▎ 摘　　要

Vertical graphene nanosheets (VGNs), normally consisting of one to several graphene layers vertically aligned on substrates, are promising in a variety of applications including field electron emitters, gas sensors and energy storage devices. Herein, we report a simple, green, easily scalable and cost-effective strategy of growing both intrinsic and nitrogen (N)-doped VGNs on stainless steel (SS) just by heating the solid thin layers of glucose and/or urea in a resistance-heating furnace. It is interesting that VGNs mainly grow on the roughened regions, which can be attributed to the more nucleation and catalyzing sites on such regions than smooth 55. Meanwhile, the N doping concentration can be adjusted by varying the urea addition. Held electron emission measurement indicates that the obtained N-doped VGNs exhibit excellent field emission with a relatively low turn-on electric field strength (similar to 2.6 V mu m(-1) at the current density of 10 mu A cm(-2)), large field enhancement factor (similar to 9428) and high stability. (C) 2018 The Authors. Published by Elsevier Ltd.