Investigation On The Control Of Surface Plasmon Resonance Performance On Noble Metal Nanostructures

Surface enhanced Raman spectroscopy has been attracted considerable interest due to its high sensitivity up to single molecule detection.Generally,the giant SERS effect was mainly originated from the strong electromagnetic field energy of the hot spots.It contained less than 2%molecules in the hot spots,but contributed over 98%of the overall SERS signal.The SERS activity of "hot spots" is closely related to the distance,morphology,size and composition.Small differences can lead to significant differences in SERS activity,besides,the distribution of hot spots is random.Therefore,activity and uniformity of SERS substrate can not be taken into account simultaneously.It is extremely unfavorable to apply SERS to the field of quantitative analysis.In this paper,we construct a uniform SERS substrate from the view point of surface plasmon coupling.The main results were listed as follows:(1)Single crystal Au microplates was fabricated and used to construct SERS substrate.Single crystal Au microplates with large areas have been synthesized in large quantities through a hydrothermal method with the presence of PVP.Various approaches,such as SEM,XRD.SAED and SERS experiments,demonstrated that Au microplates were single-crystalline.Because of the micron size of single crystal Au microplates,the SERS substrate is constructed by placing nanoparticles on Single-crystal Au microplates,the hot spots were transferred from the gap between nanoparticles to the gap between nanoparticles and single crystal Au microplates.It offers us a unique opportunity for researchers to study the adsorption configurations of molecules on single crystal surfaces.(2)Utilize the propagation characteristics of propagating surface plasmon polaritons(PSPP)on single crystal Au microplates,the highly localized electromagnetic field energy in the "hot spot" was propagated.and SERS signal of the probe far away from hot spots was obtained.A systematical investigation on the influence of the density of nanoparticles and excitation wavelength has been performed.The mechanism of SERS signal acquired in single-crystal Au microplates area was proposed and verified by theoretical simulation and SPR catalytic reaction.It opened a new approach for the construction of uniform SERS substrate.(3)A facile approach of dynamic control and observe hot spots was realized simply by evaporating the water under the Au nanoparticles monolayer film(Au MLF)during phase transfer process.The relationship between SERS effect as well as SPR catalytic efficiency and gap distance had been studied theoretically and experimentally.The SERS intensity and SPR catalytic efficiency were increased due to the decrease of interparticle spacing,and it showed considerable catalytic efficiency in some surface reactions by this strategy.This strategy is expected to further provide a significant method to understand the enhancement mechanisms of SERS and offers an alternative approach for improving the SPR catalytic efficiency.