Two-dimensional nanomaterials with engineered bandgap: Synthesis, properties, applications

•The typical methods of bandgap engineering in two-dimensional nanomaterials are presented.•The optimization of application performance for two-dimensional nanomaterials by bandgap engineering are summarized.•Challenges and opportunities in the development of two-dimensional nanomaterials are discussed. [Display omitted] Encouraged by its excellent electronic, optical, and mechanical properties, two-dimensional nanomaterials, including graphene, germanene, silicene, phosphorene, transition metal dichalcogenides, hexagonal boron nitride and so on, have generated significant research interests in a wide range of fields. In many applications, bandgap perform an important and even decisive role. However, there are very limited works that focused on a highly comprehensive overview of bandgap engineering in two-dimensional nanomaterials. Here, we review the feasibility, methods, and effects on applications of bandgap engineering in two-dimensional nanomaterials. We first provide a brief introduction on the physical significance of bandgap in two-dimensional nanomaterials. Then, based on the effect on the structure of two-dimensional nanomaterials, we introduce several methods to control and regulate the bandgap. Thereafter, bandgap engineering in different two-dimensional nanomaterials using various methods is summarized in detail. Further, we also emphasize the optimization of application performance through bandgap engineering. Finally, the challenges and outlooks in two-dimensional nanomaterials are proposed based on the current development status and future requirements.