RESUMO
Surface-enhanced Raman scattering (SERS) intensities for individual Au nanospheres, nanoshells, and nanosphere and nanoshell dimers coated with nonresonant molecules are measured, where the precise nanoscale geometry of each monomer and dimer is identified through in situ atomic force microscopy. The observed intensities correlate with the integrated quartic local electromagnetic field calculated for each specific nanostructure geometry. In this study, we find that suitably fabricated nanoshells can provide SERS enhancements comparable to nanosphere dimers.
Assuntos
Ouro/química , Teste de Materiais/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Análise Espectral Raman/métodos , Dimerização , Ouro/análise , Microscopia de Força Atômica , Tamanho da Partícula , Espalhamento de Radiação , Propriedades de SuperfícieRESUMO
We extend the plasmon hybridization method to investigate the plasmon modes of metallic nanoshell dimers. The formalism is also generalized to include the effects of dielectric backgrounds. It is shown that the presence of dielectrics shifts the plasmon resonances of the individual nanoparticles to lower energies and screens their interaction in the dimer configuration. The net result is a redshift of dimer energies compared to the system without dielectrics and a weaker dependence of the dimer plasmon energies on dimer separation. We calculate the plasmon energies and optical absorption of nanoshell dimers as a function of dimer separation. The results are in excellent agreement with the results of finite difference time domain simulations.
RESUMO
We report a facile and controllable method for the postfabrication texturing of the surface topography of Au nanoshells based on site-selective chemical etching of the polycrystalline Au nanoshell surface by a bifunctional alkanethiol molecule, cysteamine. This nanoscale surface texturing process systematically introduces dramatic changes to the plasmonic properties of the Au nanoshells. The modification of the plasmon resonant properties of nanoshells as a function of increased surface roughness was examined experimentally and modeled theoretically using three-dimensional finite difference time domain (FDTD) simulations.
