Two-Dimensional Self-Assembly of Au@Ag Core–Shell Nanocubes with Different Permutations for Ultrasensitive SERS Measurements

Abstract

Different self-assembly methods not only directly change the arrangement of noble metal particles on the substrate but also indirectly affect the local electromagnetic field distribution and intensity of the substrate under specific optical excitation conditions, which leads to distinguished different enhancement effects of the structure on molecular Raman signals. In this paper, first, the gold species growth method was used to prepare the silver-coated gold nanocubes (Au@Ag NCs) with regular morphology and uniform size, and then the two-phase and three-phase liquid–liquid self-assembly and evaporation-induced self-assembly methods were used to obtain the substrate structure with different NC arrangement patterns. The optimal arrangement of NCs was found by transverse comparison of Raman signal detection of probe molecules with the same concentration. Subsequently, surface-enhanced Raman scattering (SERS) measurements of Rhodamine (Rh6G) and aspartame (APM) were carried out. Furthermore, the finite element method (FEM) was employed to calculate the local electromagnetic fields of the substrates with different Au@Ag NC arrangements, and the calculated results were in agreement with the experimental results. The experimental results show that the SERS-active substrate was largely associated with the different arrangements of Au@Ag NCs, and the island membrane Au@Ag NCs array substrate obtained by evaporation-induced self-assembly can generate a strong local electromagnetic field due to the edge and corner bonding gap between the tightly arranged NCs; this endows the substrate with benign sensitivity and reproducibility and has great potential in molecular detection, biosensing, and food safety monitoring.

Asymmetric Heterodimer-Regulated Surface Plasmon Coupling ECL Polarization Strategy for MiRNA-182 Detection

“…Au@Ag NC exhibited four resonance peaks with a strong in-plane dipole peak at 500 nm and three weak peaks at 344, 395, and 554 nm. 23 TEM images in Figure 3B−D show uniform Au NSs of 10, 15, and 20 nm. Au@Ag NCs were homogeneous cubes of about 40 nm, as shown in Figure 3E.…”

Capillary-force-assisted self-assembly of gold nanoparticles into highly ordered plasmonic thin films for ultrasensitive SERS

“…Importantly, the characteristic peaks of Rh6G at 611, 772 and 1188 cm −1 are related to the in-plane and out-of-plane bending and C–C stretching vibrations of the C–C–C ring, respectively. 45 Fig. 2(g) shows the Rh6G Raman spectra of capillaries with different particle coverage densities at a concentration of 10 −4 M, and extracts the SERS-enhanced results of the characteristic peak at 611 cm −1 , as shown in Fig.…”

The Influence of Geometry on Plasmonic Resonances in Surface- and Tip-Enhanced Raman Spectroscopy

“…It is worth to mention that besides the spherical nanostructures in Figure 4 other nanostructures, such as mesoporous gold particles [105], nanostars/flowers [106][107][108][109][110][111][112][113] or spiky structures/superstructures [114,115], nanoshells [116], nanocubes [117][118][119][120][121][122], and hollow-structured particles [109,112], have been considered. For those as SERS substrates, their edges work as hotspots concentrating the electromagnetic field of the probing light into small volumes.…”