Near-infrared (808 and 980 nm) excited photoluminescence study in Nd-doped Y 2 O 3 phosphor for bio-imaging.

The upconversion (UC) process in lanthanide-doped nanophosphors has attracted great research interest for its extensive application potential in biological in vitro and in vivo imaging due to the high tissue penetration depth of near-infrared excitation and low autofluorescence background. In this article, the authors report the synthesis of oxide nanophosphor of size  ⩽50 nm, which forms stable aqueous dispersion. The photoluminescence study is made on the nanophosphor upon 808 and 980 nm diode laser excitations. The 808 nm excitation resulted in strong emission at 795 nm due to the 4 K13/2   →  4 I13/2 transition along with other emissions from the Nd3+ ion. The 980 nm excitation has resulted in it turning green in the 525-560 nm range and is assigned to the 4 S3/2   →  4 I15/2 transition of the Er3+ ion, which is supposed to be present in a trace amount in the sample. The observation of strong UC emission indicates that the sample can be used for UC-based bio-imaging applications.