Surface-functionalised graphene oxide nanosheets are obtained from substoichiometric oxidation of graphite, exfoliation, and in situfunctionalization. Subsequent deoxidation produces zero-gap imperfect graphenites with carrier mobilities of 10 cm(2) V-1 s(-1). These nanosheets exhibit trap-free band-like activation energies at low temperatures for electrons and holes. Field-effect transistors with zero gate-voltage threshold have been demonstrated.