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 Greens function formalism based on real-space renormalization techniques.
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