Nanofibers of p-type NiO/n-type ZnO heterojunction with different NiO content were fabricated by a facile electrospinning technique. The as-synthesized nanofibers were characterized by differential thermal analyzer (DTA) and thermal gravimetric analyzer (TGA), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The p-n junction formed between cubic NiO particle and hexangular ZnO particle in the NiO/ZnO nanofibers was confirmed and highly improved the trimethylamine (TMA) sensing properties. The influence of NiO content in nanofibers on TMA sensing properties was studied. The results showed that the NiO/ZnO nanofibers exhibited the significantly enhanced response, good selectivity, fast response and recovery rate (less than 30 s and 35 s, respectively), and excellent linearity (in a relatively wide range of 0.5-200 ppm). Especially, the NiO/ZnO nanofibers with 4 mol% of NiO has the best performance, whose response to 100 ppm TMA could reach 892 and detection limit could extend down to 0.5 ppm at 260 degrees C. The mechanism of the enhanced TMA sensing performance caused by p-type NiO/n-type ZnO heterojunctions in the NiO/ZnO nanofibers was also discussed. (C) 2014 Elsevier B.V. All rights reserved.