Enhanced Refractive Index Sensitivity of Linearly Assembled Gold Nanoantennae for Biosensing Applications

Near-field interactions between individual gold nanoparticles (AuNPs) in clusters or arrays open a new avenue for highly sensitive plasmonic biosensors, owing to their significant impact on the localized surface plasmon resonance. Compared to individual nanoparticles, supracolloidal structures offer unique plasmonic properties with the enhanced susceptibilities to variations in the local refractive index. In this study, we report on the template-assisted fabrication of large-scale (ca. 1 cm²) linear periodic assemblies of AuNPs and demonstrate their polarization dependent biosensing performance at the proof-of concept level. We explored two complementary approaches for template fabrication: (i) laser interference lithography (LIL), offering high-fidelity patterns over moderate areas, and (ii) wrinkle-assisted patterning, a more scalable and costeffective strategy. Despite structural differences, both approaches yielded comparable high biosensing performances, demonstrating broad potential utility of the developed biosensing platform. As a proof-of-concept application, we performed biofunctionalization and detection of the antibody for Tumor Necrosis Factor-Alpha (TNF-α), a pro-inflammatory cytokine that plays a multifaceted role in cancer prognosis. The shifts in plasmonic resonance peaks of the AuNP assemblies were quantified using polarized-light vis-NIR spectrometry during various stages of the functionalization and detection process. The experimental results revealed a pronounced polarization-dependent plasmonic resonance peak shift (Δλ), with up to a 5-fold increase observed in the longitudinal mode over the transversal case, a feature consistently achieved across both LIL 3 and wrinkled templates. These findings present an innovative supracolloidal structuring approach for the development and scalable production of highly sensitive, plasmonic biochips.