Green upconverted emission enhancement of ZrO₂ : Yb³⁺–Ho³⁺nanocrystals

Abstract

ZrO2 : Yb3+–Ho3+ nanocrystals with different concentrations of codopants were synthesized with a 0.0082 molar ratio of surfactant Pluronic F-127 using a sol–gel micelle method, and annealed at 1000 °C for 5 h. The dominant crystallite phase was tetragonal, with an average crystallite size of 20 nm. The upconverted signal produced by the codoped nanocrystals is an almost pure green emission centred at 540 nm caused by the radiation emitted by the 5F4 + 5S2 → 5I8 relaxation of Ho3+. The highest efficiency for the Ho3+ green emission, with a decay constant (τeff) of 360 µs, was obtained with a 2/0.001 mol% Yb/Ho composition. This yields a colour coordinate of (0.289, 0.699) with a maximum luminance of 8.7 × 10−3 lm after excitation with a 970 nm continuous wave laser diode. These results can be explained in terms of the energy transfer (ET) from the donor (Yb3+) to the acceptor (Ho3+). The ET efficiency (η) for this sample was only 5%, although an increase to 42% is possible for larger concentrations of Ho3+. Highly concentrated samples have shortened decay times, which cause highly saturated samples to exhibit larger ET efficiency values.

Improving pure red upconversion emission of Co-doped Y2O3:Yb3+–Er3+ nanocrystals with a combination of sodium sulfide and surfactant Pluronic-F127

“…In this case Yb 3+ (donor) absorbs the pumping energy and transfers it to a second trivalent rare earth ion (acceptor) that relaxes to ground state, producing an emitted signal. For example, blue, green and red emissions have been reported by using Tm 3+ , Er 3+ , Ho 3+ and Pr 3+ as acceptors [7,9,[19][20][21]. Perhaps the most studied system is Yb 3+ -Er 3+ for which green and red emissions have been reported after excitation of nanophosphor with NIR light [22][23][24].…”

Zirconia based Ho3+–Yb3+ codoped upconverting nanophosphors for green light emitting devices applications

“…An improvement in the green UC emission intensity around ∼2.7 times for AlZrO and 23 times for YZrO codoped nanophosphors as compared to ZrO codoped nanophosphors has been observed. The strongest green UC emission produced by YZrO: Ho 3+ -Yb 3+ nanophosphors is due to the better environment produced by the YZrO host around the dopants (Ho 3+ -Yb 3+ ) which avoid quenching process by preventing the creation of large number of RE ions clusters [27]. Moreover, the effect of O-H stretching vibrations on the non-radiative relaxation process cannot be neglected.…”

Doping effect of sulfur substituting on Zirconium dioxide ZrO2

“…In visible and near infrared region (NIR), the Zirconia dioxide material ZrO2 host possesses a high physical, chemical stability and optical transparency. The energy transfer from ZrO2 to rare earth ions has been proved by different doping ions such as Yb 3p, Er 3p,Tm 3p, Tb 3p, Eu 3p and Ho 3p [21][22][23][24]. In addition, the ZrO2 might be a good spectrum modifying matrix serving as a photon-conversion and an electron transporting layer.…”