Facial hydrothermal route of graphene and titanium dioxide nanotube composite with enhanced green light emission at ~ 530 nm

Herein we report a simple fabrication of graphene and titanium dioxide nanotube composite using hydrothermal method. Photoluminescence emission of the composite were investigated to study defect states in bandgap of nanotubes when the content of graphene varied from 1 wt% to 8 wt%. With the content of graphene lower than 5 wt%, the photoluminescence spectra form of the composite showed similar to that of pristine titanium dioxide nanotube. When the content of graphene reached 8 wt%, the emission positions were unchanged. However the spectrum form was dramatically changed, the intensity of green emission at about 530 nm was dominated. Thanks to the formation of graphene and titanium dioxide nanotube, excited electron was easy to diffuse from nanotube to graphene. The recombination of excited electron and trap hole on nanotube surface induced by oxygen vacancy in titanium dioxide anatas phase was enhanced which was attributed to the 530 nm emission.