Metal-enhanced fluorescence: effect of surface coating

Abstract

Metal Enhanced Fluorescence (MEF), a phenomenon arising when a fluorophore is in closed proximity to a metallic structure such as metallic films or nanostructures, is seen as a way to increase the amount of reactive oxygen species produced by the irradiation of the protoporphyrin IX (PpIX), a photosensitizer commonly used in photodynamic therapy. Here, we show a study of the distance-dependent of MEF by applying multiple layers of polyelectrolyte (PE) on silver nanoparticles (AgNPs) to progressively increase the distance between AgNPs and PpIX, covalently bond to the last polyelectrolyte layer as well as exploring the use of AgNPs of different sizes ranging from 40 to 100 nm. Up to four fold increase of PpIX fluorescence was observed when this photosensitizing agent is bounded onto 100 nm sized Ag NPs. The effective corresponding distance between AgNPs and PpIX is three layers of PE. © ? 2014 SPIE.