On-surface Double layer polymerization enhancing GNR lengths on an Au(111) surface

By performing controlled step-by-step annealing experiments of bilayers of GNR monomer reactants with multiple UHV-STM analysis of intermediate stages, we show that the coupling reaction takes place mainly in the uppermost layer of the monomer bilayer despite being separated from the Au(111) surface by the lowermost compact monomer carpet. This demonstrates that the initial monomer bilayer configuration plays acrucial role in lengthening the final GNR length once the intermediate dehalogenated polymer is cyclodehydrogenated. In this respect our experimental results directly provide the counter rationalization to the generalization of the metallic substrate catalytic role in the surface assi…