Immobilization of silver on hollow silica nanospheres and nanotubes and their antibacterial effects

The effects of hollow morphologies, i.e., hollow silica nanospheres and nanotubes, as novel hosts on the immobilization of silver has been studied in [Ag(NH3)(2)]NO3 precursor solutions with various concentrations through heat treatment process. The corresponding antibacterial properties of Ag-supported hollow silica were also investigated. The formation of silver-loaded hollow silica at various calcinating temperatures was studied with XRD and UV-vis and it indicated that the mean size of the formed silver particles increased with the raise of annealing temperature. By TEM, AAS, EDS, XRD and UV, it could be concluded that Ag loading amount on hollow silica increased with increasing concentration of precursor Ag[(NH3)(2)]NO3, and more silver contents, smaller silver nanoparticles and better dispersion could be obtained on hollow tubes than hollow spheres. The antibacterial effects of Ag-SiO2 hollow composite powders against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and bacillus were examined by the plate counting method. Both composites demonstrated an excellent antibacterial performance, and the Ag-supported tubular hollow structure showed a stronger antibacterial ability than spherical hollow structure owing to its more silver contents, smaller and more evenly dispersed silver nanoparticles. (c) 2005 Elsevier B.V. All rights reserved.