  Monolayer (1L) transition metal dichalcogenides (TMDCs) are attractive
materials for several optoelectronic applications because of their strong
excitonic resonances and valley-selective response. Valley excitons in 1L-TMDCs
are formed at opposite points of the Brillouin zone boundary, giving rise to a
valley degree of freedom that can be treated as a pseudospin and may be used as
a platform for information transport and processing. However, short valley
depolarization times and relatively short exciton lifetimes at room temperature
prevent using valley pseudospin in on-chip integrated valley devices. Recently
it has been demonstrated how coupling these materials to optical nanoantennas
and metasurfaces can overcome this obstacle. Here, we review the
state-of-the-art advances in valley-selective directional emission and exciton
sorting in 1L-TMDC mediated by nanostructures and nanoantennas. We briefly
discuss the optical properties of 1L-TMDCs paying special attention to their
photoluminescence/absorption spectra, dynamics of valley depolarization and
valley Hall effect. Then, we review recent works on nanostructures for
valley-selective directional emission from 1L-TMDCs.
