New nanoplatform based on Gd2O2S:Eu3+ core: synthesis, characterization and use for in vitro bio-labelling

Abstract

The synthesis of Gd₂O₂S:Eu³⁺ nanoparticles (NPs), from hydroxycarbonate precursor precipitation followed by sulfuration in a H₂S/Ar atmosphere at 750 °C; is reported. It is the first time that the size of Gd₂O₂S:Eu³⁺ NPs can be finely tuned from 60 nm to more than 200 nm by controlling the precipitation medium, the maturation time and the sulfuration route. The oxysulfide Gd₂O₂S:Eu³⁺ NPs emit strong red luminescence at 624 nm when excited by near UV (363 nm) or by X-rays. They may thus be considered as nano-phosphors and nano-scintillators. Then, the surface of oxysulfide NPs has been modified by an amino-silica or by a mesoporous silica shell (thickness 10–15 nm). The luminescence intensity of europium in gadolinium oxysulfide NPs has been maintained in the amino-silica coated particles Gd₂O₂S:Eu³⁺@SiO₂-APTMS, whereas it has been significantly enhanced in the mesoporous silica coated Gd₂O₂S:Eu³⁺@mSiO₂. This versatile new nanoplatform can be easily internalized in living NIH3T3 mouse cells. It is not cytotoxic up to 1 mg mL⁻¹ and can be easily imaged by epifluorescence microscopy with excitation in the NUV. Consequently this spherical monodispersed Gd₂O₂S:Eu³⁺ nanophosphor could be considered as a very promising new fluorescent probe for bio-labelling, better than the corresponding oxide or fluoride nanoparticles.