| Today,surface-enhanced Raman scattering(SERS)technology is becoming more and more widely used.In order to make the most of this enhancement effect,on the one hand,the materials which is used for surface plasmon resonance(LSPR)effect are extended from noble metals such as gold and silver to transition metals such as platinum.On the other hand,new nano metal structures have been developed to improve the sensitivity and stability of surface-enhanced Raman detection.In recent years,the detection limit of such substrates has been continuously broken,and the application in single molecule detection has become increasingly mature.The main work in this dissertation is as follows:(1)The electromagnetic enhancement mechanism of silver nanocubes(Ag NCs)dimer is discussed.The widely studied coupled plasmonic nanostructures include nanoparticle dimers or larger nanoparticle clusters.The control and adjustment of the optical properties of these structures largely depend on the ability to precisely manipulate the gap size between them.In view of this,we analyze the influence of the side length of nanocubes,the radius of curvature of the apex angle,and the gap distance on the intensity of the field and its distribution.The results show that its LSPR peak position and electric field enhancement will change with the side length,the gap distance of two Ag NCs and excitation wavelength.(2)A SERS substrate based on Ag hollow nanocube-Au film is proposed.Due to the difference in experimental preparation methods and techniques for Ag hollow nanocubes,there may be two type of hollow nanocubes in the shape of a columnar frame and a cubic frame.Therefore,we analyze field enhancement of two structures including the cylindrical frame hollow nanocube-Au film and the cubic frame hollow nanocube-gold film.For the columnar frame hollow nanocube-Au film composite structure,we discuss the enhancement effect of both Au and Ag materials.The change in the distance betwteen the hollow nanocube and Au film will cause the large change in electric field enhancement.In addition,its inner diameter also has a large effect on the electric field enhancement in the gap.For the cubic frame hollow nanocube-Au film composite structure,we not only analyze the variation of electric field enhancement factor with excitation wavelength when the gap changes,but also analyze the effects of ratio of inner and outer side length,outer length and excitation wavelength on electric field enhancement and electric field distribution.The results indicate that,for the cube frame hollow nanocube-Au film structure,the field enhancement does not reach the maximum when the gap distance is minimum.With the change of the ratio of the inner and outer side length and the outer length,different optimal gap distances will appear in the structure,and it is verified by experiments that the structure has a strong enhancement effect as a whole and is a good SERS substrate. |
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