The Characteristics And Applications Of Functionalized Molecules Surface Spectrum On Metal Nanoparticles

Nanosized particles of metals, particularly silver and gold, have recently receivedincreasing attention, due to their size, shape and environmental tunable optical andelectrical properties. They have shown various potential applications in many fields,including nanodevices, nanocatalysis, biosensors and chemical sensors. For thoseapplications, it is necessary to immobilize metal particles onto a solid substrate. Therefore,efforts have devoted to the assembly of nanoparticles in high ordered structures. Amongvarious methods that used for the assembly of metal nanoparticles, self-assembly techniqueis one of the most flexible approaches for the immobilization of metal particles onsubstrates. In addition, due to the small size effect, macroscopic quantum tunneling effect,dielectric confinement effect, the metal nanoparticles has some special physical properties.Especially the metal nanoparticles having a good optical characteristics because of thesurface plasmon. In the last few years, as further confirmation of the gold, silver and othermetal nanoparticles surface-enhanced Raman scattering effect for nanoparticle opticalproperties,the gold, silver and other metals has become a hot topic of nano-materialsresearch field. One of the most important properties of the metal nanoparticls in thenanodevices is the charge transfer at the interface between the metal nanoparticls andabsorbed functionalized molecules. The effect of the substrates on the interfacial chargetransfer of the assembled metal nanoparticls, however, has scarcely been studied. It hasbeen well known that the charge transfe at the molecules/metal interface has contributionsto the Surface-enhanced Raman scattering (SERS) of the molecules absorbed on the metalnanoparticles. Besides providing the spectral information associated the interfacial chargetransfer, the SERS spectroscopy in fact has proved to be very useful tool to study the molecule/metal nanoparticle systems, due to its richness of molecular structure information,high sensitivity and surface selectivity.In view of this, the paper will also have the optical performance of the orderedstructure of the preparation of the gold, silver and other nano-ordered structure research inorder to obtain valuable research results. Around the preparation and optical properties ofgold, silver nanostructure, the main technical route to take established as follows: first, toexplore new methods of preparation have higher SERS activity and stability of thesubstrate; second, the preparation process to achieve control of nanoparticle size,morphology and crystal structure, in order to synthesize anisotropic nanoparticles andstudy the SERS activity. In this thesis, Stable gold and silver nanoparticles has beensynthesised, the ordered nanostructures on the glass surface has been formed byself-assembly techniques. The new technology of metal/molecule/metal interface chargetransfer studied by surface-enhanced Raman spectroscopy (SERS), where to explore newways for the basic problems of the micro/nano electronic devices. The main research worksand the conclusions are as follows:1. Stable and uniform-sized gold、silver colloid has been prepared，ordered mono-、double-、tri-layer structures of silver nanoparticles on smooth glass substrates werefabricated by self-assembly technique, where p-aminothiophenol and1,4-benzen-edithiolwere used as the coupling molecules, respectively. Absorption spectra of the assembliesdemonstrate that interaction between silver nanoparticles result in surface plasmonresonance, the results of surface-enhanced Raman spectroscopic characterization show thatRaman scattering of the coupling molecules in the different self-assemblies have greatlydifferent effect.2. Uniform-sized and stable silver nanowires have been prepared by chemicalsynthesis methods. SEM showed that the ordered structure of the gold and silvernanoparticles/PATP/silver nanowires constructed on the surface of the silver nanowires byself-assembly method, where p-aminothiophenol as coupling molecules. Surface-enhancedRaman spectroscopy study showed that the coupling molecule Raman scattering has been greatly enhanced in the orderly gold, silver nanoparticles/PATP/silver nanowire assembly,which the effect mainly from charge transfer between the gold、silver nanoparticles andsilver nanowires.3. Different shapes gold material has been prepared via chemical synthesis method,just as uniform spherical shape, a star-shape,“meatball”-shape,“flower”-shape goldparticles. The effect of temperature and reactant concentration on the the product growthpattern and particle morphology and the mechanism of formation of gold nanoparticles ofdifferent shape has been studied. The interface acidity and complexation of MBA、R6G,the most widely used molecules in surface modifications of metals as well as metalnanoparticle assembly, were investigated on the different shapes gold nanoparticle bySERS technique. Through the enhancement factor is calculated as well as the study ofparticle stability, further exploration of such nanoparticles as SERS substrate tracedetection and bioassay prospects.