Graphene & New Materials Tech Digest - March 2017

Peel for filtering water

Researchers from the University of Granada (UGR) and Mexico have developed a method to clean waste-water using fruit peel. The peel - such as orange or grapefruit peel - has its structure altered to become more porous through Instant Controlled Pressure Drop treatment (a food processing technique that can be used to dry fruits and vegetables, steam cereal, and extract oils) which increases its absorption properties. The resulting material can be used in fixed bed columns to filter out metals (copper) and organic materials from waste-water. 

New material from a worm

The Laboratory for Atomistic and Molecular Mechanics (LAMM) in the Department of Civil and Environmental Engineering (CEE), in collaboration with the Air Force Research Lab (AFRL) at Wright-Patterson Air Force Base, Ohio, USA, have developed a protein-based material that expands and contracts in reaction to changing pH levels and ion concentrations. The material was inspired by the jaws of the Nereis virens worm which can form and adapt differently to various environments.  The worm’s jaw’s high structural strength is attributable to the presence of metal in its molecular structure. The presence of metal in the jaw’s and the team’s material allows for the dynamic properties as well as the strength. The team see the ability of this material to morph in response to pH as having applications in soft robotics. 

Self-healing graphene

A team of scientists from the University of Hyderabad, India, have observed graphene’s ability to self-heal. The researchers were able to observe the healing at room temperature and without the presence of any external stimuli. The team subjected single layer graphene to tensile loading, after the loading the cracks began to heal no matter the length as long as the width of the crack opening was no larger than 0.3-0.5 nanometres. The observation holds out promise for creating a self-healing artificial skin for use in robotics. 

Self-propelling water

Scientists at Brandeis' Materials Research Science and Engineering Center (MRSEC) have developed a liquid material that is able to move of its own volition. The team took microtubules – a structural component of cells that can self-transform – from the brain of a cow and placed them in a watery solution with two other cell molecules – kinesin and adenosine triphosphate (ATP).  When the microtubules came parallel to each other a kinesin molecule inserted itself between them to act as a connector. The kinesin then used the ATP as a fuel source (ATP naturally delivers chemical energy within cells)  with the result that the top and bottom of the kinesin started moving in opposite directions. This caused the microtubules to move away from each other, breaking the structure. The microtubules then formed bonds with other kinesin molecules. Due to this cyclical process the liquid began to create swirling patterns, that researchers were further able to manipulate to move in a uniform direction - pushing the liquid forward. 

Foam can absorb oil

Scientists from Argonne National Laboratory and the University of Chicago have developed a material that can absorb up to 90 times its bodyweight in oil and then be wrung out and reused up to 100 times. The material is a commercially available polymeric foam which has been altered by  sequential infiltration synthesis (SIS) (a technique to infuse a polymer with inorganic material using sequential exposures to gaseous precursors) to embed nanoscale thin film technology – silane – that increases the absorbent properties of the material. The scientists are working on making the material suitable for large-scale production. 

Graphene-oxide membrane suitable for water desalination

University of Manchester scientists have developed graphene oxide membranes that are capable of advanced sieving of salts from liquids such as seawater. Previous research into graphene oxide membranes have face the problem of swelling when immersed in water hampering the filter’s ability to trap small salt particles. The Manchester team has developed a method to stop the graphene oxide membrane from swelling, meaning the pore size can be better controlled enabling targeted filtering. The small capillaries in graphene oxide membranes are capable of trapping small salt particles as the water flows through it. This would have use in filtering seawater to turn it into usable drinking water. 

Silicon nanosheet resilience increased

Researchers at the Technical University of Munich (TUM) have demonstrated a method of embedding silicon nanosheets into a polymer which protects the nanosheet from decay and oxidation, thus improving its stability and durability. Proving the concept, the team built a nanoscale photodetector using the polymer protected silicon nanosheet. The protection offered to the silicon nanosheet by the polymer casing could potentially enable use of silicon nanosheets in industrial processing, the scientists say, meaning they could be applicable for use in mass-produced microelectronics, photosensors and flexible displays. 

2D material with a band-gap

Hexagonal boron-carbon-nitrogen (h-BCN), a new 2D material made by an international group of researchers, was created by heating a molecule containing boron, carbon and nitrogen on an iridium substrate. The resultant structure was a corrugated 2D layer of h-BCN that was then tested using scanning tunnelling microscopy (creating high resolution molecular images), X-ray photoelectron spectroscopy and low energy electron diffraction. The material exhibited signs of having an electronic band-gap (a requirement for uses as a transistor material) which the researchers believe would make it a material better suited to electronic applications than graphene. 

Square lattice copper oxide

A team of researchers from institutes in Russia and Japan have proven the existence of 2D copper oxide, a 2D material with a square crystal lattice. Previously scientists had been able to form a hexagonal lattice copper oxide, but this is claimed by the scientists to be the first time a square lattice has been synthesised. The material was synthesised on a substrate of partially oxidised graphene which was then heated causing the copper atoms to group with the oxygen atoms to form the copper-oxide sheet. After further research the material is predicted to show antiferromagnetic properties which would be unusual in copper oxide materials. If the material does show this property it could potentially be used as a storage device material in electronics as it would be able to store one bit of data on only 12 atoms, according to the university’s press release.  

Silver film

University of Michigan researchers say they have created the thinnest (seven nanometre), smoothest layer of silver that can withstand air exposure for several months. The layer was the result of a combination of 94 percent silver with 6 percent aluminium to make a silver coating which acted as a waveguide the scientists said can carry the light 10 times further than other metal waveguides. The team also applied an anti-reflective coating leading to 92.4 percent transparency – making it suitable for use as a transparent conductor in touchscreens. 

Sea urchin bone scaffold

Scientists in China and America have developed a degradable bone scaffold material from sea urchins. The researchers used hydrothermal synthesis (a method to crystallise substances from high temperature liquid solutions at high pressure) to convert sea urchin spines into a biodegradable magnesium-substituted tricalcium phosphate scaffold which retained the spines’ original structure. The material can be cut and drilled into specified shapes and sizes. Tests on beagles and rabbits demonstrated bone cells and nutrients could flow through pores and help bone formation. After new bone growth, the scaffold degraded. The scientists hope that this material could be used as the basis for a lightweight material for repairing bones.   

Testing materials

Researchers at the National Institute of Standards and Technology (NIST) in the USA have developed a method of imbuing nanoscale damage sensing probes into lightweight materials made of silk and epoxy. The probe, a mechanophore, uses a dye known as rhodamine spirolactam (RS) that reacts by lighting up on application of force to materials embedded with it. Using a red laser and microscope the scientists could see where the material had small fractures and breaks. The probe could increase the speed of product testing and reduce the amount of time and material needed for the development of new composites according to NIST.


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