Synthesis of compositionally graded nanocast NiO/NiCo2O4/Co3O4 mesoporous composites with tunable magnetic propertiesElectronic supplementary information (ESI) available: Supplementary Figs S1-S3. See DOI: 10.1039/c0jm00406e

A series of mesoporous NiO/NiCo 2 O 4 /Co 3 O 4 composites has been synthesized by nanocasting using SBA-15 silica as a hard template. The evaporation method was used as the impregnation step. Nickel and cobalt nitrates in different Ni( ii ) : Co( ii ) molar ratios were dissolved in ethanol and used as precursors. The composites show variable degrees of order, from randomly organized nanorods to highly ordered hexagonally-packed nanowires as the Ni( ii ) : Co( ii ) molar ratio decreases. The materials exhibit moderately large surface areas in the 60-80 m 2 g −1 range. Their magnetic properties, saturation magnetization ( M S ) and coercivity ( H C ), can be easily tuned given the ferrimagnetic (NiCo 2 O 4 ) and antiferromagnetic (NiO and Co 3 O 4 ) character of the constituents. Moreover, the NiCo 2 O 4 rich materials are magnetic at room temperature and consequently can be easily manipulated by small magnets. Owing to their appealing combination of properties, the nanocomposites are expected to be attractive for myriad applications. Mesoporous nanocast NiO/NiCo 2 O 4 /Co 3 O 4 composites with tunable magnetic properties have been synthesized. The NiCo 2 O 4 rich powders are magnetic at room temperature and can be easily remotely manipulated using small fields.