Heterostructured Co3O4/PEI-CNTs composite: fabrication, characterization and CO gas sensors at room temperature

In this paper, a new controllable dispersion of Co3O4 nanoparticles (NPs) on multiwalled carbon nanotubes (CNTs) functionalized with branched polyethylenimine (PEI) is synthesized by a noncovalent method. In Co3O4/PEI-CNTs composite, CNTs not only prevent Co3O4 NPs from aggregation, but also provide an electron transfer path. The domain sizes of Co3O4 NPs on Co3O4/PEI-CNTs composite synthesized with hydrothermal time 5 h at 190 degrees C (named C-5) is about 4-8 nm. The surface area to volume ratio increases, the overlapped parts of Co3O4 grains contain high density of defects, which provides a greater number of available active centers for gas/surface reactions. The Co3O4/PEI-CNTs composite displays excellent sensitive characteristics to CO even at a level of 5 ppm at room temperature (RT). The C-5 sensor with rapid response property and excellent stability at RT shows highly promising applications in gas sensing.