Easy synthesis and characterization of single-crystalline hexagonal prism-shaped hematite α-Fe2O3 in aqueous media

Abstract

A simple, mild and environmentally friendly one-pot aqueous synthesis route using urea devoid of surfactant and chelating agents is demonstrated for the first time to fabricate high yield crystalline uniform hexagonal prism-shaped weakly magnetic a-Fe 2 O 3 nanocrystals. As synthesized a-Fe 2 O 3 nanocrystals show ferromagnetic behavior with coercivity values of 0.8 and 0.2 T at 5 and 300 K, respectively. The urea and reaction temperature plays a crucial role, regulating the morphology and the size.Novel high quality magnetic materials of desired size and shape play an important role in modern science and technology. Amongst various nanostructured materials, highly crystalline monodisperse magnetic nanostuructures with various sizes and morphologies are attracting considerable attention due to their attractive potential applications in the fields of magnetics, catalysis, ferrofluids, high density magnetic recording media; biomedical technology, drugdelivery, colored pigments, medical diagnostics, imaging, synthesis of other nanocomposites and so on. 1-8 Hematite (a-Fe 2 O 3 ) is the most stable, non-toxic, biocompatible, corrosion-resistant magnetic iron oxide under ambient condition and also an n-type semiconductor with 2.1 eV band gap.To date, many efforts have been devoted to control the morphology of a-Fe 2 O 3 by employing different synthesis and processing routes. Rice and cube-shaped a-Fe 2 O 3 structures were reported using the hydrothermal method, 9 while hollow spindle and microsphere a-Fe 2 O 3 , 10 and rhombohedral hematite were prepared by forced hydrolysis. 11 Mitra et al. have synthesized different morphology of a-Fe 2 O 3 by the solvothermal method, 12 whereas Zhang et al. 13 prepared various shaped magnetic microstructures by varying the pH of potassium salt solution. A microwave-assisted hydrothermal process was also used to control shape and aspect ratio of monodisperse a-Fe 2 O 3 nanoarchitectures. 14 Recently, uniform porous a-Fe 2 O 3 nanorods with controlled aspect ratios were synthesized from b-FeOOH nanorods prepared by regulating HCl concentration. 15 Furthermore, 3D flowerlike nanostructures have been self-assembled by an ethylene glycol-mediated process. 16

Nanosecond and ultrafast optical power limiting in luminescent Fe2O3 hexagonal nanomorphotype

“…19 Chaudhari et al presented a simple, mild, and environment friendly one-pot aqueous synthesis route for hexagonal prism-shaped Fe 2 O 3 nanocrystals. 20 revealed the differences in the magnetic signatures. 21 However, there is lack of reports from the nonlinear optical properties of nanomaterials with hexagonal shapes especially in Fe 2 O 3 nanostructures.…”

Tuning the Morphology of Metal Oxides for Catalytic Applications

“…174 Since the (110) plane has a higher density in Fe atom and its exposure would be catalytically more reactive than the (111) or (110) planes, 175 ␣-Fe 2 O 3 nanocubes with the lengths of 15-300 nm have been synthesized by aqueous-phase precipitation and hydrothermal processes with the aid of surfactants ( Figure 10.12b-d). [176][177][178][179] Polyhedral nanoparticles, such as rhombohedra, 180, 181 oblique parallelepiped, 182, 183 dodecahedra/ octahedral, 184 and tetrakaidecahedra, 185,186 are characterized with higher density of atomic steps, ledges, and kinks of high-index facets. Simple hydrolysis of FeCl 3 yielded ␣-Fe 2 O 3 rhombohedral crystals with the lateral size of 35-45 nm.…”

Facile shape and size-controlled growth of uniform magnetite and hematite nanocrystals with tunable properties

“…However, owing to the intrinsic agglomerating behavior of magnetic nanomaterials, the synthesis of monodisperse iron oxide nanocrystals is usually more difficult than others [22]. Most of the reported aqueous routes often result in large nanocrystals with poor size-uniform [23,24]. In order to prevent their agglomeration, high boil point organic solvents such as oleic acid and organic surfactants have been widely used [18,20,25,26].…”

“…In addition, those routes usually lead to the yield of spherical nanoparticles in a dimension of several nanometers. They are too small to show strong magnetic properties and their practical applications are limited in many fields [22][23][24]. In order to effectively address these issues for iron oxide nanocrystals, it is still a challenge and important to develop some facile methods to obtain monodisperse magnetic nanocrystals with reasonable sizes.…”