Multiband bonding/anti-boding interaction and selective electric field confinement in the complementary metamaterial.

We report the experimental and theoretical study on the complementary planar metamaterial with asymmetrical air nanorods. Three high-quality samples are fabricated by the focused ion beam technique. Multi-band Fano-like resonances and selective electric field confinement in the visible-near infrared range are presented and well explained by the bonding/anti-boding and coupled mode theories of plasmonic resonators.

Atomic layer deposition assisted non-destructive strategy for cleaning Ag dendrites based SERS substrates.

Ag dendrites have recently been widely reported due to their excellent surface-enhanced Raman scattering (SERS) properties. However, prepared pristine Ag dendrites are usually contaminated by organic impurities, which has a huge negative impact on their Raman detection and greatly limits their practical applications. In this paper, we reported a facile strategy to obtain clean Ag dendrites by high temperature decomposition of organic impurities. With the assistance of ultra-thin coating via atomic layer deposition (ALD), the nanostructure of Ag dendrites can be retained at high temperature. SERS activity can be recovered after etching ALD coating. Chemical composition tests indicate that the organic impurities can be effectively removed. As a result, the clean Ag dendrites can obtain more clearly discernible Raman peaks and lower limits of detection than the pristine Ag dendrites. Furthermore, it was demonstrated that this strategy is also applicable to clean other substrates, such as gold nanoparticles. Therefore, high temperature annealing with the help of ALD sacrifice coating is a promising and non-destructive strategy to clean the SERS substrates.

Selectively enhanced Raman/fluorescence spectra in photonic-plasmonic hybrid structures.

The manipulation of the interaction between molecules and photonic-plasmonic hybrid structures is critical for the application of surface-enhanced spectroscopy (SES). Herein, we report a study on the mode coupling mechanism and SES performance in a typical optoplasmonic system constructed with a polystyrene microsphere (PS MS) resonator and gold nanoparticles (Au NPs). The mode coupling mechanism was found to be closely dependent on the relative positions of PS MS, Au NPs, and molecules in the optoplasmonic system, based on which selectively enhanced Raman and fluorescence signals of molecules can be realized via the collaboration of enhancement and quenching channels of the PS MS and Au NPs. We demonstrate two arrangements of the photonic-plasmonic hybrid structure, which can support fluorescence signals with sharp whispering-gallery modes and apparently enhanced Raman signals with relatively low detection limits and good robustness, respectively.