Upconverting YbPO₄:RE monospheres (RE=Ho, Er, Tm)

Abstract

Uniform spheres of (Yb0.98RE0.02)PO4 orthophosphate (RE=Ho, Er, and Tm, respectively) were synthesized via a homogeneous precipitation procedure mediated by SO42− anions. The as‐precipitated and 1100°C calcined products were determined via laser‐diffraction particle sizing to have the average diameters of ~2.04 ± 0.67 and 1.80 ± 0.93 μm, respectively. The upconversion luminescence of RE3+ under sensitization by the host Yb3+ was studied for the calcination products under 978 nm laser excitation, and it was found that the emissions are dominated by a red band at ~650 nm for Ho3+ (5F5 → 5I8 transition), similarly strong green (~515‐565 nm, 2H11/2/4S3/2 → 4I15/2 transition) and red (~640‐680 nm, 4F9/2 → 4I15/2 transition) bands for Er3+, and a near‐infrared band at ~800 nm for Tm3+ (3H4 → 3H6 transition). The number of laser photons needed to populate the emitting state was determined by varying the excitation power, and the possible photon reactions leading to the observed upconversion were discussed.

Upconversion luminescence and favorable temperature sensing performance of eulytite-type Sr3Y(PO4)3:Yb3+/Ln3+ phosphors (Ln=Ho, Er, Tm)

“…Figure 5(a) shows the UC luminescence spectra of Yb 3+ /Ho 3+ codoped Sr 3 Y(PO 4 ) 3 under varying excitation power, where the four groups of emission bands centered at~485 nm (blue, negligible), 545 nm (green, weak), 657 nm (red, overwhelmingly strong) and 767 nm (red in NIR, weak) can be assigned to 5 [9][10][11][12], respectively. Raising excitation power from 1.00 to 3.00 W did not produce any new emission but successively improved the intensity of the existing luminescence.…”

“…The host lattice for UC should assure not only a satisfactory luminescence efficiency, but also excellent physicochemical stability, safety, and low toxicity. A handful of inorganic compounds have been developed as UC host so far, typically including fluorides [5,6], oxides [7,8], oxysulfides [9], phosphates [10,11] and other oxygenates [12][13][14][15], and new hosts are also under active exploration and/or perfection.…”

Phase evolution, structure, and up‐/down‐conversion luminescence of Li6CaLa2Nb2O12:Yb3+/RE3+ phosphors (RE = Ho, Er, Tm)

“…It is also seen from Figure A that the green band well splits into four sharp peaks centered at ~ 524, 540, 551 and 568 nm, respectively, which indicates that the 2 H 11/2 and 4 S 3/2 energy levels of Er 3+ are subjected to substantial splitting by the dodecahedral coordination environment in Li 6 CaLa 2 Nb 2 O 12 . Such a phenomenon was found for Gd 2 O 3 :Yb/Er, Y 2 O 3 :Yb/Er, LiYF 4 :Yb/Er, and NaLu(WO 4 ) 2 :Yb/Er, but hardly for YbPO 4 :Er, YPO 4 :Yb/Er and Sr 3 Y(PO 4 ) 3 :Yb/Er orthophosphates, La 2 O 2 S:Yb/Er oxysulfide, and La 2 O 2 SO 4 :Yb/Er oxysulfate . In addition, the broad and diffuse red luminescence extending from ~ 640 to 700 nm (Figure A) was similarly observed for Ba 5 Gd 8 Zn 4 O 21 :Yb/Er UC phosphor in the ~ 640‐680 nm spectral region, which was ascribed to widening of the 4 F 9/2 energy level by electronic interactions and spin‐orbit coupling .…”

Extensive tailoring of REPO4 and REVO4 crystallites via solution processing and luminescence

“…99 Mechanism analysis revealed that the UC luminescence of REPO 4 :Yb 3+ ,Er 3+ nanoparticles (RE = Y, La, Gd) and t-YPO 4 :Yb 3+ ,Ln 3+ /YbPO 4 :Ln 3+ monospheres (Ln = Ho, Er, Tm) mostly occur via a two- or three-photon process. 100–102 Kang et al prepared poly(acrylic acid)@GdVO 4 :Ln 3+ (Ln = Yb/Ho, Yb/Er, Yb/Tm) up-converting hollow spheres by photoinduced polymerization and showed their potential as contrast agents and pH-dependent drug carriers (Fig. 9).…”