Luminescence switching behavior through redox reaction in Ce3+ co-doped LaPO4:Tb3+ nanorods: Re-dispersible and polymer film

Abstract

Re-dispersible Tb(3+) doped LaPO(4) nanorods have been prepared using ethylene glycol (EG) as a capping agent as well as reaction medium at a relatively low temperature of 150 °C. The X-ray diffraction study reveals that all the doped samples are well crystalline with a monoclinic structure of the LaPO(4) phase. The luminescence intensity of (5)D(4)→(7)F(5) transition at 543 nm (green) is more prominent than that of (5)D(4)→(7)F(6) transition at 487 nm (blue) for all the samples. This is related to the polarizing effect from [PO(4)](3-) to the Tb(3+) site. Concentration dependent luminescence study shows that the luminescence intensity of Tb(3+) increases up to 10 at.% and decreases above this. This is due to the concentration quenching effect arising from cross relaxation among Tb(3+)-Tb(3+) ions. The results show that nanoparticles prepared in EG medium gives an enhanced luminescence compared to that prepared in water. This is attributed to the multiphonon relaxation effect from O-H groups surrounding over nanoparticles as well as the extent of increase of agglomeration among particles for samples prepared in water. Significant enhancement in the emission of Tb(3+) is also observed when Ce(3+) is used as the sensitizer in LaPO(4):Tb(3+)nanorods. The optimum concentration of Ce(3+) for maximum luminescence is found to be 7 at.% in Ce(3+) sensitized LaPO(4):Tb(3+) (5 at.%). Based on the energy transfer process from Ce(3+) to Tb(3+), the luminescence of Tb(3+) can be switched OFF and ON by performing oxidation and reduction of Ce(3+)↔Ce(4+) using KMnO(4) and ascorbic acid, respectively. The samples are re-dispersible in water, methanol and can be incorporated into polyvinyl alcohol (PVA) films. They show a dark green emission under ultraviolet radiation.

Core/shell-type nanorods of Tb3+-doped LaPO4, modified with amine groups, revealing reduced cytotoxicity

“…There are many well-known inorganic phosphors based on lanthanide ions, e.g., simple fluorides, borates, vanadates, manganates, phosphates, and their complex analogs. Phosphates with the general formula: LnPO 4 or hydrated ones (LnPO 4 · n H 2 O) doped with activator ions (e.g., Eu 3+ , Tb 3+ , Tm 3+ ) can exhibit bright, multicolor luminescence dependent on their crystal structure, chemical composition and morphology (Yu et al 2006; Phaomei et al 2010; Phaomei et al 2011); high refractive index and thermal stability (Ghosh et al 2010; Blasse and Grabmaier 1994); biocompatibility, which are the well-known properties of many phosphate species (Hirsch et al 2007). As the nanostructures discussed reveal such properties, the phosphates have been successfully applied fluorescent lamps, tracers, sensors and bio-sensors, contrast agents, drug carriers, and as other biocompatible species (Xu et al 2011; Hölsä 2009; Kim 2000; Chander 2005; Shionoya and Yen 1999).…”

Intense red emitting monoclinic LaPO4:Eu3+ nanoparticles: host–dopant energy transfer dynamics and photoluminescence properties

“…Inorganic compounds bearing f 0 , f 7 or f 14 lanthanide ions have a negligible chance of undergoing quenching effect through cross relaxation from Ln 3+ ion and hence they are the preferred choice as a host material. 7 In that context LaPO 4 is good luminescence host.…”

“…Inorganic compounds bearing f 0 , f 7 or f 14 lanthanide ions have a negligible chance of undergoing quenching effect through cross relaxation from Ln 3+ ion and hence they are the preferred choice as a host material. 7 In that context LaPO 4 is good luminescence host. Also because of its other desirable properties such as low toxicity, environmental stability, ability to accommodate large lanthanide ions, high refractive index and high thermal and chemical stability, it is extensively used as a host matrix.…”

Multifunctional LaPO4:Ce/Tb@Au mesoporous microspheres: synthesis, luminescence and controllable light triggered drug release

“…A similar band in all three samples at 3345 cm -1 and 1082 cm -1 is due to the -OH stretching and bending vibrations of water and hydroxyl groups. 23 For the precursor, the characteristic absorption bands of O-C-O (1523 and 1401 cm -1 ), π-CO 3 2-(843 cm -1 ) and δ-CO 3 2-(753 and 688 cm -1 ) can be observed in the precursor, which indicate the existence of La(OH)CO 3 :Ce/Tb. 24 The unique absorption peaks at 1640, 1443, and 1392 cm -1 are from the internal vibration of -NH 2 and -CN which reveals the presence of PEI on the LaPO 4 :Ce/Tb@Au.…”