The endeavor to develop novel fluorescent nanomaterials in the fields of nanobiotechnology, photonics and optoelectronics has been burgeoning in the past decade. The synthesis of rare earth compound nanocrystals has attracted considerable attention due to their potential applications in biological chemical probes and medical diagnostics. Rare earth (RE) compound nanocrystals have many advantages as biolabels due to their large Stokes shift, sharp emission spectra, long lifetime, multiphoton and up-conversion excitation, reduced photobleaching and low toxicity over semiconductor nanocrystals like quantum dots and organic phosphors molecule.

The current work reports the synthesis, characterization and bio-functionalization of rare-earth (RE) doped and co-doped Y2O3 nanocrystals for potential bio-imaging application. We have used other RE dopants such as europium (Eu), erbium (Er) and ytterbium (Yb). These RE ions are successful doped, and Er-Yb co-doped into Y2O3 nanocrystals. Room temperature photoluminescence (PL) spectra showed characteristic emission peaks of Tb, Eu, Er, Yb ions doped and Er-Yb co-doped Y2O3 samples at 255 and 365nm excitations. Co-doped samples showed enhanced PL intensity which is attributed to the presence of a sensitizer. By varying RE concentrations in the range of 0.2 - 20mol%, it was observed that 5mol% dopant PL intensity was the highest in both cases (see Figure). The nanocrystals were surface functionalized with amine (NH2) group via reverse microemulsion method to render the nanocrystals highly water soluble and also afford them further functionalization by other molecules for potential bio-imaging applications. Cytotoxicty of the modified nanocrystals was also investigated. The current nanomaterials have demonstrated potential in Bioimaging.