Antibiotic-Mediated Plasmonic-Mie Resonance for Biosensing Applications on a Novel Silicon Nanopillar Metasurface

This study demonstrates a biosensing platform facilitated by localized surface plasmonic resonance (LSPR) on a silicon (Si) nanopillar metasurface mediated by the presence of cephalexin (Cef) antibiotics in solution. The metasurface is designed to exhibit narrow quadrupolar Mie resonances that when coupled with bovine serum albumin-coated (BSA-coated) plasmonic gold nanospheres (BSANS) will produce an appreciable redshift at the peak resonance wavelength, occurring only in the presence of the target antibiotic. To optimize the performance of the Si nanopillars, the finite element method is utilized to fine-tune their diameters, heights, and periodicity, along with improvements to the fabrication techniques, under the BSANS-antibiotic binding assay. The metasurface sensor is directly fabricated via a facile photolithographic process using silicon wafers. Through the detection assay, this device exhibited a significant 22 nm wavelength shift resulting from changes to the local refractive index in the presence of the BSANS-antibiotic coupling. This phenomenon is facilitated through the presence of cephalexin down to 0.3 μg mL^-1 for the binding between the plasmonic nanoparticles and the metasurface allowing for sensitive and real-time detection.