Fabrication of nanowire network AAO and its application in SERS

In this paper, nanowire network anodized aluminum oxide (AAO) was fabricated by just adding a simple film-eroding process after the production of porous AAO. After depositing 50 nm of Au onto the surface, nanowire network AAO can be used as ultrasensitive and high reproducibility surface-enhanced Raman scattering (SERS) substrate. The average Raman enhancement factor of the nanowire network AAO SERS substrate can reach 5.93 × 10(6), which is about 14% larger than that of commercial Klarite® substrates. Simultaneously, the relative standard deviations in the SERS intensities are limited to approximately 7%. All of the results indicate that our large-area low-cost high-performance nanowire structure AAO SERS substrates have a great advantage in chemical/biological sensing applications

Multiple magnetic dipole excitation in permittivity-asymmetric all-dielectric metamaterials induced by quasi-bound states in the continuum

In this work, we numerically investigate multiple magnetic dipole (MD) excitation in an all-dielectric metamaterial of permittivity-asymmetric nanodisk dimer with symmetric geometric parameters. Besides the original MD mode, the permittivity-asymmetric metamaterials can support symmetry-protected dual quasi-bound states in the continuum (BICs), which show inverse square dependence of Q-factors on the asymmetric parameter. Far-field multiple decompositions and magnetic near-field enhancements further indicate that such two quasi-BICs are governed by MD responses, where asymmetric localized MD distributions in near-infrared wavelength realize indirectly manipulate the localized magnetic field. Further, multiple MDs with high Q-factors are designed as a multiwavelength sensor with a near theoretical FOM of ~2300

Optical Extinction Properties of Perforated Gold-Silica-Gold Multilayer Nanoshells

Symmetry breaking in gold nanoshell (or multilayer nanoshells) can supply many interesting optical properties, which has been studied in gold nanostrucutres such as nanocup, nanoegg, and core offset gold-silica-gold multilayer nanoshells. In this work, the optical extinction properties of the perforated gold-silica-gold multilayer nanoshells are studied by the discrete dipole approximation method simulations and plasmon hybridization theory. The extinction spectra of these particles are sensitive to the orientation of the particle with respect to polarization of the light due to the symmetry breaking. Because of the coupling of the plasmon resonance modes between the inner gold sphere and the outer nanocup structure, the perforated gold-silica-gold nanoshell provides the additional plasmon resonance peak and an even greater spectral tunability comparing with the nanocup of similar dimensions. By changing the geometry of the particles, the extinction peaks of the particles can be easily tuned into the near-infrared region, which is favorable for biological applications. The local refractive index sensitivity of the particles is also investigated, and the multiple extinction peaks simultaneous shift is found as surrounding medium is altered. The perforated gold-silica-gold multilayer nanoshells may provide various applications ranging from angularly selective filters to biological sensors