Liquid-Phase Synthesis of Doped Nanoparticles:  Colloids of Luminescing LaPO₄:Eu and CePO₄:Tb Particles with a Narrow Particle Size Distribution

Abstract

Nanocrystals of LaPO 4 :Eu and CePO 4 :Tb with a mean particle size of 5 nm and a narrow size distribution have been prepared by reacting the corresponding metal chlorides, phosphoric acid, and a base at 200°C in tris(ethylhexyl) phosphate. Highly crystalline material was obtained as confirmed by X-ray powder diffraction measurements and high-resolution transmission electron microscopy. Successful doping with europium was evident from the splitting and the intensity pattern of the luminescence lines. Luminescence lifetime measurements were used to confirm doping and energy transfer in both materials. Colloidal solutions of CePO 4 :Tb exhibit an overall luminescence quantum yield of 16%.

Synthesis and functionalization of biocompatible Tb:CePO4 nanophosphors with spindle-like shape

“…5. In agreement with previous reports, the excitation spectrum (monitored at 352 nm) consisted of a broad band at 273 nm and a shoulder at 255 nm, which are due to 4f→5d electronic transitions of Ce 3+ (Riwotzki et al 2000). Also as expected, the emission spectrum, which was recorded using an excitation wavelength of 255 nm for a better observation of all the emission features of the Ce 3+ ions, displayed a broad band centred at 352 nm corresponding to the transition from the excited 5d 1 configuration to the 2 F 5/2 and 2 F 7/2 levels of Ce 3+ (Guan et al 2007).…”

“…6 (top), the excitation spectrum monitored at the main Tb emission line at 542 nm (Riwotzki et al 2000) for sample Tb 0.02 Ce 0.98 PO 4 prepared by conventional heating was quite similar to that of undoped CePO 4 (Fig. 5) indicating that the Tb emission is produced after an energy transfer from excited Ce 3+ to Tb 3+ cations, which confirmed the success of the doping procedure.…”

Ionoluminescence in the Helium Ion Microscope

“…Rare Earth doped lanthanum phosphate (LaPO 4 ) nanocrystals (K. Riwotzki et al, 2000) are a class of luminescent nanoparticle with similar dimensions to QDs but with a different mechanism responsible for their luminescence. QD luminescence originates from transitions across size dependent band gaps whereas the luminescence in doped LaPO 4 nanocrystals is a result of transitions between f electron states.…”

“…The Eu doped LaPO 4 nanocrystals emit light because f electrons in the Eu 3+ dopants gain energy and are excited into the D states. Here they undergo non-radiative energy loss to the 5 D 0 state and then emit a photon and drop down to an F state, producing the spectral peaks shown in Figure 9(d), the positions of which correspond to photoluminescence (PL) results from Riwotzki et al (Riwotzki et al, 2000). The same applies to emission from Ce/Tb doped LaPO 4 particles, where the peaks correspond to the f electron transitions in Tb 3+ from the state labelled 5 D 4 in the PL spectrum from Riwotzki et al (Riwotzki et al, 2001).…”

LaPO4:Ce,Tb and YVO4:Eu nanophosphors: Luminescence studies in the vacuum ultraviolet spectral range

“…28,29 In recent years, LaPO 4 has been also shown to be a useful host lattice for lanthanide ions to produce phosphors that emit in a broad range of colors. 23,27,[30][31][32] Even in 1963, it was already known that LaPO 4 :0.01Ce 3þ is a "short luminescence delay time phosphor" and emits ultraviolet (UV) light, which peaks spectrally at about 340 nm, when excited with cathode rays, and its luminescence decay time is about 24 ns. 33 27,34,35 Nowadays, LaPO 4 :Ce,Tb is known as one of the most promising highly luminescent green phosphors which is one of the best candidates for biomedical applications, such as fluorescence resonance energy transfer (FRET) assays, biolabeling, optical imaging, or phototherapy, [36][37][38] where green emission from Tb 3þ is highly important.…”