The Study Of Plasmonic Tweezers Enabled Dynamic Gap Structured SERS

Surface-enhanced Raman spectroscopy (SERS) is an enhanced Raman spectroscopy, based on field confinement and enhancement of metal nanostructures. Plasmonic tweezers enabled dynamic Gap structured SERS has the dynamic manipulation ability of plasmonic tweezers and the ability of structure analysis and molecule recognition deriving from SERS. Plasmonic tweezers attach two dimensional space positioning and addressing capability to this configuration. Because of the unique field hybridization mechanism, Raman signal has got ultrahigh enhancement factor, and super resolution is achieved. To design and build plasmonic tweezers enabled dynamic Gap structured SERS platform, field distribution of SPPs excited by tightly focus radially polarization beam, the robust manipulation of metal nanoparticle of plasmonic tweezers, the field confinement and enhancement in dynamic Gap structured SERS substrate, and its repeatability, and the nanoscale spatial resolution have composed the content of this article.Theoretical research of electromagnetic field distribution of SPPs excited by radially polarized beam is implemented. Formed by coherent superposition of SPPs, longitudinal field components accounted for more than84.74%of the total electromagnetic field energy of SP virtual probe, and under the given conditions in this paper, the FWHM of electromagnetic field is185nm, steep gradient distribution of electromagnetic field promises the stability of the metal nanoparticles trapping. What ensures the effective field hybridization of SPPs and LSP is that the longitudinal field polarizes in the Gap structure orientation.The trapping of metal nanoparticle in plasmonic tweezers system is analyzed in details. The pN forces pointing to virtual probe center exert on the metal nanoparticles at different positions in transverse direction of plasmonic tweezers. Meanwhile the forces pointing to metal film in longitudinal direction decay exponentially. In our plasmonic tweezers, manipulations of metal nanoparticles ranging from tens of nanometers to microns in diameter are realized, the feasible control of metal nanoparticle is proved. Theoretical analysis of field confinement and enhancement in the dynamic Gap are implemented. Because of the hybridization of SPPs and LSP, the FWHM shrink to23nm. The spatial compress of electromagnetic field surges the energy density leading to the elevation of SERS enhancement factor104-105times to that of SPPs of smooth metal film. The simulation results demonstrate that the Raman enhancement factor can reach1010in total.The heat absorption of metal lead to photo-thermal effect of dynamic Gap structured SERS substrate and further the stability problem. Theoretical simulation results show that, in accordance with the actual experiment condition, system temperature rise1.94℃. The perturbation can’t lead to significant brown motion increasing. Based on statistical characteristics of Brownian motion, it reveals that the Brownian motion introduce no effects to SERS signals stability. Convection caused by thermal effect introduces a convection force to the SERS substrate, which plays an important role in dynamic Gap structure.Plasmonic tweezers based dynamic Gap structured SERS platform is established. The enhancement factor stability of the platform is proved by repetitive experimental verification. The variance of signal strength, that stands for stability of dynamic Gap structured SERS substrate, is less than7.8%. Corresponding experiments have confirmed the enhancement factor of the system, which is up to109. On the basis of the dynamic Gap structured SERS platform experiment is carried out to obtain the spatial resolution of the system. The preliminary results admit100nm spatial resolution of the system, which is optimizable.