Synthesis of Distinct Iron Oxide Nanomaterial Shapes Using Lyotropic Liquid Crystal Solvents

Abstract

A room temperature reduction-hydrolysis of Fe(III) precursors such as FeCl3 or Fe(acac)3 in various lyotropic liquid crystal phases (lamellar, hexagonal columnar, or micellar) formed by a range of ionic or neutral surfactants in H2O is shown to be an effective and mild approach for the preparation of iron oxide (IO) nanomaterials with several morphologies (shapes and dimensions), such as extended thin nanosheets with lateral dimensions of several hundred nanometers as well as smaller nanoflakes and nanodiscs in the tens of nanometers size regime. We will discuss the role of the used surfactants and lyotropic liquid crystal phases as well as the shape and size differences depending upon when and how the resulting nanomaterials were isolated from the reaction mixture. The presented synthetic methodology using lyotropic liquid crystal solvents should be widely applicable to several other transition metal oxides for which the described reduction-hydrolysis reaction sequence is a suitable pathway to obtain nanoscale particles.

Novel Trends in Lyotropic Liquid Crystals

“…This produced silica structures with ordered nanochannels of 20 nm diameter. The method of using a lyotropic structure for the synthesis of nanoparticles [177] and nanostructured materials [178] was quickly picked up and used for a variety of different systems [179,180] (Figure 14a-c). For further information, one may refer to a review article by Hegmann et al [181] and references therein.…”

Block copolymer self-assembly derived mesoporous magnetic materials with three-dimensionally (3D) co-continuous gyroid nanostructure

“…Using soft matter as a way to structure magnetic materials should open doors to new research of fundamental and technological relevance by offering morphological control at the mesoscale, allowing the use of a wide variety of materials classes, and providing access to scalable solution-based synthesis approaches to a range of form factors. 8 Several soft matter methodologies of generating nanomagnetic arrays have already been investigated, such as using liquid crystal templating, 9,10 colloidal assembly, 11,12 micellar templating, 13 surfactant templating, 14,15 and block copolymer (BCP) self-assembly (SA) based templating and structure direction. [15][16][17][18] Of particular interest to the authors are BCPs.…”