Reduced graphene oxide: an introduction - Page 9

Researchers from China's National Tsing Hua University found a new use for graphene: photothermal antibacterial therapy. The researchers say that during experiments both gram-positive Staphylococcus aureus and gram-negative Escherichia coli were efficiently captured by glutaraldehyde and concentrated (or immobilized) by the magnetic property of a magnetic reduced graphene oxide functionalized with glutaraldehyde.

The bacteria were rapidly killed by multiple means, including conventional oxidative stress as well as physical piercing and photothermal heating of graphene by near-infrared (NIR) laser irradiation.

Graphenea has launched an online store, and the company now offers several graphene materials including CVD graphene films (on SiO₂, copper and any substrate that the customer provides), graphene oxide and reduced graphene oxide. The company is also building a distribution network in main graphene markets (such as the US, Japan and Korea).

Graphenea has a pilot line with a capacity of 50,000 cm²/year and they plan to expand it during 2013. Graphenea says that their customer list includes Nokia, Philips, Corning and ASML.

Some scientists are concerned that Graphene may be hazardous and toxic - for humans, animals and the natural environment. Researchers from Singapore's A*STAR have published a study on how graphite, graphite oxide, graphene oxide and reduced graphene oxide may effect bacteria (Escherichia coli in the study).

The researchers showed that the graphene-based materials kill substantially more bacteria than graphite-based materials. Graphene Oxide was the most dangerous material. The researchers say that most of the E.coli cells were individually wrapped by layers of graphene oxide. In contrast, E. coli cells were usually embedded in the larger reduced-graphene-oxide aggregates (see image above).

MIT scientists have shown (in simulations) that nanoporous graphene can filter salt from water at a rate that is 2-3 orders of magnitude faster than today’s best commercial desalination technology, reverse osmosis (RO). This could lead to more efficient and smaller water desalination facilities.

Simulated nanoporous graphene filtering salt ions

The graphene is used as a membrane material that allows a flow of water with full salt refection via size exclusion. Other materials have been investigated for the same purpose, but the researchers say that graphene is the "ultimate" thin membrane as it's the thinnest one possible and as water flux across a membrane scales inversely with the membrane’s thickness.

The following article was sent to us by Corey McCarren and Dr. Elena Polyakova from Graphene Laboratories (a Graphene-Info sponsor), discussing Graphene Oxide and its applications:

Graphene, a multi or single layer sheet of graphite, is considered a key material in producing the next generation of low-cost carbon-based transparent and flexible electronics. Graphene is the strongest material available, as well as being highly transparent, flexible, and the best conductor of heat and electricity. Great effort is devoted to developing an effective yet inexpensive way to produce graphene materials in industrial quantities.

Graphene Supermarket announced that they have expanded their product line and reduced the prices of many current graphene products. They are now offering highly concentrated graphene oxide at the lowest price per gram. The company also added two high-surface area materials, Reduced Graphene Oxide and ultrafine Graphene Nanoplatelets.

Graphene Supermarket is operated by Graphene Laboratories and is a sponsor of Graphene-Info.

Rigoberto Gobet Advincula, a polymer chemist from the University of Houston has developed two different materials that are both equally effective against E. coli. One of them is graphene based - which is proving to be an effective antimicrobial.

This is not the first time we hear that Graphene can be used against E. coli - back in 2010, researchers from Shanghai University has developed two water-based dispersible graphene derivatives (graphene oxide and reduced graphene oxide) that can effectively inhibit the growth of E.coli and have minimal toxic effects on harming cells (cytotoxicity).

Researchers from Shanghai University has developed two water-based dispersible graphene derivatives that can effectively inhibit the growth of E.coli and have minimal toxic effects on harming cells (cytotoxicity). The two derivatives are based on graphene oxide (GO) and reduced graphene oxide (rGO).

The group tested the antibacterial properties of the GO sheets with E.coli DH5 cells via a luciferase-based ATP assay kit. After two hours incubation with the GO sheets of 20 µg/mL at 37C, the cell metabolic activity of the bacteria fell to around 70 per cent. With a GO concentration of 85 µg/mL, the activity of the E.coli cells fell to just 13 per cent suggesting a strong inhibition ability of GO nanosheets to E.coli, said the researchers.

Korean researchers have made a new type of composite material made from reduced graphene oxide and magnetite that could effectively remove arsenic from drinking water. Arsenic is one of the most carcinogenic elements known and its presence in drinking water is a huge problem in many areas of South Asia and the western United States. Arsenic is usually removed using bare magnetite, but adding graphene makes it much more efficient.

The new magnetite composite was used to remove over 99.9% of arsenic in a sample. The composite can be dispersed in water, and then removed after it has absorbed the arsenic (by using a permanent hand-held magnet).

Scientists have made a breakthrough toward creating nanocircuitry on graphene, widely regarded as the most promising candidate to replace silicon as the building block of transistors. They have devised a simple and quick one-step process based on thermochemical nanolithography (TCNL) for creating nanowires, tuning the electronic properties of reduced graphene oxide on the nanoscale and thereby allowing it to switch from being an insulating material to a conducting material.

The technique works with multiple forms of graphene and is poised to become an important finding for the development of graphene electronics.