NO Adsorption on Copper Phthalocyanine Functionalized Graphite

Abstract

NO dosed on a CuPc monolayer deposited on Au(111) and HOPG is observed by scanning tunneling microscopy. After dosing NO with a supersonic molecular beam source onto CuPc/Au(111), about 7% of CuPc molecules form chemisorbates with NO. Conversely, after dosing onto CuPc/HOPG, only about 0.1% CuPc molecules form chemisorbates with NO, even though the reaction sites appear nearly identical. DFT calculations were employed to elucidate the mechanism which causes the >10× difference in saturation coverage between NO/CuPc/Au(111) and NO/CuPc/HOPG. DFT calculations show NO chemisorption with CuPc/Au(111) induces only negligible perturbation in the density of states (DOS) in Au(111) due to large density of states on Au. Conversely, for NO/CuPc/HOPG, there is a large decrease of DOS in graphene around 1 eV due to NO chemisorption on CuPc/graphene consistent with negative charge transfer from graphene to NO. This DOS perturbation of graphene results in decreased binding energy of NO chemisorption in secondary NO sit...