Nanogaps in 2D Ag‐nanocap arrays for surface‐enhanced Raman scattering

Abstract

The surface-enhanced Raman scattering substrate of Ag-Ag nanocap arrays are prepared by depositing Ag film onto twodimensional (2D) polystyrene colloidal nanosphere templates. When the original colloidal arrays are used as the substrate for Ag deposition, surface-enhanced Raman scattering (SERS) enhancements show the strong size-dependence behaviours. When O 2 -plasma etched 2D polystyrene templates are used as the substrate for Ag deposition to form nanogaps, the gap sizes between adjacent Ag nanocaps from 5 to 20 nm generate even greater SERS enhancements. When SiO 2 coverage is deposited to isolate the Ag nanocaps from the neighbours, the SERS signals are enhanced more. The significant SERS effects are due to the coupling between Ag nanocaps controlled by the distance, which enhances the local electric-field intensity.

Ordered Nanocap Array Composed of SiO2-Isolated Ag Islands as SERS Platform

“…Figure shows the fabrication process of SiO 2 –Ag nanocap arrays by NSL and magnetic control sputtering. First, the close-packed 2D PS arrays with diameter 200 nm are prepared on Si wafer by self-assembly method, and the ordered area of the PS array is >1 cm 2 . , Second, Ag and SiO 2 are sputtered along the perpendicular direction onto the closed-pack colloidal sphere arrays by cosputtering method, and the SiO 2 –Ag nanocap forms on PS (Figure a). The uniform reflected color of film indicates that the PS monolayer is distributed on silicon wafer homogeneously from point to point, as shown in Figure b.…”

Two-Step Photonic Reduction of Controlled Periodic Silver Nanostructures for Surface-Enhanced Raman Spectroscopy

“…2D or 3D metallic nanoparticle patterns on substrates can be easily controlled using laser direct writing techniques as nanoparticles are only produced in laser-irradiated regions. Such patterns have been used for dye molecule detection through Raman signal enhancement [11], which can be further improved when both the nanoparticles' shape and nanostructures are considered [6,12]. To date, researchers have focused on either regulating nanoparticle shape or producing controlled nanostructures; to the best of our knowledge, there has been no relevant research combining laser and light-emitting diode (LED) to form nanostructures comprised of different nanoparticle shapes.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part VIII

“…The Ag‐Ag nanocap arrays were prepared by depositing a Ag film onto 2D polystyrene colloidal nanosphere templates. Here, it is found that significant SERS effects are due to the coupling between Ag nanocaps controlled by distance, which enhances the local electric field intensity …”