Synthesis, characterization, and ammonia gas sensing properties of Co3O4@CuO nanochains

The Co3O4@CuO composite nanochains (CCNCs) were fabricated by electrospinning approach and controlled annealing route. The formation of nanochains was attributed to the interactions between N,N-Dimethylformamide and metal ions (Cu2+ or Co2+) acted as a cross-linking point or a bridge among the entangled polyvinylpyrrolidone (PVP) chains. The calcined samples were composed of porous single-crystal CuO particles (Ps), the size of which was 100-300 nm, and smaller p-type Co3O4 nanoparticles (NPs) on the surface of Ps, which was characterized by XRD, FT-IR, RAMAN, XPS, BET, SEM, and TEM techniques. The electrical properties of the samples and the response to ammonia gas at room temperature (RT) have been investigated. The highest sensing response was up to 5.72 for 100 ppm NH3 with a fast response time of 1.3 s, which was over 4.6 times higher than that of pristine CuO at RT, and the lowest detection limit was down to 1 ppm. In addition, the NH3 gas sensing mechanism of CCNC-2 (Cu:Co molar ratio of 5:2) was also discussed. These results indicated that the Co3O4@CuO composite nanochains were promising candidates for reliable high-performance gas sensors at room temperature.