Monthly Archives: April 2018

Perovskite Solar Cells One Giant Step Closer To The Market

Harnessing energy from the sun, which emits immensely powerful energy from the center of the solar system, is one of the key targets for achieving a sustainable energy supplyLight energy can be converted directly into electricity using electrical devices called solar cells. To date, most solar cells are made of silicon, a material that is very good at absorbing light. But silicon panels are expensive to produce.

Scientists have been working on an alternative, made from perovskite structures. True perovskite, a mineral found in the earth, is composed of calcium, titanium and oxygen in a specific molecular arrangement. Materials with that same crystal structure are called perovskite structuresPerovskite structures work well as the light-harvesting active layer of a solar cell because they absorb light efficiently but are much cheaper than silicon. They can also be integrated into devices using relatively simple equipment. For instance, they can be dissolved in solvent and spray coated directly onto the substrate.

Materials made from perovskite structures could potentially revolutionize solar cell devices, but they have a severe drawback: they are often very unstable, deteriorating on exposure to heat. This has hindered their commercial potential. The Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), led by Prof. Yabing Qi, has developed devices using a new perovskite material that is stable, efficient and relatively cheap to produce, paving the way for their use in the solar cells of tomorrow. This material has several key features:

  • First, it is completely inorganic – an important shift, because organic components are usually not thermostable and degrade under heat. Since solar cells can get very hot in the sun, heat stability is crucial. By replacing the organic parts with inorganic materials, the researchers made the perovskite solar cells much more stable..  “The solar cells are almost unchanged after exposure to light for 300 hours,” says Dr. Zonghao Liu, an author on the paper.
  • Second feature: Inorganic perovskite solar cells tend to have lower light absorption than organic-inorganic hybrids, however, but the OIST researchers doped their new cells with manganese in order to improve their performance. Manganese changes the crystal structure of the material, boosting its light harvesting capacity.  “Just like when you add salt to a dish to change its flavor, when we add manganese, it changes the properties of the solar cell,” says Liu.
  • Thirdly, in these solar cells, the electrodes that transport current between the solar cells and external wires are made of carbon, rather than of the usual gold. Such electrodes are significantly cheaper and easier to produce, in part because they can be printed directly onto the solar cells. Fabricating gold electrodes, on the other hand, requires high temperatures and specialist equipment such as a vacuum chamber.

The findings are published in Advanced Energy Materials. Postdoctoral scholars Dr. Jia Liang and Dr. Zonghao Liu made major contributions to this work.


How To Deliver Drug Deep In The Brain

By learning how rabies virus travels in the brain, Anti-Parkinson’s drug can be delivered deep in the brain where currently the drugs are not able to reachRabies virus has the capability to trick the nervous system and cross the blood brain barrier. This trick could be used for drug design. Glycoprotein 29 present on the rabies virus is attached to a nanoparticle stuffed full of deferoxamine ( Anti-Parkinson’s medication) and injected into the brain to trick the brain.

Rabies virus may have some tricks to bypass the blood brain barrier, this trick can be used to treat disease that require drugs to effectively cross the blood brain barrier, finds a new study.

The researchers can now exploit rabies viruses machinery to deliver a Parkinson’s disease medication directly to the brain. Upon injection the nanoparticles grab excess iron and relieve symptoms. While the common cause of Parkinson’s disease is unknown, it has been proved that accumulation of iron in neurons is one of the commonest features of Parkinson’s disease.

Deferoxamine is a metal-grabbing compound and sop up the excess iron in patients. But a large quantity of this drug needs to reach the brain in order for them work.
To usher deferoxamine into the brain, the researchers Yan-Zhong Chang, Xin Lou, Guangjun Nie took advantage of a key part of the rabies virusGlycoprotein 29.
When they injected this iron-grabbing nanoparticles into mouse models of Parkinson’s disease, the iron levels dropped and this reduced brain damage caused by Parkinson’s disease.

The findings of this study is published in the ACS Nano journal.


Squeeze And Get More Power Out Of Solar Cells

Physicists at the University of Warwick have published new research in the Journal Science  that could literally squeeze more power out of solar cells by physically deforming each of the crystals in the semiconductors used by photovoltaic cells. The paper entitled the “Flexo-Photovoltaic Effect” was written by Professor Marin Alexe, Ming-Min Yang, and Dong Jik Kim who are all based in the University of Warwick’s Department of Physics.

The Warwick researchers looked at the physical constraints on the current design of most commercial solar cells which place an absolute limit on their efficiency. Most commercial solar cells are formed of two layers creating at their boundary a junction between two kinds of semiconductors, p-type with positive charge carriers (holes which can be filled by electrons) and n-type with negative charge carriers (electrons). When light is absorbed, the junction of the two semiconductors sustains an internal field splitting the photo-excited carriers in opposite directions, generating a current and voltage across the junction. Without such junctions the energy cannot be harvested and the photo-exited carriers will simply quickly recombine eliminating any electrical charge. That junction between the two semiconductors is fundamental to getting power out of such a solar cell but it comes with an efficiency limit. This Shockley-Queisser Limit means that of all the power contained in sunlight falling on an ideal solar cell in ideal conditions only a maximum of 33.7% can ever be turned into electricity.

There is however another way that some materials can collect charges produced by the photons of the sun or from elsewhere. The bulk photovoltaic effect occurs in certain semiconductors and insulators where their lack of perfect symmetry around their central point (their non-centrosymmetric structure) allows generation of voltage that can be actually larger than the band gap of that material. Unfortunately the materials that are known to exhibit the anomalous photovoltaic effect have very low power generation efficiencies, and are never used in practical power-generation systems. The Warwick team wondered if it was possible to take the semiconductors that are effective in commercial solar cells and manipulate or push them in some way so that they too could be forced into a non-centrosymmetric structure and possibly therefore also benefit from the bulk photovoltaic effect.

Extending the range of materials that can benefit from the bulk photovoltaic effect has several advantages: it is not necessary to form any kind of junction; any semiconductor with better light absorption can be selected for solar cells, and finally, the ultimate thermodynamic limit of the power conversion efficiency, so-called Shockley-Queisser Limit, can be overcome“,  explains Professor Marin Alexe  (University of Warwick).


Nanoscale Transistor

Flexible televisions
, tablets and phones as well as ‘truly wearable’ smart tech are a step closer thanks to a nanoscale transistor created by researchers at The University of Manchester and Shandong University in China. The international team has developed an ultrafast, nanoscale transistor – known as a thin film transistor, or TFT, – made out of an oxide semiconductor. The TFT is the first oxide-semiconductor based transistor that is capable of operating at a benchmark speed of 1 GHz. This could make the next generation electronic gadgets even faster, brighter and more flexible than ever before. A TFT is a type of transistor usually used in a liquid crystal display (LCD). These can be found in most modern gadgets with LCD screens such as smart phones, tablets and high-definition televisions.

How do they work? LCD features a TFT behind each individual pixel and they act as individual switches that allow the pixels to change state rapidly, making them turn on and off much more quickly. But most current TFTs are silicon-based which are opaque, rigid and expensive in comparison to the oxide semiconductor family of transistors which the team from the UK and China are developing. Whilst oxide TFTs will improve picture on LCD displays, it is their flexibility that is even more impressive.

Aimin Song, Professor of Nanoelectronics in the School of Electrical & Electronic Engineering, The University of Manchester, explains:

TVs can already be made extremely thin and bright. Our work may help make TV more mechanically flexible and even cheaper to produce. “But, perhaps even more importantly, our GHz transistors may enable medium or even high performance flexible electronic circuits, such as truly wearable electronics. “Wearable electronics requires flexibility and in many cases transparency, too. This would be the perfect application for our research. “Plus, there is a trend in developing smart homes, smart hospitals and smart cities – in all of which oxide semiconductor TFTs will play a key role.

Oxide-based technology has seen rapid development when compared to its silicon counterpart which is increasingly close to some fundamental limitations. Prof Song says there has been fast progress in oxide-semiconductors in recent years and extensive efforts have been made in order to improve the speed of oxide-semiconductor-based TFTs. So much so some oxide-based technology has already started replacing amorphous silicon in some gadgets. Prof Song thinks these latest developments have brought commercialisation much closer.


How Solar Cells Absorb 20 % More Sunlight

Trapping light with an optical version of a whispering gallery, researchers at the National Institute of Standards and Technology (NIST) have developed a nanoscale coating for solar cells that enables them to absorb about 20 percent more sunlight than uncoated devices. The coating, applied with a technique that could be incorporated into manufacturing, opens a new path for developing low-cost, high-efficiency solar cells with abundant, renewable and environmentally friendly materials.

Illustration shows the nanoresonator coating, consisting of thousands of tiny glass beads, deposited on solar cells. The coating enhances both the absorption of sunlight and the amount of current produced by the solar cells

The coating consists of thousands of tiny glass beads, only about one-hundredth the width of a human hair. When sunlight hits the coating, the light waves are steered around the nanoscale bead, similar to the way sound waves travel around a curved wall such as the dome in St. Paul’s Cathedral in London. At such curved structures, known as acoustic whispering galleries, a person standing near one part of the wall easily hears a faint sound originating at any other part of the wall.

Using a laser as a light source to excite individual nanoresonators in the coating, the team found that the coated solar cells absorbed, on average, 20 percent more visible light than bare cells. The measurements also revealed that the coated cells produced about 20 percent more current.


How To Turn On Cancer-Killing Immune Cells

A remote command could one day send immune cells on a rampage against a malignant tumor. The ability to mobilize, from outside the body, targeted cancer immunotherapy inside the body has taken a step closer to becoming reality. Bioengineers at the Georgia Institute of Technology have installed a heat-sensitive switch into T-cells that can activate the T-cells when heat turns the switch on. The method, tested in mice and published in a new study, is locally targeted and could someday help turn immunotherapy into a precision instrument in the fight against cancer.

Immunotherapy has made headlines with startling high-profile successes like saving former U.S. President Jimmy Carter from brain cancer. But the treatment, which activates the body’s own immune system against cancer and other diseases, has also, unfortunately, proved to be hit-or-miss.

In patients where radiation and traditional chemotherapies have failed, this is where T-cell therapies have shined, but the therapy is still new,” said principal investigator Gabe Kwong. “This study is a step toward making it even more effective.”

Cancer is notoriously wily, and when T-cells crawl into a tumor, the tumor tends to switch off the T-cellscancer-killing abilities. Researchers have been working to switch them back on.

Kwong’s remote control has done this in the lab, while also boosting T-cell activity. In the study, Kwong’s team successfully put their remote-control method through initial tests in mice with implanted tumors (so-called tumor phantoms, specially designed for certain experiments).


Adaptive Materials

Engineers at the U.S. Army Research Laboratory (ARL) and the University of Maryland have developed a technique that causes a composite material to become stiffer and stronger on-demand when exposed to ultraviolet light. This on-demand control of composite behavior could enable a variety of new capabilities for future Army rotorcraft design, performance and maintenance.

ARL‘s Dr. Frank Gardea, a research engineer, said the focus of the research was on controlling how molecules interact with each other. He said the aim was to “have them interact in such a way that changes at a small size, or nanoscale, could lead to observed changes at a larger size, or macroscale.”

Dr. Bryan Glaz, chief scientist of ARL‘s Vehicle Technology Directorate said “an important motivation for this work is the desire to engineer new structures, starting from the nanoscale, to enable advanced rotorcraft concepts that have been proposed in the past, but were infeasible due to limitations in current composites. One of the most important capabilities envisioned by these concepts is a significantly reduced maintenance burden due to compromises we make to fly at high speeds”, he said. The reduced scheduled maintenance of future Army aviation platforms is an important technological driver for future operating concepts.

Army researchers imagine a rotorcraft concept, which represents reactive reinforcements that when exposed to ultraviolet light will increase the mechanical behavior on-demand. The engineers said control of mechanical behavior could potentially lead to increased aerodynamic stability in rotorcraft structures.

The enhanced mechanical properties with potentially low weight penalties, enabled by the new technique, could lead to nanocomposite based structures that would enable rotorcraft concepts that we cannot build today,” Glaz said.

The joint work, recently published in Advanced Materials Interfaces (DOI: 10.1002/admi.201800038), shows that these composite materials could become 93-percent stiffer and 35-percent stronger after a five minute exposure to ultraviolet light. The technique consists of attaching ultraviolet light reactive molecules to reinforcing agents like carbon nanotubes. These reactive reinforcing agents are then embedded in a polymer. Upon ultraviolet light exposure, a chemical reaction occurs such that the interaction between the reinforcing agents and the polymer increases, thus making the material stiffer and stronger.


How To End Malaria

Gene-editing technologies that alter mosquitoesDNA could prove critical in the fight against malaria, Bill Gates said on Wednesday, and ethical concerns should not block progress in such gene-modifying research.

Speaking at the Malaria Forum conference in London, the billionaire Microsoft co-founder and philanthropist said that while gene editing raises “legitimate questions”, that should not jeopardize exploration of tools such as CRISPR gene editing and so-called “gene drive” technologies.

I’m very energized about the potential of gene drive. (It’s) the kind of breakthrough we need to support,” Gates said. “It may prove critical here.” 

Gene drive technologies alter DNA and drive self-sustaining genetic changes through multiple generations by overriding normal biological processes. CRISPR technology enables scientists to find and modify or replace virtually any gene. The techniques are being explored across science – from human medicine to livestock– and crop-breeding. In mosquitoes that transmit malaria, genetic alterations can be used to induce infertility to reduce populations, or alter the insects’ ability to carry and pass on the malaria parasite. 

The technologies can be extremely powerful, but they are also controversial, since such genetically engineered organisms released into the environment could have an unknown and irreversible impact on the ecosystem. Asked in a interview with Reuters about that controversy, Gates said there were understandable concerns about safety and efficacy that would need to be addressed in research and trials. But he countered: “Malaria itself is quite controversial – it kills about 400,000 kids a year. So we’re definitely not on the side of malaria.”

He also noted that at their summit in January, leaders of the African Union endorsed gene drive research as part of the fight against a disease that continues to kill their people.


Tool Speeds Up Manufacturing Of Powered Wearable

People could soon power items such as their mobile phones or personal health equipment by simply using their daily movements, thanks to a new research tool that could be used by manufacturers.

In a new paper published by Nano Energy, experts from the Advanced Technology Institute (ATI) at the University of Surrey (UK) detail a new  methodology that allows designers of smart-wearables to better understand and predict how their products would perform once manufactured and in use.

The technology is centred on materials that become electrically charged after they come into contact with each other, known as triboelectric materials – for example, a comb through hair can create an electrical charge. Triboelectric Nanogenerators (TENGs), use this static charge to harvest energy from movement through a process called electrostatic induction. Over the years, a variety of TENGs have been designed which can convert almost any type of movement into electricity. The University of Surrey’s tool gives manufacturers an accurate understanding of the output power their design would create once produced.

This follows the news earlier this year of the ATI announcing the creation of its £4million state-of-the-art Nano-Manufacturing Hub. The new facility will produce plastic nanoscale electronics for wearable sensors, electronic tags and other electronic devices.

Ishara Dharmasena, lead scientist on this project from the University of Surrey, said: “The future global energy mix will depend on renewable energy sources such as solar power, wind, motion, vibrations and tidal. TENGs are a leading technology to capture and convert motion energy into electricity, extremely useful in small scale energy harvesting applications. Our work will, for the first time, provide universal guidance to develop, compare and improve various TENG designs. We expect this technology in household and industrial electronic products, catering to a new generation of mobile and autonomous energy requirements.”


Plastic-Eating Enzyme

Scientists have engineered an enzyme which can digest some of our most commonly polluting plastics, providing a potential solution to one of the world’s biggest environmental problems. The discovery could result in a recycling solution for millions of tonnes of plastic bottles, made of polyethylene terephthalate, or PET, which currently persists for hundreds of years in the environment. The research was led by teams at the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory (NREL) and is published in Proceedings of the National Academy of Sciences (PNAS).

 Professor John McGeehan at the University of Portsmouth and Dr Gregg Beckham at NREL solved the crystal structure of PETase—a recently discovered enzyme that digests PET— and used this 3D information to understand how it works. During this study, they inadvertently engineered an enzyme that is even better at degrading the plastic than the one that evolved in nature. The researchers are now working on improving the enzyme further to allow it to be used industrially to break down plastics in a fraction of the time.


Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans, or washed up on once pristine beaches all over the world. “We can all play a significant part in dealing with the plastic problem, but the scientific community who ultimately created these ‘wonder-materials’, must now use all the technology at their disposal to develop real solutions,” said Professor McGeehan, Director of the Institute of Biological and Biomedical Sciences in the School of Biological Sciences at Portsmouth,