Hola todos
Deseamos difundir el siguiente seminario:
THEORETICAL INVESTIGATIONS ON CARBON NANOTUBES: SIDEWALL
FUNCTIONALIZATION AND ENCAPSULATION OF NANOCRYSTALLITES
Antonio Sgamellotti
Department of Chemistry, CNR-ISTM and UdR INSTM
University of Perugia, Via Elce di Sotto 8, 06123 Perugia
Jueves, 6 de Marzo 2008 a las 13 h
Aula de Seminario INQUIMAE- 3er piso
Adjuntamos el Abstract
Esperamos contar con su presencia
Dr. R. Candal
Dra. S. Goyanes
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Ю Є Ю № З ' ' ' ' ' ' ' § § G Ь ' ' ' X ' ' ' ' $ ( ( № № № № № № џџџџ Theoretical investigations on carbon nanotubes: sidewall functionalization and encapsulation of nanocrystallites
Antonio Sgamellotti
Department of Chemistry, CNR-ISTM and UdR INSTM
University of Perugia, Via Elce di Sotto 8, 06123 Perugia
The investigation of nanostructured systems and materials is currently a topic of great interest, in view of future technological applications. In this field modelling plays an important role; theoretical calculations provide insight into the microscopic properties and behaviour of these systems. In this work we present theoretical investigations on the properties of carbon nanotubes (CNTs), one of the most studied and promising species in the field of nanotechnology.
The chemical functionalization of CNTs represents an attractive target for study, since it can improve their solubility and processability. Accurate theoretical investigations of functionalized CNT may clarify the effects of chemical modifications on their electronic and structural properties. Static and dynamical density functional theory calculations have been performed to analyze the interaction of different species with CNTs. The areas of applications considered in this work include several functionalization routes and related properties. As a first example, investigations have concerned the functionalization of CNTs with transition metal complexes, which is found to affect the electronic properties of the adduct. Moreover, the interaction between small molecules and the CNT sidewall has been analyzed in order to investigate eventual technological applications of CNTs in fields like gas-sensing or hydrogen storage in nanostructured fuel cells. In all cases, special attention has been devoted to the definition of proper models for the sidewall, which constitute a mandatory step to achieve the required accuracy.
Another field of investigation has concerned the confined growth of ionic species by encapsulation in CNTs, which has recently attracted growing interest. The ability to encapsulate different materials has indeed constituted one of the first applications of CNTs. Besides the possibility of creating intrinsically monodimensional materials through nanotube-driven template syntheses, one of the most interesting aspects of encapsulation concerns the formation of ordered structures in the hollow of CNTs, in the form of nanocrystallytes. The one-dimensional confined growth of different compounds has been viewed as a suitable route to the development of new low-dimensional materials, like nanowires. In our work, the morphologies of AgI nanocrystallites grown inside (n,n) single-walled CNTs are investigated by means of molecular dynamics simulations. All crystal structures found are formally constituted by (n,m) AgI nanotubes, with chiral vectors n and m depending on the CNT diamenter and on the local environment. In particular, for narrow CNTs unprecedented low-dimensional AgI nanoribbons appear, actively stabilized by a deformation of the CNT, as observed in experiments. In larger diameter CNTs, inorganic (n,m) AgI nanotubes are typically formed, giving rise to a scenario of polymorphism in the nanoregime.
An extention of the Clar sextet theory of aromatic systems is proposed for finite-length models of metallic and semiconducting carbon nanotubes (CNTs). For metallic CNTs, the electronic properties of finite-length models converge monotonically to the values expected for quasi-monodimensional metallic systems. For semiconducting CNTs, the use of finite-length models leads to a fast convergence of the electronic properties to the values expected for the corresponding infinite nanotube.
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