3D Surface-Enhanced Raman Scattering Substrate Based on an Array of Self-Assembled Au@SiO₂ Microspheres

A quasi-periodic array of 3D gold-nanoparticle-capped SiO₂ microspheres (Au@SiO₂) was designed and prepared with a facile approach to enhance the Raman signal intensity of adsorbed biomolecules. Through adjusting the thickness and annealing of Au thin films initially deposited on arrays of self-assembled SiO2 microspheres, we were able to control the diameter of Au nanoparticles and their interparticle spacing to produce two types of plasmonic near-field hot spots, locating at the gaps of such densely arranged Au nanoparticles on individual SiO₂ microspheres and in the gap regions of neighboring SiO₂ microspheres, respectively. Such double near-field enhancement mechanism leads to a surface-enhanced Raman scattering (SERS) enhancement factor up to 3 × 10⁶ for Rhodamine 6G molecules. The SERS signal intensity was highly uniform with a relative standard deviation of 4.5%. This 3D SERS substrate has significant potential for various applications in the field of SERS detection of analytes and wearable biosensing. © 2024 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.