▎ 摘　　要

Graphene/zinc oxide nanowires/graphene (G/ZnO NWs/G) sandwich composites were firstly synthesized on nickel foam by electrostatic spray deposition technique and hydrothermal reaction in sequence. Microstructure and chemical analysis showed the dense and uniform ZnO NWs encapsulated by bottom and upper graphene layers. The G/ZnO NWs/G composites as cold cathodes for field emission (FE) exhibited improved performances with a lower turn-on electric field of 7.45 V/mu m, a higher field enhancement factor of 5328 and higher emission current stability over 10 h than G/ZnO NWs. The enhanced FE properties of G/ZnO NWs/G were mainly attributed to its sandwich structure, which introduced more surface defects and numerous emission sites, simultaneously decreased the work function and resistivity of emitters. This investigation paves a new way for developing high-performance cold cathode FE materials. (C) 2017 Elsevier B.V. All rights reserved.