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The Theory Study Of The Optical Properties Of Gold And Silver Nanoparticles

Posted on:2016-01-05Degree:MasterType:Thesis
Country:ChinaCandidate:Y M XiaoFull Text:PDF
GTID:2181330467991643Subject:Condensed matter physics
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The small size of nanoparticles determines its special properties, which are quitedifferent from bulk materials.Nanomaterials have played its important roles in material,medicine, energy, industrial, electronic, environmental, and other fields,which not onlypromote the development of the industrialization process, but also convenient and improve thePeople’s Daily life.At present, the preparation and characteristics of nanometer materials aswell as the study of the theory of the physical properties such as the surface plasmonresonance, surface enhanced Raman scattering, quantum size effect, macroscopic quantumtunneling effect, has been relatively mature.However, the depolarization effect ofnanoparticles is one of the characteristics which began to research in recent years, this resultis not very mature.In order to study the depolarization spectrum, and the relation and distinction betweenplasma resonance absorption spectrum, we have established a depolarization field model ofspherical nanoparticles, and deduced the equation of the depolarization field of sphericalnanoparticles in detail.Due to the polarization formula is relate to the dielectric constant,so thedielectric constant of the metal and core-shell structure composite nanoparticles of werediscussed,that are different from ordinary magnetic medium.The research object are sphericalgold, silver, gold and silver composite nanoparticles, core-shell structure compositenanoparticles of gold and silver. We used the matlab software programming to simulate itsdepolarization behavior in homogeneous scattering field,and measured its depolarizationoptical absorption spectra. And discussed the influence of radius of the metal nanoparticles,external media, light intensity and the ratio of core-shell particles.The results show that gold, silver, gold and silver composite nanoparticles, core-shellstructure composite nanoparticles all have only one depolarization band. Under the light ofdifferent energy, the depolarization spectral is varied with the different dielectric constant, yetthe maximum depolarization peak of Au-Ag composite nanoparticles and core-shell structurecomposite nanoparticles is always between the depolarization peak of pure Au and pure Ag nanoparticles.The spectrum shows that the depolarization field of relative intensity oftransmitted light will red shift with the increase of particle size,and with the increase ofdielectric constant surround the particle.The large of the particle size and the dielectricconstant,the greater of the relative intensity of transmitted light.For metal compositenanoparticles, the depolarization peak will almost linear red shift or blue shift with the changeof components or the core-shell ratio in composite materials.This is due to the existence of thedepolarization field,which changes the surface plasmon resonance of metal.This inspires us that we can control the depolarization spectral of metal nanoparticles bychange the energy of incident light,radius of the metal nanoparticles,external media, thevolume ratio of Au or Ag,and the ratio of core-shell particles,in order to realize the moreselective in terms of medical imaging applications.
Keywords/Search Tags:Nanoparticles, Depolarization spectral, Dielectric constant, red shift, blue shift
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