Synthesis of Oil-Dispersible Hexagonal-Phase and Hexagonal-Shaped NaYF₄:Yb,Er Nanoplates

Abstract

Oil-dispersible α-NaYF4 spherical nanoparticles and β-NaYF4 hexagonal-shaped nanoplates were synthesized by the liquid−solid two-phase approach at different reaction temperatures. The TEM and FE-SEM images reveal that the nanoplates have a relatively narrow size distribution. In comparison with other methods, pure β-NaYF4 hexagonal-shaped nanoplates were prepared under a relatively mild condition. The nanoplates grew at the liquid−solid interface with slow crystallization rate, which may be preferable for achieving β-NaYF4.

Synthesis of β-Phase NaYF4:Yb,Er Upconversion Nanocrystals and Nanorods by Hot-Injection of Small Particles of the α-Phase

“…The method is based on the synthesis procedure for NaYF 4 particles published by Wei et al which was modified as given below [35]. 2.2 Synthesis of "sacrificial" -NaYF 4 :Yb,Er "Sacrificial" -NaYF 4 :Yb,Er and -NaYF 4 particles were prepared by using between 10 mmol to 60 mmol of rare-earth oleates and a 2.5 fold excess of sodium oleate.…”

“…During the last years, a large number of research papers was pub-lished on the synthesis of NaREF 4 nanocrystals (RE = rare-earth), since NaREF 4 and LiREF 4 are attractive host lattices for a variety of functional optical materials such as upconversion phosphors, [6][7][8][9][10][11][12][13][14] quantum-cutting phosphors, [15][16][17][18][19] laser materials, [20,21] and materials for solar cell applications [22][23][24][25][26]. A variety of synthetic methods has been described for producing solvent-dispersible sodium rare-earth tetrafluoride nanocrystals with controlled size, shape and capping ligand, including thermal decomposition, [7,[27][28][29][30][31][32] co-precipitation, [6,11,[33][34][35][36][37][38][39][40] or solvothermal methods [41][42][43][44][45][46][47]…”

Lanthanide‐Doped Nanocrystals: Strategies for Improving the Efficiency of Upconversion Emission and Their Physical Understanding

“…Shan et al [66] synthesized monodisperse b-NaY-F 4 :Yb,Er/Tm/Ho upconverted nanocrystals by using a single solvent (trioctylphosphine oxide). A thermal decomposition method for synthesizing a-and b-phase NaYF 4 :Yb,Er upconverted nanocrystals by using rare-earth oleate complexes as the precursors and 1-octadecene as the reaction solvent was reported by Chen et al [67] Capobianco et al [68] used a novel approach for the synthesis of water-dispersible ligand-free upconverting lanthanide-doped NaYF 4 :Er 3 + ,Yb 3 + nanoparticles with high UC luminescence intensities in aqueous solutions. Monodisperse a-NaYF 4 :Yb,Er and b-NaYF 4 :Yb,Er nanocrystals with controlled size, chemical composition, and surface state were synthesized by Yan et al [35] Sun et al [56] reported a hydrothermal synthesis of a-and bphase NaYF 4 :Yb,Er upconverted nanocrystals by using rareearth EDTA or rare-earth citrate complexes as precursors, and they found that the particle size was dependent on the nucleation rate, which could be controlled by the concentration of the reactants, molar ratio of the rare earth, and choice of capping ligands.…”

Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4

“…More recently, synthesis procedures for lanthanide-doped nanocrystals of a-NaYF 4 [23][24][25][26][27][28][29][30][31][32] and bNaYF 4 [24,25,[31][32][33][34][35][36] have been developed. These nanocrystals can be homogeneously dispersed in suitable solvents allowing to excite upconversion luminescence in transparent colloidal solutions.…”