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

Abstract

Up-conversion (Gd,Yb,Tb)PO(4) 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)PO(4) nanocrystals synthesized via a hydrothermal method at 150 °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 Yb(3+) ions, depends on the Yb(3+)/Tb(3+) concentration ratio, calcination temperature and particle size. Strong green up-conversion emission of Tb(3+) is observed at 543 nm for the (5)D(4)→(7)F(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.

Bifunctional Luminomagnetic Rare-Earth Nanorods for High-Contrast Bioimaging Nanoprobes

“…Recently for bio-applications including investigations, metal oxide nanoparticles such as TiO 2 , ZnO, Fe 3 O 4 , carbon based structures such as carbon black and carbon nanotubes, graphene quantum dots as well as plasmonic metal nanoparticle (gold, silver or aluminum) have been studied281617181920. Among rare earth containing compounds, gadolinium based MRI contrast agents have been studied extensively but so far only very few have been reported about lanthanide oxides21222324. Besides size, morphology also plays an important role in bioimaging application of nanomaterials.…”

White light emission and effect of annealing on the Ho 3+ –Yb 3+ codoped BaCa 2 Al 8 O 15 phosphor

“…From the upconversion emission spectra, it could be clearly visualized that as the annealing temperature increases the prominent peaks of holmium ion in the green and red region increases remarkably rather the peak in the blue region which does not get influenced much. The green and red upconversion bands originating from 5 F 4, 5 S 2 and 5 F 5 get easily populated by the ET-I and also the GSA and ESA process but the blue band originating from the 5 F 2 get populated solely by the phonon assisted co-operative energy transfer from the Yb 3+ ions to the Ho 3+ ions which is comparatively the less efficient process of energy transfer than GSA and ESA processes 44 …”

Down- and up-converting dual-mode YPO4:Yb3+,Tb3+ nanocrystals: synthesis and spectroscopic properties

“…[42][43][44] However, investigations of down-and up-conversion in co-doped phosphates, especially in the nanocrystalline form, have been limited. [45][46][47][48][49] The Tb 3+ ion exhibits high quantum efficiencies for luminescence due to the large energy gap between the 7 F J ground state and the 5 D 4 excited state, which results in the lack of multiphonon relaxation of the 5 D 4 excited state and the high usage of this ion as a dopant in efficient phosphors. In addition, Yb 3+ ions have many advantages as dopants resulting in their wide application as effective sensitizers for NIR radiation.…”