Iron oxide nanoparticles: Diagnostic, therapeutic and theranostic applications.

Towards zero-waste valorisation of rare-earth-containing industrial process residues: a critical review

Chemical crosslinking of biopolymeric scaffolds: Current knowledge and future directions of crosslinked engineered bone scaffolds

A review of current coupling agents for modification of metal oxide nanoparticles

The rare earths (REs) are a family of 17 elements that exhibit pronounced chemical similarities as a group, while individually expressing distinctive and varied electronic properties. These atomistic electronic properties are extraordinarily useful and motivate the application of REs in many technologies and devices. From their discovery to the present day, a major challenge faced by chemists has been the separation of RE elements, which has evolved from tedious crystallization to highly engineered solvent extraction schemes. The increasing incorporation and dependence of REs in technology have raised concerns about their sustainability and motivated recent studies for improved separations to achieve a circular RE economy.

Rare earth elements: Mendeleev's bane, modern marvels.

Superparamagnetic iron oxide nanoparticles can provide multiple benefits for biomedical applications in aqueous environments such as magnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles' surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality water- dispersible nanoparticles around 10 nm in size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.

/pdf/improved-functionalization-of-oleic-acid-coated-iron-oxide-15yw6sigen.pdf

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Magnetic (Fe3O4) and nonmagnetic (SiO2 and TiO2) nanoparticles were decorated on their surface with N-[(3-trimethoxysilyl)propyl]ethylenediamine triacetic acid (TMS-EDTA). The aim was to investigate the influence of the substrate on the behavior of these immobilized metal coordinating groups. The nanoparticles functionalized with TMS-EDTA were used for the adsorption and separation of trivalent rare-earth ions from aqueous solutions. The general adsorption capacity of the nanoparticles was very high (100 to 400 mg/g) due to their large surface area. The heavy rare-earth ions are known to have a higher affinity for the coordinating groups than the light rare-earth ions but an additional difference in selectivity was observed between the different nanoparticles. The separation of pairs of rare-earth ions was found to be dependent on the substrate, namely the density of EDTA groups on the surface. The observation that sterical hindrance (or crowding) of immobilized ligands influences the selectivity could pr...

Selective Uptake of Rare Earths from Aqueous Solutions by EDTA-Functionalized Magnetic and Nonmagnetic Nanoparticles

Core–shell Fe3O4@SiO2 nanoparticles were prepared with a modified Stober method and functionalized with N-[(3-trimethoxysilyl)propyl]ethylenediamine triacetic acid (TMS-EDTA). The synthesis was optimized to make core–shell nanoparticles with homogeneous and thin SiO2 shells (4.8 ± 0.5 nm) around highly superparamagnetic Fe3O4 cores (14.5 ± 3.0 nm). The core–shell Fe3O4@SiO2(TMS-EDTA) nanoparticles were then used for the extraction and separation of rare-earth ions. By comparing them with previously published results for Fe3O4(TMS-EDTA) and SiO2(TMS-EDTA) nanoparticles, it was clear that the core–shell nanoparticles combine the advantage of magnetic retrieval observed for Fe3O4(TMS-EDTA) nanoparticles with the higher selectivity observed for SiO2(TMS-EDTA). The advantages of the SiO2 shell include a lower specific weight and a larger grafting density compared to Fe3O4 surfaces, but also the improved resistance to acidic environments required for the stripping of rare-earth ions.

Acid-Stable Magnetic Core–Shell Nanoparticles for the Separation of Rare Earths

Rare earth atoms exhibit several interesting properties, for example, large magnetic moments and luminescence. Introducing these atoms into a different matrix can lead to a material that shows multiple interesting effects. Holmium atoms were incorporated into an iron oxide nanoparticle and the concentration of the dopant atom was changed in order to determine its influence on the host crystal. Its magnetic and magneto-optical properties were investigated by vibrating sample magnetometry and Faraday rotation measurements. The luminescent characteristics of the material, in solution and incorporated in a polymer thin film, were probed by fluorescence experiments.

https://www.mdpi.com/1996-1944/7/2/1155/pdf

Synthesis and Characterization of Holmium-Doped Iron Oxide Nanoparticles

The value of the magnetization has a strong influence on the performance of nanoparticles that act as the contrast agent material for MRI. In this article, we describe processing routes for the synthesis of FePt nanoparticles of different sizes, which, as a result, exhibit different magnetization values. “Single-core” FePt nanoparticles of different sizes (3–15 nm) were prepared via one-step or two-step synthesis, with the latter exhibiting twice the magnetization (m
 (1.5T) = 14.5 emu/g) of the nanoparticles formed via the one-step synthesis (m
 (1.5T)  20 nm) leads to an increase in the magnetization m
 (1.5T) from 8 to 19.5 emu/g, without exceeding the superparamagnetic limit. Stable water suspensions were prepared using two different approaches: (a) functionalization with a biocompatible, zwitterionic, catechol ligand, which was used on the FePt nanoparticles for the first time, and (b) coating with SiO2 shells of various thicknesses. These FePt-based nanostructures, the catechol- and SiO2-coated “single-core” and “multi-core” FePt nanoparticles, were investigated in terms of the relaxation rates. The higher r
 2 values obtained for the “multi-core” FePt nanoparticles compared to that for the “single-core” ones indicate the superiority of the “multi-core” FePt nanoparticles as T
 2 contrast agents. Furthermore, it was shown that the SiO2 coating reduces the r
 1 and r
 2 relaxation values for both the “single-core” and “multi-core” FePt nanoparticles. The high r
 2/r
 1 ratios obtained in our study put FePt nanoparticles near the top of the list of candidate materials for use in MRI.

Maarten Bloemen

Papers

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Selective Uptake of Rare Earths from Aqueous Solutions by EDTA-Functionalized Magnetic and Nonmagnetic Nanoparticles

Acid-Stable Magnetic Core–Shell Nanoparticles for the Separation of Rare Earths

Synthesis and Characterization of Holmium-Doped Iron Oxide Nanoparticles

“Single-” and “multi-core” FePt nanoparticles: from controlled synthesis via zwitterionic and silica bio-functionalization to MRI applications