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Using electronics to solve common biological problems

Posted By Graphene Council, The Graphene Council, Wednesday, December 4, 2019
Researchers from multiple disciplines are working together at KAUST to develop bioelectronics that can detect diseases, treat cancers and track marine animals; they may even discover the next generation of computing systems.

Cancer-killing magnets

Jurgen Kosel is an electrical engineer who loves to play with magnets. His research group has developed a technique to fabricate unique magnetic iron-oxide nanowires that can kill cancer cells1.

“Certain kinds of iron-based magnetic nanoparticles were approved many years ago by the U.S. Food and Drug Administration for use inside the human body. They are regularly used as contrast agents in magnetic resonance imaging and as nutritional supplements for people with iron deficiency,” says Kosel.

The magnetic nanoparticles currently in use are spherical in shape. Kosel and his team developed wire-shaped magnetic nanoparticles that can be rotated like a compass needle, creating a pore in cancer cell membranes that induces natural cell death. These cancer-killing nanowires can be made even more effective when coated with an anti-cancer drug or heated with a laser. They are "eaten" by cancer cells, and once released inside, they can wreak havoc.

Kosel has been working closely with cell biologist Jasmeen Merzaban, and more recently, with organic chemist Niveen Khashab to "functionalize" the surfaces of his magnetic nanowires to ensure the body’s immune system does not treat them as foreign. They are also working on preventing the wires from sticking together and on targeting cancer cells more specifically by coating them with antibodies that recognize specific antigens on their cell membranes.

Kosel has also worked with electrical engineer Muhammad Hussain to use magnets for improving the safety of cardiac catheters. They have developed a flexible magnetic sensor that is sensitive enough to detect the Earth’s magnetic field. When these sensors are placed on the tip of a cardiac catheter, for example, clinicians can detect its orientation inside blood vessels. This enables them to direct it where it is needed in order to insert a stent, for example, to relieve blockage in a heart artery. This reduces the need for prolonged doses of X-rays and contrast dyes during procedures like coronary angioplasty.

Disease detection

“Over the past 50 years, the 500-billion-dollar semiconductor industry has mainly focused on two applications: computing and communications,” says KAUST electrical engineer, Khaled Salama. “But this technology holds a lot of promise for other areas, including medical research, as people are living longer and needing more care. We need a paradigm shift to leverage some of the technologies we’ve developed for use in this area.”

Salama has developed a sensor that can detect "C-reactive proteins," a biomarker of cardiovascular disease2. He’s done this by functionalizing electrodes with nanomaterials and gold nanoparticles to improve their sensitivity. The electrodes give a signal that is proportional to the amount of C-reactive protein in a blood sample. His group developed a unique process that 3D prints the microfluidic channels that deliver samples to the sensor for biological detection.

Elsewhere at KAUST, Sahika Inal is developing a device that can make life easier for diabetics.

Inal comes from a textile manufacturing background, but her studies on the electrical properties of polymers, which are biocompatible, have led her down the route of bioelectronics. 

Her team has developed inkjet-printed, disposable, polymer-based sensors that can measure glucose levels in saliva3. “We inkjet-print conducting polymers. The biological ink contains the enzymes used for glucose sensing, an encapsulation layer that protects the enzymes, a layer that only allows glucose penetration and an insulating layer to protect the electronics,” she explains. “And then you have a paper-based sensor within a few minutes!”

Inal is also developing other biochemical sensors that can generate their own energy from compounds already present in the body to power implantable devices, such as cardiac pacemakers.

“To conduct impactful bioelectronics work, I need to be in an environment where there are biologists, the people who can give me feedback on what I develop,” says Inal.

Bio-inspired computers and animal tracking
Bioelectronics not only encompass electronic devices designed to solve biological problems, they are also electronic solutions inspired by biology.

Khaled Salama is interested in a relatively new type of bio-inspired device called a "memristor"4. These are electrical components inspired by the neural networks and synapses of the brain. Researchers hope they will lead to the next generation of computing systems and that they will be better equipped to very rapidly process huge amounts of data. Salama has developed an approach that improves their computational efficiency while reducing power consumption in these typically energy-intensive devices.

Sensing data in harsh marine environments can be particularly challenging, says Kosel. Researchers have often resorted to electronic tags placed on large marine animals to track their movements. They also use electronic sensors to conduct flow, salinity, pressure and temperature measurements in the sea. Smaller, lighter, less power-hungry tags are needed to resist corrosion, and withstand biofouling, a bacterial crust that forms on almost anything that stays in the sea for too long.

Kosel’s solution was to develop graphene sensors fabricated with a single-step laser-printing technique for marine applications. These laser-induced graphene sensors are resistant to corrosion and can survive high temperatures. They are very light and flexible, making them suitable for attaching to smaller marine animals. They also developed a technique5 that involves conducting high-frequency measurements that allow them to withstand the effects of an accumulating biofouling layer.

The group have started a conference, which will be held annually at KAUST. Last year, among the many esteemed attendees was George Malliaras, a Prince Philip Professor of Technology at the University of Cambridge. Malliaras praised the university for its world-class instrumentation, access to excellent collaborations within the campus and mechanisms to collaborate with people abroad. He says, "Taken together, these attributes have made KAUST very successful at addressing some of the most important problems that humanity faces today." 

Tags:  Bioelectronics  George Malliaras  Graphene  Healthcare  Jasmeen Merzaban  Jurgen Kosel  Khaled Salama  King Abdullah University of Science and Technology  Muhammad Hussain  nanoparticles  Niveen Khashab  Sahika Inal  semiconductor  University of Cambridge 

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Smog-eating graphene composite reduces atmospheric pollution

Posted By Graphene Council, The Graphene Council, Wednesday, December 4, 2019
Graphene Flagship partners the University of Bologna, Politecnico di Milano, CNR, NEST, Italcementi HeidelbergCement Group, the Israel Institute of Technology, Eindhoven University of Technology, and the University of Cambridge have developed a graphene-titania photocatalyst that degrades up to 70% more atmospheric nitrogen oxides (NOx) than standard titania nanoparticles in tests on real pollutants.

Atmospheric pollution is a growing problem, particularly in urban areas and in less developed countries. According to the World Health Organization, one out of every nine deaths can be attributed to diseases caused by air pollution. Organic pollutants, such as nitrogen oxides and volatile compounds, are the main cause of this, and they are mostly emitted by vehicle exhausts and industry.

To address the problem, researchers are continually on the hunt for new ways to remove more pollutants from the atmosphere, and photocatalysts such as titania are a great way to do this. When titania is exposed to sunlight, it degrades nitrogen oxides – which are very harmful to human health – and volatile organic compounds present at the surface, oxidising them into inert or harmless products.

Now, the Graphene Flagship team working on photocatalytic coatings, coordinated by Italcementi, HeidelbergCement Group, Italy, developed a new graphene-titania composite with significantly more powerful photodegradation properties than bare titania. "We answered the Flagship's call and decided to couple graphene to the most-used photocatalyst, titania, to boost the photocatalytic action," comments Marco Goisis, the research coordinator at Italcementi. "Photocatalysis is one of the most powerful ways we have to depollute the environment, because the process does not consume the photocatalysts. It is a reaction activated by solar light," he continues.

By performing liquid-phase exfoliation of graphite – a process that creates graphene – in the presence of titania nanoparticles, using only water and atmospheric pressure, they created a new graphene-titania nanocomposite that can be coated on the surface of materials to passively remove pollutants from the air. If the coating is applied to concrete on the street or on the walls of buildings, the harmless photodegradation products could be washed away by rain or wind, or manually cleaned off.

To measure the photodegradation effects, the team tested the new photocatalyst against NOx and recorded a sound improvement in photocatalytic degradation of nitrogen oxides compared to standard titania. They also used rhodamine B as a model for volatile organic pollutants, as its molecular structure closely resembles those of pollutants emitted by vehicles, industry and agriculture. They found that 40% more rhodamine B was degraded by the graphene-titania composite than by titania alone, in water under UV irradiation. "Coupling graphene to titania gave us excellent results in powder form – and it could be applied to different materials, of which concrete is a good example for the widespread use, helping us to achieve a healthier environment. It is low-maintenance and environmentally friendly, as it just requires the sun's energy and no other input," Goisis says. But there are challenges to be addressed before this can be used on a commercial scale. Cheaper methods to mass-produce graphene are needed. Interactions between the catalyst and the host material need to be deepened as well as studies into the long-term stability of the photocatalyst in the outdoor environment.

Ultrafast transient absorption spectroscopy measurements revealed an electron transfer process from titania to the graphene flakes, decreasing the charge recombination rate and increasing the efficiency of reactive species photoproduction – meaning more pollutant molecules could be degraded.

Xinliang Feng, Graphene Flagship Work Package Leader for Functional Foams and Coatings, explains: "Photocatalysis in a cementitious matrix, applied to buildings, could have a large effect to decrease air pollution by reducing NOx and enabling self-cleaning of the surfaces – the so-called "smog-eating" effect. Graphene could help to improve the photocatalytic behaviour of catalysts like titania and enhance the mechanical properties of cement. In this publication, Graphene Flagship partners have prepared a graphene-titania composite via a one-step procedure to widen and improve the ground-breaking invention of "smog-eating" cement. The prepared composite showed enhanced photocatalytic activity, degrading up to 40% more pollutants than pristine titania in the model study, and up to 70% more NOx with a similar procedure. Moreover, the mechanism underlying this improvement was briefly studied using ultrafast transient absorption spectroscopy."

Enrico Borgarello, Global Product Innovation Director at Italcementi, part of the HeidelbergCement Group, one of the world's largest producers of cement, comments: "Integrating graphene into titania to create a new nanocomposite was a success. The nanocomposite showed a strong improvement in the photocatalytic degradation of atmospheric NOx boosting the action of titania. This is a very significant result, and we look forward to the implementation of the photocatalytic nanocomposite for a better quality of air in the near future."

The reasons to incorporate graphene into concrete do not stop here. Italcementi is also working on another product – an electrically conductive graphene concrete composite, which was showcased at Mobile World Congress in February this year. When included as a layer in flooring, it could release heat when an electrical current is passed through it. Goisis comments: "You could heat your room, or the pavement, without using water from a tank or boiler. This opens the door to innovation for the smart cities of the future – particularly to self-sensing concrete," which could detect stress or strain in concrete structures and monitor for structural defects, providing warning signals if the structural integrity is close to failure.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel, adds: "An ever-increasing number of companies are now partners, or associate members of the Graphene Flagship, since they recognize the potential for new and improved technologies. In this work, Italcementi, leader in Italy in the field of building materials, demonstrated a clear application of graphene for the degradation of environment pollutants. This can not only have commercial benefits, but, most importantly, benefit of society by resulting in a cleaner and healthier environment"

Tags:  Andrea C. Ferrari  Eindhoven University of Technology  Enrico Borgarello  Graphene  Graphene Flagship  Healthcare  HeidelbergCement Group  Israel Institute of Technology  Italcementi  nanoparticles  University of Bologna  University of Cambridge  Xinliang Feng 

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Microcavities save organic semiconductors from going dark

Posted By Graphene Council, The Graphene Council, Monday, December 2, 2019
More and more electronics manufacturers are favoring organic LED displays for smartphones, TVs and computers because they are brighter and offer a greater color range.

The organic semiconductors that drive these devices are highly flexible and easily controlled. They also have the potential to be mass produced more readily than inorganic semiconductors such as silicon, which require higher temperatures for processing.

But there is a dark side to purely organic LEDs: They can be incredibly wasteful, losing up to 75% of their energy because organic semiconductors have a tendency to enter “dark states” in which they don’t emit light. These states sometimes even lead to the devices breaking down. Researchers have been looking for ways to either harness these dark states or jettison them altogether.

A collaboration led by Andrew Musser, assistant professor of chemistry and chemical biology in the College of Arts and Sciences, and Jenny Clark of the University of Sheffield, United Kingdom, has found a way to keep these organic semiconductors from going dark. Musserused tiny sandwich structures of mirrors, called microcavities, to trap light and force it to interact with a layer of molecules, forming a new hybrid state, known as a polariton, that mixes light and matter.This approach could lead to brighter, more efficient LEDs, sensors and solar cells.

The team’s paper, “Manipulating Molecules with Strong Coupling: Harvesting Triplet Excitons in Organic Exciton Microcavities,” published in Chemical Science.

“In the LED world, people are putting huge efforts into designing these vast libraries of molecules and testing them in different device configurations to see if, by tweaking the bonds or changing energy levels, they can harvest these dark states more efficiently,” Musser said. “It’s a cumbersome, difficult battle because it’s really hard to design molecules. And you don’t necessarily know how to make them do what you want.

“So what we’ve done here is address that problem with a standard molecule, purely by putting it between these mirrors and tuning the way it interacts with light,” he said. “This suggests that, for some phenomena, we can bypass a lot of this cumbersome synthetic exploration and tune the molecules at a distance.”

Musser’s interest in polaritons began while he was studying the ways organic semiconductors can improve light-harvesting efficiency in solar cells. In that case, molecules undergo a process called singlet fission, in which they absorb one photon and split that energy into two “packets” – essentially two excited electrons – thereby doubling the photon current efficiency in the solar cell.

Musser began investigating how the reverse process can also occur, with two packets of energy combining into a single, high-energy state that can emit a high-energy photon. That led him to microcavities and the ways these simple optical structures can have a profound effect on organic material through light.

In addition to manipulating a molecule’s electronic properties for enhanced brightness, recent research has demonstrated that these structures also can be used to target specific bonds and change their chemical reactivity.

Musser said different molecules interact with light in the microcavities in different ways, and further research is needed to explore the rules that underpin their behavior.

“Right now, it serves to show that when you have these complex materials and you do something even more complicated with them – putting them between these mirrors – weird and wonderful things can happen,” Musser said.

“This work literally sheds light on dark states,” said Clark. “We’ve shown that we can use polaritons to force dark states to emit light. Apart from immediate applications for LEDs, this offers a new method for studying organic semiconductors more broadly, using previously unavailable techniques.” 

Tags:  Andrew Musser  Chemical Science  energy  Graphene  Jenny Clark  LED  Semiconductor  silicon  smartphones  solar cell  U.S. Department of Energy  University of California  University of Cambridge  University of Kentucky  University of Sheffield 

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