Theoretical Study On The Surface Plasmonic Properties And Dielectric Sensitivity Of Bimetallic Au@Pd Nanorods

Noble metal nanomaterials have been widely studied because of their unique local surface plasmon resonance(SPR)properties in the visible-near infrared(Vis-NIR)region.Numerous theoretical and experimental results show that the SPR properties not only are strongly dependent on the size,morphology and composition of particles,but also are highly sensitive to the dielectric environment.In recent years,the noble metal nanomaterials with different dimensions and morphologies have been successfully synthesized in the experiment.Especially,Au nanorods,the SPR peak is widely adjustable in the Vis-NIR region with increasing aspect ratio of Au nanorods.With the development of nanotechnology and materials science,one component of noble metal nanomaterials(such as Au and Ag)can not meet the requirements in practical applications,and bimetallic nanoparticles have been received considerable interest due to their unique optical,electronic,magnetic and catalytic properties which are different from that of their individual constituent metals.In this paper,we report a facile route to the synthesis of Au@Pd bimetallic nanorods.And the finite-different time-domain(FDTD)solutions is also applied to simulate the SPRL characteristics and dielectric sensitivity of surrounding environment for two different layered growth modes.In comparation,simulational and experimental results are showed and a detailed theoretical analysis of the similarities as well as differences between them is demonstrated.1.In the introduction,we not only introduce the characteristics and applications of noble metal nanomaterials,but also summarize the research progress of SPR in detail.2.The optical properties of noble metal nanoparticles are mainly derived from their unique SPR.First,we introduce the derivation of the Mie theory and Gan equation of spherical nanoparticles and ellipsoidal nanoparticles.Then,we introduce the principle of FDTD numerical calculation methods,and it is more convenient and intuitive to study the optical properties of the complex or multi component noble metal nanomaterials.Finally,the basic parameter setting of FDTD numerical calculation method is also introduced in this paper.3.To begin with,the Au nanorods with specific size are prepared,and the Au@Pd bimetallic nanorods with different layered growth pattern are prepared by using Au nanorods as seed in the experiment.Next,the optical properties of Au nanorods and Au@Pd nanorods are simulated by FDTD.Finally,the absorption spectra of FDTD solutions and the corresponding experimental spectra are compared,and the moving rules of absorption peaks and the differences between them are analyzed and explained.4.The dielectric sensitivity of Au nanorods and Au@Pd bimetallic nanorods on the surrounding environment is simulated by FDTD solutions.Comparing the size of their dielectric sensitivity,we explore the influences of aspect ratio and morphology of nanoparticles on the dielectric sensitivity.