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Magnetosomes
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
Marta Masó-Martínez, Paul D Topham, Alfred Fernández-Castané
Magnetite-producing MTBs, such as the cubo-octahedral shaped magnetosomes from the Magnetospirillum species, are the most common and well-studied crystals among MTB. In contrast, greigite-producing MTBs have not yet been grown in a laboratory setting. Magnetite is a mixed-valence iron oxide mineral that contains both ferrous and ferric iron in a 1:2 ratio, respectively [Fe(II)Fe(III)2O4]. Magnetosomes exhibit high crystallographic perfection. Examination of the magnetosome morphology using electron microscopy techniques revealed the wide diversity of magnetosome crystal shapes, such as square-like, hexagonal, elongated prismatic, tooth-shaped, arrowhead-shaped, rectangular, or bullet-shaped morphologies. Besides the magnetosome morphology, crystal size is also a species-specific feature, ranging from 35 to 120 nm.
High-Temperature Thin Films and Coatings
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Protective Thin Coatings Technology, 2021
Xingang Luan, Xingmin Liu, Yuchang Qing
Magnetic materials have been known with the finding of magnetite (Fe3O4) for more than 2500 years [140]. Starting with the invention of compass, they have been a crucial part of human civilization and allowed explorers to travel around the world and explore the lands unknown. Nowadays, with the developments in technology, magnetic materials can be found everywhere from magnetic storage technology, credit cards, magnetic brakes in hybrid vehicles, power transformers, to even biomedical applications. Typically, properties of magnetic materials varies significantly with reduced dimensions. By now, magnetic coatings represent the foundation of most device applications.
Raw Materials: Characterization and Preparation
Published in Ram Pravesh Bhagat, Agglomeration of Iron Ores, 2019
The mineral magnetite is an oxide of iron having the chemical formula Fe3O4 . It is ferromagnetic and attracted to a magnet. Magnetite contains both ferrous and ferric iron. Magnetite differs from most other iron oxides in that it contains both divalent and trivalent iron. Magnetite is black or brownish-black with a metallic luster.[5]
Physio-chemical characterization, in-vitro biocompatibility, and antimicrobial activity of magnetite nanoparticles synthesized via sol-gel route
Published in Inorganic and Nano-Metal Chemistry, 2023
Abhishek Nigam, Bharat Singh, Sheetal Saini, Ambak Kumar Rai, S. J. Pawar
The XRD pattern of Magnetite refers to the single-phase crystalline structure of hexagonal spinel ferrite has obtained. The crystallite size was obtained as 36.56 nm. The SAED pattern also matched with the planes from XRD data that reflect the conformation of Fe3O4 formation. The HRTEM analysis revealed the d-spacing value as 0.295. The TEM analysis depicts the spherical morphology with an average particle size of 80-200 nm. The particles are randomly oriented with a clear vision of dark and bright particles. The elemental analysis of the Magnetite sample confirms that only Fe and O elements are present in the sample, favoring the formation of Fe3O4. The VSM revealed the high magnetic saturation (Ms) value of the Magnetite sample as 66.15 emu/g. The FTIR of Magnetite particles revealed the Fe-O bond formation. The biocompatibility assays with human RBCs and PBMCs reveals the biocompatible nature of synthesized Magnetite (Fe3O4) NPs as there was no decrease in RBC count, no hemolysis and no decrease in cell viability upon treatment, thus these NPs are safe for human use. The synthesized NPs also showed good anti-bacterial activity against gram-negative (E. coli) as well as gram-positive (S. aureus) bacteria. The cumulative results describe that Magnetite is a suitable candidate for biomedical applications.
As(V) and As(III) sequestration by starch functionalized magnetite nanoparticles: influence of the synthesis route onto the trapping efficiency
Published in Science and Technology of Advanced Materials, 2020
Mbolantenaina Rakotomalala Robinson, Romain Coustel, Mustapha Abdelmoula, Martine Mallet
Here we propose to evaluate starch-functionalized magnetite (Fe3O4) nanoparticles for As(V) and As(III) removal. Magnetite is a ubiquitous iron oxide that occurs in the lithosphere, pedosphere and biosphere and contains both ferrous and ferric iron species. Among the available magnetite functionalizing agents, starch, a polysaccharide, appears very attractive owing to the fact that it is among the most abundant and renewable biopolymers, it is a low cost and an environmentally friendly material. Starch-stabilized magnetite nanoparticles were prepared by adapting two standard synthesis protocols and were then compared for As(V) and As(III) removal. The first protocol consisted in the coprecipitation of Fe(II) and Fe(III) ions under alkaline conditions and in the presence of starch while the second route implied alkaline precipitation of Fe(II) in oxidative conditions [15,16]. Previous studies devoted to arsenic remediation only used the co-precipitation approach to synthesize magnetite nanoparticles [10,11]. The primary objective of the study was therefore to understand how the synthesis procedure affects the reactivity and the sorption capacities of starch-functionalized magnetite nanoparticles. It must be mentioned that to the best of our knowledge, this is the first attempt to investigate the influence of the starch-functionalized magnetite synthesis procedure, i.e. coprecipitation vs oxidation approach, on arsenic removal efficiency. The starch to iron ratio was a key parameter that was deeply evaluated. More specifically, the effects of pH, adsorbent dose, and initial As(III) and As(V) concentrations were determined. The effects of phosphate and sulfate as competing anions and the arsenic adsorption kinetics were also determined.
Magnetically separable nanocomposites based on ZnO and their applications in photocatalytic processes: A review
Published in Critical Reviews in Environmental Science and Technology, 2018
Maryam Shekofteh-Gohari, Aziz Habibi-Yangjeh, Masoud Abitorabi, Afsar Rouhi
Magnetite (Fe3O4) is an excellent iron-oxide, which shows prominent physico-chemical properties due to existence of Fe2+ and Fe3+ ions in its structure. As particle size of Fe3O4 decreases to nanometer, it exhibits superparamagnetic behavior (Su, 2017). Magnetite has an inverse-spinel structure [Fe3+]tetrahedral [Fe2+ + Fe3+]octahedral at normal pressure and temperature conditions (Bengtson, Morgan, & Becker, 2013). In this iron oxide, half of the octahedral lattice sites are occupied with ferrous ions due to great ferrous crystal field stabilization energy and the other octahedral lattice sites and all tetrahedral lattice sites are occupied by ferric ions (Blaney 2007). Curie temperature of bulk magnetite is 850 K. Below the Curie temperature, particles on tetrahedral and octahedral sites exhibit ferromagnetic and antiferromagnetic properties, respectively. Combination of two different magnetic properties leads to elimination of each other and appearance of ferromagnetic behavior. With increasing temperature to Curie point, net magnetization becomes zero and particles show superparamagnetic behavior (Ghazanfari, Kashefi, Shams, & Jaafari, 2016). When the size of Fe3O4 particles decreases to nano scale, its magnetic behavior starts to change. The magnetite nanoparticles exhibit paramagnetic or superparamagnetic magnetization. Moreover, thermal energy of particles increases, which leads to superparamagnetic magnetization. Furthermore, reduction in diameter of Fe3O4 particles affects the Curie temperature, which defines the critical temperature where ferrimagnetic changes to superparamagnetic magnetization. As particles show superparamagnetic behavior at room temperature, the effective Curie temperature of magnetite nanoparticles (738 K) must be lower. The magnetization of nanoparticles is larger than bulk magnetite in the presence of external magnetic field, which is beneficial for enhanced magnetic separation capabilities (Blaney, 2007; Pang et al., 2016). This oxide has special features such as excellent chemical stability, appropriate mechanical hardness, cost-effectiveness as well as control of its composition with easy magnetic separation. These features make magnetite to be one of the best candidates for using along with other semiconductors to fabricate promising magnetically separable photocatalysts (Nabiyouni, Ghanbari, Karimzadeh, & Samani Ghalehtaki, 2014).