Precision‐Engineered Plasmonic Nanostar Arrays for High‐Performance SERS Sensing

Abstract Surface‐enhanced Raman scattering (SERS) spectroscopy has emerged as a powerful tool for ultrasensitive and rapid analysis, with applications across several fields. The core mechanism of SERS is the interaction between molecules and plasmonic nanostructures, where localized surface plasmon resonances induce strong electromagnetic fields resulting in remarkable enhancements of Raman signals. The effectiveness of SERS substrates depends on their ability to generate strong electromagnetic fields at nanoscale hot spots, but achieving both reliable enhancement and reproducibility remains a challenge. This work presents a novel SERS substrate that combines a top‐down fabrication approach with bottom‐up wet chemistry to obtain an array of nanostars. Using electron beam lithography (EBL), uniform nanodisk arrays are first created, providing a controlled template. A subsequent chemical transformation reshapes these structures into nanostars, introducing sharp protrusions that significantly intensify localized electromagnetic fields. Finite‐difference time‐domain (FDTD) shows that nanodisks produce weak, symmetric field enhancements, while nanostars generate intense, highly localized electric fields at their spikes. Experimental SERS measurements using 1‐naphthalenethiol (1‐NAT), and tryptophan validate this transformation, demonstrating notable signal amplification with nanostar substrates. This work introduces a scalable and reproducible fabrication method for high‐performance plasmonic SERS substrates, paving the way for a wide range of applications in distinct fields.