FDTD for plasmonics: Applications in enhanced Raman spectroscopy

The exact electromagnetic enhancement mechanism behind SERS, TERS, HERS and SHINERS is one of the issues focused on in the study of enhanced Raman spectroscopy. The three dimensional finite difference time domain method (3D-FDTD), which is widely used in nanoplasmonic simulations, not only provides us with a powerful numerical tool for theoretical studies of the ERS electromagnetic enhancement mechanism, but also serves as a useful tool for the design of ERS-active systems with higher sensitivities and spectral spatial resolution. In this paper, we first introduce the fundamental principles of FDTD algorithms, and then the size-dependent dielectric function of dispersive metallic material is discussed. A comparative study of FDTD and rigorous Mie evaluations of electromagnetic fields in the vicinity of a system of self-similar nanospheres shows an excellent correlation between the two computational methods, directly confirming the validity and accuracy of 3D-FDTD simulations in ERS calculations. Finally, we demonstrate, using a TERS calculation as an example, that the non-uniform mesh method can be more computationally efficient without loss of accuracy if it is applied correctly.National Natural Science Foundation of China [20703032, 10625418, 10874233, 10904171]; National Basic Research Program of China [2009CB930703, 2006DFB02020, 2009CB930700]; Natural Science Foundation of Fujian Province of China [E0710028]; Chinese Academy of Science

Near-field coupling and SERS effects of palladium nanoparticle dimers

The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonstrate that the near-field coupling effect greatly influences the absorption, scattering and extinction spectra of nanoparticle dimers. The surface plasmon resonance wavelength red-shifts dramatically as the separation between nanoparticles decreases. Because of the near-field coupling between nanoparticles and the size effect, the maximum SERS enhancement factor at the' hot spot' between palladium nanoparticle dimers is as high as 10(7)-10(8), while the averaged SERS enhancement factor over the entire nanoparticle surface is in the range of 10(5)-10(6). The deviation between the position of the peak in the extinction spectrum and the wavelength for maximum surface-averaged enhancement for the Pd nanoparticle dimers indicates that localized surface plasmon resonance has different influences on the far and near fields. These theoretical results may help to reveal the relationship between the far and near fields, as well as understand the mechanism of electromagnetic enhancement in the surface-enhanced scattering of transition metals.National Natural Science Foundation of China [20703032]; National Basic Research Program of China [2009CB930703]; Natural Science Foundation of Fujian Province of China [E0710028

Freestanding palladium nanosheets with plasmonic and catalytic properties

通讯作者地址: Huang, XQ (通讯作者), Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 2. Xiamen Univ, Dept Chem, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 3. Xiamen Univ, Dept Phys, Xiamen 361005, Peoples R China 电子邮件地址: [email protected] metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties(1-7). Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques(7), but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.NSF of China 20925103 20871100 20721001 20703032 MOST of China 2009CB930703 2011CB932403 Fok Ying Tung Education Foundation 121011 NSF of Fujian 2009J06005 Key Scientific Project of Fujian Province 2009HZ0002-

Freestanding palladium nanosheets with plasmonic and catalytic properties

Ultrathin metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties(1-7). Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques(7), but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.NSF of China[20925103, 20871100, 20721001, 20703032]; MOST of China[2009CB930703, 2011CB932403]; Fok Ying Tung Education Foundation[121011]; NSF of Fujian[2009J06005]; Key Scientific Project of Fujian Province[2009HZ0002-1

Correlating the Shape, Surface Plasmon Resonance, and Surface-Enhanced Raman Scattering of Gold Nanorods

We report the study correlating the shape, surface plasmon resonance (SPR), and surface-enhanced Raman scattering (SERS) of gold nanorods (NRs) in dilute colloids. A series of gold NRs with various aspect ratios was prepared via an improved seed-mediated technique. Increasing the aspect ratio finely tunes the position of the longitudinal plasmon mode of the NRs in a wide spectral range. This shape-dependent SPR behavior was simulated by Gans theory and the discrete dipole approximation method. The subtle influence of SPR on SERS was then demonstrated by gradually tuning the SPR wavelength across a fixed excitation line. SERS experiments and theoretically predicted electromagnetic enhancement by the three-dimensional finite-difference time domain method clearly demonstrate that overlapping SPR and the excitation line maximizes the SERS enhancement. This correlation thus enables a quick diagnosis of SERS intensity by looking at the position of the SPR band.Natural Science Foundation of China [20603008, 20703032]; 973 program [2009CB930703]; Hunan Provincial Natural Science Foundation of China [06JJ3006]; Natural Science Foundation of Fujian Province of China [E0710028]; State Key Laboratory for Physical Chemistry of Solid Surfaces ; "985" Foundation of Ministry of Education of Chin