Anchoring of gold nanoparticles on graphene oxide and noncovalent interactions with porphyrinoids

Abstract

The interaction of tetrasulfonated aluminium phthalocyanine (AlPcS4) and meso-tetraarylporphyrin monosubstituted with poly-l-lysine (MM-PLL), with graphene oxide (GO) is studied in aqueous solution using spectroscopic and microscopic techniques. The study is also performed in the presence of gold nanoparticles (AuNP) grown on the surface of GO using a sonochemical method. The strong quenching of the porphyrin luminescence demonstrates the important interactions between the excited state of the molecule with GO which are absent in the case of the phthalocyanine. However, in the presence of AuNP@GO hybrid a concomitant increase of the phthalocyanine fluorescence intensity takes place together with a decrease of the fluorescence lifetimes involving a surface plasmon coupling effect. The latter is overcome in case of MM-PLL due to stronger interactions with GO, and is corroborated for deposited samples using fluorescence lifetime imaging microscopy (FLIM). These new nanostructures are thus expected to have selective sensing abilities.