An Interfacial Europium Complex on SiO2 Nanoparticles: Reduction-Induced Blue Emission System

In this study, Eu-coated SiO2 nanoparticles have been prepared, consisting of an interfacial complex of Eu and 1,10-phenanthroline (phen) at the solid surfaces of the SiO2/Eu nanostructures. The as-prepared SiO2/Eu/phen nanoparticles exhibits sharp red emission via energy transfer from the phen to the Eu(III). After sintering at 200 °C in air, the emission is tuned from red to blue. The blue emission is originated from Eu(II). This reduction-induced emissive phenomenon resulted from the electron-donating environment created by the surrounding phen and SiO2, which is the first reported fabrication of a stable Eu(II)-based emissive material using mild conditions (reaction in air and at low temperature) and an organic-inorganic hybrid nanostructure. The existence of two different stable oxidation states with characteristic emissions, blue emissive Eu(II) and red emissive Eu(III), suggests significant potential applications as novel luminescent materials with inorganic-organic hybrid structures.