Synthesis of NaYF₄ Nanocrystals with Predictable Phase and Shape

Abstract

In this Full Paper, a water/alcohol/oleic acid system was developed to prepare NaYF4 nanocrystals with predictable size, shape and phase. The structural and kinetic factors that govern the phase and shape evolution of NaYF4 nanocrystals have been carefully studied, and the influence of NaF to Y3+ ratio, reaction time and temperature on the phase and shape evolution of the as‐prepared NaYF4 samples was systematically investigated and discussed. It was found that the NaF to Y3+ ratio was responsible for the shape evolution while temperature and reaction time was the key for the phase control of the NaYF4 nanocrystals. This study would be suggestive for the precisely controlled growth of inorganic nanocrystals, especially for those usually crystallizing in diverse crystal structures.

Dopant-controlled synthesis of water-soluble hexagonal NaYF4 nanorods with efficient upconversion fluorescence for multicolor bioimaging

“…In general, the hexagonal phase NaREF 4 is more thermodynamically stable than the cubic form, and the cubic-to-hexagonal phase transition is a disorderto-order character which requires sufficient free energy to overcome the activation barrier. Thus, high temperature has often been used to provide enough energy to overcome the energy barrier between the cubic and hexagonal NaREF 4 [27,28,32]. The ionic radius dependence of the energy barriers for hexagonal NaREF 4 has been systematically studied by Yan et al [28].…”

“…Great efforts have been devoted to phase-controlled synthesis of NaYF 4 NCs in special organic surfactants [25][26][27][28][29][30][31][32][33][34][35][36][37]. Drastic conditions such as extended annealing time, prolonged reaction time, and high temperature have often been used to overcome the free energy barrier to obtain hexagonal NaYF 4 NCs.…”

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

“…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]…”

Synthesis and enhancement of red UC luminescence properties of ordered hexagonal NaYF 4 :Yb 3+ /Er 3+ nanowire arrays

“…Er 3+ /Yb 3+ co-doped fluorides are efficient materials for nearinfrared to visible UC [21][22][23][24][25][26][27][28]. Fig.…”