Comparitive STM and LEED study of the self-assembly of theobromine on Au(111) and few layer graphene on SiC(0001)

Graphene has unique electronic and structural properties and is of interest in a broad range of applications. The functionalization of graphene by molecular adsorbates enables applications like organic sensors and solar cells. As the weak interaction between substrate and adsorbate is important, graphene and Au(111) are suitable substrates due to their low reactivity. Compounds of the xanthine group have a great effect on the human central nervous system resulting in energy arousal and increased cognitive function^1,2. Hence they are of great significance for applications in pharmacology, toxicology, and biochemistry^3,4.

Here we present the first experimental results of the xanthine derivate theobromine weakly bonded to graphene and to Au(111) at room temperature. The molecule layers are characterized utilizing STM and LEED to compare the self-assembly on Au(111) and on graphene. The molecule structures show different domains and also the existence of glide planes.

1. Smit, H. J. et al., Psychopharmacology, 176, 412-419, (2004)
2. Wang, A. et al., Anal. Chim. Acta., 419, 235-242, (2000)
3. Sun, J. -Y. et al., Colloids Surf. B: Biointerfaces, 84, 421-426, (2011)
4. Kim. D. H. et al., Appl. Phys. Lett., 95, 133701-133703, (2009)