Quantitative Mid-Infrared Plasmonic Biosensing on Scalable Graphene Nanostructures

Graphene nanostructures, exhibiting tunable and nanoscale-confined mid-infrared (mid-IR) plasmons, prevail as a powerful spectroscopic platform for novel surface-enhanced molecular identification. Particularly, graphene shows exciting opportunities for biosensing applications due to its versatile functionalization methods with different biomolecular building blocks (e.g., enzymes, proteins, and DNA). Here, a quantitative bioassay based on the mid-IR localized surface plasmon resonance (LSPR) modulation in functionalized graphene nanostructures is demonstrated. Specifically, vitamin B₁₂ (vB₁₂) using the specific recognition elements on modified graphene nanoribbons (i.e., pyrene linkers via π − π stacking + anti-vB₁₂ antibody fragments via amide bond) is detected. Different concentrations of vB₁₂ spotted on an arrayed panel of a single chip are quantified by the graphene LSPR shifts, where a limit of detection (LOD) of 53.5 ng mL⁻¹ is obtained. The upscaling potential of the bioassay using large area nanostructured graphene films produced by nanoimprinting 2D hole arrays is illustrated. The integration of quantitative bioassay with scalable graphene nanostructures shows promising routes of graphene-based mid-IR platforms toward prospective industrial applications.