You should investigate GNR band structure:
1) In Builder, the nanoribbon plugin to build a GNR.
2) In Scripter, set up a Calculator (DFT or semi-empirical), and also add Bandstructure analysis.
4) Run the calcualtion, e.g. using Job Manager.
5) On LabFloor, select the Bandstructure item and visualize it using Bandstructure Analyzer.