Mixed protein templated iron-nanoclusters exhibit photoluminescence in the visible and near-infrared region

Abstract

Here we demonstrate the first successful synthesis of photoluminescent, water-soluble iron (Fe) nanoclusters (NCs) using the mixed proteins of an aqueous egg white (EW) solution. High resolution transmission electron micrographs (HR TEM) of NCs synthesized from a 5mM FeCl3 solution show the cluster sizes ranging from 1.6nm to 5.8nm with the most abundant size being 2.2nm. The energy dispersive x-ray spectra (EDS) confirm the clusters to be composed of Fe atoms. These newly synthesized iron nanoclusters (EW:FeNCs) exhibit strong photoluminescence in the visible and near-infrared (IR) regions upon excitation with ultra-violet (UV) light. The EW:FeNCs exhibit photoluminescence peaks at 450 nm and 845 nm with excitation by UV light at 374nm and 360nm, respectively. The EW:FeNCs also exhibit strong fluorescence emission when excited at 365nm with an average Imax of 444nm. However, this emission is masked by the fluorescence of the templating-protein, making a definitive assignment difficult. These novel EW:FeNCs exhibit remarkable chemical and photostability in addition to moderate thermal stability and can be used in a wide range of imaging and sensing applications.