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)...