(La0.97RE0.01Yb0.02)2O2S Nanophosphors Converted from Layered Hydroxyl Sulfate and Investigation of Upconversion Photoluminescence (RE=Ho, Er)

Abstract

Phase-pure (La0.97RE0.01Yb0.02)2O2S upconversion (UC) nanophosphors (average crystallite size ~ 45 nm; RE=Ho, Er) were annealed from their hydrothermally crystallized layered hydroxyl sulfate precursors in flowing hydrogen at 1200 °C for 1 h, with water vapor as the only exhaust. Under 978-nm laser excitation (up to 2.0 W), the Ho3+-doped phosphor exhibited green (medium), red (weak), and near-infrared (strong) emissions at ~ 546 (5F4 → 5I8), 658 (5F7 → 5I8), and 763 nm (5F4 → 5I7), respectively, and has the stable chromaticity coordinates of about (0.30, 0.66) in the visible-light region (400–700 nm). The Er3+-doped UC phosphor, on the other hand, showed weak green (~ 527/549 nm, 2H11/2,4S3/2 → 4I15/2), weak red (~668/672 nm, 4F9/2 → 4I15/2), and strong near-infrared (~ 807/58 nm, 4I9/2 → 4I15/2) luminescence, whose emission color in the visible region drifted from yellowish-green [(0.36, 0.61)] to green [(0.32, 0.64)] with increasing excitation power. Analysis of the power-dependent UC luminescence found three- and two-photon processes for RE=Ho and Er, respectively, and the possible UC mechanisms were proposed.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2277-4) contains supplementary material, which is available to authorized users.

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

“…Such an upconversion behavior is similar to those reported for 2 at% of Yb 3+ and 1 at% of Tm 3+ ‐doped La 2 O 2 SO 4 and La 2 O 2 S but is quite different from the UC luminescence of REPO 4 (RE=La, Gd, Y and Lu) doped with 20 at% of Yb 3+ and 0.5 at% of Tm 3+ , which showed strong blue (~475 nm), secondly strong red (~650 nm) and weak near‐infrared (~800 nm) emissions . The upconversion behavior of a phosphor is known to be remarkably influenced by the type of host lattice, lattice defects, and the content/lattice occupancy/distribution uniformity of the sensitizer/activator pair . Analyzing the emission intensity against excitation power yielded slope ( n ) values of around 3 (~2.85) and 1 (~1.13) for the 695 and 800 nm bands (Figure A, the inset), respectively.…”

Band Gap Engineering from Cation Balance: The Case of Lanthanide Oxysulfide Nanoparticles

“…1,2 From these pioneering works, numerous studies were published on the preparation of these phases and their optical properties. In particular, doped Ln 2 O 2 S (Ln = La, Gd, Y) turned out to be excellent phosphors with good efficiencies for scintillators, 3,4 upconversion materials [5][6][7][8] and bioimaging capabilities. [9][10][11] These crystalline phases are stable in air.…”

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

“…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.…”