Ag@SiO₂core–shell nanoparticles on silicon nanowire arrays as ultrasensitive and ultrastable substrates for surface-enhanced Raman scattering

Abstract

Ag nanoparticles (NPs) coated with silica nanolayers were decorated onto a large-scale and uniform silicon nanowire array (SiNWA) by simple chemical etching and metal reduction processes. The three-dimensional Ag/SiNWAs thus formed are employed as a substrate for surface-enhanced Raman scattering (SERS), and a detection limit for rhodamine 6G as low as 10(-16) M and a Raman enhancement factor as large as 10(14) were obtained. Simulation results show that two kinds of inter-Ag-NP nanogaps in three-dimensional geometry create a huge number of SERS 'hot spots' where electromagnetic fields are substantially amplified, contributing to the higher SERS sensitivity and lower detection limit. The excellent SERS stability of Ag/SiNWAs is attributed to the presence of the SiO2 nanolayer around Ag NPs that prevented the Ag NP surface from being oxidized. The calibration of the Raman peak intensities of rhodamine 6G and thiram allowed their quantitative detection. Our finding is a significant advance in developing SERS substrates for the fast and quantitative detection of trace organic molecules.

Spectroelectrochemical behavior of 4-aminobenzenethiol on nanostructured platinum and silver electrodes

“…Noble metal nanostructures exhibit a surface-enhanced Raman scattering in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon [2]. This enhancement factor can be in the order of 10 4 -10 14 [3] in comparison to that present in the adsorption on a metallic smooth surface although the claim of extremely high enhancement factors of 10 14 in single-molecule SERS is critically discussed, in particular in the view of recent experimental and theoretical results that limits the electromagnetic enhancement to 10 11 [4]. It is generally accepted that two different mechanisms must be involved in SERS:…”

Highly sensitive surface enhanced Raman scattering substrates based on Ag decorated Si nanocone arrays and their application in trace dimethyl phthalate detection

“…The bands at 612, 773 and 1126 cm -1 can be assigned to C-C-C ring in-plane, out-of-plane bending, and C-H in-plane bending vibrations, respectively, while the bands at 1183, 1362, 1508, and 1650 cm -1 are all associated with the symmetric modes of C-C in-plane stretching vibrations [24,25]. The intensities of the Raman bands of 612, 1362, and 1650 cm -1 as functions of Ag sputtering duration were plotted in Fig.…”

“…4g and 4h, all these gaps are enough small to induce effective electromagnetic coupling between Page 9 of 23 A c c e p t e d M a n u s c r i p t AgNPs. Furthermore, the 3D array of the substrates might enhance the trapping of excitation light [25], and provide a much larger surface area for adsorbing probe molecules within the detection volume [24,25]. All these features contribute to the high SERS sensitivity.…”

“…identified though a relatively low signal-to-noise ratio.To estimate the enhancement factor (EF) of Ag-decorated SiNC array SERS substrate, we employed a SiNC array without AgNP decorating as a reference substrate, with the following equation[25,28]:where I SERS and I Raman are the integrated Raman intensities of a specific SERS bands of R6G adsorbed on the substrates with and without AgNPs, respectively. N SERS and N Raman are the numbers of R6G molecules within detection volume on the substrates with and without AgNPs, respectively.…”

Low-cost Au nanoparticle-decorated cicada wing as sensitive and recyclable substrates for surface enhanced Raman scattering

“…3D finite-difference time-domain (FDTD) method [29] was used to study the spatial distribution of the electric fields. Fig.…”