Nano News: 03/19/15

Finding an affordable way to use graphene is the key to its success

Graphene is a remarkably strong material given it’s only a single carbon-atom thick. But finding ways to do something with it – that’s also affordable too – have always been a challenge. Scientists have long been excited about the potential for graphene to revolutionise technologies, and even consider it a technology itself. Graphene is the best known conductor of electricity and heat. It is also the thinnest surface and represents the next generation wonder material for everyday applications in electronics. The 2010 Nobel Prize in Physics was awarded to Konstantin Novoselov and Andre Geim for their pioneering work on the electronic properties of graphene. There followed much hype in the science world with concepts to revolutionise electronic displays and circuitry. These two areas form the basis of many technologies so the impact of graphene was extensive.

Graphene powder can be manufactured. (Image: Dr Mohammad Choucair) How to make graphene For such applications, graphene had to be industrially produced as large thin films on a supporting material. This highlighted two avenues where graphene could be directed: as an electronic component; or as the chief technology. But these directions were rather narrow, as they only focused on potential commercial exploits involving the electronics industries. Exaggerated demand for graphene to be commercialised quickly outpaced the overlapping challenges concerning the processing of nanomaterials. As such, despite all the excitement, graphene has not yet found widespread use because it is chemically difficult to process. Let chemistry find a use In 2009 I developed the first technique to chemically produce graphene in industrial scale quantities ("Gram-scale production of graphene based on solvothermal synthesis and sonication"). It was clear chemistry had a key role to play in the future use of the material. We could now create gram and kilogram quantities of the graphene sheets atom by atom using chemical reactions. My work has led to many attempts by researchers world-wide to find more viable techniques to produce graphene. Each attempt reaching out to be inventive, quirky, or more innovative over the prior art. We found an avenue where expensive apparatus was no longer required and graphene powder could be transported with an extended shelf life. This is now a common goal among researchers. This development overcame a key tenant which was overlooked during the physics era: graphene is essentially a material which is all surface. The interface at a surface is where exciting things occur and where chemists operate. To do something useful with a surface you need a lot of it, and we now had a lot of graphene. The options to obtain a lot of graphene material are simple. Either start by digging graphite out of the ground from natural deposits, or you make it chemically in the lab. Chemically produced graphene offers a relatively large amount of surface to perform exciting chemical reactions. This is equivalent to having a nice smooth football field to move a football around on. Non-sticky stuff this graphene But changing the chemical structure of graphene while retaining its superb physical properties is incredibly difficult. This is due to a paradox that allows for the very existence of graphene: the remarkable stability of the graphene surface. Molecules like metals and gases required for energy storage simply do not stick to graphene. Imagine if everything you placed on your table simply kept falling off – the table would not be of much use. Attempts to change the chemical nature of graphene focused on attaching a small number of molecules. This has limited the utilisation of graphene in nanotechnologies, as the next generation of batteries, solar energy films and fuel cells involve more complex chemical reactions. Applications that would see graphene used in these technologies would require molecules with versatile chemistry stuck to graphene. Get boron onboard Together with my colleagues, we have created a new graphene hybrid material by directly attaching boron clusters to the graphene surface ("Carborane functionalization of the aromatic network in chemically-synthesized graphene"). The trick was to use the stable conjugated network in graphene to trap a highly reactive boron cluster. Attaching these kinds of chemicals unlocks entirely new and interesting material properties, such as improved functionality and hierarchically organised responsiveness. For example, the material may now soon be used to interact with biological molecules, harvest sunlight for use in solar cells, and anchor metals for efficient hydrogen storage. The work will provide an insight into how graphene materials retain their function after large scale processing. We can now perform exact chemical reactions on graphene that will ultimately translate into more reliable and affordable graphene-based technologies. We have pushed the boundaries at the nanoscale and started to find new ways to create materials from the ground up with fascinating properties that can be commercialised.

Quantum computing: one step closer with defect-free logic gate

What does hair styling have in common with quantum computing? The braiding pattern has inspired scientists as a potential new approach to quantum calculation. The idea is to rely on a network of intersecting chains, or nanowires, containing two-dimensional quasi-particles. The way these quasi-particles evolve in space time produces a braid-like pattern. These braids could then be used as the logic gate that provides the logical function required for calculations in computers. Due to their tight assembly, such braids are much more difficult to destabilise and less error-prone. Yet, local defects can still arise along nanowires. In a study published in ("Fermionic and Majorana bound states in hybrid nanowires with non-uniform spin-orbit interaction"), Jelena Klinovaja from the University of Basel, and Daniel Loss from Harvard University, Cambridge, MA, USA, identify the potential sources of computer errors arising from these defects. Scientists have now created a 2D network of intersecting nanowires within which quasi particles create braided patterns in space time; these are called Majorana Bound States, or MBSs. In this context, the electrons' inner degree of freedom, called spin, interacts with their own movement, leading to spin-orbit interaction (SOI). The trouble is that the SOI direction is not uniform in such braided networks, resulting in local defects along nanowires and at nanowire junctions. The authors therefore focus on how such defects arise in relation to the SOI direction. They show that the nanowires, in which the SOI changes direction, host novel states referred to as Fermionic Bound States (FBSs). These FBSs, the study shows, occur simultaneously with Majorana fermions, albeit at different locations in the network. FBSs could therefore destabilise quantum information units, or qubits, and accelerate their loss of coherence, thus becoming a source of errors in quantum computing. The authors believe that such new knowledge of the characteristics of FBSs can help identify the best remedy to avoid their negative effects on MBSs.

Breast implants could become safer thanks to nanopatternd surface

Scientists at The University of Manchester have created an enhanced surface for silicone breast implants which could reduce complications and make them less likely to be rejected by the body. In the US alone almost 400,000 cosmetic breast augmentations and reconstructions are carried out each year, and the number is growing. Some of these cases are for reconstruction after surgery for breast cancer and can have important psychological benefits. However, around one in five people who has a breast implant suffers from capsular contracture where scar tissue forms and can shrink after the surgery – causing pain, deformity and the need for further surgery. Fluid from the body can also build up, (known as a seroma) and the scar tissue can also cause leaks in the implants. Capsular contracture is caused by the body resisting the implantation of a foreign object. It has previously been shown that rougher surfaces (also known as textured surfaces) reduce the amount of scar tissue formed around breast implants, but the Manchester scientists felt that they could improve this by creating a pattern which mimicked body’s own surface, such as the basal layer of the skin, providing a better environment for the cells to grow on. “The surfaces of breast implants in use today have relatively large features on their surface, which have no discernible correlation with biological features required for cells to interact with. Importantly, the micro environment created by the features of a breast implant is critical for breast tissue cells to adhere to that surface and grow on,” said Dr Ardeshir Bayat, from the University’s Institute of Inflammation and Repair, who led the study (, "Development and functional evaluation of biomimetic silicone surfaces with hierarchical micro/nano-topographical features demonstrates favourable in vitro foreign body response of breast-derived fibroblasts"). “Compared to the size of the cells, these bumps on existing implants are so large that they’re effectively a smooth cliff face compared to the dimensions required for the cell to interact with. “Our approach was to create a novel surface which mimics the basal layer of the skin, which the body’s cells are more likely to recognise and interact with favourably.” The tests were carried out in the lab over a period of one week – a critical early period after surgery, and while the researchers acknowledge that much more work is yet to be done, the new surface reduced the foreign body reaction of the cells when compared to the smooth and larger textured surfaces currently available on the market. These findings suggest that it this unique surface may help to reduce the likelihood of adverse inflammation and subsequent scarring in the form of so-called breast capsular fibrosis. Dr Bayat added: “Some of the surfaces seen on implants today were designed originally in the 60s and 70s and therefore there is an unmet need for delivering the next generation of biomimetic breast implant surfaces. “The original designers found that surface features so-called ’bumps’ on the existing surfaces had an adverse effect, but what we did was to reduce the size, dimension and appearance of these bumps down from the size of say, a hill, to that of a pebble. “This makes interaction at the cellular level much better. Nevertheless, we need to do a lot more work to bring this to the clinic, and the increasing numbers of women having these operations means, that it is an important process to go through.”