(Gd,Yb,Tb)PO4 up-conversion nanocrystals for bimodal luminescence-MR imaging

authors	Debasu, ML; Ananias, D; Pinho, SLC; Geraldes, CFGC; Carlos, LD; Rocha, J
nationality	International
journal	NANOSCALE
keywords	COOPERATIVE ENERGY-TRANSFER; PHOSPHORIC-ACID SOLUTION; CONTRAST AGENTS; YB3+ IONS; NANOPARTICLES; TB3+; EMISSION; BLUE; CRYSTALS; GLASS
abstract	Up-conversion (Gd,Yb,Tb)PO4 materials and their potential for bimodal imaging have received little attention in the literature. Herein, we report the first study on the up-conversion emission of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal method at 150 degrees C. These materials exhibit ultraviolet, blue and green up-conversion emissions upon excitation with a 980 nm continuous wave laser diode. The intensity of the blue-emission band at 479 nm, ascribed to the cooperative up-conversion emission of a pair of excited Yb3+ ions, depends on the Yb3+/Tb3+ concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb3+ is observed at 543 nm for the D-5(4) -> F-7(5) transition. Relaxometry measurements reveal that the nanocrystals are efficient T-2-weighted (negative) contrast agents which, combined with visible-light emission generated by infrared excitation, affords them considerable potential for being used in bimodal, photoluminescence-magnetic resonance, imaging.
publisher	ROYAL SOC CHEMISTRY
issn	2040-3364
year published	2012
volume	4
issue	16
beginning page	5154
ending page	5162
digital object identifier (doi)	10.1039/c2nr31226c
web of science category	Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied
subject category	Chemistry; Science & Technology - Other Topics; Materials Science; Physics
unique article identifier	WOS:000306855500045