Well-aligned Titanium Dioxide with Very High Length-to-diameter Ratio Synthesized under Magnetic Field

Abstract

The synthesis of well-aligned titanium dioxide with a very high length-to-diameter ratio is demonstrated for the first time using a solgel method under a magnetic field (up to 9.4 T), with cetyltrimethylammonium bromide as a structure-aligning agent.Titanium dioxide (TiO 2 ) is currently one of the most important, widespread, and investigated materials owing to its low toxicity, high thermal stability, and broad applicability. As a semiconductor, titanium dioxide has shown outstanding performances in photocatalysis, 1 water splitting, 2 and self-cleaning applications. 3 It is also useful in medical applications 4 because of its good biocompatibility. Moreover, titanium dioxide plays a crucial role in dye-sensitized solar cells. 5 Different shapes and sizes of titanium dioxide have been reported to give different effects in various reactions. 6 Significant attention has been paid to the effect of a magnetic field on the nucleation and growth processes of magnetic materials 7,8 and the self-assembly behaviors of molecules. 911 A clear effect of an external magnetic field was shown vividly in the growth of magnetic materials such as Fe and Co, since magnetic materials possess easy magnetic axes. The growth of ferromagnetic materials under a magnetic field produced crystals in a wire formation. 7 Over many years, scientists have developed several methods for the structural control of organized molecular assemblies, such as the use of flow and electric fields. The use of a magnetic field is also a potential method for the alignment and orientation of molecules and domains, because it has the advantage that any materials, even diamagnetic materials, can be aligned as long as they possess magnetic anisotropy. It is well established that diamagnetic assemblies having magnetic anisotropy will become oriented and rotate in a magnetic field to achieve their minimum-energy state. 9 Protocols for producing orientated ordered inorganic surfactants have been reported but are based only on simulation theory. 10 The use of TiO 2 as an inorganic precursor and an organic surfactant, however, has not been reported.Here, well-aligned titanium dioxide was synthesized successfully through a solgel method by using tetra-n-butyl orthotitanate (TBOT) as the titanium dioxide precursor. In a typical experiment, cetyltrimethylammonium bromide (CTAB) was weighed (0.023 mg) and placed into a 5-mL sample bottle. Subsequently, 2-propanol (2.057 mL) and water (0.016 mL) were added to the sample bottle. TBOT as the TiO 2 precursor (0.1 mL) was then added dropwise into the sample bottle. Finally, the solution was transferred quickly into a petri dish and covered with perforated aluminum foil.The petri dish containing TBOT, CTAB, 2-propanol, and water was placed under a magnetic field and allowed to self-dry for 47 days. The relative humidity was 60%. The hydrolysis rate was controlled by varying the apparent area of the liquidair interphase by putting the reaction mixture in narrow-bore and large-bore tubes. A superconducting magnet (Oxford magnet)...

Synthesis and assembly of nanomaterials under magnetic fields

“…121 Well-aligned TiO 2 nanowires were synthesized by a sol-gel method under a high magnetic field (9.4 T). 41 SEM images of the prepared TiO 2 samples are shown in Fig. 10.…”

“…For example, in the case of ferro/ferrimagnetic materials that possess easy magnetization axes, the growth in the presence of weak magnetic fields can induce anisotropy, leading to the formation of nanowires elongated in the direction of the easy magnetization axis. However, for paramagnetic and diamagnetic materials such as carbon, 39 bismuth (Bi), 40 and titanium dioxide (TiO 2 ), 41 high magnetic fields should be employed in the reaction systems to control their nanostructures. To date, there are many examples of nanomaterials with particular morphologies, and enhanced properties have been achieved in diverse chemical systems (gas, solution and solid phase) under magnetic fields ranging from several Tesla down to lower than 1 T. It is worth noting that magnetic-field-induced synthesis is usually a template-free strategy, which is of significant interest, since the post-treatment of templates may have a negative effect on both the photonic and electronic properties of the resulting nanomaterials.…”

Magnetic Field-Assisted Laser Ablation of Titanium Dioxide Nanoparticles in Water for Anti-Bacterial Applications

“…Thus, the present study was designed for preparation of TiO 2 nanoparticles by magnetic eld -assisted laser ablation in liquid MFALAL technique and evaluate its antibacterial performance on both Grampositive and Gram-negative bacterial organisms [18].…”

MoS2 ultrathin nanosheets obtained under a high magnetic field for lithium storage with stable and high capacity

“…21 With the development of synthesis and assembly methods, the magnetic field, similar to conventional reaction conditions, such as temperature, pressure, and surfactant, has been used as a new parameter for synthesizing and assembling special nanostructures. 34 To date, there have been many examples of nanomaterials with particular morphologies and enhanced properties achieved in diverse chemical systems (gas, solution and solid phases) under magnetic fields ranging from several Tesla down to lower than 1 T, such as carbon (10 T), 35 TiO 2 (9.4 T) 36 and Bi (8 T). 37 During the synthesis process, when a high field is employed, the magnetic energy and magnetic force produced by magnetic fields become remarkable.…”