An international team of nanotechnology specialists have found a cheap and effective way to produce carbon nanotubes by synthesizing them on old newspapers. Not only will the discovery provide for a low cost, eco-friendly method for carbon nanotube production, but the technique can be adapted for large scale production, a major challenge for the nanotechnology industry.
As Bruce Brinson, the study’s lead researcher explains, the newspapers are, “… used as a catalyst-bearing substrate [creating] … a very high surface-area growth medium compatible with continuous-flow production methods.” Adding that, “Newspapers have the benefit of being used in a roll-to-roll process in a stacked form making it an ideal candidate as a low-cost stackable 2D surface to grow carbon nanotubes.”
The study is a collaboration between Rice University in Texas and the Energy Safety Research Institute (ESRI) at Swansea University in Wales, and is a work that could increase the number of applications for carbon nanotubes by making them even more affordable to produce. It also avoids single surface growth, which had only previously been possible, and has the potential to solve the problem of economically viable, mass production of carbon nanotubes by drastically lowering the cost of preparing a suitable surface for chemical growth.
“While there has been previous research that shows that graphene, carbon nanotubes, and carbon dots can be been synthesised on a variety of materials, such as food waste, vegetation waste, animal, bird or insect waste and chemically grown on natural materials, to date, this research has been limited,” says ESRI Director Andrew Barron, who is also a professor at Rice University in Texas. “With our new research, we have found a continuous flow system that dramatically reduces the cost of both substrate and post synthesis process which could impact on the future mass manufacture of single walled carbon nanotubes.”
The new process also minimises the use of toxic materials and greenhouse gases in nanotube growth, giving further advantages to nanotechnology companies which wish to progress to bulk production.
Interestingly, not all newspaper is suitable, as the researchers found that carbon nanotubes can only be grown on non-inked paper produced with sizing made from kaolin, also known as china clay.
As the Rice University press release describes, “Sizing is a filler incorporated into paper to change its absorption, color and wear characteristics. The researchers found that kaolin facilitates the reduction of iron to nanoscale catalyst particles that minimize the aggregation of nanotubes in the final product.”
“Many substances including talc, calcium carbonate, and titanium dioxide can be used in sizing in papers which act as a filler to help with their levels of absorption and wear,” explains the study’s co-author Varun Shenoy Gangoli. “However, it was our observation that kaolin sizing, and not calcium carbonate sizing, showed us how the growth catalyst, which in our case was iron, is affected by the chemical nature of the substrate.”
But the need for paper produced with kaolin should not be a problem, as Brinson estimates that 60% of the world’s paper products incorporate kaolin. “It’s whiter and brighter than most,” he said. “A key to newsprint is that it is thin, cheap and light. We only need the surface; the bulk between the front and back surfaces doesn’t count for much.”
The team have now published their results in the Journal of Carbon Research, where they, “… report the successful use of newspaper as a substrate for the growth of single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) with intriguing results demonstrating that (a) the large surface area of newspaper stock allows for SWCNT growth and (b) only newspaper produced with kaolin clay sizing allowed for SWCNT growth.”
At present, nanotubes can be found in a wide range of products such as conductive films for touchscreen displays, energy creating wearable fabrics, flexible electronics and antennas for 5G networks. However, their unique properties of low-weight and high strength also make them ideal for non-hi-tech products, such as in plastics, coatings, rubber composites and more, if only the production costs could be reduced.
By developing a continuous flow system that employs a waste product with low preparation costs carbon nanotube producers have been given a big boost.
It is only unfortunate that the birth of industrial scale carbon nanotube production with old newspapers is happening at the same time as the death of print media.