arXiv subjects

Gustavo Ceballos

Publications and source records attributed to Gustavo Ceballos.

3 recordsLinked to original sources

arXiv2018

Critical role of phenyl substitution and catalytic substrate on the surface-assisted polymerization of dibromobianthracene derivatives

Understanding the nature and hierarchy of on surface reactions is a major chal- lenge for designing coordination and covalent nanostructures by means of multistep synthetic routes. In particular, intermediates and final products are hard to predict since reaction paths and their activation windows depend on the choice of both the molecular precursor design and the substrate. Here we report a systematic study of the effect of the catalytic metal surface to reveal how a single precursor can give rise to very distinct polymers that range from coordination and covalent non planar polymer chains of distinct chirality, to atomically precise graphene nanoribbons and nanoporous graphene. Our precursor consists on adding two phenyl substituents to 10,10'-dibromo 9,9'-bianthracene, a well-studied precursor in the on-surface synthesis of graphene nanoribbons. The critical role of the monomer design on the reaction paths is inferred from the fact that the phenyl substitution leads to very distinct products in each one of the studied metallic substrates.

cond-mat.mtrl-sci↗

arXiv2018

Bottom up synthesis of multifunctional nanoporous graphene

Nanosize pores can turn semimetallic graphene into a semiconductor and from being impermeable into the most efficient molecular sieve membrane. However, scaling the pores down to the nanometer, while fulfilling the tight structural constraints imposed by applications, represents an enormous challenge for present top-down strategies. Here we report a bottom-up method to synthesize nanoporous graphene comprising an ordered array of pores separated by ribbons, which can be tuned down to the one nanometer range. The size, density, morphology and chemical composition of the pores are defined with atomic precision by the design of the molecular precursors. Our measurements further reveal a highly anisotropic electronic structure, where orthogonal one-dimensional electronic bands with an energy gap of ~1 eV coexist with confined pore states, making the nanoporous graphene a highly versatile semiconductor for simultaneous sieving and electrical sensing of molecular species.

cond-mat.mtrl-sci↗

arXiv2014

Atomic monolayer deposition on the surface of nanotube mechanical resonators

We studied monolayers of noble gas atoms (Xe, Kr, Ar, and Ne) deposited on individual ultra- clean suspended nanotubes. For this, we recorded the resonance frequency of the mechanical motion of the nanotube, since it provides a direct measure of the coverage. The latter is the number of adsorbed atoms divided by the number of the carbon atoms of the suspended nanotube. Monolayers formed when the temperature was lowered in a constant pressure of noble gas atoms. The coverage of Xe monolayers remained constant at 1/6 over a large temperature range. This finding reveals that Xe monolayers are solid phases with a triangular atomic arrangement, and are commensurate with the underlying carbon nanotube. By comparing our measurements to theoretical calculations, we identify the phases of Ar and Ne monolayers as fluids, and we tentatively describe Kr monolayers as solid phases. These results underscore that mechanical resonators made from single nanotubes are excellent probes for surface science.

cond-mat.mes-hall↗