▎ 摘　　要

The dependence of the absorbance of few-layer graphene oxide on reduction level is shown to originate from different inter- and intra-band transitions using infrared-visible spectroscopy. In addition, the band-gap of reduced graphene oxide is tunable from 2 to 0.02 eV depending on its reduction level. These results indicate that reduced graphene oxide possesses great potential as a candidate for photodetection in the mid-infrared range by controlling its band-gap. This study not only gives further insight into the absorption mechanism of graphene oxide reduced to different levels, but also reveals a way to tune and measure the band-gap of graphene-based materials using a simple, economical, and nondestructive approach. This approach should be readily adapted for use in photodetection applications. (c) 2013 Elsevier Ltd. All rights reserved.