  In this work we address the effects on the conductance of graphene
nanoribbons (GNRs) at which organic molecules are side-attached on the ribbon
ends. For simplicity, only armchair (AGNRs) and zigzag (ZGNRs) nanoribbons are
considered and quasi one-dimensional molecules, such as linear poly-aromatic
hydrocarbon (LPHC) and poly(para-phenylene), are chosen. The conductance of the
GNRs exhibit a particular behavior as a function of the length of the organic
molecules: the energy spectrum of the quasi one-dimensional system is clearly
reflected in the conductance curves of the GNRs. The results suggest that GNRs
can be used as an spectrograph-sensor device. An even-odd parity effect, as a
function of the length of the attached molecules, can be observed in the
conductance of these system. The nanostructures are described using a
single-band tight binding Hamiltonian and the electronic conductance and the
density of states of the systems are calculated within the Green's function
formalism based on real-space renormalization techniques.
