Fabrication of Maghemite Nanoparticles with High Surface Area

Abstract

Maghemite nanoparticles with high surface area were obtained from the dehydroxylation of lepidocrocite prismatic nanoparticles. The synthesis pathway from the precursor to the porous maghemite nanoparticles is inexpensive, simple and gives high surface area values for both lepidocrocite and maghemite. The obtained maghemite nanoparticles contained intraparticle and interparticle pores with a surface area ca. 30 × 103 m2/mol, with pore volumes in the order of 70 cm3/mol. Both the surface area and pore volume depended on the heating rate and annealing temperature, with the highest value near the transformation temperature (180–250 °C). Following the transformation, in situ X-ray diffraction (XRD) allowed us to observe the temporal decoupling of the decomposition of lepidocrocite and the growth of maghemite. The combination of high-angle annular dark-field imaging using scanning transmission electron microscopy (HAADF-STEM) and surface adsorption isotherms is a powerful approach for the characterization of nanomaterials with high surface area and porosity.

Performance Evaluation of Synthetic Goethite and Lepidocrocite Nanoadsorbents for the Removal of Aniline from a Model Liquid Fuel through Kinetic and Equilibrium Studies

“…The last step changes at about 375 °C are due to the transformation of magnetite to hematite and maghemite, respectively. All three weight loss stages are in consistency with the results reported in the literature. − The total weight loss for goethite and lepidocrocite was 13.3 and 11.3%, respectively. Comparison of weight loss values in each stage indicates that the most difference in weight losses of two adsorbents belongs to the dehydroxylation step, which suggests that goethite includes approximately 20% more hydroxyl groups than lepidocrocite.…”

Extraction of gamma iron oxide (γ-Fe2O3) nanoparticles from waste can: Structure, morphology and magnetic properties

“…The primary purpose of this invention is to recover metal values from iron-containing waste materials and convert them to magnetic γ-Fe 2 O 3 nanoparticles having a wide range of applications from catalysis to waste management [ 9 , 10 ]. It is widely used for the production of, e.g., magnetic materials [ [11] , [12] , [13] ], sensing materials [ 14 ], pigments [ 15 ], sorbents [ 16 , 17 ], photocatalysts [ 16 ], storing data [ 18 ], for biomedical applications such as drug delivery [ 19 , 20 ], contrast agents for resonance imaging [ [21] , [22] , [23] ] and hyperthermia treatment [ 18 , 24 ], as well as being key components for adsorption and storage purposes [ 25 , 26 ]. Recently, iron oxides have been used in a huge amount as electrodes for sodium-ion, lithium-ion, and alkaline-ion batteries [ [27] , [28] , [29] , [30] , [31] ].…”

Semiconductor-Type Gas Sensors Based on γ-Fe2O3 Nanoparticles and Its Derivatives in Conjunction with SnO2 and Graphene

“…Maghemite is a post-product of Fe 2+ -containing compounds, such as magnetite or titanomagnetite, made by erosion or controllable oxidation at lower temperatures [23]. These methods were considered to produce γ-Fe 2 O 3 in a proper particle size and surface area [24] in this study. The electronic structure of γ-Fe 2 O 3 suggests an n-type semiconductor due to vacancies in the valence band and a conduction band populated by electrons [25].…”