Bandgap engineering of ultrathin graphene-like carbon nitride nanosheets with controllable oxygenous functionalization

Seeking effective approaches of bandgap engineering with increased carrier lifetime is critical for designing semiconductor photoelectronic devices and photocatalysis systems. Ultrathin graphene-like carbon nitride nanosheets have shown promising prospect in photocatalysis, whereas no preparation strategy for adjusting their bandgap in a wide range has ever been reported. Here in, high yield-rate synthesis of ultrathin two-dimensional carbon nitride nanosheets with controllable oxygenous functionalization (the relative mass ratio of oxygen ranges from 0.523% to 19.9%) was firstly achieved by an improved hummer's method combining concentrated sulfuric acid protonation and potassium permanganate assisted exfoliation, and reduction employing hydrazine hydrate. Protonation and intercalation behavior of different acids in the treatment of bulk-g-C3N4 was elaborated at molecule level for the first time. Introduced oxygenous groups are firstly found to have the capability for adjusting the bandgap of graphene-like carbon nitride nanosheets from 2.54 eV to 3.07 eV and significantly increased the lifetime of the photo carriers. Our strategy may open a new vista for design and construction of various carbon nitride nanocomposites and give detailed instructions in bandgap engineering of other two-dimensional functional materials for wider applications. (C) 2016 Elsevier Ltd. All rights reserved.