Relation of Crystallinity and Fluorescent Properties of LaF₃ :Nd³⁺ Nanoparticles Synthesized with Different Water-Based Techniques

Abstract

We use two water based synthetic approaches to LaF 3 :Nd 3 + nanoparticles (NPs), hydrothermal microwave treatment (HTMW) and co-precipitation (CO) technique, with different temperature of the reaction mixture to study the correlation between the degree of crystallinity of LaF 3 :Nd 3 + NPs and their fluorescence properties. We showed that the fluorescence spectra and quenching kinetics can be a powerful tool to reveal the crystal lattice defects, namely agglomerations of the dopant ions (Nd 3 + ) and the OH À positioned in the volume of the doped NPs. We found that reduced number of such crystal lattice defects as Nd 3 + pairs and clusters and the OH groups in the volume of the HTMW NPs leads to much higher fluorescence brightness than for CO NPs. The higher temperature of reaction mixture during HTMW synthesis results in better crystallinity and much higher fluorescence brightness of the produced NPs. But we believe that these results could be applied more generally to the development of synthetic strategies for bright fluorescent NPs. In sum, it's not the condition of NPs surface, but the degree of their crystallinity should be a major concern while choosing the synthetic path, as it generally predetermines their fluorescent properties.

In Vivo Subcutaneous Thermal Video Recording by Supersensitive Infrared Nanothermometers

“…Synthesis of Er‐Yb@Yb‐Tm LaF 3 NPs—Materials : The samples were all synthesized in the Institute of Physics of the Universidade Federal de Alagoas by the coprecipitation technique in aqueous solution . Lanthanum (III) chloride (LaCl 3 , >99.99%), erbium (III) chloride (ErCl 3 , ≥99.99%), ytterbium chloride (YbCl 3 , 99.99%), thulium chloride (TmCl 3 , 99.99%), and ammonium fluoride (NH 4 F, ≥99.99%) were purchased from Sigma‐Aldrich.…”

Characterization of Pr-Doped LaF3 Nanoparticles Synthesized by Different Variations of Coprecipitation Method

“…In [54], it is shown that the shape of rare-earth-doped dielectric NPs can affect the luminescence lifetime. Moreover, it is shown in [55] that the use of water-based coprecipitation method leads to the presence of OH groups into the NP's core as well. Hence, in the case of the MW-treated samples, the lifetime increasing can be attributed by two processes.…”

Luminescence Nanothermometry Based on Pr3+ : LaF3 Single Core and Pr3+ : LaF3/LaF3 Core/Shell Nanoparticles

“…e shape of the lifetime curves is more complicated obviously due to a set of different physical processes taking place in the NPs. In [36], the complicated shape of lifetime curves of Nd 3+ : LaF 3 NPs synthesized via the coprecipitation method is explained by the presence of defects such as water molecules in the NPs core as well as on the NPs surface and by inhomogeneous distribution of doping ions. For these reasons, the effective luminescence lifetimes (τ eff ) were calculated using equation (3) [39] in order to compare the lifetimes of the samples: Advances in Materials Science and Engineering…”

“…ese phenomena affect the crystal field around the doping ions which makes the shape of the lifetime curves more complicated in comparison with analogous bulk crystals [35,36]. For these reasons, the modern theoretical approaches for some rare earth ions in some matrices are developed [36][37][38]. However, universal theories are still in the design phase.…”