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Mesoporous Co3O4 nanowires were synthesized with the nanocasting method, and then the dispersed Co 3O4 nanowires (Co3O4-DNWs) were separated from the bundled Co3O4 nanowires (Co3O4-BNWs) by the centrifugation technique. From the characterization with TEM, X-ray diffraction, UV–vis spectra and nitrogen adsorption-desorption isotherm, both samples present the same mesoporous-structure, diameter and the similar defects due to the same synthesis conditions. All results indicate that the microstructures and morphology of Co3O4 nanowires greatly affect the toluene gas sensing performance. Owing to the mesoporous-structures with the high surface area, the sensitivities of both samples are higher than others’. Co3O4-DNWs exhibit the higher specific surface area (44.98 m2 g−1) than Co3O4-BNWs, leading to the excellent gas-sensing properties to toluene gas at the optimized operating temperature of 210℃. Moreover, both samples present the excellent stability and selectivity to toluene gas. The gas-sensing mechanism results from the surface oxygen and toluene gas adsorption through comparing the sensitivity of Co3O4-DNWs and Co3O4-BNWs.

The magnetic Co3O4 nanowires were synthesized using the templates of SBA-15, and then the well-dispersed nanowires (D-wires) were separated from the bundled ordered nanowires (B-wires) with the centrifugal technique. TEM images indicated that D-wires were highly dispersed Co3O4 nanowires and B-wires existed in bundles. All samples possessed the antiferromagnetism and superparamagnetism at high temperature. After revealing the intrinsic magnetic properties of Co3O4 nanowires with D-wires, the magnetic behavior of B-wires was discussed in detail, and then the magnetic interaction between neighboring nanowires could be deduced. The exchange bias effect from the body Co3O4 antiferromagnetism and surface ferromagnetism was observed at low temperature. The magnetization of B-wires was higher than that of D-wires, which was attributed to the constraint of the surface spin coupling between the neighboring nanowires to the surface affect of nanostructures.