Supramolecular functionalization of single-walled carbon nanotubes with uncharged water-soluble porphyrins

Abstract

We synthesized an uncharged water-soluble porphyrin, meso-tetrakis-(3,4,5-tri-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-phenyl)-porphyrin, to solubilize single-walled carbon nanotubes (SWNTs) in aqueous solutions through supramolecular interactions. The porphyrin-SWNTs composites in aqueous solution are stable for several weeks. The porphyrin-SWNTs composites in aqueous solution have been characterized by UV-vis absorption and fluorescence spectroscopy and with atomic force microscope (AFM). The fluorescence emitted from the porphyrin ring in the aqueous solution of the porphyrin-SWNTs composite is highly quenched, evidently implying the presence of strong electronic interactions between the SWNTs and the porphyrin molecules in aqueous solution. The AFM investigation furthermore supports that the porphyrin molecules are complexed on the SWNTs side wall through π-π interaction.