Graphene, a 2D sheet of carbon atoms arranged in a chicken wire pattern, is a fascinating material that boasts many exciting properties like mechanical strength, thermal and electrical conductivity, intriguing optical properties and more. Graphene is the focus of vigorous R&D, but its relatively high price is a hindrance at the moment.
Graphene oxide is a form of graphene that includes oxygen functional groups, and has interesting properties that can be different than those of graphene. By reducing graphene oxide, these oxidized functional groups are removed, to obtain a graphene material. This graphene material is called reduced graphene oxide, often abbreviated to rGO. rGO can also be obtained from graphite oxide, a material made of many layers of graphene oxide, after a series of reduction to graphene oxide and then to rGO.
How is rGO produced?
Since effective yet inexpensive ways to make graphene (or closely related materials, such as rGO) are being intensively sought for, the reduction of graphene oxide (or graphite oxide) to rGO is popular and attractive. Several methods of reduction into rGO exist, and are rather cost-efficient and simple.
While rGO is indeed a form of graphene with properties similar to that of graphene (good conductive properties etc.), rGO usually contains more defects and is of lesser quality than graphene produced directly from graphite. Reduced graphene oxide (rGO) contains residual oxygen and other heteroatoms, as well as structural defects. Despite rGO’s less-than-perfect resemblance to pristine graphene, it is still an appealing material that can definitely be sufficient in quality for various applications, but for more attractive pricing and manufacturing processes. Reduced graphene oxide can be used (depending on the specific material’s quality) for the same various applications suitable for graphene use, like composite materials, conductive inks, sensors and more.
Reduced GO is often a natural and understandable choice for applications that call for large amounts of material due to the relative ease in creating sufficient quantities of graphene in a relatively low cost.
The process of reducing graphene oxide to produce reduced graphene oxide is extremely important as it has a large impact on the quality of the rGO produced, and therefore will determine how close rGO will come, in terms of structure and properties, to pristine graphene.
A number of processes exist for the reduction of GO, based on chemical, thermal or electrochemical approaches. Some of these techniques are able to produce very high quality rGO, similar to high-quality graphene, but can be complex, expensive or time consuming to carry out.
Once reduced graphene oxide has been produced, there are ways to functionalize the material for specific use in different applications. By treating rGO with various chemicals or by creating new compounds by combining rGO with other two-dimensional materials, it’s possible to enhance the properties of the compound to suit commercial applications.
In some applications, the reduction of the GO to rGO is performed as part of the device manufacturing process. For example, a process could start with GO, mix it with a material to create a composite, and reduce the GO into rGO as part of the composite creation process or afterwards.
In general, it can be said that rGO is suitable for the same sorts of applications as graphene, as the properties of these materials are similar, albeit normally less impressive at the rGO end. As was said before, the properties of rGO can vary depending on the method of preparation and the resulting morphology and chemistry of the specific rGO.
Reduced GO can be used for many applications, among these are: energy storage, composite materials, field effect transistors and more.
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The latest reduced graphene oxide news:
Researchers from Tecnológico Nacional de México, McGill University and Centro de Investigación en Materiales Avanzados S.C. have examined the use of Graphene nanobuds (GNBs), formed on copper (Cu) foil via chemical vapor deposition, as an anode in lithium-ion batteries.
Producing high-performance anode materials that possess excellent specific capacities and extended cyclic ability is currently one of the key development areas in lithium-ion batteries. The energy storage capacity of lithium-ion batteries heavily depends on the anode materials used and their structure. Carbonaceous substances remain the anode materials of choice because of the strong attraction between lithium (Li) and graphitic carbon. Graphene possesses a large capacity to accommodate lithium ions in its framework because of its significant surface area and excellent electrical conductivity.
An international research team of the Graphene Flagship project, led by Empa, has conducted a study on the health risks of graphene-containing nanoparticles and found that graphene-based particles released from polymer composites after abrasion induce negligible health effects.
Graphene-related materials (GRMs) are often used to reinforce polymers. In small concentrations of up to five weight percent, GRMs can significantly enhance the strength, electrical conductivity and thermal transport of composites for a variety of applications. However, being a relatively new set of materials, graphene and GRMs need to be carefully assessed in order to identify potential adverse effects prior commercialization.
A new work by scientists at India's National Institute of Technology Rourkela describes the fabrication of extremely flexible, accurate, and robust strain sensors employing electrochemically produced reduced graphene oxide (rGO).
Conventional silicon-based strain sensors have relatively low flexibility of less than 5% and inadequate responsiveness, making them unsuitable for detecting both small and large strains. Aside from the flexibility constraint, typical silicon-based strain sensors need sophisticated manufacturing procedures such as microelectromechanical and deposition of thin films. Flexibility, responsiveness, and endurance are critical characteristics of wearable devices because they aid in the integration of the sensors over non-uniform interfaces such as the human body. Aside from elasticity, these products also need a sensor capable of detecting minute deformations caused by physiological factors and physical activity.
Tirupati Graphite has commissioned Stage 1 of the Tirupati graphene and mintech research center (TGMRC) in India. Tirupati says this marks the start of revenue generation at TGMRC and allows the company to advance commercialization engagements.
In Stage 1, the facility can initially produce up to 1 kilogram per day – of graphene oxide ('GO'), reduced graphene oxide ('rGO') and aluminium graphene composite – via the zero-chemical process developed by the company. Ongoing development and expansion of the facility will enable up to 10 kgs per day.
Major pharma company Merck has announced a collaboration agreement with Innervia Bioelectronics, a start-up and subsidiary of Inbrain Neuroelectronics S.L., Barcelona, Spain. The aim of the collaboration is to co-develop the next generation of graphene-based bioelectronic vagus nerve therapies targeting severe chronic diseases within the therapeutic areas addressed by Merck.
“We aim to accelerate developments in the emerging field of bioelectronics by boosting the novel modality of selective neurostimulation,” said Laura Matz, Chief Science and Technology Officer of Merck. “Today’s agreement with Innervia Bioelectronics gives Merck access to a unique technology that increases energy efficiency in neurostimulators and could therefore become a true enabler for digital personalized treatment of patients suffering from severe and chronic diseases such as inflammatory disorders.”