Fig. 3: Molecular fluorescence enhancement and single molecule capture.

a Illustration and b fluorescence images of streptavidin capture inside the nanocavities using tail-end (left) as well as full (right) illumination modes. Hotspot is visible at the end of taper within the 20 nm-wide tip. Scale bars are 1 µm. c SEM image (left) of a 3D-tapered nanocavity with tip length 500 nm and fluorescence image (right) obtained from the tip after antibody immobilization. 1D-array of antibodies is expected within the tip. Scale bar is 100 nm. d SEM image (left) of a 3D-tapered nanocavity tip with length 20 nm and fluorescence image (right) obtained from the short tip after antibody immobilization. Volumetric-limitation enables specific capture of single antibody at the end of the tip. Scale bar is 100 nm.