Preparation of silver decorated silica nanocomposite rods for catalytic and surface-enhanced Raman scattering applicationsElectronic supplementary information (ESI) available: The amount of Ag nanoparticles loaded on SiO2@Ag nanocomposite rods; TEM images of SiO2@Ag nanocomposite rods with complete Ag shells. See DOI: 10.1039/c5ra08076b

This paper describes a straightforward approach for the decoration of Ag nanoparticles onto the surface of mesoporous silica nanorods (denoted as SiO 2 @Ag nanocomposite rods), in which polyvinylpyrrolidone (PVP) serves as both a reductant and stabilizer. In this approach, mesoporous silica nanorods are initially synthesized through a binary surfactant template method by using CTAB and F127 in a basic aqueous solution. Subsequently, through the electrostatic attraction between the negatively charged silanol groups and the positively charged [Ag(NH 3 ) 2 ] + ions, the silver precursor-[Ag(NH 3 ) 2 ] + ions can be adsorbed onto the surfaces of mesoporous silica nanorods. Then, those [Ag(NH 3 ) 2 ] + are in situ reduced to metallic Ag nanoparticles and stay there with the protection of PVP, consequently, SiO 2 @Ag nanocomposite rods are formed. By adjusting the concentration of [Ag(NH 3 ) 2 ] + ions, the size of Ag nanoparticles and the surface coverage of mesoporous silica nanorods by Ag nanoparticles can be easily tailored. During the synthesis, neither additional reductants nor surface modifications are necessary. These as-synthesized SiO 2 @Ag nanocomposite rods show excellent catalytic activity for the reduction of organic dyes, which may be useful for wastewater treatment. Furthermore, these SiO 2 @Ag nanocomposite rods are ideal candidates as surface-enhanced Raman spectroscopy (SERS) active substrates for the trace detection of antibiotics, i.e. , penicillin G sodium and chloramphenicol. This SERS feature may be applicable for organic residue detection in food. A straightforward approach is presented to prepare SiO 2 @Ag nanocomposite rods with excellent catalytic activities and surface-enhanced Raman scattering properties.