Controlled synthesis of CoFe2O4 nano-octahedra

Magnetostrictive-Piezoelectric-Triggered Nanocatalytic Tumor Therapy

Magnetic-based theranostics feature a high efficiency, excellent tissue penetration, and minimal damage to normal tissues, are noninvasive, and are widely used in the diagnosis and therapy of clinical diseases. Herein, a conceptually novel magnetostrictive-piezoelectric nanocatalytic medicine (MPE-NCM) for tumor therapy is proposed by initiating an intratumoral magneto-driven and piezoelectric-catalyzed reaction using core-shell structured CoFe₂O₄-BiFeO₃ magnetostrictive-piezoelectric nanoparticles (CFO-BFO NPs) under an alternating magnetic field. The CFO-BFO NPs catalyze the generation of cytotoxic reactive oxygen species (ROS): superoxide radicals (•O₂^-) and hydroxyl radicals (•OH). The simulation calculation demonstrates the highly controllable electric polarization, facilitating the above catalytic reactions under the magnetic stimulation. Both a detailed cell-level assessment and the tumor xenograft evaluation evidence the significant tumor eradication efficacy of MPE-NCM. This study proposes an original and novel magneto-responsive nanocatalytic modality for cancer therapy, which displays promising prospects for the future clinic translation owing to its excellent catalytic dynamic responsiveness, high therapeutic efficacy, and biosafety in vivo.

Correlation between size, shape and magnetic anisotropy of CoFe2O4 ferrite nanoparticles

The present work reports the effect of particle size and shape of CoFe₂O₄ (CFO) nanoparticles on magnetic properties and their use in device applications as permanent magnets at room temperature. A set of CFO samples with different particle sizes and shapes were synthesized via the polymeric method by sintering at temperatures ranging from 300 °C to 1200 °C. These materials were characterized structurally by x-ray diffraction, morphologically by scanning electron microscopy, and microstructurally by transmission electron microscopy. The morphology of these CFO samples shows size-dependent shapes like spherical, pyramidal, lamellar, octahedral and truncated octahedral shapes for the particle sizes ranging from 7 to 780 nm with increasing sintering temperature. The emergence of magnetic properties was investigated as a function of particle size and shape with a special emphasis on permanent magnet applications at low and room temperatures. The values of saturation and remanent magnetization were found to increase monotonously with a particle size up to 40 nm and from thereafter they were found to remain almost constant. The other magnetic parameters such as coercivity, squareness ratio, anisotropy constant and maximum energy product ([Formula: see text]) were observed to increase up to 40 nm and then decreased thereafter as a function of particle size. The underlying mechanism responsible for the observed behavior of the magnetic parameters as a function of particle size was discussed in the light of coherent rotation, domain wall motion and shape induced demagnetization effects. The significant values of [Formula: see text] - the figure of merit of permanent magnets - observed for single domain particles (particularly, 14 nm and 21 nm) were found to have suitability in permanent magnetic technology.

Almessiere M, Baykal A. Exchange-coupling behavior in SrTb0.01Tm0.01Fe11.98O19/(CoFe2O4)x hard/soft nanocomposites

The M against H loops and single peaks in dM/dH vs. H curves were noticed in SrFe₁₂O₁₉/MnCe_0.04Fe_1.96O₄, SrFe₁₂O₁₉/CuCe_0.04Fe_1.96O₄ and SrFe₁₂O₁₉/ZnCe_0.04Fe_1.96O₄ hard/soft nanocomposites that indicated the manifestation of well exchange-coupled effect among hard and soft phases in these composites.

Magnetoelectrically Driven Catalytic Degradation of Organics

Here, the catalytic degradation of organic compounds is reported by exploiting the magnetoelectric nature of cobalt ferrite-bismuth ferrite (CFO-BFO) core-shell nanoparticles. The combination of magnetostrictive CFO with multiferroic BFO gives rise to a magnetoelectric engine that purifies water under wireless magnetic fields via advanced oxidation processes, without involvement of any sacrificial molecules or cocatalysts. Magnetostrictive CoFe₂ O₄ nanoparticles are fabricated using hydrothermal synthesis, followed by sol-gel synthesis to create the multiferroic BiFeO₃ shell. Theoretical modeling is performed to study the magnetic-field-induced polarization on the surface of magnetoelectric nanoparticles. The results obtained from these simulations are consistent with experimental findings of the piezoforce microscopy analysis, where changes in piezoresponse of the nanoparticles under magnetic fields are observed. Next, the magnetoelectric-effect-induced catalytic degradation of organic pollutants is investigated under AC magnetic fields, and 97% removal efficiency for synthetic dyes and over 85% removal efficiency for routinely used pharmaceuticals are obtained. Additionally, trapping experiments are performed to elucidate the mechanism behind the magnetic-field-induced catalytic degradation of organic pollutants by using scavengers for each of the reactive species. The results indicate that hydroxyl and superoxide radicals are the main reactive species in the magnetoelectrically induced catalytic degradation of organic compounds.

Oxidative dehydrogenation of ethylbenzene to styrene over the CoFe2O4–MCM-41 catalyst: preferential adsorption on the O2−Fe3+O2− sites located at octahedral positions

The present study describes the catalytic performance of cobalt ferrite supported on MCM-41 for the oxidative dehydrogenation of ethylbenzene.