Enhanced room temperature NO2 sensing performance based on N-doped carbon nanosheets@ZnO nanoplates by morphology transition and white light illumination

Highly-sensitive gas sensors operating at room temperature (RT) have been pursued by researchers due to their high security, energy saving and long-term stability. Herein, N-doped carbon nanosheets-incorporated zinc oxide (NCZ) was synthesized via solution calcination combined with hydrothermal method and utilized for ppb level detection of NO(2 )at RT. Intriguingly, the construction of N-doped carbon nanosheets was accompanied by generation of ZnO nanoparticles, and then be transferred into mesoporous nanoplates. The as-synthesized NCZ (120)-300 nanocomposites demonstrated high sensitivity to 3 ppm NO2 (|R-g-R-0|/R-0=~ 28.2), along with fast response/recovery (60 s/129 s) speed, excellent selectivity and cyclic stability. In particular, the morphology transition of ZnO greatly enhanced the RT NO2 sensing performance of the as-prepared sensor. Meanwhile, the white light illumination further ameliorated the sensor's properties involving ~ 2.1 times enhancement of sensitivity and shorter recovery process (accelerated from 563 s to 129 s). These enhancements are ascribed to the heterostructure between ZnO nanoplates and N-doped carbon nanosheets, and the modulation of electron structure by photo-generated electron-hole pairs. In addition, the 2D N-doped carbon nanosheets and mesoporous ZnO nanoplates offer numerous active adsorption-sites, which improved the surface chemical activity of NCZ(120)-300.