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.
keywords
COOPERATIVE ENERGY-TRANSFER; PHOSPHORIC-ACID SOLUTION; CONTRAST AGENTS; YB3+ IONS; NANOPARTICLES; TB3+; EMISSION; BLUE; CRYSTALS; GLASS
subject category
Chemistry; Science & Technology - Other Topics; Materials Science; Physics
authors
Debasu, ML; Ananias, D; Pinho, SLC; Geraldes, CFGC; Carlos, LD; Rocha, J
our authors
Duarte Ananias
Assistant Researcher
João Rocha
Full Professor
Luís Carlos
Full professor
Mengistie Leweyehu Debasu
Researcheracknowledgements
We thank FCT for the financial support from Fundacao para a Ciencia e a Tecnologia (FCT) through PEst-C/CTM/LA0011/2011, grant SFRH/BD/67108/2009, Project REDE/1509/RME/2005 for the access of TEM. The NMR spectrometers are part of the National NMR Network (RNRMN) funded by FCT. We acknowledge Dr R.A.S. Ferreira for her help with measuring absolute emission quantum yields.