Selective Growth of Upconverting YbPO₄:Ln (Ln = Er or Tm) Crystals in a Micro Reaction Cell

Abstract

Highly crystalline upconversion fluorescence crystals of ytterbium phosphate (YbPO 4 ) doped with Er 3þ or Tm 3þ were selectively and directly grown on a hydrophilic/hydrophobic self-assembled monolayer (SAM) template patterned by vacuum ultraviolet (VUV, λ = 172 nm) light irradiation. First, a gelatin gel with an inner solution [(NH 4 ) 2 HPO 4 ] was selectively adsorbed on a hydrophilic surface, and the adsorbed gel was successfully used as the micro reaction cell between the inner solution and the outer solution [(CH 3 COO) 3 Yb 3 4H 2 O]. The low crystalline YbPO 4 :Ln (Ln = Er or Tm) nanospheres, which are densely aggregated, were selectively and directly grown on the hydrophilic surface at 5 °C for 5 days. After annealing at 1100 °C for 10 h, their shape changed dramatically from an aggregation of nanospheres to an aggregation of well-formed nanocubes (200-600 nm). In addition, atoms and molecules of Yb, PO 4 , and Ln were highly and uniformly distributed in the YbPO 4 :Ln crystal. The YbPO 4 :Er and YbPO 4 :Tm crystals clearly show green and blue upconversion fluorescence, respectively, under 980 nm (near-infrared) laser irradiation.

Recent Advances in Design and Fabrication of Upconversion Nanoparticles and Their Safe Theranostic Applications

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Novel fabrication of NIR-vis upconversion NaYF4:Ln (Ln = Yb, Er, Tm) crystal layers by a flux coating method

“…We successfully fabricated a green upconversion fluorescence crystal of ytterbium phosphate (YbPO 4 ) doped with Er 3+ using a two-step process involving the synthesis of spherical YbPO 4 :Er$nH 2 O precursors in naturally derived gel matrices and their subsequent annealing. 16 For optomaterials (and optodevices), fluorides are advantageous as a host matrix because of their low phonon energy. For example, the phonon energy of fluoride upconversion materials is much lower than that of oxides.…”

Studies on Morphology and Photoluminescent Properties of Tb3+ Doped YbPO4 Nanostructures Synthesized by Different Synthetic Methods

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