The LSPR Optical Properties Of Anisotropic Metal Nanostructures And Its Application In Orientation Probes And Polarization Information Encryption

Metal nanostructures possess rich optical properties ascribe to their localized surface plasmon resonances. The unique plasmonic properties can be applied in various applications, such as biomedical science, metamaterials, renewable energy, and information technology. The anisotropic metal nanostructure is one of the most important parts of the metal nanostructures. They possess unique polarization and orientation dependent optical properties due to their geometric anisotropic. This has the potential applications in detecting three-dimensional(3D) polarization encryption information and evaluating distances as small as few nanometers of molecular and nanoparticle labels or monitoring rotations and bending of biomolecules. However, up to now, there are few studies to investigate the application of anisotropic nanostructures as nanoprobes to detect the 3D rotations of biomolecules or 3D polarization encryption information.Firstly, we systematically investigate the 3D polarization- and orientation-dependent nearand far-field optical properties of a kind of fascinating anisotropic nanostructures, i.e., gold nanostar, gold nanorod,(Au core)-(dielectric shell) nanorice and plasmonic nanoparticle pairs. It shows that the scattering spectrum of the anisotropic nanostructures induced by arbitrary incident polarizations or particle orientations is a linear superposition of a set of basic scattered spectra, which can be described as formula 2.4. And due to the Fano resonances in nanorice caused by the efficient coupling between the dielectric elliptical shell and the gold core, the transverse plasmon mode is highly intensified. This has the potential to expand the sensing property of nanorod as 3D orientation sensor.Based on the 3D polarization and orientation dependence of the scattering trait, and using coordinate transformation, we have demonstrated that the gold nanostar is useful for designing orientation-unlimited polarization information detector. And we develop a new method to detect the 3D orientation of single nanoparticle, that is, by fitting the scattering intensity under different incident polarization directions based on our analytic formula. Due to the Fano resonances, we found that the 3D orientation of single nanorice could be confirmed from either the transverse or longitudinal plasmon mode polarization-dependent scattering trait, while it is almost impossible for single gold nanorod based on the transverse plasmon mode. It is worth noting that the transverse plasmon mode of the nanorice is mostly insensitive to the aspect ratio then it allows nanorices with different lengths to be 3D orientation sensors without altering the incident laser wavelength. And the self-rotation problem of the gold nanorod, i.e., rotation around the gold nanorod's long axis cannot be resolved, can be solved by replacing it with gold nanostar. In addition, the precision of the 3D polarization angles and 3D orientation angles confirmed by our method is only with subdegree uncertainty.Based on the 3D polarization- and orientation-dependent scattering trait of the plasmonic nanoparticle pairs, we develop a 3D plasmon nanoprotractor which can be utilized to determine the total 3D information(S,?,?) of the nanolabel. At the same time, we systematically investigate the electromagnetic enhancement effect in metal nanoparticle pair, and the influence of metal nanoparticle relative positions on enhancement effect. We develop the relationship between the relative positions of the particles and SERS enhancement. This makes the realization of 3D SERS nanoprotractor become possible.