Reduced graphene oxide: an introduction - Page 8

Researchers from Australia's Anstro institute and Deakin University developed an efficient method to prepare porous and reduced graphene oxide. They say that this one-step, catalyst-free, high penetration and through-put technique offers for the first time a significant advantage over previously reported graphene oxide (GO) solution reduction mechanisms.

The new technique, which uses gamma irradiation, maintains the naturally densely packed morphology of GO bucky-papers without causing the dramatic exfoliation of the graphene layers caused by chemically reduced routes.

Researchers from Nankai University developed a single-cell sensor (optical refractive index sensor) based on graphene field-effect transistors. This new sensor is able to detect a single cancer cell.

The researchers managed to obtain such ultrahigh sensitivity by controlling the thickness of high-temperature reduced graphene oxide. The resolution obtained is the highest values reported for refractive index sensors."

Researchers from Australia and Ireland developed a flexible yarn made from graphene oxide. This strong, lightweight, highly conductive and high capacitance fiber may be a great material for wearable textiles.

The researchers report that the new yarns and fibers exhibit the best electrochemical capacitance ever - of as high as 410 F/g. To create the fiber, the researchers used a novel wet-spinning technique that can produce both GO and r-GO yarns of unlimited lengths. Those yarns are strong (with a Young’s modulus that is greater than 29 GPa), have a high electrical conductivity of around 2500 S/m and a very large surface area about 2600 m2/g for graphene oxide and 2210 m2/g for the reduced material.

Back in May, Lomiko Metals, Stony Brook University (SBU) and Graphene Labs signed an agreement to investigate graphene based applications - mainly supercapacitors and batteries. Today the companies announced that they have reached a significant milestone by receiving a prototype graphene supercapacitor and a report from Stony Brook University and New York State’s Center for Advanced Sensor Technology (Sensor CAT).

The supercapacitor prototype was made using graphene composite material prepared using a proprietary technology developed at Graphene Labs. The measured specific capacitance of the prototype was found to be around 500 Farad per gram of the material. This value is comparable with the best values reported in the literature for a supercapacitor of this type.

Reduced graphene oxide is a promising way to produce graphene materials, but currently used methods use harsh chemicals and are not environmentally friendly. A possible green method is photoreduction, but the dynamics behind this reduction aren't fully understood.

Now researchers from Germany's Max Planck Institute demonstrate and measure the ultrafast (picosecond) ultimate and fundamental time scale of graphene oxide photoreduction. The researchers explain that their research demonstrates the nature and fundamental timescale of GO reduction in water by UV irradiation.

Researchers from Korea's Gwangju Institute of Science and Technology in Korea developed high-performance supercapacitors based on graphene. They say these capacitors can store almost as much energy as a Li-Ion battery and can charge/discharge in seconds. They also last for many tens of thousands of charging cycles.

The researchers use a highly porous graphene that has a huge internal surface area. To fabricate this material they reduced graphene oxide with hydrazine in water agitated with ultrasound. This results in a graphene powder that they then packed into a cell shaped like a cell and dried it at 140 degrees Celsius under pressure for five hour. The material was used as an electrode.

Researchers from Korea's Incheon National University developed a new way to make conductive, flexible, and durable textiles (fabrics) wrapped with reduced graphene oxide (RGO). They report that those materials are useful to make conductive wires or functional fabrics in wearable electronics and more.

The main breakthrough is the choice of bovine serum albumin (BSA) - an amphiphilic protein that can be attached to organic and inorganic materials through hydrophobic and hydrophilic interactions - basically this is molecular "glue" that helps with graphene-oxide adsorption into any textile. The researchers fabricated those electrostatic self-assembly of BSA molecules onto all sorts of textiles (nylon yarns, cotton yarns, etc.) and then used a low-temperature chemical reduction.

Graphene Laboratories announced that they have successfully managed to convert Lomiko Metal's Quatre Milles property graphite to graphene. They have actually produced graphene oxide (GO) and reduced graphene oxide (RGO) samples. The companies hope that they will be able to create graphene materials on a larger scale and at a reduced price.

In the first step of the conversion process the natural graphite flakes were oxidized and turned into GO by modified Hummer's method. This resulted in a stable aqueous dispersion with concentration of 40 g/L. The GO was then converted into RGO, with a surface area of 500 m² /g and an electrical conductivity 4 S/cm.

Researchers from Korea suggest a new simple, high-yield method (single-step microwaves radiation) to synthesize a new graphene-carbon nanotube-iron oxide (G-CNT-Fe) 3D functional nanostructures. The researchers report that these unique 3D structures can be excellent arsenic absorbents.

Those structures are carbon nanotubes vertically standing on graphene sheets and iron oxide nanoparticles well distributed on both the graphene and the CNTs. These are excellent to absorb arsenic due to the high surface-to-volume ratio and open pore network.

Lockheed Martin says that they have developed a new energy-efficient graphene-based water desalination technology. Lockheed developed new graphene filters that has nanometer-sized holes in them that allow water to pass through - but not salt molecules. The energy required to "push" seawater through these filters is very low because graphene is so thin. In fact graphene is 500 times thinner than the filter available today, and this filter will require about 100 times less energy. Lockheed patented the new filtration system, and calls the new material Perforene.

Simulated nanoporous graphene filtering salt ions

Lockheed is not ready to commercialize this technology yet. They are still refining the process for making the holes in graphene, and also the production process of the graphene itself. They expect to have a prototype filter by the end of 2013. This prototype will be a drop-in replacement for current filters used in reverse osmosis (RO) plants. They hope to commercialize this technology by 2014-2015 and are looking for partners in the filter manufacturing arena.