Extended Data Fig. 1: Differential conductance dI/dV measurements for ZnPor-3ZGNRs segments of increasing length.

(a) STM images of ZnPor-3ZGNR dimer (N_ZnPor = 2), trimer (N_ZnPor = 3), tetramer (N_ZnPor = 4), pentamer (N_ZnPor = 5) and hexamer (N_ZnPor = 6). The length of ZnPor-3ZGNR is defined by the number N of ZnPor units in the hybrid ribbon. The color dots in each STM image refer to the tip positions where the dI/dV spectra were taken. (b) dI/dV spectra taken from dimer to hexamer. The color of each spectrum corresponds to the color of the dots shown in (a). The arrows highlight the frontier states that define the bandgap. Both the HOMO (developing into the valence band, VB) and the LUMO (developing into the conduction band, CB) move towards the Fermi level as the length of the ZnPor-3ZGNR increases. From the pentamer onwards, the HOMO / VB resonance disappears from the spectrum due to its dispersive character. The LUMO / CB position saturates at 0.2 eV in the hexamer. (c) Comparison of experimental (Exp) and DFT calculated (DFT_GP refers to gas phase calculations, DFT_AuSub refers to calculations with Au(111) substrate) bandgaps of ZnPor-3ZGNR dimer to hexamer. Although the calculated band gaps are underestimated by DFT, the trend of decreasing band gap as ribbon length increases is well reproduced. (a) U = −1.5 V, I = 100 pA for dimer to hexamer.