  Boron nitride is a promising material for nanotechnology applications due to
its two-dimensional graphene-like, insulating, and highly-resistant structure.
Recently it has received a lot of attention as a substrate to grow and isolate
graphene as well as for its intrinsic UV lasing response. Similar to carbon,
one-dimensional boron nitride nanotubes (BNNTs) have been theoretically
predicted and later synthesised. Here we use first principles simulations to
unambiguously demonstrate that i) BN nanotubes inherit the highly efficient UV
luminescence of hexagonal BN; ii) the application of an external perpendicular
field closes the electronic gap keeping the UV lasing with lower yield; iii)
defects in BNNTS are responsible for tunable light emission from the UV to the
visible controlled by a transverse electric field (TEF). Our present findings
pave the road towards optoelectronic applications of BN-nanotube-based devices
that are simple to implement because they do not require any special doping or
complex growth.
