Carboxylated Polypyrrole-Silica Nanocomposite: Surface Analysis by XPS

Carboxylated polypyrrole-silica colloids are synthesized in aqueous media by the oxidative copolymenzation of molar equivalents of pyrrole and 1-(2-carboxyethyl) pyrrole in the presence of ultrafine (20 nm) silica particles [see Maeda et al., Macromolecules 28, 2901 (1995)]. The resulting nanoparticles have a diameter of ∼100 nm as evidenced by transmission electron microscopy and disk centrifuge photosedimentometry and obtain 24–43 wt. % of silica. The conducting polymer component imparts intense coloration to the nanoparticle and the silica component ensures good colloidal stability. The surface carboxylic groups allow the covalent attachment of biological ligands of interest, such as antibodies. Thus these functional nanoparticles can be used as colored “markers” for immunodiagnostic assays.