Mosquitoes are not only annoying to many people, they can also transmit dangerous diseases such as the West Nile virus and malaria . Currently, chemical preparations are used mainly as protection against the insects , which are applied either directly to the skin or to clothing. Scientists at Brown University have now developed a new mosquito repellent that consists of graphene , whose ultra-thin lattice of carbon atoms is flexible and at the same time extremely stable.
Robert Hurt, co-author of the study published by PNAS, explains that “mosquitoes are important disease carriers and therefore there is a great interest in non-chemical defense strategies.”
A thin layer of graphene in textiles protects against mosquito bites and thus replaces chemical repellents. At the moment, however, the material loses its effectiveness when wet.
Graphene is integrated into the fabric:
The scientists came up with the idea of developing protection against mosquito bites on the basis of graphene when they were busy producing graphene-containing textiles that are supposed to protect when working with toxic chemicals. In order to test whether the new material with the thin graphene layer can also protect against mosquitoes, the researchers examined this using 100 yellow fever mosquitoes (Aedes aegypti) and a number of volunteers in the laboratory.
For this purpose, the test subjects received a cover that covers the forearm and hand. They then placed the part of the body protected in this way in a chamber in which the hungry insects were. Some of the subjects only received a cheesecloth instead of the graphene protection, the third group received no protection at all. Afterwards it was evaluated how often the three comparison groups were stung under the same conditions except for the protection.
History of the discovery of graphene:
With a view to producing and discovering graphene, the scientists first attempted to produce graphene by chemical stripping. They incorporate large atoms and macromolecules in graphite to obtain graphite intercalation compounds. In its three-dimensional structure, each graphite layer can be viewed as an individual graphene layer. However, after the chemical reaction treatment, the graphene sludge was obtained and the scientists did not investigate it further because it was difficult to analyze the nature of the sludge.
In 2005, the team from Manchester University and Columbia University researchers confirmed that the quasi-graphene particles were massless Dillac fermions, and similar results triggered a research boom in graphene. Since then, hundreds of researchers with excellent academic achievements have entered this new area.
Other scientists have used chemical vapor deposition to epitaxially grow graphene films on a variety of substrates, but the initial quality is not good.
By 2004, physicists Andrei Heim and Konstantin Novoselov from Manchester University had successfully experimented with graphite and confirmed that it can exist on its own. The two also won the 2010 Nobel Prize in Physics.
Graphene oxide (GO) protects against mosquitoes in two ways:
The results clearly show that the protection made of multi-layer graphene oxide (GO) in a gauze coat effectively protects against mosquitoes, since none of the test subjects was stung even once. The other two groups, however, were stung almost as often.
Surprisingly, the mosquitoes didn’t even land on the protection from graphene oxide, as Cintia Castilho, the study’s lead authors, explains. According to the scientists, complete ignoring shows that the insects do not perceive their target due to the graphene film. The plan was to create physical protection based on graphene.
To confirm the assumption, the scientists then applied sweat from the outside to the graphene barrier, which caused the insects to be attracted as if by bare skin. However, it was found that graphene also physically protects against mosquito bites, since the animals cannot penetrate the material.
Unfortunately, the protective effect is significantly reduced when wet, which means that the required puncture resistance of the graphene oxide was no longer provided. An alternative material that is also resistant to wet conditions could also be produced, but as Hurt explains, it has “the disadvantage of not being breathable”, which makes it unusable for clothing.
In the future, the scientists now want to try to produce a reduced graphene oxide that is breathable and still protects against insect bites when it is wet and dry. If this succeeds, the graphene film could be integrated into clothing in the future, according to the scientists involved, in order to protect people from dangerous mosquito bites without the need for chemical repellants that are harmful to both the user and the environment .
First jacket with graphene coating:
It is not only bulletproof, but that could come in the next versions with more graphene layers.
Nevertheless, the list of impressive properties of the world’s first graphene jacket is long. It is manufactured by the London-based outdoor supplier Vollebak, who managed to coat a nylon jacket on one side with graphene nanoplates. If the graphene-coated side of the reversible jacket is worn inside, it should not only compensate for heat differences between body regions.
According to Vollebak, the graphene layer can also store heat and give it to the wearer if it has previously been in the sun. In addition, the jacket is absolutely leakproof for most gases and liquids, only water vapor lets it out. But even if sweat accumulates on the graphene layer, no unpleasant smells develop because the bacteria contained in the sweat cannot multiply on the graphene layer.
Vollebak has reduced the electrical conductivity of the graphene layer for safety reasons, but you could perhaps use it later to charge a cell phone wirelessly in your jacket pocket.
Graphene is currently the thinnest but hardest nanomaterial in the world. It is almost completely transparent and only absorbs 2.3% of the light. Its thermal conductivity is higher than that of carbon nanotubes and diamond. Its resistivity is lower than that of copper and silver. It is currently in the world. The material with the lowest specific resistance. Put simply, graphene is a transparent, good conductor that is suitable for the production of touchscreens, light panels and even solar cells.
Siliconized epitaxial surface growth
The silicon is removed by heating the single crystal silicon carbide and the graphene layer is decomposed on the single crystal surface.
Oxidation diluted graphite sheet process
With a strong oxidizing agent, the intercalation oxidation is carried out in the middle of the layer structure of graphite, so that there is a negatively charged oxidative functional group between the layers, which overcomes the Van der Waals force between the graphites and the distance between the layers is strong enlarged by embedding water molecules. For easier stripping of the graphene oxide.
Method of making graphene:
In 2008, graphene made by mechanical stripping was one of the most expensive materials in the world.
Tear tape method / light rubbing method
The graphene layers were cut directly from the larger crystals. In 2004 Heim et al. used this method to produce single-layer graphene that can exist only in the external environment.