SiO₂ Microsphere Array Coated by Ag Nanoparticles as Raman Enhancement Sensor with High Sensitivity and High...

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) requires substrates with high sensitivity and uniformity.
• Developing cost-effective and efficient SERS substrates is crucial for various sensing applications.
• Existing SERS substrates often face limitations in sensitivity, uniformity, or fabrication complexity.

Purpose of the Study:

• To fabricate a novel double-layer "Ag@SiO2" SERS substrate with enhanced sensitivity and uniformity.
• To investigate the electromagnetic field distribution and theoretical enhancement factors of the fabricated substrate.
• To evaluate the substrate's performance for detecting trace analytes like Rhodamine 6G.

Main Methods:

• Self-assembly of a monolayer SiO2 microsphere (MS) array on a silicon substrate.
• Transfer of dense silver nanoparticles (AgNPs) onto the MS array using a liquid-liquid interface method.
• Electromagnetic distribution analysis using Lumerical FDTD Solutions software and calculation of theoretical enhancement factors.

Main Results:

• A double-layer "Ag@SiO2" SERS substrate with high sensitivity and uniformity was successfully prepared.
• The optimal AgNPs diameter for maximal electric field enhancement at the nanoparticle gap was determined to be 30 nm.
• The substrate achieved an ultra-low limit of detection (LOD) of 10^-16 mol/L for Rhodamine 6G.
• An analytical enhancement factor (AEF) of approximately 2.3 × 10^13 and a relative standard deviation (RSD) of ~5.78% were recorded, indicating high uniformity.

Conclusions:

• The developed "Ag@SiO2" SERS substrate demonstrates exceptional sensitivity and uniformity.
• The substrate's design effectively enhances the electromagnetic field, leading to superior SERS performance.
• This work presents a promising platform for highly sensitive and reliable chemical detection.