Correction

The key reference to work of Mortier and Patriarche had been inadvertently omitted from this article [1]. The statement below in the original INTRODUCTION section is not very accurate and appropriate:

"Unfortunately, ever since the first report on oxyfluoride GCs, there have been much research on the properties of nano-particles in GCs but no publication has been reported about how to obtain free nano-particles in aqueous solution from the GC-host and how to apply it to the fields mentioned above, especially in biological field."

The authors amend it as follows:

Mortier and Patriarche [2] showed that PbF2 nanoparticles could be produced by dissolving the amorphous GeO2-PbO phase of GCs with HF. Unfortunately, the corrosion between GeO2-PbO and HF can hardly be complete so that the nanoparticle had an amorphous phase as a shell in their experiment. Therefore, no publication has been reported about how to obtain free and pure crystalline nano-particles in aqueous solution from the GC-host and how to apply it to the fields mentioned above.