Flutelike Porous Hematite Nanorods and Branched Nanostructures: Synthesis, Characterisation and Application for Gas-Sensing
Flute-like porous a-Fe2O3nanorods and branched nanostructuressuch as pentapods and hexapods wereprepared through dehydration and recrystallisationofhydrot hermally synthesisedb-FeOOH precursor. Transmissionelectron microscopy (TEM),high-resolution TEM and selected areaelectron diffraction analyses reveal thatthe nanorods, which grow along the direction, have nearly hollow cavitiesand porous walls with a pore sizeof2050 nm. The hexapods have sixsymmetric arms with a diameter of6080 nm and length of40090 0 nm. Thegrowth direction ofthe arms in thehexapod-like nanostructure is alsoalong the  direction, and there is adihedral angle of69.5 o between adjacentarms. These unique iron oxidenanostructures offer the first opportunityto investigate their magnetic andgas sensing properties. The nanostructuresexhibited unusual magnetic behaviour,with two different Morin temperaturesunder field-cooled and zerofield-cooled conditions, owing to theirshape anisotropy and magnetocrystallineanisotropy. Furthermore, the a-Fe2O3 nanostructures show muchbetter sensing performance towardsethanol than that ofthe previously reportedpolycrystalline nanotubes. Inaddition, the a-Fe2O3 nanostructurebased sensor can selectively detectformaldehyde and acetic acid amongother toxic, corrosive and irritant vapoursat a low working temperaturewith rapid response, high sensitivityand good stability.