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Carbon nanotubes with single and few walls are highly appreciated for their technological applications, regardless of the limited availability due to their high production cost. In this paper we present an alternative process that can lead to lowering the manufacturing cost of CNTs of only few walls by means of the use of the spray pyrolysis technique. For this purpose, ferrocene is utilized as a catalyst and aliphatic alcohols (methanol, ethanol, propanol or butanol) as the carbon source. The characterization of CNTs was performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The study of the synthesized carbon nanotubes (CNTs) show important differences in the number of layers that constitute the nanotubes, the diameter length, the quantity and the quality as a function of the number of carbons employed in the alcohol. The main interest of this study is to give the basis of an efficient synthesis process to produce CNTs of few walls for applications where small diameter is required.

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The cytotoxicity of the carbon nanotubes (CNTs) is an important factor for the manufacture of nanovaccines. The aim of this work was to evaluate the relationship of the purification method of CNTs in cellular toxicity using macrophages (MOs) from the J774 cell line. Viability test was performed with MTT assays at 24 h of exposure at concentrations of 0.06, 0.6, and 6 mg/L of unpurified (UP-CNTs) or purified (P-CNTs) CNTs by two different methods: (1) reflux with 3M HNO3and (2) sonication in H2SO4/HNO3. Characterization and COOH content of CNTs was performed using scanning electron microscopy, raman spectroscopy, and titration with NaHCO3. P-CNTs1had lengths >100 μm and 2.76% COOH content, while P-CNTs2had lengths >1 μm and 7% COOH content. This last particle showed a lower toxic effect. The results suggest that the lenght and COOH content are important factors in the toxicity of the CNTs.

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