A monomer graphene object comprising a graphene single crystal, wherein the graphene single crystal comprises parallel graphene planes which are densely packed and chemically bonded, the graphene planes have a graphene plane spacing of 0.335 to 0.40nm and an oxygen content of 0.0 1 to 10% by weight, and the monomer graphene layer or graphene single crystal is obtained by heat-treating graphene oxide gel at a temperature higher than100 DEG C.

During the drying and heat treatment, the molecules in the graphene oxide gel are chemically interconnected and integrated into a single graphene object without discrete graphite scales or graphene sheets. Graphene shows an excellent combination of thermal conductivity, electrical conductivity, mechanical strength, surface smoothness, surface hardness and scratches.