Photocharge Trapping in Two-Sheet Reduced Graphene Oxide–Ti_0.87O₂ Heterostructures and Their Photoreduction and Photomemory Applications

Two-sheet devices of different 2D materials fabricated from the mechanical transfer technique have been well studied to explore their genuine interactions, and many interesting properties have been found in them. However, the study of two-sheet heterostructures fabricated from colloidal 2D materials is rarely reported. In this work, a facile construction method of two-sheet assembly from colloidal 2D materials, i.e., reduced graphene oxide (rGO) and titania nanosheets (Ti0.87O20.52–), has been developed. Massive trapping of photocharges is observed in their two-sheet devices because of the unique band electronic structure of Ti0.87O20.52– nanosheets and its high surface charge density of ∼1015 cm–2. We demonstrated that this photocharge trapping could be used for photoreduction of GO, which showed an over 108-fold enhancement of conductivity for the film. When this phenomenon was used for photomemory application, the device showed the longest retention time (>105 s), a good photo/dark current ratio (∼10), and the largest data storage capacity (0.013 C), among all 2D material-based devices. The developed technique for the two-sheet structure of colloidal 2D materials may open a new avenue to study the properties of 2D materials.