Surface-enhanced Raman scattering by the composite structure of Ag NP-multilayer Au films separated by Al₂O₃

Abstract

In the present study, a nanoparticle-multilayer metal film substrate was presented with silver nanoparticles (Ag NPs) assembled on a multilayer gold (Au) film by employing alumina (Al2O3) as a spacer. The SERS performance of the proposed structures was determined. It was suggested that the SERS effect was improved with the increase in the number of layers, which was saturated at four layers. The SERS performance of the structures resulted from the mutual coupling of multiple plasmon modes [localized surface plasmons (LSPs), surface plasmon polaritons (SPPs), as well as bulk plasmon polaritons (BPPs)] generated by the Ag NP-multilayer Au film structure. Furthermore, the electric field distribution of the hybrid system was studied with COMSOL Multiphysics software, which changed in almost consistency with the experimentally achieved results. For this substrate, the limit of detection (LOD) was down to 10−13 M for the rhodamine 6G (R6G), and the proposed SERS substrate was exhibited prominently quantitatively detected capability and high reproducibility. Moreover, a highly sensitive detection was conducted on toluidine blue (TB) molecules. As revealed from the present study, the Ag NP-multilayer Au film structure can act as a dependable SERS substrate for its sensitive molecular sensing applications in the medical field.

Graphene-Covered Silver Nanoisland Array Coupling with Hyperbolic Metamaterials for SERS Sensing

“…The Si wafer was cleaned with acetone, ethanol, and deionized water (DI water) sequentially using an ultrasonic cleaner for 20 min to remove contaminants from the Si surface. We used a previously reported method to prepare the HMM . A 9-nm Au film (0.1 Å/s, 7 × 10 –5 Pa) was first deposited on the Si wafer.…”

Silver Nanopillar Arrayed Thin Films with Highly Surface-Enhanced Raman Scattering for Ultrasensitive Detection

“…Thanks to the real-time and ultrasensitive detection of molecules in trace amounts, , surface-enhanced Raman scattering (SERS) as an up-and-coming technique has been commonly used in various applications, including biosensors, − medicine technology, , plasmon-driven catalytic reactions, − etc. To realize these applications, as a suitable SERS substrate, there should be high-density hotspots that result from strongly enhanced electromagnetic fields caused by the localized surface plasmon resonance (LSPR). − Various types of SERS substrates have been fabricated by controllable fabrication methods to form effective hotspots, such as arrayed nanopore silver (Ag) thin films, Ag-coated polymeric nanopillar arrays, Ag nanoparticles assembled on a multilayer gold film by employing alumina as a spacer, RGO@MoS 2 @Ag ternary nanocomposites for recyclable SERS detection, hydrophilic–hydrophobic Ag-modified PMMA substrates, a sandwiched Ag cap nanoparticles/SiO 2 /silver film system that can significantly enhance local electric-field intensity and increase the density of electromagnetic hot spots, leading to a SERS enhancement factor of 2.38 × 10 9 , and nanosculptured thin films of silver that perform a fast, accurate, and stable detection performance . Additionally, the continuous metal films can also act as good electrodes for (Spectro)-electrochemistry. − However, the complex fabrication process and the cost of SERS substrates are considered as the main obstacles to the widespread commercialization of SERS spectroscopy technology .…”

Bimetallic Au–Ag on a Patterned Substrate Derived from Discarded Blu-ray Discs: Simple, Inexpensive, Stable, and Reproducible Surface-Enhanced Raman Scattering Substrates

“…The SERS substrate efficiency depends on several factors consisting of composition, morphology, size, and shape of plasmonic materials as well as the location of analytes on the substrate . The strongest enhancement is received when the analyte molecules are located in “hot spot” regions, where intense EM fields are confined. − Hot spots can be found at the gap between adjacent metal nanostructures or nanoparticles (NPs); − thus, the design of structures or patterns on the substrate surface to obtain the dense hot spot area is vital for the development of SERS-active substrates. The nanostructures or nanopatterns with ordered or periodic arrangements have attracted much attention in recent years for SERS applications due to uniform hot spots over the sensing area. − Such well-organized nanostructures including nanohole array, nanowell array, nanopillar array, , triangular array, nanorod array, and disc array , structures have been developed based on mask or template-based fabrications and plasmonic material coating.…”