▎ 摘　　要

Graphene nanotubes (GNTs), as a rising member among the carbon nanomaterials family, has drawn significant research interest. The fabrication of the GNTs-based coessential composites could be a more facile and effective strategy to promote GNTs performances. Herein, based on the self-prepared N-doped graphene tubes (N-GNTs), multi-layer carbon wrapped N-doped GNTs (MLC@N-GNTs) and numerous stacked wrinkled graphene sheets encapsulated N-doped GNTs (GS@N-GNTs) are constructed via a facile free-template, one-step CVD method. The growth mechanism of the two types of coessential carbon composites was investigated in detail. The products, especially GS@N-GNTs display the most excellent field emission properties with a very low E-to, of 0.33 V/mm, E-thr of 0.96 V/mm and a high field enhancement factor of 50237. The excellent field emission properties is attributed to the synergistic effect of the improved electronic conductivity, the high density of structure defects, the abundance of effective electron emission sites along with the high field enhancement factor and the electronic properties changes induced by the winkled graphene. In addition, MLC@N-GNTs and GS@N-GNTs show the more intense photoluminescence emission than that of pristine N-GNTs, because the coessential coatings induces the interfaces and large amounts of structure defects, which can act as trapping sites for the excitation energy. (C) 2020 Elsevier B.V. All rights reserved.