Clean green graphene separation
- ผู้เขียน:Ella Cai
- ปล่อยบน:2017-08-18
Clean graphene be set free without damage to its growth substrate, using only simple safe chemicals, according to researchers at the University of Illinois at Urbana-Champaign – aiming to release it for use in flexible transparent electronics.
The 2D material is synthesised using chemical vapour deposition onto a metal substrate, typically copper foil.
“One particularly tricky aspect of producing graphene is how to separate this atomically thin material from its native metal substrate for integration into useful devices,” said the University. “This typically involves either dissolving away the metal or delaminating it from the substrate – which require the use of chemicals that leave stubborn residue.”
Their answer is to first coat the graphene with a layer of bio-derived ethyl cellulose polymer, which can be dissolved using simple ethanol and is therefore compatible with later processing on a variety of polymeric and soft biological materials which will not tolerate harsher solvents, such as common plastics and hydrogels.
Then carbonic acid is used to de-laminate the graphite from the copper substrate.
This does not damage the substrate, so it can be re-used multiple times, and carbonic acid evaporates away as carbon dioxide and water, leaving clean graphene.
If “using electrolytes such as NaOH or NaCl, for example, the sodium tends to remain on the graphene, whichis very difficult to completely get rid of”, said Illinois scientist SungWoo Nam. “If you are interested in making the best transistor in the world, you have to have the cleanest, purest material that you can synthesise and transfer. In addition, a lot of people are trying to measure the intrinsic properties of other materials as well. Our approach will help them do that.”
The findings are published in the most recent Journal of Materials Chemistry C as ‘A sustainable approach to large area transfer of graphene and recycling of the copper substrate‘.
The 2D material is synthesised using chemical vapour deposition onto a metal substrate, typically copper foil.
“One particularly tricky aspect of producing graphene is how to separate this atomically thin material from its native metal substrate for integration into useful devices,” said the University. “This typically involves either dissolving away the metal or delaminating it from the substrate – which require the use of chemicals that leave stubborn residue.”
Their answer is to first coat the graphene with a layer of bio-derived ethyl cellulose polymer, which can be dissolved using simple ethanol and is therefore compatible with later processing on a variety of polymeric and soft biological materials which will not tolerate harsher solvents, such as common plastics and hydrogels.
Then carbonic acid is used to de-laminate the graphite from the copper substrate.
This does not damage the substrate, so it can be re-used multiple times, and carbonic acid evaporates away as carbon dioxide and water, leaving clean graphene.
If “using electrolytes such as NaOH or NaCl, for example, the sodium tends to remain on the graphene, whichis very difficult to completely get rid of”, said Illinois scientist SungWoo Nam. “If you are interested in making the best transistor in the world, you have to have the cleanest, purest material that you can synthesise and transfer. In addition, a lot of people are trying to measure the intrinsic properties of other materials as well. Our approach will help them do that.”
The findings are published in the most recent Journal of Materials Chemistry C as ‘A sustainable approach to large area transfer of graphene and recycling of the copper substrate‘.
