Synthesis, characterization and physical properties of carbon and boron nitride low dimensional systems.

Tesis (Doctorado en Nanociencias y Materiales)"Carbon nanotubes are versatile materials with promising applications based on their exceptional physical properties. Their applications depend strongly on the interactions that nanotubes have with their environment. In this sense, doping of carbon nanotubes, understood as the incorporation of foreign species into the nanotube lattice, has proven as a very good method for modifying and tuning their physical and chemical properties, broadening the range of possible applications. In this work, the heteroatomic doping of multiwalled carbon nanotubes with phosphorus and nitrogen atoms is presented. These nanotubes were successfully synthesized and thoroughly characterized by several electron microscopy and microanalysis techniques, and changes in their chemical properties were surveyed by thermogravimetric analysis. In addition, first principles calculations were performed to understand the structural and electronic modifications that heteroatomic doping cause on single walled nanotubes. In the other hand, small carbon clusters and one-dimensional nanostructures could occur during doping of carbon nanostructures by heat treatment procedures. In this context, the energetic and electronic properties of small carbon clusters of 10, 12 and 14 atoms were studied by ab initio calculations, with special interest in their spin polarization. In addition, the vibrational properties of monoatomic carbon chains occurring during the boron doping process of double walled nanotubes and their relation with the Coalescence Induce Mode of their Raman spectra was also studied. Finally, the properties of boron nitride nanoribbons synthesized by a substitution reaction in carbon nanostructures that exhibit a surprising metallic behavior are explored by ab initio calculations.