The limit of layers in black phosphorous
In the 2D "flatlands", graphene stands tall as the most exciting discovery for future technologies. Despite its many attractive properties however, graphene lacks a natural band gap that would allow electrical flow to be switched on and off (it is a zero gap semiconductor). Luckily the physical realisation of graphene has led to an explosion of interest in other 2D and/or layered (nano)materials for specific applicaitions. For example the elemental allotropes silicene, german
