Hybrid dielectric-graphene nanostructured SERS substrates for antibody sensing.

We present a hybrid surface-enhanced Raman spectroscopy (SERS) platform based on a nanostructured silicon substrate integrated with functionalized graphene for the selective detection of biomolecules such as prolactin and SARS-CoV-2 antibodies. The high-index substrate comprises an array of subwavelength silicon nanopillars that support Mie-type optical resonances, enabling strong electromagnetic field confinement with minimal heating and optical losses. Graphene monolayers are transferred onto the nanopillar array and functionalized using 1-pyrenebutanoic acid succinimidyl ester (PBASE), thus facilitating the selective immobilization of target antibodies via π-π interactions and covalent bonding. Graphene transfer, functionalization, and analyte binding are confirmed by the SERS enhancement, which enables label-free detection at low laser power, avoiding photodamage and ensuring compatibility with sensitive biomolecules. Strain and doping analysis, performed through Raman vector decomposition, reveals distinct responses associated with each antibody, validating the sensor's capability for molecular discrimination.