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

Abstract

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 °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.