Photoluminescence of Rhodamine from Nano-Confinement Inside 3D Sculptured Coatings

The effect of confinement of fluorophores (Rhodamine 6G) in nano-cavities of porous 3D sculptured coatings made by glancing angle deposition (GLAD) was investigated by fluorescence-lifetime imaging microscopy (FLIM). Shortening of fluorescence/photoluminescence lifetime by ~ 10% was observed from the dye-permeated (in liquid) structure; however, there was no rotational hindrance of dye molecules. When dried, a strong rotational hindrance 89% was observed for the orientation along the ordinary optical axis (fast-axis), and the hindrance was smaller than 57% for the extraordinary direction (fast axis). Light intensity distribution inside the nano-structure with a form-birefringence was numerically modelled using plane wave illumination and a dipole source. Nanoscale localisation of light intensity due to dipole nature I ~ 1/radius^6 and boundary conditions for E-field allows efficient energy deposition inside the region of lower refractive index (nanogaps).