We report a novel plasmonic tuning technique which allows colorimetric, naked-eye detection of protein-protein binding
at extreme sensitivities. Utilizing an engineered approach to molecularly-driven plasmonic-coupling, we construct three-part
plasmonic “bowtie” structures within protein nanoarrays using single biomolecular binding events. Precise
molecular positioning of single gold nanaoparticles inside plasmonic bowties allows us to shape the plasmon supported
by each array element in order to engineer a visible color-shift. By ensuring that only a single binding site is available
inside each feature, we ensure plasmon homogeneity across the array, a unique technological solution which is essential
to providing the sensitivity and observability we demonstrate here. This work represents a step-change in molecularly-mediated
plasmonics and colorimetric biosensing, enabling biologically-controlled nanoengineering at single-protein
resolutions. The potential applications of this powerful technique are not limited to biosensing and point-of-care
diagnostics, and will also impact the emerging fields of molecularly driven nanoengineering and electronics.
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