Reproducible and Sensitive Plasmonic Sensing Platforms Based on Au-Nanoparticle-Internalized Nanodimpled Substrates

Electromagnetic enhancement effects through localized surface plasmon resonance considerably amplify the intensity of incident light when molecules are positioned in the vicinity of miniscule nanogaps. The aggregation of plasmonic nanoparticles synthesized using bottom-up methods has been extensively used to generate hot spots in solutions. These methods assist in obtaining non-periodic plasmonic signals, because the realization of uniform nanogaps through particle aggregation is difficult. Nanostructured substrates with gaps of 20–100 nm have also been fabricated using the top-down approach. However, the fabrication of smaller nanogap templates using these methods is difficult owing to high costs and low throughput. Therefore, a nanodimple array internalized with AuNPs is developed in this study to mitigate the challenges encountered in the bottom-up and top-down approaches. Precise nanogaps are generated by regularly internalizing AuNPs in the cavities of nanodimples through DNA hybridization. Simulations of the electric field distribution indicate that the incorporation of 80 nm-sized AuNPs into a curved nanodimpled Au substrate generate high-density volumetric hot spots within a detection volume, and result in a high plasmonic enhancement factor of 8.25 × 10⁷. The tremendous potential of the proposed plasmonic platform as an SERS-based biomedical diagnostic device is also verified.