Copper and a variety of metal oxides have been used with similar frequencies; the oxides are most commonly used in sensors as nanopowders, although nanobelts and nanorods of zinc oxide are found relatively often in sensors. MoS2 is used in a variety of morphologies in sensors ; it has been used as a lubricant additive in a variety of circumstances which may have led to the understanding and exploration of its nanoscale morphologies.