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The Preparation And Surface-enhanced Raman Scattering Effect Of Metal Nanoparticle

Posted on:2008-06-24Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiFull Text:PDF
GTID:2121360218451075Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
The assembly of nano-sized metal with functionalized molecules is a rapidly emerging field of great fundamental and practical interest due to the prospective applications in future nanoelectronic devices. The charge transfer properties of individual particles are dependent of the particle size and the distance between the particles. importantly, the activation energy for the electron transfer between the particles can be varied by the structure of the interconnected molecules. In particular, tunneling charge transfer may occur for the particles covalently linked with n-conjugated molecules. On the other hand, recent progresses in surface-enhanced Raman spectroscopy (SERS) study have made single-molecule detection possible, which is considerably interesting for the communities of nanomaterials, analytical chemistry, and single-molecule spectroscopy. An enhancement factor of approximately 1011 has been estimated at the junctions between the closely spaced nanoparticles due to the electromagnetic (EM) enhancement mechanism. The contribution of the charge transfer (CT) mechanism has also been suggested to play important role in the single-molecule SERS.In most of SERS studies, the difficulty to experimentally gain deep insight into the enhancement associated with the CT mechanism is that the chemical enhancement is normally inextricably linked with the EM enhancement. Considering that the EM enhancement is strongly related to the SPR of the metal particles in the visible spectral region, in the present study, we measured the SERS spectra with a 1064 run excitation, which is far way from the SPR bands of the nanoparticles in the assemblies. Therefore, the SERS spectral features obtained under the present experimental conditions may be relatively largely associated with the CT effect.In this thesis, the main research works and the conclusions are as follows:1. Stable and uniform-sized silver colloid has been prepared and formed two-dimensional assembly on glass substrate. Absorption spectra of the assemblies demonstrate that interaction between silver nanoparticles result in large shifts of dipolar surface plasmon resonance, whereas only slight effect was observed for quadrupolar surface plasmon resonance. It illustrates there may stands somewhat close relativity between enhancement of electric field in nearby particles and dipolar interaction.2. The monolayer and double layer structure of silver nanoparticle were assembled on a polyvinylpyridine modified glass surface. It finds that the positive charge in polyvinylpyridine greatly weakens the charge transfer between DTO, CCTTF molecules and metal particles by studying its Surface-enhanced Raman scattering spectroscopy. In, addition, Surface-enhanced Raman spectroscopy demonstrate that the absorption orientation of CCTTF molecules will change with the Ag+ on the assembly.3. Gold nanospheres and nanorods prepared by chemical synthesis methods, uniform spherical and rod gold nanoparticles synthesized by the use of seed-induced growth methord. We study the inspection of the shape of gold nanoparticles on the surface plasmon resonance, as probe molecules to R6G, learn its surface enhanced Raman (?)cattering of gold spheres nanoparticles comparing to rods.
Keywords/Search Tags:Nanoparticle, Self-assembly, Surface-enhanced Raman Spectroscopy, Charge transfer, Absorption spectrum, nanorods
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