Preparation and characterization of various PVPylated divalent metal-doped ferrite nanoparticles for magnetic hyperthermia.

There is an incessant demand to keep improving on the heating responses of polymeric magnetic nanoparticles (MNPs) under magnetic excitation, particularly in the pursuit for them to be utilized for clinical hyperthermia applications. Herein, we report the fabrication of a panel of PVP-capped divalent metal-doped MFe2O4 (M ≅ Co, Ni, Zn, Mg, and Sn) MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology and assess their magneto-thermal abilities. The physiochemical, structural, morphological, compositional, and magnetic properties of the doped ferrites were fully characterized using various techniques mainly TEM, XRD, EDX, FTIR, and VSM. The obtained doped MNPs exhibited stabilized quasi-spherical sized particles (10-17 nm), pure well-crystallized cubic spinel phases, and high saturation magnetizations (Ms = 26-81 emu g-1). In response to a clinically-safe alternating magnetic field (AMF) (f = 332.8 kHz and H = 170 Oe), distinctive heating responses of these doped ferrites were attained. Hyperthermia temperatures of 42 °C can be reached very fast in only ∼5 min, with heating temperatures slowly increasing to reach up to 55 °C. The highest heating performance was observed for PVP-NiFe2O4 and the lowest for PVP-Sn-doped NPs (SAR values: PVP-NiFe2O4 > PVP-CoFe2O4 > PVP-ZnFe2O4 > PVP-MgFe2O4 > PVP-SnFe2O4). This trend was found to be directly correlated to their observed magnetic saturation and anisotropy. Heating efficiencies and specific SAR values as functions of concentration, frequency, and amplitude were also systematically investigated. Finally, cytotoxicity assay was conducted on aqueous dispersions of the doped ferrite NPs, proving their biocompatibility and safety profiles. The PVPylated metal-doped ferrite NPs prepared here, particularly Ni- and Co-doped ferrites, are promising vehicles for potential combined magnetically-triggered biomedical hyperthermia applications.

Spinel ferrite nanoparticles as potential materials in chlorophenol removal from wastewater.

Persistent organic pollutants (POPs) including chlorophenols (CPs) are increasing in water effluents, creating serious problems for both aquatic and terrestrial lives. Several research attempts have considered the removal of CPs by functionalised nanomaterials as adsorbents and catalysts. Besides the unique crystal structure, spinel ferrite nanomaterials (SFNs) own interesting optical and magnetic properties that give them the potential to be utilised in the removal of different types of CPs. In this review, we highlighted the recent research work that focused on the application of SFNs in the removal of different CP substances based on the number of chlorine atom attached to the phenolic compound. We have also discussed the structure and properties of SFN along with their numerous characterisation tools. We demonstrated the importance of identifying the structure, surface area, porosity, optical properties, etc. in the efficiency of the SFN during the CP removal process. The reviewed research efforts applied photocatalysis, wet peroxide oxidation (WPO), persulfate activated oxidation and adsorption. The studies presented different paths of enhancing the SFN ability to remove the CPs including doping (ion substitution), oxide composite structure and polymer composite structure. Experimental parameters such as temperature, dosage of CPs and SFN structure have shown to have a major effect in the CP removal efficiency. More attention is needed to investigate the different properties of SFN that can be tailored through different techniques and expected to have major role in the removal mechanism of CPs.

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe3O4 Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field.

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe3O4 phases, high saturation magnetizations (Ms = ~40 emu·g-1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm2/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τR = 5.41 × 10-7 s), which was compared to the Brownian relation time value (τB = 11 × 10-7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe3O4 MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications.

Thermally induced oxygen related defects in eco-friendly ZnFe2O4 nanoparticles for enhanced wastewater treatment efficiencies.

Herein, a simple but highly effective strategy of thermal annealing to modulate oxygen vacancies related defects in ZnFe2O4 (ZFO) nanoparticles for obtaining enhanced wastewater treatment efficiencies is reported. The as-prepared nanoparticles were thermally annealed at three different temperatures (500 °C, 600 °C and 700 °C) and their phase purity was confirmed by X-ray diffraction (XRD). All samples were found to exhibit pure phases of ZFO with different crystallite sizes ranging from 10 nm to 25 nm. The transmission electron microscope (TEM) images showed well dispersed nanoparticles and a strong correlation of grain size growth with annealing temperature was established. The optical absorption and emission characteristics were estimated through UV-visible and Photoluminescence (PL) spectroscopy. Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) confirmed the variation of oxygen vacancies in the synthesized samples' lattice. The photocatalytic activities of all samples were investigated and the highest efficiencies were recorded for the ZFO samples annealed at 500 °C. Under high salinity condition, the organic dye degradation efficiency of the same sample remained the highest among all. The excellent dye degradation abilities in ZFO samples can be attributed to the abundance of oxygen vacancies in the crystal lattice that slow down the recombination rate during the photocatalysis process. Moreover, cytotoxicity tests revealed that all prepared ZFO samples showed insignificant cell structure effects on Picochlorum sp microalgae, as verified by Fourier-transform infrared (FTIR) spectroscopy. On the other hand, no significant changes were detected on the viable cell concentration and Chlorophyll a content. This work presents a systematic way to finely tune the crystal sizes and to modulate oxygen related defects in ZFO through a highly effective annealing approach to signify their potential in industrial wastewater and seawater treatment processes.

Structural, Optical, and Magnetic Properties of Zn-Doped CoFe2O4 Nanoparticles.

The effect of Zn-doping in CoFe2O4 nanoparticles (NPs) through chemical co-precipitation route was investigated in term of structural, optical, and magnetic properties. Both XRD and FTIR analyses confirm the formation of cubic spinel phase, where the crystallite size changes with Zn content from 46 to 77 nm. The Scherrer method, Williamson-Hall (W-H) analysis, and size-strain plot method (SSPM) were used to study of crystallite sizes. The TEM results were in good agreement with the results of the SSP method. SEM observations reveal agglomeration of fine spherical-like particles. The optical band gap energy determined from diffuse reflectance spectroscopy (DRS) varies increases from 1.17 to 1.3 eV. Magnetization field loops reveal a ferromagnetic behavior with lower hysteresis loop for higher Zn content. The magnetic properties are remarkably influenced with Zn doping; saturation magnetization (Ms) increases then decreases while both coercivity (HC) and remanent magnetization (Mr) decrease continuously, which was associated with preferential site occupancy and the change in particle size.