravimetric analysis. We observed linear decrease of ablated mass with the increase of carrier gas molecular mass. Also the collected mass follows the same trend. TGA allowed us to calculate the mass of SWCNTs contained in the soot and the highest value was obtained in helium, 10 times more than in argon. Also, it was found the thermal conductivity of the carrier gas has a strong influence upon ablated mass and product deposition. The RBM and G Raman bands analysis have shown no influence of carries gas over the SWCNTs diameters distribution, respectively semiconducting character of SWCNTs, in all cases semiconducting SWCNTs being obtained. Our work concludes that helium is the best ablation gas, being 2 times more expensive than nitrogen but producing 8 times more SWCNTs.

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