Graphene oxide paper

Graphene oxide paper or graphite oxide paper is a material fabricated from graphite oxide. Micrometer thick films of graphene oxide paper are also named as graphite oxide membranes (in the 1960s) or (more recently) graphene oxide membranes. The membranes are typically obtained by slow evaporation of graphene oxide solution or by the filtration method. The material has exceptional stiffness and strength, due to the intrinsic strength of the two-dimensional graphene backbone and to its interwoven layer structure which distributes loads. The starting material is water-dispersed graphene oxide flakes. The aqueous dispersion is vacuum filtrated to produce free standing foils. The thickness of these foils is typically in the range of 0.1-50 micrometers. Depending on application the graphene oxide laminates are named either as papers or as membranes. Alternative methods to prepare free standing graphene oxide multilayers/laminates is to use repeated drop casting or spin coating. These flakes may be chemically bonded, leading to the development of additional new materials. Like the starting material, graphene oxide paper is an electrical insulator; however, it may be possible to tune this property, making the paper a conductor or semiconductor, without sacrificing its mechanical properties. Detailed studies of graphite oxide paper by V. Kohlschütter and P. Haenni date back to 1918. Studies of graphite oxide membranes were performed by Hanns-Peter Boehm, the German scientist who invented the term "graphene", in 1960. The paper titled "Graphite Oxide and its membrane properties" reported synthesis of "paper-like foils" with 0.05 mm thickness. The membranes were reported to be not permeable by gases (nitrogen and oxygen) but easily permeable by water vapors and, suggestively, by any other solvents which are able to intercalate graphite oxide. It was also reported that the membranes are not permeable by "substances of lower molecular weight".