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

TL;DR

This paper studies how rhodamine's light emission changes when confined in nano-structures made by a special coating technique.

Contribution

The study reveals how nano-confinement affects fluorescence lifetime and molecular orientation without rotational hindrance in liquid state.

Findings

Fluorescence lifetime shortened by ~10% in liquid-filled nano-cavities without rotational hindrance.

Dried structures showed 89% rotational hindrance along the ordinary axis and less than 57% along the extraordinary axis.

Light intensity localization in nanogaps was modeled, showing efficient energy deposition in low refractive index regions.

Abstract

The effect of the 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 (slow-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 modeled using plane-wave illumination and a dipole source. Nanoscale localization of light intensity due to dipole nature I∼1/radius6 and boundary conditions for E-field allows efficient energy deposition inside the region of lower refractive index (nanogaps).

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