Contrasting bonding behavior of thiol molecules on carbon fullerene structures Article uri icon

abstract

  • We have performed semiempirical as well as ab initio density-functional theory (DFT) calculations at [Formula Presented] to analyze the equilibrium configurations and electronic properties of spheroidal [Formula Presented] as well as of cylindrical armchair (5, 5) and (8, 8) fullerenes passivated with [Formula Presented] and [Formula Presented] thiols. Our structural results reveal that the lowest-energy configurations of the adsorbates strongly depend on their chain length and on the structure of the underlying substrate. In the low-coverage regime, both [Formula Presented] and [Formula Presented] molecules prefer to organize into a molecular cluster on one side of the [Formula Presented] surface, providing thus a less protective organic coating for the carbon structure. However, with increasing the number of adsorbed thiols, a transition to a more uniform distribution is obtained, which actually takes place for six and eight adsorbed molecules when using [Formula Presented] and [Formula Presented] chains, respectively. In contrast, for the tubelike arrangements at the low-coverage regime, a quasi-one-dimensional zigzag organization of the adsorbates along the tubes is always preferred. The sulfur-fullerene bond is considerably strong and is at the origin of outward and lateral displacements of the carbon atoms, leading to the stabilization of three-membered rings on the surface (spheroidal structures) as well as to sizable nonuniform radial deformations (cylindrical configurations). The electronic spectrum of our thiol-passivated fullerenes shows strong variations in the energy difference between the highest occupied and lowest unoccupied molecular orbitals as a function of the number and distribution of adsorbed thiols, opening thus the possibility to manipulate the transport properties of these compounds by means of selective adsorption mechanisms. © 2003 The American Physical Society.

publication date

  • 2003-01-01