Dielectric Nanoparticles Coated upon Silver Hollow Nanosphere as an Integrated Design to Reinforce SERS Detection of Trace Ampicillin in Milk Solution

• Main Authors: Han Lee, Jia-Wei Yang, Jiunn-Der Liao, Jaya Sitjar, Bernard Haochih Liu, Kundan Sivashanmugan, Wei-En Fu, Guo Dung Chen
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Coatings
• Subjects: surface-enhanced Raman scattering; non-specific binding; silver hollow nanosphere; dielectric nanoparticle; ampicillin
• Online Access: https://www.mdpi.com/2079-6412/10/4/390

Surface-enhanced Raman scattering (SERS) technique is competent to trace detection of target species, down to the single molecule level. The detection sensitivity is presumably degraded by the presence of non-specific binding molecules that occupy a SERS-active site (or hot spot) on the substrate surface. In this study, a silver hollow nano-sphere (Ag HNS) with cavity has been particularly designed, followed by depositing dielectric nanoparticles (Di NPs) upon Ag HNS. In the integrated nanostructures, Di NPs/Ag HNS were furthermore confirmed by cutting through the cross sections using the Focused Ion Beam (FIB) technique, which provides the Scanning Electron Microscope (SEM) with Energy-dispersive Spectroscope (EDS) mode for identifying the distribution of Di NPs upon Ag HNS. The results have indicated that Di NPs/Ag HNS exhibits small diameter of cavity, and among Di NPs in this study, Al₂O₃ with lower dielectric constant provides a much higher SERS enhancement factor (e.g., ~6.2 × 10⁷). In this study, to detect trace amounts (e.g., 0.01 ppm) of Ampicillin in water or milk solution, Al₂O₃ NPs/Ag HNS was found to be more efficient and less influenced by non-specific binding molecules in milk. A substrate with integrated plasmonic and dielectric components was designed to increase the adsorption of target species and to repulse non-specific binding molecules from SERS-active sites.