Electrical Conductivity

Electrical conductivity is another property observed to change at the nanoscale compared with bulk behaviour. The chapter's example is the carbon nanotube: depending on its exact structure (specifically, how the graphite sheet making up its wall is rolled up, though the chapter does not go into that structural detail here), a carbon nanotube can behave either as an electrical conductor or as a semiconductor. This is a genuinely unusual property for a single chemical substance (essentially pure carbon) to display -- an ordinary bulk material is either a conductor or an insulator/semiconductor, not something that can switch between the two categories depending purely on its nanoscale structural details, which is exac …