Preparation Of Silver-Based Nanomaterials And Their Potential Applications

Silver nanoparticles, due to its specific physical and chemical properties, show excellent characteristics in the optical, catalytic, electrical and many other fields. At present, the silver nanoparticles are still the research focus. The research of this thesis focuses on the synthesis, properties and potential application of silver nanoparticles and their composites such as Ag/ZnO and Ag/GO. The principal results of the dissertation are discussed as follows:1. Silver nanoparticles, which were produced by the sodium borohydride reduction of silver nitrate, were stabilized by means of 1-dodecanethiol providing sulfur atom. (n-dodecyl)trimethylammonium bromide (DTAB) which was used as phase transfer agent in two-phase system involving water and toluene played an significant role in the formation of monolayer-protected silver nanoparticles. It was also found that different organic solvent played major role in the particle size of silver nanoparticles. The results indicate that the particles size of silver nanoparticles were quite different under the three kind of condition. Furthermore,1-dodecanethiol-capped silver nanoparticles are found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH4, where the size of silver nanoparticles is found to play the determining role on catalytic activity.2. Superlattice of silver nanoparticles were prepared using a liquid-liquid two-phase method with hydrazine hydrate (N2H4·H2O), tetra-n-butylammonium bromide ((C4H9)4NBr) and 1-dodecanethiol as reducing agent, phase transfer agent and stabilized agent, respectively. The reaction time plays a major role in the formation of superlattice of silver nanoparticles. Furthermore, the superlattice of silver nanoparticles are found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH4. The results indicate that the formed silver nanoparticles are so small, only about 3 nm, but they have a high catalytic activity, the kinetic reaction rate constant (defined as Kap) of which reaches to 21.3×10-3s-1.3. The size-controlled synthesis of silver nanoparticles were prepared in a cetyl trimethyl ammonium bromide (CTAB)/toluene reverse micelle system using oleic acid or sebacic acid as stabilizing agents. The formation of silver nanoparticles was influenced by factors such as reaction time, concentration of CTAB, the quantity of fatty acid and so on. It can be seen that the formed silver nanoparticles are monodispersed with a narrow size distribution.4. Single-crystal silver slices with different shapes such as hexagon, trapezium, triangle were synthesized at room temperature with chitosan by a facile, one-pot, and totally green method. The results showed that chitosan, a novel environmentally benign and excellently biocompatible material, serves not only as a reducing agent but also as a stabilizer for the growth of anisotropic silver nanoparticles. The single-crystal silver slices with major facet of (111) can be used as a surface-enhanced Raman scattering (SERS) substrate, and crystal violet (CV) as a Raman probe to evaluate its enhancement ability. It was found that the enhancement ability of the silver slices was remarkable and enhancement factor(EF) reached to 2.6×103.5. The Ag nanoparticles-stabilized ZnO nanosheets were prepared using a liquid-liquid two-phase method with (n-dodecyl)trimethylammonium bromide (DTAB) as a phase transfer agent at the room temperature. The results demonstrate that the silver nanoparticles load on the surface of ZnO sheets and make the ZnO sheets stabilize. Furthermore, the formation mechanism of ZnO sheets stabilized by silver nanoparticles was also proposed and discussed in detail. Moreover, the photocatalysis test shows that the ZnO sheets stabilized by silver nanoparticles exhibit a higher photocatalytic activity than the pure ZnO nanosheets.6. A widely soluble graphene oxide sheets decorated by silver nanoprisms were prepared through green synthesis at the room temperature using gelatin as reducing and stabilizing agent. The results demonstrate that these silver-nanoprisms assembled on graphene oxide sheets are flexible and can form stable suspensions in aqueous solutions. Furthermore, the formation mechanism of soluble graphene oxide sheets decorated by silver nanoprisms was successfully explained. The anti-bacterial properties of graphene oxide sheets decorated by silver nanoprisms were tested against Escherichia coli.