Synthesis and Characterization of Rare‐Earth Orthoferrite LnFeO₃ Nanoparticles for Bioimaging

Abstract

A combination of sol-gel synthesis and thermal decomposition was developed for preparing nanosized, perovskite-type LnFeO 3 (Ln = Eu, Gd, Tb) powders. Perovskite-type powders with crystalline particles of 100 nm average size, as determined by transmission electron microscopy (TEM), could be obtained after a thermal treatment at 800°C. The perovskite nanoparticles (NPs) were further characterized by X-ray powder diffraction and Mössbauer spectroscopy. These were in agreement with the pure perovskite LnFeO 3 structure with the expected Zeeman sextet corresponding to a magnetically ordered [a]

Synthesis of GdFeO3 nanoparticles via low-temperature reverse co-precipitation: the effect of strong agglomeration on the magnetic behavior

“…One of these possible substances is gadolinium orthoferrite (GdFeO 3 ), which has been previously suggested as an MRI contrast agent in the form of nanoparticles [6][7][8][9]. The perovskite structure of GdFeO 3 contains gadolinium, which is involved in T 1 -contrast agents [10,11], and iron oxide, which is used as a T 2 -contrast agent as nanoparticles [12,13].…”

The Influence of Co-Precipitation Technique on the Structure, Morphology and Dual-Modal Proton Relaxivity of GdFeO3 Nanoparticles

“…To quantitatively describe the T 1 and T 2 relaxations of the obtained GdFeO 3 nanoparticles, the corresponding values of relaxivities (r 1 and r 2 ) were calculated by linearizing the 1/T 1 and 1/T 2 dependences on concentration (Figure 9). The obtained values of relaxivity are given in Table 4, supplemented with data on the relaxivities of other orthoferrites of rare-earth elements [13]. It should be noted that the T 1 relaxivity (r 1 ) increases from 0.28 to 0.81 mM −1 •s −1 with an increase in the specific surface area from 4.4 to 10.5 m 2 /g, which is explained by an increase in the contact amounts of high-spin paramagnetic Gd 3+ cations with water protons.…”

“…Nanocrystalline gadolinium orthoferrite (GdFeO 3 ) with orthorhombic perovskite structure containing gadolinium, which is involved in T 1 contrast agents [8,9], and iron oxide, which is used as a T 2 contrast agent as nanoparticles [10,11], seems to be promising as a T 1 -T 2 dual-modal MRI contrast agent. Gadolinium orthoferrite nanoparticles have been previously proposed as a contrast agent for MRI [12][13][14][15]. For example, Söderlind et al [12] synthesized very small (~4 nm) GdFeO 3 nanoparticles with longitudinal relaxivity r 1 = 11.9 mM −1 •s −1 and transverse relaxivity r 2 = 15.2 mM −1 •s −1 , whereas Pinho et al [13] synthesized GdFeO 3 nanoparticles with an average size of 115 nm, very small T 1 relaxivities (r 1 = 0.59−0.60 mM −1 •s −1 ) and larger T 2 relaxivities (r 2 = 3.84−5.65 mM −1 •s −1 ).…”

“…Gadolinium orthoferrite nanoparticles have been previously proposed as a contrast agent for MRI [12][13][14][15]. For example, Söderlind et al [12] synthesized very small (~4 nm) GdFeO 3 nanoparticles with longitudinal relaxivity r 1 = 11.9 mM −1 •s −1 and transverse relaxivity r 2 = 15.2 mM −1 •s −1 , whereas Pinho et al [13] synthesized GdFeO 3 nanoparticles with an average size of 115 nm, very small T 1 relaxivities (r 1 = 0.59−0.60 mM −1 •s −1 ) and larger T 2 relaxivities (r 2 = 3.84−5.65 mM −1 •s −1 ). However, in order to achieve a T 1 -T 2 dual-modal contrast effect, the size of GdFeO 3 nanoparticles should be sufficiently small, since with a decrease in the particle size a high specific surface area of nanoparticles is achieved, which is necessary for effective T 1 relaxation with the participation of near-surface Gd 3+ cations on the one hand, and the superparamagnetic state of nanoparticles at room temperature is reached, which is necessary for the manifestation of T 2 MRI contrast properties on the other hand.…”

The effect of co-precipitation temperature on the crystallite size and aggregation/agglomeration of GdFeO3 nanoparticles

“…Gadolinium orthoferrite (GdFeO 3 ) is one of the representatives of orthorhombic (Pbnm space group) complex oxides -orthoferrites of rare-earth elements (REE) with the general formula of RFeO 3 (R = Sc, Y, Ln) [20,21]. Due to the perovskite-like structure of this compound, as well as the unique combination of semiconducting, magnetic, thermal and chemical properties, materials based on GdFeO 3 are now widely used as (photo)catalysts [22][23][24], electromagnetic materials [25], biomedical agents [26,27], etc. In our previous work [15], it was shown that aggregation/agglomeration processes play a key role in the magnetic behavior of GdFeO 3 -based nanopowders, and it was assumed that varying the co-precipitation temperature of gadolinium and iron(III) hydroxides could be an effective way to control the processes of the spatial organization of GdFeO 3 nanocrystals, and, consequently, their promising functional properties.…”