Preparation of Nanoscale Ag Semishell Array with Tunable Interparticle Distance and Its Application in Surface-Enhanced Raman Scattering

Abstract

Nanoscale Ag semishell arrays with controlled size and tunable interparticle distance were prepared by combining nanosphere lithography with reactive ion etching. First, a large-area ordered monolayer of polystyrene (PS) nanospheres was deposited on glass substrates using the Langmuir−Blodgett (LB) technique. The PS spheres with different diameters were employed in LB procedures. Second, the monolayers of PS spheres were etched to control the diameter and tune the interparticle distance. Finally, a Ag layer was evaporated on the etched PS templates. Ag films with periodical nanostructures were obtained and can be used as surface-enhanced Raman scattering (SERS) substrates. These substrates exhibited homogeneity and good enhancement ability. SERS enhancement factor (EF) was represented on the order of 104−105. The correlation between nanoscale morphology and SERS activity of the substrates was investigated. When the size of Ag-semishell was fixed, the EF value decreased with the increase of interparitcle distance. Both local surface plasmon mode and delocalized surface plasmon mode contributed to the total enhancement. The controlled size, tunable interparticle distance, and large-area ordered arrays of these substrates suggest their promising applications as functional components in spectroscopy, immunoassay, biosensors, and biochips.

Structural, morphological and optical properties of Ag–AgO thin films with the effect of increasing film thickness and annealing temperature

“…Closely spaced Ag NPs result in larger enhancement of electromagnetic coupling between NPs due to strong confinement of local electric field [5]. The SPR wavelength was observed in blue region for smaller size of NPs to that of bigger NPs due to an increase of surface energy resulting from an increased surface to volume ratio [21].…”

“…Ag films hold a wide range of applications such as chemical sensors [3], biological sensors [4], surface enhanced Raman spectroscopy (SERS) [5], surface enhanced fluorescence spectroscopy (SEFS) [6] and photovoltaics [7]. Hence, it is very important to reinforce and tune the resonance in Ag nanostructure.…”

Hot-Volumes as Uniform and Reproducible SERS-Detection Enhancers in Weakly-Coupled Metallic Nanohelices

“…Currently, the generation of near-fields satisfying such demanding conditions is attempted by regular arrays of rounded and conveniently spaced individual nanostructures (monomers)31112. So far, there are two basic shapes studied to design monomer-based substrates: nanospheres1112 and –rods35.…”

Preparation of metal@silica core–shell particle films by interfacial self-assembly

“…Compared to the reference sample (10 À1 M R6G), the Raman scattering intensity of R6G was so greatly enhanced that the Raman peaks of 10 À6 M solution of R6G were still detectable. Comparing the intensity of the peak at 1652 cm À1 of 10 À6 M R6G with that of reference, an average enhancement factor was estimated to be larger than 10 5 [19]. Using Ag@SiO 2 films to enhance Raman signals can be regarded as a kind of SHINERS technology, which has been shown to be nondestructive and flexible [6].…”