Flexible Nanoribbons of Crystalline Phosphorus are a World First – They could Revolutionize Electronics and Fast-Charging Battery Technology.


Phosphorous Nanoribbons 5cadc15c710a9
Credit: University College London

Tiny, individual, flexible ribbons of crystalline phosphorus have been made by UCL researchers in a world first, and they could revolutionise electronics and fast-charging battery technology.

Since the isolation of 2-dimensional phosphorene, which is the phosphorus equivalent of graphene, in 2014, more than 100  have predicted that new and exciting properties could emerge by producing narrow ‘ribbons’ of this material. These properties could be extremely valuable to a range of industries.

In a study published today in Nature, researchers from UCL, the University of Bristol, Virginia Commonwealth and University and École Polytechnique Fédérale de Lausanne, describe how they formed quantities of high-quality ribbons of phosphorene from crystals of black phosphorous and lithium ions.

“It’s the first time that individual phosphorene nanoribbons have been made. Exciting properties have been predicted and applications where phosphorene nanoribbons could play a transformative role are very wide-reaching,” said study author, Dr. Chris Howard (UCL Physics & Astronomy).

The ribbons form with a typical height of one , widths of 4-50 nm and are up to 75 μm long. This  is comparable to that of the cables spanning the Golden Gate Bridge’s two towers.

“By using advanced imaging methods, we’ve characterised the ribbons in great detail finding they are extremely flat, crystalline and unusually flexible. Most are only a single-layer of atoms thick but where the ribbon is formed of more than one layer of phosphorene, we have found seamless steps between 1-2-3-4 layers where the ribbon splits. This has not been seen before and each layer should have distinct electronic properties,” explained first author, Mitch Watts (UCL Physics & Astronomy).

While nanoribbons have been made from several materials such as graphene, the phosphorene nanoribbons produced here have a greater range of widths, heights, lengths and aspect ratios. Moreover, they can be produced at scale in a liquid that could then be used to apply them in volume at low cost for applications.

The team say that the predicted application areas include batteries, solar cells, thermoelectric devices for converting waste heat to electricity, photocatalysis, nanoelectronics and in quantum computing. What’s more, the emergence of exotic effects including novel magnetism, spin density waves and topological states have also been predicted.

Wonder material—individual 2-D phosphorene nanoribbons made for the first time

Credit: University College London

The nanoribbons are formed by mixing black phosphorus with lithium ions dissolved in  at -50 degrees C. After twenty-four hours, the ammonia is removed and replaced with an organic solvent which makes a solution of nanoribbons of mixed sizes.

“We were trying to make sheets of  so were very surprised to discover we’d made ribbons. For nanoribbons to have well defined properties, their widths must be uniform along their entire length, and we found this was exactly the case for our ribbons,” said Dr. Howard.

“At the same time as discovering the ribbons, our own tools for characterising their morphologies were rapidly evolving. The high-speed atomic force microscope that we built at the University of Bristol has the unique capabilities to map the nanoscale features of the ribbons over their macroscopic lengths,” explained co-author Dr. Loren Picco (VCU Physics).

Wonder material—individual 2-D phosphorene nanoribbons made for the first time

Credit: University College London

“We could also assess the range of lengths, widths and thicknesses produced in great detail by imaging many hundreds of ribbons over large areas.”

While continuing to study the fundamental properties of the nanoribbons, the team intends to also explore their use in energy storage, electronic transport and thermoelectric devices through new global collaborations and by working with expert teams across UCL.


Explore further

Small tweaks to nanoribbon edge structures can drastically alter heat conduction

Advertisements

Squid inspires camouflaging smart materials


squidcamox250Researchers from the Univ. of Bristol have shown it is possible to create artificial skin that can be transformed at the flick of a switch to mimic one of nature’s masters of camouflage, the squid.

The research team, from the university’s Dept. of Engineering Mathematics, have designed a smart materials system, inspired by biological chromatophores, which creates patterns that change and morph over time and mimic biological patterning.

The paper, published in Interface, describes the design, mathematical modeling, simulation and analysis of a dynamic biomimetic pattern generation system.

The researchers have shown the artificial skin, made from electroactive dielectric elastomer, a soft, compliant smart material, can effectively copy the action of biological chromatophores. Chromatophores are small pigmented cells embedded on cephalopods skin which can expand and contract and that work together to change skin color and texture.

The system achieves the dynamic pattern generation by using simple local rules in the artificial chromatophore cells, so that they can sense their surroundings and manipulate their change. By modelling sets of artificial chromatophores in linear arrays of cells, the researchers explored whether the system was capable of producing a variety of patterns.

The researchers found that it is possible to mimic complex dynamic patterning seen in real cephalopods such as the Passing Cloud display, which is when bands of color spread as waves across the skin. This visual effect acts to distract and divert predators.

Aaron Fishman, Visiting Fellow in Engineering Mathematics, said: “Our ultimate goal is to create artificial skin that can mimic fast acting active camouflage and be used for smart clothing such as cloaking suits and dynamic illuminated clothing.

“The cloaking suit could be used to blend into a variety of environments, such as in the wild. It could also be used for signaling purposes, for example search and rescue operations when people who are in danger need to stand out.”

The researchers investigated making bio-inspired artificial skin embedded with artificial chromatophores using thin sheets (five to ten millimeter) of dielectric elastomer, a soft, rubbery material that can be electrically controlled to be compliant.

In the future the team will consider changing the system to improve propagation control and to generate new patterns using other local rules. They will also carry out a more extensive analysis of the different pattern types that can be achieved under alternative system parameters, as well as developing the model to simulate patterns in two-dimensional array systems. The researchers expect this could produce more patterns, which could resemble those in the natural world.

Source: Univ. of Bristol

Designing antibiotics of the future


2-antibody enzyme1-articlex250Scientists have used computer simulations to show how bacteria are able to destroy antibiotics, a breakthrough which will help develop drugs which can effectively tackle infections in the future.

Researchers at the Univ. of Bristol focused on the role of enzymes in the bacteria, which split the structure of the antibiotic and stop it working, making the bacteria resistant.

The new findings, published in Chemical Communications, show that it’s possible to test how enzymes react to certain antibiotics.

It’s hoped this insight will help scientists to develop new antibiotics with a much lower risk of resistance, and to choose the best medicines for specific outbreaks.

2-antibody enzyme1-articlex250

A carbapenem molecule, a last resort antibiotic, enters the carbapenemase enzyme (blue arrow), where the crucial beta-lactam structure gets broken down. The ineffective molecule then leaves (orange arrow)

Using a Nobel Prize-winning technique called QM/MM—quantum mechanics/molecular mechanics simulations—the Bristol research team were able to gain a molecular-level insight into how enzymes called “beta-lactamases” react to antibiotics.

Researchers specifically want to understand the growing resistance to carbapenems, which are known as the “last resort” antibiotics for many bacterial infections and super bugs such as E. coli.

Resistance to carbapenems makes some bacterial infections untreatable, resulting in minor infections becoming very dangerous and potentially deadly.

The QM/MM simulations revealed that the most important step in the whole process is when the enzyme ‘spits out’ the broken down antibiotic. If this happens quickly, then the enzyme is able to go on chewing up antibiotics and the bacterium is resistant. If it happens slowly, then the enzyme gets “clogged up” and can’t break down any more antibiotics, so the bacterium is more likely to die.

The rate of this ‘spitting out’ depends on the height of the energy barrier for the reaction—if the barrier is high, it happens slowly; if it’s low, it happens much more quickly.

Professor Adrian Mulholland, from Bristol Univ.’s School of Chemistry, said: “We’ve shown that we can use computer simulations to identify which enzymes break down and spit out carbapenems quickly and those that do it only slowly.

“This means that these simulations can be used in future to test enzymes and predict and understand resistance. We hope that this will identify how they act against different drugs – a useful tool in developing new antibiotics and helping to choose which drugs might be best for treating a particular outbreak.”

Source: Univ. of Bristol