Plasmonic Core–Shell–Satellites with Abundant Electromagnetic Hotspots for Highly Sensitive and Reproducible SERS Detection

Abstract

In this work, we develop a Ag@Al2O3@Ag plasmonic core–shell–satellite (PCSS) to achieve highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection of probe molecules. To fabricate PCSS nanostructures, we employ a simple hierarchical dewetting process of Ag films coupled with an atomic layer deposition (ALD) method for the Al2O3 shell. Compared to bare Ag nanoparticles, several advantages of fabricating PCSS nanostructures are discovered, including high surface roughness, high density of nanogaps between Ag core and Ag satellites, and nanogaps between adjacent Ag satellites. Finite-difference time-domain (FDTD) simulations of the PCSS nanostructure confirm an enhancement in the electromagnetic field intensity (hotspots) in the nanogap between the Ag core and the satellite generated by the Al2O3 shell, due to the strong core–satellite plasmonic coupling. The as-prepared PCSS-based SERS substrate demonstrates an enhancement factor (EF) of 1.7 × 107 and relative standard deviation (RSD) of ~7%, endowing our SERS platform with highly sensitive and reproducible detection of R6G molecules. We think that this method provides a simple approach for the fabrication of PCSS by a solid-state technique and a basis for developing a highly SERS-active substrate for practical applications.

A Novel 3D Hierarchical Plasmonic Functional Cu@Co3O4@Ag Array as Intelligent SERS Sensing Platform with Trace Droplet Rapid Detection Ability for Pesticide Residue Detection on Fruits and Vegetables

“…Combined with the analysis of SERS properties and morphology, the optimal substrate was determined to be prepared from 40 M of silver-ammonia solution. High density gaps between Ag NPs of moderate size and tightly packed are more likely to form stronger and denser hotspots, and this has been demonstrated in a study by Puran Pandey et al that FDTD simulations show that there are electromagnetic field (hotspots) enhancements formed by high density gaps between Ag core and Ag satellites, and between Ag satellites in PCSS nanostructures [45].…”

Hierarchically Assembled Plasmonic Metal-Dielectric-Metal Hybrid Nano-Architectures for High-Sensitivity SERS Detection

“…To maintain the specific sub-nanometer gap, a dielectric layer can be considered as a nanogap spacer between two layered plasmonic metal nanostructures-namely, metal-dielectric-metal hybrid nano-architectures [27][28][29][30]. The dielectric spacer offers several benefits: protecting the plasmonic core from oxidation, tunning the LSPR properties, and maintaining a sub-nanometer gap between metal nanostructures to obtain a strong EM hotspot [31][32][33][34]. Therefore, it is of great significance to construct a unique 3D nano-architecture SERS substrate that comprises a hierarchical assembly of plasmonic NPs, separated by a dielectric spacer, for achieving an extremely high SERS activity.…”