RESUMO
The composition and hyperfine structures of Nd3+-Ho3+ ions cosubstituted CoNi nanospinel ferrites (Co0.5Ni0.5NdxHoxFe2-2xO4 (x ≤ 0.05) NSFs) as well as their magnetic and electrodynamic behavior have been presented. The compound Nd-Ho â CoNiFe2O4 (x ≤ 0.05) NSFs were produced using the sol-gel method. XRD powder patterns indicated phase- and substituent-induced modifications of crystallites. The SEM analysis indicated the homogeneous distribution of grains with Nd-Ho cosubstitution. It was found that the values of x had an impact on the hyperfine magnetic field of the A and B sites. The cation distribution was determined by using Mössbauer spectroscopy. The M-H loops' investigations showed that the current NSFs behave ferrimagnetically at both room and low temperatures. An almost continuous rise in the strength of the coercive field was noticed with a rise in Ho-Nd content. The value of calculated squareness ratio values was above 0.5 at both temperatures, entailing that the studied NSFs' structure is made of single magnetic domains. The electromagnetic characteristics of the samples can be explained by the main contribution to electromagnetic absorption being the electric energy losses. Electromagnetic absorbed materials can be applied to provide electromagnetic compatibility and develop functional electromagnetic shields.
RESUMO
[Ni0.4Cu0.2Zn0.4](Fe2-x Dy x )O4 spinel ferrite nanoparticles with different Dy3+ concentrations (0.00 ≤ x ≤ 0.04) were prepared by a citrate sol-gel auto-combustion technique. A strong correlation among Dy concentration, structural parameters, and magnetic, electrical, and microwave properties was established. An increase in the Dy3+ concentration is the reason for a rise in the crystal structure parameters (due to different ionic radii of Fe and Dy ions) and a slight increase in the average particle size with a minor reduction in the specific surface area. It was observed that Dy3+ ions prefer to occupy the octahedral B site due to their large ionic radius (0.91 Å). The explanation of the electrical and magnetic properties was given in terms of the features of Dy3+-O2--Fe3+ dysprosium-oxygen-iron indirect exchange. The occurrence of the intensive changes in amplitude-frequency characteristics was observed from 1.6 to 2.7 GHz. The explanation of electromagnetic absorption was given in terms of the peculiarities of the microstructure (resonance of domain boundaries). The results open perspectives in the utilization of [Ni0.4Cu0.2Zn0.4](Fe2-x Dy x )O4 spinel ferrite nanoparticles as functional materials for targeted drug delivery and hyperthermia applications.
RESUMO
This study investigates the impact of an engineered magnetic nanoparticle (MNP) on a crop plant. For this purpose, a sonochemical synthetic approach was utilized in order to dope magnetic elements (Co and Nd) into technologically important iron oxide NPs. After being characterized by using TEM, SEM, and XRD instruments, the MNPs were hydroponically applied to barley plants with varying doses (from 125 to 1000 mg/L) both in germination (4 days) and early growing stages (3 weeks). Physiological responses, as well as expression of photosystem marker genes, were assessed. Compared to the untreated control, MNP treatment enhanced germination rate (~ 31%), tissue growth (8% in roots, 16% in shoots), biomass (~ 21%), and chlorophyll (a, b) (~ 20%), and carotenoids (~ 22%) pigments. In general, plants showed the highest growth enhancement at 125 or 250 mg/L treatment. However, higher doses diminished the growth indices. Compared to the control, the catalase activity was significantly reduced in the leaves (~ 33%, p < 0.005) but stimulated in the roots (~ 46%, p < 0.005). All tested photosystem marker genes (BCA, psbA, and psaA) were overexpressed in MNP-treated leaves than non-treated control. Moreover, the gene expressions were found to be proportionally increased with increasing MNP doses, indicating a positive correlation between MNPs and the photosynthetic machinery, which could contribute to the enhancement of plant growth.