Graphene oxide - what is it?
Graphene oxide is a form of a new super-material called graphene. Graphene as such is a one atom-thick layer of carbon oxides organized into a hexagonal lattice of benzene rings. The unique seemingly two-dimensional structure gives it a rather unusual set of properties – extreme durability, flexibility, insolubility, and conductivity.
What’s the difference between graphene and graphene oxide? Graphene oxide, as the name suggests, is a graphene layer containing oxygen and oxygen-bearing groups (O, OH etc.). In order to maintain the uniform structure of graphene, the oxide form may not be produced through oxidation, but rather by reduction. Using a more usual approach, graphene oxide can be produced by oxidation of graphene.
The oxides cause changes in the physical characteristics of the material.
How do characteristics change? The two main impacts are on solubility and conductivity.
Graphene oxide easily dissolves in water and other organic solvents. Furthermore, graphene oxide is conductive only after special modifications. Paired with the fact that it easily attaches to substrates, the oxide form allows for specific uses in high-tech fields.
Uses of graphene oxide The aforementioned propensity to attach to substrates and conductivity only in particular conditions are now a basis for graphene oxide-based conductive films.
These films can be used in solar panel cells, sensors, and – since graphene is biocompatible – wearable electronics.
The solubility of graphene oxide allows for its use in hybrid material production. The oxide can be mixed with polymers to increase their electrical and physical parameters (especially in terms flexibility and durability). The improvement of desired electrical parameters can be two-fold – as such it is an insulator, however with appropriate treatment, it is a conductor. Meaning the same material on the same substrate, after undergoing a certain process, can shift conductivity in either direction.
Use in medicals is also a possibility. Due to its solubility and biocompatibility, graphene oxide can be used to deliver drugs, and replace amines. Bio-devices can profit from the compatibility, as can future optoelectrical applications.
Graphene oxide - how is it made?
In laboratory volumes, there are several methods of synthesizing graphene oxide which are already well established. These methods comprise Hummers', Hofmann's, and Staudenmaier's. The choice of methods matter because it influences the affinity towards heavy metals and carboxyl groups; which is important e.g. for predicted uses in filtration.
What about industrial volumes? The development of methods allowing for feasible production of industrial volumes is still under way. Still, graphene oxide may actually receive more attention than its predecessor, graphene, because the oxide’s production is so far less costly.
Since the market for graphene-based products is projected to grow between 5 to 50 times in the next 8 years, there is a strong competition between various research teams and companies.
Economical production of graphene oxide may have added value in the production of pure graphene, as graphene oxide is its precursor. Hence this solution could also provide a solution for feasible graphene production.
What’s the current state of graphene oxide production?Nowadays, the most widespread method of synthesizing graphene oxide is through chemical oxidation of natural graphite; albeit there are other avenues such as electrochemical oxidation. This process is continuously being tweaked in an effort to discover the solution to production of industrial volumes.