Tailoring the Synthesis of LnF₃ (Ln = La–Lu and Y) Nanocrystals via Mechanistic Study of the Coprecipitation Method

Abstract

Here, 15 LnF nanocrystals are synthesized using coprecipitation method with citrate stabilization to allow the fast, easy, and reproducible synthesis of several nanoscaled structures in water. General trends related to the behavior of LnF nanocrystals are highlighted due to their broad range of application in several fields (e.g., medical applications). The same nature for all Ln cations is expected due to the internal role of f orbitals. However, we found that the use of different lanthanide elements is crucial in the final size, shape, assembly, and crystalline structure. In addition, the decrease of the cation size of the lanthanide series changes the behavior of these compounds, resulting in hexagonal, orthorhombic, and cubic crystalline structures. In addition, we are able to tune the cubic crystalline phase to pure orthorhombic by modifying the pH of the system using HBF instead of tetramethylammonium citrate. Via B NMR, we demonstrated the mechanism of HBF as fluorinating agent if an additional source of F is not added during the synthesis. H NMR and IR techniques were performed to unravel the picture of the surface chemistry of the two representative metal cations (Y and La). Finally, HRTEM and SAED were performed to uncover the shape of the obtained nanocrystals and the preferential orientation of the assembled particles, giving crucial information on the involved mechanisms. This study reveals not only the dependence of the crystalline structure on the used metal and pH but also ability to achieve LnF assembled particles depending on the final shape and temperature.

Tunable Self-Assembly of YF3 Nanoparticles by Citrate-Mediated Ionic Bridges

“…We expect to report further examples of the use of the present technique in a variety of NP systems in the near future. 40…”

“…As an example, we show the obtained TEM images for SmF 3 in Figure 5a. TEM images and XRD patterns for the NPs (5 °C) and supraparticles (100 °C) obtained with SmF 3 , EuF 3 , and LuF 3 are also shown in Figure S14 (more extensive analysis for these and other systems will be reported in a forthcoming publication 40 ). After this study with different NPs, we considered again the YF 3 case but now we used different multidentate carboxylic ligands to show that the ionic-mediated bridge is not exclusive of citrate anions.…”

Using evolved gas analysis – mass spectrometry to characterize adsorption on a nanoparticle surface

“…Particles were obtained following a previous study, 23 based on a modied co-precipitation method in water at 100 C to obtain YF 3 supraparticles and LaF 3 NPs. To obtain YF 3 NPs with a small size ($5 nm), we used kinetic control during the synthesis at a temperature of 5 C. 21 As shown in Fig.…”

Faceted‐Charge Patchy LnF3 Nanocrystals with a Selective Solvent Interaction

“…First of all, we recall that the faceting of the NCs strongly depends on the metal cation radii. [16] If the metal radius decreases, NC shape becomes more spherical or less faceted avoiding the spontaneous formation of patches by the hexagonal-faceted shape. In this case, faceted NCs are obtained for LaF 3 and CeF 3 but the particles obtained with PrF 3 NCs start to form self-assembly in supraparticles containing some NCs (Figure 4c).…”

“…The choice of lanthanide fluoride NCs for the inorganic core is due to the fact that a broad range of LnF 3 NCs has been synthesized and studied in detail in the last years [13,14] . Our recent studies [15,16] of LnF 3 NCs with several of the smallest lanthanides show strong interaction of the NCs with ions, which induces tunable self-assembly. Previous studies show that certain LnF 3 NCs have the appropriate faceting required in the mechanism shown in Figure 1.…”