  The emerging two-dimensional (2D) materials exhibit a wide range of
electronic properties, ranging from insulating hexagonal boron nitride,
semiconducting transition metal dichalcogenides such as molybdenum disulfide,
to semi-metallic graphene. Here, we first review the optical properties and
applications of a variety of 2D materials, followed by two different approaches
to enhance their interactions with light: through their integration with
external photonic structures and through their intrinsic polaritonic
resonances. Finally, we cover a narrow bandgap layered material, black
phosphorus, which serendipitously bridges the zero gap graphene and the
relatively large-bandgap TMDCs. The plethora of 2D materials and their
heterostructures, together with the approaches for enhancing light-matter
interaction offers the promise of scientific discoveries and nanophotonics
technologies across a wide range of electromagnetic spectrum.
