Hydrophilic, upconverting, multicolor, lanthanide-doped NaGdF4 nanocrystals as potential multifunctional bioprobes.

Monodisperse water-soluble hexagonal phase Ln(3+)-doped NaGdF(4) upconverting nanocrystals (UCNCs) have been successfully fabricated by means of a fast, facile, and environmentally friendly microwave-assisted route with polyethylenimine as the surfactant. Fine-tuning of the UC emission from visible to near-IR and finally to white light has been achieved. Furthermore, studies of the magnetic resonance imaging as well as the magnetization (magnetization-magnetic field curves) and the targeted recognition properties of FA-coupled amine-functionalized NaGdF(4)@SiO(2) UCNCs indicate that the obtained NaGdF(4) UCNCs can be potential candidates for dual-mode optical/magnetic bioapplications.