The structure and phase composition of colloidal SPM Fe3O4 NPs
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Author : LZH
Update time : 2023-06-14 12:47:30
What is Fe3O4? Hydrophilic Fe3O4 NPs were synthesized on a large scale by controlled coprecipitation in an automated batch reactor Atlas Potassium (Syrris), equipped with two syringe pumps (Syrris), temperature control system LH85 PLUS (Julabo), overhead stirrer, as well as temperature, pH, and turbidity probes. Briefly, 40.75 mmol of FeCl2·4H2O (99%, Sigma-Aldrich) and 74 mmol of FeCl3·6H2O (99%, Sigma-Aldrich) was dissolved in a 2 L glass reaction vessel filled with 1.1 L of ultrapure water (produced by Milli-Q Advantage A10 system, Millipore) to obtain a clear orange solution. The solution was heated to 363 K, and then 60 mL of aqueous ammonia solution (28−30%, Sigma-Aldrich) was added at 10 mL/min using a syringe pump.
The structure and phase composition of colloidal SPM Fe3O4 NPs The structure and phase composition of colloidal SPM Fe3O4 NPs remains puzzling despite the availability of increasing amounts of structural information. Various spectroscopic measurements have shown that the structure of SPM Fe3O4 NPs can be described as a magnetite core with a thin overoxidized (Fe3+) surface shell, which is compositionally close to a maghemite polymorph (γ-Fe2O3).9a, The putative Fe3O4@γ-Fe2O3 core−shell structure has not been observed by X-ray diffraction or electron microscopy studies, supporting smooth nonstoichiometric Fe3O4+δ formulation of magnetite NPs. This is most likely attributed to the topotactic oxidation of the Fe3O4 surface with the formation of solid solution Fe3O4−γ-Fe2O3. Unambiguous determination of the structure and phase composition of SPM Fe3O4 NPs is important because these parameters dramatically affect the Ms values. For instance, improved purity and crystallinity of colloidal SPM Fe3O4 NPs produced at elevated temperatures are believed to be responsible for their enhanced Ms (70−85 emu/g),7,9 thus both bulk and surface composition information may be pertinent for elucidating the structure−property relationships for NPs. The capping ligand is another surface-based factor thought to be capable of enhancing Ms. 7,16 A better understanding of how the structure and phase composition of Fe3O4 NPs depend on their synthesis is thus necessary for more precise control over their magnetic properties.
Magnetic properties of nanoparticles determine their performance in magnetic hyperthermia A process of heating SPM NPs by magnetization reversal effects induced under exposure to an external oscillating magnetic field. For example, hyperthermia induced in SPM NPs can be used to locally heat and thus destroy cancer cells. The mechanism of magnetic hyperthermia is not fully understood, despite multiple previous theoretical and experimental studies. Rosensweig developed the first theoretical approach, in which the specific absorption rate (SAR) produced by hyperthermia in diluted SPM ferrofluids is attributed to Neel and Brown relaxation processes. At the same time, for ́ particles ≥25 nm in size, ferromagnetic or FiM heat release is ascribed to hysteresis losses.18 This separation of relaxation and hysteresis losses has been subsequently criticized by Carrey and co-workers, who proposed a more comprehensive theoretical framework that combined Stoner−Wohlfarth-based theories, linear response theories, and equilibrium functions, intending to explain the SAR produced by magnetic NPs of any size. Later, Vallejo-Fernandez and co-workers concluded that the susceptibility losses are negligible and the heat is mostly generated by hysteresis loss. Despite the large amount of SAR data found in the literature, none of the models have been confirmed experimentally due to complex contributions of the colloidal parameters, such as anisotropy constant, particle volume, and viscosity of the medium, involved in magnetic hyperthermia mechanisms.
Price of Fe3O4 Fe3O4 particle size and purity will affect the product's Price, and the purchase volume can also affect the cost of Fe3O4. A large amount of large amount will be lower. The Price of Fe3O4 is on our company's official website.
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