The metal oxide semiconductor (MOS) core-shell heterostructure nanofibers (NFs) have been successfully fabricated via a facile and environmentally friendly coaxial electrospinning approach. In this work, p-type semiconductor Co3O4 and n-type semiconductor ZnO are chosen for the synthesis of the core-shell heterostructured NFs. The Co3O4-ZnO core-shell NFs show a normal p-type response to formaldehyde in spite of the n-type ZnO shell. This conversion of sensing behavior may attribute to the formation of p-n heterojunction. Additionally, Co3O4-ZnO core-shell NFs exhibits enhanced sensing performance including a high response to the target gas and rapid response/recover processes. A possible mechanism of the improved sensing abilities is also illustrated, which can provide theoretical guidance for the further development of advanced gas-sensitive NFs with p-n heterojunction. (C) 2017 Elsevier B.V. All rights reserved.