The Structure And Property Dependence On The Finite Size Effect For Nano α-Fe₂O₃ And α-FeOOH

α- Fe₂O₃ nanocrystals (10-63nm) with controlled diameters were successfully prepared by hydrolysis mothod, and different particle size of α-FeOOH nanocrystals (12.8-31.6nm) were prepared using hydrothermal mothod. The finite size effects in α-Fe₂O₃ nanocrystals and α-FeOOH nanocrystals were probed by X-ray diffraction (XRD) , infrared spectroscopy (IR) , thermogravimetric analysis (TG-DTA) , UV-visible spectrum (UV-VIS) , and magnetization measurements. With a size reduction, α-Fe₂O₃ nanocrystals showed a lattice expansion and an enlarged axial ratio of c/a that is in apparent contradiction to the previous conjecture of high lattice symmetry for α- Fe₂O₃ nanocrystals at small sizes. The surface terminations of α- Fe₂O₃ nanocrystals were found to be highly hydrated with a size dependence. The lattice vibrations, electronic transitions, and magnetic properties of α- Fe₂O₃ nanocrystals were significantly modified by surface hydration and lattice expansion. The finite size effects that occurred in α-Fe₂O₃ nanocrystals at small sizes were first...