Fluorescence enhancement on nanocup array structure (nanoLCA).
(A) A schematic representation of the fluorescence enhancement on the nanocup array structure is presented. The nanocup array polymer substrate is in gray, gold layer deposited on the substrate is in yellow, and two different refractive indexed media are in blue and purple color. Green and red point sources are HEX and TEX dye, respectively. In different media, reflected light intensity (hνref) and scattered light intensity (hνscat) differ despite the same excitation light intensity (hνex), resulting in different fluorescence emission intensities (hνem). (B) The SEM image of nanocup arrays. (C) The scattering peak position shifts to red with increasing concentration of glycerol. (D) Dynamic fluorescence image brightness response with alternate flows of air (A) and water (W). (E) The radiative decay rate on the surface of the nanocup structure with different surrounding refractive indices. (F) Integrated fluorescence emission curves of HEX and TEX show their maxima at different refractive indices. HEX has maximum integrated fluorescence intensity with 20% glycerol, but TEX has it with 80% glycerol (A–F adapted from Ref.  with permission from The Royal Society of Chemistry).