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Gold and Silver Nanomaterials: Synthesis, Characterization and Research in SERS

Author: ZhengPengCheng
Tutor: YuRuQin
School: Hunan University
Course: Analytical Chemistry
Keywords: Rich in gold - gold and silver Bimetallic Nanoparticles Silver nanowires Silver nanoparticles Rich in silver - Ag-Au Bimetallic Nanoparticles Surface Enhanced Raman Spectroscopy Aminothiophenol
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 939
Quote: 1
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Abstract

Human preparation and application of nano-materials has a long history. In recent years, nanomaterials because of their body or molecules are not unique surface effect, volume effect and quantum size effect performance, making nanomaterials in optical, electrical, magnetic, sensing, biomedical and many other aspects great potential to attract more and more people to engage in the study of nanomaterials. In these studies, especially gold, silver nanomaterials because of their excellent optical and electrical properties, has become the object of attention of many basic research and applied research. These unique properties of the nanomaterials are determined by a nano-particle size, shape, composition, crystal type, the aggregation structure, and thus the size of the morphology of the nano-materials prepared controllable becomes very important. So far it has been the development of the number of gold, silver nanoparticles preparation method, but most of the methods are more complicated. How to use a simple method of synthesis of controlled size and shape of gold, silver nanoparticles is still a necessary prerequisite for people to broaden its field of application and in-depth study of the nature and important challenges. In addition, because gold and silver nanoparticles internal free electrons generated in the external electromagnetic field under the action of a certain frequency of surface plasmon resonance, the electromagnetic field around the particles is enhanced, based on this phenomenon, gold and silver nanoparticles surface-enhanced pull Raman spectroscopy is currently one of the hotspots. This article is mainly engaged in silver as well as gold and silver bi-metallic nanomaterials synthesis, characterization, and its behavior in the SERS enhancement, as well as the interaction between molecules and metal nanoparticles surface-enhanced Raman Spectroscopy. The details are as follows: 1. Controlled size and morphology of rich gold - gold and silver double metal nanoparticles synthesis and study of its structure and growth mechanism (Chapter 2). By ascorbic acid after the AgNO3 solution at room temperature, in the traditional gold nanoparticles in the growth liquid, in the case no seeds obtained lacing double metal nanoparticles. The size of these nanoparticles is relatively homogeneous distribution of the standard deviation in the range of 10 ~ 15%. The concentration regulator of this size and morphology of the nanoparticles can be achieved by changing the surfactant cetyl trimethyl ammonium bromide (CTAB). The size distribution of 64 ± 8 nm at the bi-metal nanoparticles, we study the behavior of the enhancements of the Raman spectra, the enhancement factor of up to 4.3 x 104 to 1.1 x 105. In addition, cyclic voltammetry experiments show that the synthesized nanoparticles is rich in gold - gold and silver bi-metal nanoparticles. This structure may be due to the disproportionation reaction of the silver ions procure gold (Ⅰ) and silver in the surface of the gold the underpotential deposition caused by the. Silver nanowires, nanoparticles, and rich in silver - Ag-Au Bimetallic Nanoparticles Synthesis, characterization, and its structure and growth mechanism (3). Ascorbic acid at room temperature in a solution of CTAB do protecting agent, in the case of no seed exists reduction AgNO3, we prepared of Silver nanowires and nanoparticles, and by centrifugation, the product enrichment and purification. In addition, when the concentration of CTAB higher reduction reaction can not proceed HAuCl4 solution was added to the reaction mixture to continue, and in the case of 40 ° C heating step to restore the chloroauric acid and silver nitrate to prepare a silver-rich silver - gold double metal nanoparticles. UV-visible spectrophotometer (UV-Vis), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) The above product was characterized. The results showed that the production of of Silver nanowires and sterling silver nanoparticles after centrifugation. The length of the nanowire is approximately 4μm diameter of approximately 23 nm; diameter of the nanoparticles is approximately 47 nm. Silver-rich silver - gold double metal nanoparticles, UV - visible absorption spectra show that: prepared by step reduction of silver - gold double metal nanoparticles optical absorption spectrum with a single peak plasma absorption characteristics, its absorption peak near the absorption peak in the traditional sterling silver nanoparticles characteristics, and have moved to longer wavelengths as the reduction in the concentration of gold ions or the increase in the concentration of CTAB absorption peak, SEM show that the size of the nanoparticles also increased. 3 bi-functional molecules at the nano-junction region aminothiophenol (PATP) adsorption orientation change SERS study (Chapter 4). By means of gold and silver nanoparticles self-assembled SERS active substrates, the system of the dual-function molecular the PATP adsorption behavior. SERS spectrum of effects of different laser power, laser frequency and temperature change, in-depth analysis of the laser-induced molecular junction formation and its mechanism.

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