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The Preparation Of Noble Metal Nanoparticles And The Application In Raman Spectroscopy

Posted on:2008-03-23Degree:MasterType:Thesis
Country:ChinaCandidate:L P DingFull Text:PDF
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It is well known that nanoscale materials are very attrictive for biophysical, biochemical, and material due to their special optical properties, magnetic properties, catalytic properties. With the development of science and technology, there are many different preparation methods of nanoparticlas. As we know, chemical reduction method, vapor phase synthetic method, sputtering method, laser ablation method and so on are all usual methods to prepare metal nanoparticles, but there are also needed to be improving on.In this paper, we prepared noble metal (Cu/Ag/Au) nanoparticles, according to the literatures with some modified. With the measuring tools of transmission electron microscope (TEM) and scan eletron microscope (SEM), we analyzed the influences of the prepared technique to the netal nanoparticles' scaled-size, dispersibility and uniformity.Employing photons as probes, Raman spectroscopy is potentially an ideal technique for studying chemical structures and physical interface phenomena. The photons with ultraviolet (UV) frequency have high energy, which could induce resonance or near resonance transitions between electron energy levels of molecules. Moreover, UV Raman can avoid the fluorescence. On the other hand, it is barely obtained the UV-SERS spectrums using metal aqueous colloids as substrates. In the present work, we report the surface resonance Raman scattering spectrums of p-Hydroxybenzoic acid (PHBA) molecular adsorbed onto the Cu nanoparticles with UV excitation at 325nm.Surface-enhanced Raman scattering (SERS) is a highly sensitive technique for probing the interfacial phenomena and the behavior of molecules adsorbed on metal nanoparticles surface. In SERS optical spectroscopy, the noble metal Ag/Au nanoparticles can serve as a highly efficient substrate for SERS investigation. Ag/Au colloid solution, produced by silver/gold ion reduction , was modified by the active Quanta Ray Nd:YAG laser system, λ=1064nm, we prepared a relative small, spherical Ag/Au nanoparticles with a narrow size distribution. It is crucially necessary to studythe properties of modified particles to obtain precise understanding of the mechanism, employing Transmission Electron Micrograph (TEM) images, surface plasmon absorption (SPA) spectrums and so on.In the end, Quantitative and slow-speed filter papers, microporous filter films, thin-layer chromatoplate aluminum sheets (TLCAS) and silica gel glass sheets (SGGS) coated with Ag nanoparticles were used as SERS-active substrates, on which high-quality surface-enhanced Raman scattering (SERS) spectra of p-Hydroxybenzoic acid (PHBA) were obtained with some fine distinction. The impressive contrast of experimental results and calculated Raman spectra with DFT-B3PW91 is illuminated that the richer Ag particles were coated on the surface, the more PHBA molecules were adsorbed. Based on these results, a rather essential influence to the mechanism of SERS effect is given.
Keywords/Search Tags:Cu/Ag/Au nanoparticles, Ultraviolet (UV) Raman Spectroscopy, Surface Enhanced Raman Scattering (SERS) Spectroscopy, Adsorption behavior, Density Function theory (DFT)
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