Preparation Of Nanometer Silver And Its Surface Enhancement Raman (SERS), Catalytic Performance Study

Nanoparticles are also called the superfine particles. Nano material has very superior performance because of its unique microstructure, which makes it different from other common particles. In recent years, some precious metal nanometer materials have always been a research focus to some researchers. Silver nanoparticles possess four effects:volume effect, surface effect, quantum size effect and macroscopic quantum tunneling effect. These characteristics make silver nanoparticles widely applied in many aspects such as catalytic industry, biological medicine industry, electronic industry and so on. Properties of silver nanoparticles depend mainly on its morphology and size. Hence, it is of great importance to make preparations for silver nanoparticles in a controllable way. Silver nanoparticles with complex structures have specific morphology and larger specific surface area and it has a good application in surface enhanced Raman spectra(SERS) and catalysis. Many literatures have reported that seeded growth method can be applied to the preparation of the metal nanoparticles with complex structure. Crystal practice is a two step chemical reduction method with a double reductant, the morphology and size of the produced metal particle can be controlled by adjusting the concentration of reactants and the dosage.This paper is mainly about the preparation of flower-like nano silver with crystal seed method and the synthesis of calcium phosphate-silver nano composite materials on the basis of flower-like nano silver. It discusses about SERS, catalytic properties of nano silver, the SERS performance of calcium phosphate-silver nano materials. In the last chapter of this article, biological reduction method was used to successfully prepare nano silver particles and its catalytic properties were studied. Main content contains several aspects as follows:1. The preparation, characterization of flower-like nano silver along with the SERS, catalytic performance researchUse silver nitrate as the source of silver, sodium citrate as reducing agent in the first step and ascorbic acid as reducing agent in the next step without any surface active agent. We determined the optimum experimental conditions of flower-like nano silver at room temperature. When the amount of silver seeds is 10 mL, the concentration of silver nitrate is 0.02 mol/L and the concentration of ascorbic acid is 0.01 mol/L, the high purity of flower-like silver nanoparticles (face-centered cubic structure, size of about 200 nm) can be prepared. With rhodamine 6G (R6G) as a probe molecule, we discussed the the performance of the flower-like silver nanoparticles which are used as SERS active substrate. The minimum detection limit (LOD) to R6G is 5×10-9 mol/L, the result is satisfactory compared to the same size of silver particles. In addition, silver nanoparticles have good catalytic effect on the tetranitro-phenol and methylene blue because of its high specific surface area. Among them, catalytic rate constant Kapp of the tetranitro-phenol reached 0.02252 S-1.2. The preparation, characterization of calcium phosphate-nano silver materials and SERS performance research.On the basis of flower-like silver nanoparticles obtained in the first chapter, it can form a layer of inorganic calcium phosphate on the surface layer and gain calcium phosphate-silver nano composite materials of different calcium layer thickness with calcium lactate as the calcium source and trisodium phosphate as the phosphorus source. From the study, when the quantity of trisodium phosphate and calcium lactate are both 300 uL, we can get nano silver composite particles whose calcium layer thickness is about 6 nm. In comparison with nano silver on Hela, the toxicity of this nano particle reduced a lot. At the same time, it has a good SERS effect on R6G and adriamycin.3. The preparation of silver nanoparticles with biological reduction method along with their characterization and application research.For the first time, we successfully synthesized nano silver particles from low-cost green coffee bean extract as a reductant (size between 12-31 nm, high purity, high crystallinity). These pony-size nano silver particles have a strong inhibitory effect on gram negative bacteria and gram positive bacteria, for and staphylococcus aureus. The minimum bacteriostasis concentration were 0.04 μmol/L and 0.1 μmol/L. Small size silver nanoparticles have high specific surface area so that they have a great catalytic effect on tetranitro-phenol and methylene blue.