Tunable Fabrication of Nanoscale Structures via Solid-State Thermal Dewetting for Label-Free Biosensing Applications

Plasmonic biosensors leveraging localized surface plasmon resonance (LSPR) in metallic nanostructures offer a powerful platform for label-free, real-time molecular detection with high sensitivity. In this study, we present a tunable fabrication approach for LSPR-based biosensing substrates using solid-state thermal dewetting (SSTD) of ultrathin nanostructured gold films sputtered onto glass substrates. By varying the sputtering duration, e.g., 9 and 12 s, and applying up to five sequential thermal dewetting cycles, we systematically investigated the morphological and optical evolution of the resulting gold nanoantenna arrays. Scanning electron microscopy (SEM) and image analysis revealed precise control over nanoparticle size and spatial distribution, while broadband spectroscopy and finite-difference time-domain (FDTD) simulations were used to assess resonance behavior and nearfield enhancement. A spectral integral (SI)-based quantification method was employed to evaluate refractive index sensitivity and determine the theoretical limit of detection (LOD) of the system. The optimized structure, fabricated with a 9 s sputtering time and two dewetting cycles, exhibited the highest figure of merit (FOM) and strongest simulated field enhancement. This nanoscale configuration was selected for proof-of-concept detection of human immunoglobulin G (IgG) using a protein A/G-functionalized surface. The platform demonstrated a theoretical LOD of approximately 80 pg/mL, confirming its applicability for ultrasensitive label-free biosensing in diagnostic applications.