Coordination Polymer-Derived Multishelled Mixed Ni-Co Oxide Microspheres for Robust and Selective Detection of Xylene

Multishell, stable, porous metal-oxide microspheres (Ni-Co oxides, Co3O4 and NiO) have been synthesized through the amorphous coordination polymer-based self-templated method. Both oxides of Ni and Co show poor selectivity to xylene, but the composite phase has substantial selectivity (e.g., S-xylene/S-ethanol = 2.69) and remarkable sensitivity (11.5-5 ppm xylene at 255 degrees C). The short response and recovery times (6 and 9 s), excellent humidity-resistance performance (with coefficient of variation = 11.4%), good cydability, and long-term stability (sensitivity attenuation of similar to 9.5% after 30 days and stable sensitivity thereafter) all show that this composite is a competitive solution to the problem of xylene sensing. The sensing performances are evidently due to the high specific surface area and the nano-heterostructure in the composite phase.