Design and construction of Co3O4/PEI-CNTs composite exhibiting fast responding CO sensor at room temperature

In this paper, a new controllable dispersion of Co3O4 nanoparticles on multiwalled carbon nanotubes (CNTs) functionalized with branched polyethyleneimine (PEI-(CH2CHNH)(n)) has been synthesized by a noncovalent method. The higher density of Co3O4 particles of 8-12 nm are well deposited on the functional defect sites of CNTs and the carbon chains of PEI. Co3O4 crystalline phase of the Co3O4/PEI-CNTs composite, whose contents of Co3O4 is about 41.7 mass% is synthesized by a hydrothermal method at 190 degrees C. The Co3O4/PEI-CNTs composite characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) shows unique electrical properties, high surface-to-volume ratios and excellent sensitive characteristics to CO even at the level of 5 ppm, showing its potential in sensor and related nanodevices. The possible gas sensing mechanism of the unique 1-D composite structure is explained by a model in which the effect of CO adsorption on Co3O4 nanoparticles and electronic transport properties are discussed.