Rational Solution Growth of alpha-FeOOH Nanowires Driven by Screw Dislocations and Their Conversion to alpha-Fe2O3 Nanowires

We report the rational synthesis of alpha-FeOOH (goethite) nanowires following a dislocation-driven mechanism by utilizing a continuous-flow reactor and chemical equilibria to maintain constant low supersaturations. The existence of axial screw dislocations and the associated Eshelby twist in the nanowire product were confirmed using bright-/dark-field transmission electron microscopy imaging and twist contour analysis. The alpha-FeOOH nanowires can be readily converted into semiconducting single-crystal but porous alpha-FeOOH (hematite) nanowires via topotactic transformation. Our results indicate that, with proper experimental design, many more useful materials can be grown in one-dimensional morphologies in aqueous solutions via the dislocation-driven mechanism.