Rational assembly and dual functionalization of Au@MnO heteroparticles on TiO2 nanowires

Au-MnO heteroparticles were immobilized on the surface of TiO2 nanowires and tagged subsequently with a fluorescent ligand. The immobilization of the Au@MnO heteroparticles was achieved by functionalizing the TiO2 nanowire support with a polymer containing catechol anchor groups for binding to the metal oxide surface and amine groups for conjugation to the Au domains of the Au@MnO heteroparticles. The Au domain of the resulting TiO2@Au-MnO nanocomposite could be functionalized selectively with a thiol-tagged 24 mer oligomer containing Texas red (SH-ODN-TXS red), whereas a green dye (NBD-Cl) could be anchored selectively to the TiO2 "support'' using the free amine groups of the polymeric ligand. The binding of the NBD and the Texas red fluorophors was monitored by confocal microscopy and the functionalization of the metal oxide nanoparticles was monitored by UV-Vis spectroscopy. All composite products were characterized by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX), confocal laser scanning microscopy (CLSM) and UV-Vis spectroscopy.