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) is served as both 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 the additional reductants nor the 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 the wastewater treatment. Furthermore, these SiO 2 @Ag nanocomposite rods are ideal candidates as the 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 the organic residue detection in food.
A facile approach was proposed to decorate silver nanoparticles on sulfonated polystyrene microspheres (denoted as SPS@Ag composite microspheres), in which polyvinylpyrrolidone (PVP) served both as the reductant and stabilizer. In this approach, first, sulfonated polystyrene (SPS) microspheres were synthesized via the sulfonation of monodisperse polystyrene (PS) microspheres in the concentrated sulfuric acid, which were used as the active template cores. Upon the electrostatic attraction between the negatively charged -SO 3 H groups and the positively charged [Ag(NH 3 ) 2 ] + ions, silver precursor-[Ag(NH 3 ) 2 ] + ions were easily adsorbed onto the surfaces of sulfonated polystyrene microspheres. These [Ag(NH 3 ) 2 ] + ions were in situ reduced to metallic Ag nanoparticles and simultaneously protected by PVP, forming the stable SPS@Ag composite microspheres. During the reaction, neither additional reducing agents nor stabilizers were needed. Moreover, by simply adjusting the concentration of [Ag(NH 3 ) 2 ] + ions, the size of Ag nanoparticles and the surface coverage of SPS with Ag nanoparticles can be easily tailored. Finally, it has been proven that these as-synthesized SPS@Ag composite microspheres were the ideal active substrates for the surface-enhanced Raman spectroscopy (SERS) for the trace detection trace of the antibiotics (i.e., penicillin G sodium and chloramphenicol), and showed an enhanced antibacterial activity against both Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Grampositive bacteria) as well.
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