Structural, Magnetic, and Mossbauer Parameters' Evaluation of Sonochemically Synthesized Rare Earth Er3+ and Y3+ Ions-Substituted Manganese-Zinc Nanospinel Ferrites.

The effect of Er3+ and Y3+ ion-co-substituted Mn0.5Zn0.5Er x Y x Fe2-2x O4 (MZErYF) (x ≤ 0.10) spinel nanoferrites (SNFs) prepared by a sonochemical approach was investigated. Surface and phase analyses were carried out using SEM, TEM, and XRD. Hyperfine parameters were determined by fitting room-temperature (RT) Mossbauer spectra. Magnetic field-dependent magnetization data unveiled the superparamagnetic nature at RT and ferrimagnetic nature at 10 K. RT saturation magnetization (M S) and calculated magnetic moments (n B) are 34.84 emu/g and 1.47 µB, respectively, and have indirect proportionalities with increasing ion content. M S and n B data have a similar trend at 10 K including remanent magnetizations (M r). The measured coercivities (H C) are between 250 and 415 Oe. The calculated squareness ratios are in the range of 0.152-0.321 for NPs and assign the multidomain nature for NPs at 10 K. The extracted effective magnetocrystalline constants (K eff) have an order of 104 erg/g except for Mn0.5Zn0.5Er0.10Y0.10Fe1.80O4 SNFs that has 3.37 × 105 erg/g. This sample exhibits the greatest magnetic hardness with the largest magnitude of H C = 415 Oe and an internal anisotropy field H a = 1288 Oe among all magnetically soft NPs.

Influence of Dy3+ Ions on the Microstructures and Magnetic, Electrical, and Microwave Properties of [Ni0.4Cu0.2Zn0.4](Fe2-x Dy x )O4 (0.00 ≤ x ≤ 0.04) Spinel Ferrites.

[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.

Nickel ferrite nanoparticles for simultaneous use in magnetic resonance imaging and magnetic fluid hyperthermia.

We demonstrate magnetic resonance imaging (MRI) contrast enhancement and ac-field induced heating abilities of tetramethylammoniumhydroxide (TMAH) coated nickel ferrite (NiFe2O4) nanoparticles and discuss the underlying physical mechanisms. The structural characterization revealed that the NiFe2O4 particles synthesized with a modified co-precipitation method have a very narrow size distribution with a 4.4 nm magnetic core and 15 nm hydrodynamic diameters, with relatively small fraction of agglomerates. The as-prepared particles presented superparamagnetic behavior at room temperature. The in vitro hyperthermia experiments, performed in ac-field conditions under human tolerable limits, showed that the suspensions of the synthesized nanoparticles exhibit a maximum specific absorption rate (SAR) value of 11 W/g. The 1H nuclear magnetic resonance (NMR) relaxometry measurements indicated the suspensions of NiFe2O4 have a transverse-to-longitudinal relaxivity ratio r2/r1 greater than two, as required for superparamagnetic MRI contrast agents. On the basis of the parameters obtained from the magnetic measurements, by comparing the relevant theoretical models with the experimental results, we found that the presence of agglomerates, and particularly the interactions within the agglomerated nanoparticles, caused a significant increase in the hyperthermia and MRI efficiencies. On the other hand, from an applicative point of view, both the MRI contrast enhancement and the heating capabilities allow the simultaneous use of nickelferrites in diagnostic and therapeutic applications as theranostic agents.

Manganese/Yttrium Codoped Strontium Nanohexaferrites: Evaluation of Magnetic Susceptibility and Mossbauer Spectra.

Manganese (Mn)- and yttrium (Y)-substituted Sr-nanohexaferrites (MYSNHFs) of composition Sr1-xMnxFe12-xYxO19 (with 0.0 ≤ x ≤ 0.5) were prepared by citrate sol-gel autocombustion method. As-prepared MYSNHFs were characterized via diverse analytical techniques to determine the influence of Mn and Y cosubstitution on their microstructures and magnetic properties. 57Fe Mössbauer spectra of the MYSNHFs were used to evaluate the variation in the line width, isomer shift, quadrupole splitting, and hyperfine magnetic field values. It was shown that the dopant ions could preferentially occupy the 12k, 4f2, and 2b sites. Furthermore, the observed shift in the blocking temperatures of the studied MYSNHFs towards lower values with rising Mn2+ and Y3+ contents was attributed to the overall particles size reduction. Meanwhile, the AC susceptibility of the proposed MYSNHFs revealed that the magnetic interactions were weakened with the increase in dopant contents which was ascribed to the replacement of both Sr2+ and Fe3+ ions by the Mn2+ and Y3+ dopants.

Effect of medications for root canal treatment on bonding to root canal dentin.

Use of resin-based restorative materials recently has become widely accepted for treatment of endodontically treated teeth. However, some solutions routinely used during endodontic treatment procedures may have an effect on bond strengths of adhesive materials to root canal dentin. The purpose of this in vitro study was to evaluate the effect of various medications on microtensile bond strength to root canal dentin. Fourteen extracted human single-rooted teeth were used. The crowns and the pulp tissues were removed. The root canals were then instrumented and widened to the same size. The teeth were randomly divided into seven groups of two teeth each. The root canal dentin walls of the roots were treated with 5% sodium hypochloride (NaOCI), 3% hydrogen peroxide (H2O2), the combination of H2O2 and NaOCl, or 0.2% chlorhexidine gluconate for 60 s; or calcium hydroxide or formocresol for 24 h. The teeth in control group were irrigated with water. The root canals were obturated using C&B Metabond. After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut, and approximately 12 samples were obtained from each group. Microtensile bond strengths to root canal dentin were then measured by using an Instron machine. The data were recorded and expressed as MPa. The results indicated that NaOCI, H2O2, or a combination of NaOCl and H2O2 treatment decreased bond strength to root canal dentin significantly (p < 0.05). The teeth treated with chlorhexidine solution showed the highest bond strength values (p < 0.05). In conclusion, chlorhexidine is an appropriate irrigant solution for root canal treatment before adhesive post core applications.