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Magnetite IJFe 3 O 4 ) polyhedral nanocrystals have been prepared successfully by a simple solvothermal reaction using a mixture of ethylene glycol (EG) and H 2 O as the solvent without the addition of any surfactants or templates. Based on SEM and TEM characterization, the products were determined to be 50-facet Fe 3 O 4 nanocrystals, 200-300 nm in diameter, enclosed by {100}, {110}, {111}, and high-index {311} facets. The morphological evolution of 50-facet Fe 3 O 4 polyhedra was studied carefully and in detail by adjusting the reaction parameters such as the reaction temperature, the reaction time, the amount of urea, and the volume ratio of EG to H 2 O in the solvent. The results indicated that an appropriate EG/H 2 O ratio in the solvent was crucial for the formation of the polyhedral nanocrystals and when the solvent was fixed, the size of the polyhedral nanocrystals could be tuned in a certain range by changing the amount of urea. A possible growth mechanism involving the aggregation and oriented attachment of Fe 3 O 4 seed nanoparticles is proposed on the basis of time-dependent experiments. 22 23737305 † Electronic supplementary information (ESI) available: XPS spectrum, low magnification SEM image, IR spectrum, TG and DSC curves of as-synthesized polyhedral 50-facet Fe 3 O 4 nanocrystals, TEM images and corresponding models projected from different directions. See

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Non-stoichiometric Co(ii), Ni(ii), Zn(ii)-ferrite nanospheres with controllable size, superior magnetic property and gas-sensing behavior were synthesized and characterized thoroughly.