Researchers at the University of Glasgow have now found a way to produce large sheets of graphene using the same cheap type of copper used to manufacture lithium-ion batteries found in many household devices.
In a new paper published in the journal Scientific Reports, a team led by Dr Ravinder Dahiya explain how they have been able to produce large-area graphene around 100 times cheaper than ever before.
Graphene is often produced by a process known as chemical vapour deposition, or CVD, which turns gaseous reactants into a film of graphene on a special surface known as a substrate.
They believe that large scale and low cost synthesis of high quality graphene films and the compatibility of our method to the roll-to-roll fabrication would open an avenue through the realization of graphene based flexible optoelectronic systems such as cell phones with roll-up displays, e-paper, radio-frequency identification (RFID) tags, as well as medical patches that can be attached to the skin to deliver drugs or monitor vital signs, and tactile or electronic skin for robotics and prosthetics
Effects of Cu surface morphology on graphene growth: (a) The optical microscope image of rough Cu foil (Alfa Aesar Cu foil) commonly used in graphene growth. Deep scratches on the rough Cu foil due to the rolling process are clearly visible (b) Scanning electron microscopy (SEM) image of the rough Cu surface. (c) The magnified SEM image of graphene flakes on rough Cu foil surface. The growth was terminated after 10 seconds to obtain dispersed graphene flakes. (d) Optical microscope image of commercially available ultra-smooth Cu foil (Mitsui mining and smelting co. LTD., B1-SBS) and (e) SEM image of ultra-smooth Cu surface. (f) Ultra-smooth Cu surfaces with graphene flakes. The density and shape of the graphene flakes are different on the rough and smooth foils. The sizes of individual grains along the Cu surface are clearly visible
The research team used a similar process to create high-quality graphene across the surface of commercially-available copper foils of the type often used as the negative electrodes in lithium-ion batteries. The ultra-smooth surface of the copper provided an excellent bed for the graphene to form upon.
They found that the graphene they produced offered a stark improvement in the electrical and optical performance of transistors which they made compared to similar materials produced from the older process.
Dr Dahiya, of the University of Glasgow’s School of Engineering, said: “The commercially-available copper we used in our process retails for around one dollar per square metre, compared to around $115 for a similar amount of the copper currently used in graphene production. This more expensive form of copper often required preparation before it can be used, adding further to the cost of the process.
“Our process produces high-quality graphene at low cost, taking us one step closer to creating affordable new electronic devices with a wide range of applications, from the smart cities of the future to mobile healthcare.
“Much of my own research is in the field of synthetic skin. Graphene could help provide an ultraflexible, conductive surface which could provide people with prosthetics capable of providing sensation in a way that is impossible for even the most advanced prosthetics today.
This work demonstrates an attractive low-cost route to obtain large area and high-quality graphene films by using the ultra-smooth copper foils which are typically used as the negative electrodes in lithium-ion batteries. We first compared the electronic transport properties of our new graphene film with the one synthesized by using commonly used standard copper foils in chemical vapor deposition (CVD). We observed a stark improvement in the electrical performance of the transistors realized on our graphene films. To study the optical properties on large area, we transferred CVD based graphene to transparent flexible substrates using hot lamination method and performed large area optical scanning. We demonstrate the promise of our high quality graphene films for large areas with ~400 cm2 flexible optical modulators. We obtained a profound light modulation over a broad spectrum by using the fabricated large area transparent graphene supercapacitors and we compared the performance of our devices with the one based on graphene from standard copper. We propose that the copper foils used in the lithium-ion batteries could be used to obtain high-quality graphene at much lower-cost, with the improved performance of electrical transport and optical properties in the devices made from them.
SOURCES – University of Glasgow, Nature Scientific Reports