Size Control of Nearly Monodisperse β-NaGdF₄ Particles Prepared from Small α-NaGdF₄ Nanocrystals

Abstract

NaGdF 4 nanocrystals of the hexagonal β-phase can be prepared with very narrow size distribution from small particles of the cubic α-phase of NaGdF 4 , but, until now, this method does not allow to control the final particle size. Here we show that the size of β-NaGdF 4 particles can be varied between 4 nm and more than 60 nm by using small α-phase particles with different sodium content as precursor. Heating of the 3-4 nm α-phase particles dispersed in oleic acid/octadecene solvent leads to Ostwald ripening and the formation of β-NaGdF 4 particles with narrow size distribution in all cases. The size of the β-NaGdF 4 particles increases with increasing sodium deficiency of the α-phase particles indicating that the number of β-phase seeds nucleating in the system depends on the ratio of sodium to gadolinium used in the synthesis of the α-phase material.

Rapid Synthesis of Sub‐10 nm Hexagonal NaYF4‐Based Upconverting Nanoparticles using Therminol® 66

“…Thisr esults in manipulated host lattices, which has ad etrimentale ffect on the luminescent properties of the final materials. [25][26][27][28][29] Other popular strategiest oo btain sub-10 nm UCNPs involve the use of an additional high-boiling solvent such as oleylamine (OM) [30] or trioctylphosphine oxide (TOPO) [31][32][33][34] in the reaction formulation under harsh synthesis conditions (high temperatures and long reaction times), which limits the choice of compatible solvent systemsthat can be used.…”

Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent

“…This mixed phase was seen in all dopant concentrations and the compositions of these two phases are estimated to ~88% α-NaGdF 4 phase (cubic) and ~12% β-NaGdF 4 phase (hexagonal). The mixed phase in the system is most likely due to the precursor ratio of Na-Gd/Lu in the host crystal where the phase and size can be effected [31]. We determined that the NGL cubic phase is within the Fm-3m (225) space group with the cell parameters a = b = c = 5.5180 Å.…”

Rare earth based nanostructured materials: synthesis, functionalization, properties and bioimaging and biosensing applications

“…For example, ultra-small NaGdF 4 NPs (3-4 nm) have been produced from sodium and Gd oleates and N(CH 3 ) 4 F in a mixture of octadecene, oleic acid and oleylamine at 220°C [71], and NaGdF 4 :Yb 3+ , Er 3+ nanospheres (from 15 to 25 nm) have been synthesized from the corresponding RE oleates and NaF in octadecene and oleic acid at 320°C. The synthesis of ultra-small BaLuF 5 :Yb 3+ , Er 3+ NPs with sizes below 10 nm in octadecene/oleic acid solutions at 300°C from RE stearates has also been reported [72].…”