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Interesting facts about plastics and rubber

We come across plastics and rubber everywhere in our daily lives. Discover fascinating stories, surprising facts and interesting background information – from historical developments and well-known products to key figures and innovations in the industry.

Results (423)

  • Coffee stains inspire optimal printing technique for electronics

    Particle trajectories of drying droplets, with red arrows showing the trajectory end. Credit: Tawfique Hasan Have you ever spilled your coffee on your desk? You may then have observed one of the most puzzling phenomena of fluid mechanics - the coffee ring effect. This effect has hindered the industrial deployment of functional inks with graphene, 2D materials, and nanoparticles because it makes printed electronic devices behave irregularly. Now, after studying this process for years, a team of researchers have created a new family of inks that overcomes this problem, enabling the fabrication of new electronics such as sensors, light detectors, batteries and solar cells. Coffee rings form because the liquid evaporates quicker at the edges, causing an accumulation of solid particles that results in the characteristic dark ring. Inks behave like coffee - particles in the ink accumulate around the edges creating irregular shapes and uneven surfaces, especially when printing on hard surfaces like silicon wafers or plastics. Researchers, led by Tawfique Hasan from the Cambridge Graphene Centre of the University of Cambridge, with Colin Bain from the Department of Chemistry of Durham University, and Meng Zhang from School of Electronic and Information Engineering of Beihang University, studied the physics of ink droplets combining particle tracking in high-speed micro-photography, fluid mechanics, and different combinations of solvents. Their solution: alcohol, specifically a mixture of isopropyl alcohol and 2-butanol. Using these, ink particles tend to distribute evenly across the droplet, generating shapes with uniform thickness and properties. Their results are reported in the journal Science Advances. "The natural form of ink droplets is spherical - however, because of their composition, our ink droplets adopt pancake shapes," said Hasan. While drying, the new ink droplets deform smoothly across the surface, spreading particles consistently. Using this universal formulation, manufacturers could adopt inkjet printing as a cheap, easy-to-access strategy for the fabrication of electronic devices and sensors. The new inks also avoid the use of polymers or surfactants - commercial additives used to tackle the coffee ring effect, but at the same time thwart the electronic properties of graphene and other 2D materials. Most importantly, the new methodology enables reproducibility and scalability - researchers managed to print 4500 nearly identical devices on a silicon wafer and plastic substrate. In particular, they printed gas sensors and photodetectors, both displaying very little variations in performance. Previously, printing a few hundred such devices was considered a success, even if they showed uneven behaviour. "Understanding this fundamental behaviour of ink droplets has allowed us to find this ideal solution for inkjet printing all kinds of two-dimensional crystals," said first author Guohua Hu. "Our formulation can be easily scaled up to print new electronic devices on silicon wafers, or plastics, and even in spray painting and wearables, already matching or exceeding the manufacturability requirements for printed devices." Beyond graphene, the team has optimised over a dozen ink formulations containing different materials. Some of them are graphene two-dimensional 'cousins' such as black phosphorus and boron nitride, others are more complex structures like heterostructures - 'sandwiches' of different 2D materials - and nanostructured materials. Researchers say their ink formulations can also print pure nanoparticles and organic molecules.This variety of materials could boost the manufacturing of electronic and photonic devices, as well as more efficient catalysts, solar cells, batteries and functional coatings. The team expects to see industrial applications of this technology very soon. Their first proofs of concept - printed sensors and photodetectors - have shown promising results in terms of sensitivity and consistency, exceeding the usual industry requirements. This should attract investors interested in printed and flexible electronics. "Our technology could speed up the adoption of inexpensive, low-power, ultra-connected sensors for the internet of things," said Hasan. "The dream of smart cities will come true." Reference Hu et al., A general ink formulation of 2D crystals for wafer-scale inkjet printing, Science Advanced 6 (2020), http://dx.doi.org/10.1126/sciadv.aba5029

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  • Perovskite and organic solar cells rocketed into space

    This photograph shows the launch of the sounding rocket with the OHSCIS experiment aboard in the course of the MAPHEUS 8 campaign at the European Space and Sounding Rocket Range in Kiruna, Sweden in June 2019. Credit: DLR MORABA For the first time, researchers in Germany sent perovskite and organic solar cells on a rocket into space. The solar cells withstood the extreme conditions in space, producing power from direct sunlight and reflective light from the Earth's surface. The work, published August 12 in the journal Joule, sets the foundation for future near-Earth application as well as potential deep space missions. One of the goals for space missions is to minimize the weight of equipment that the rocket carries. While current inorganic silicon solar panels used in space missions and satellites have high efficiencies, they are also very heavy and rigid. The emerging technology of hybrid perovskite and organic solar cells that are incredibly light and flexible becomes an ideal candidate for future applications. "What counts in this business is not the efficiency, but the produced electric power per weight, which is called specific power," says senior author Peter Müller-Buschbaum of Technical University of Munich in Germany. "The new type of solar cells reached values between 7 and 14 milliwatts per square centimeter during the rocket flight." This photograph shows a close-up of the experiment 'Organic and Hybrid Solar Cells In Space' (OHSCIS) in a laboratory test environment. Credit: Benjamin Predeschly, Chair of Functional Materials, Technical University of Munich "Transferred onto ultra-thin foils, one kilogram (2.2 pounds) of our solar cells would cover more than 200 square meters (2,153 square feet) and would produce enough electric power for up to 300 standard 100-W light bulbs," says first author Lennart Reb, of Technical University of Munich in Germany. "This is ten times more than what the current technology is offering." In June 2019, the rocket launched in northern Sweden, where the rocket entered space and reached 240 kilometers (149 miles) in altitude. The perovskite and organic solar cells, located at the payload, successfully withstood extreme conditions on the rocket ride--from the rumbling forces and heat at liftoff to the strong UV light and ultra-high vacuum in space. "The rocket was a big step," says Reb. "Going to the rocket was really like going into a different world." In addition to operating efficiently in space, the perovskite and organic solar cells can also function in low-light conditions. When there's no direct light on the traditional solar cell, the cell typically stops working, and the power output turns zero. However, the team discovered an energy output fueled by the weak diffuse light reflected from Earth's surface from perovskite and organic solar cells that weren't exposed to direct sunlight. Peter Müller-Buschbaum (l.) and Lennart Reb (r.) in the laboratories of the Chair of Functional Materials at TU Munich with the experiment 'Organic and Hybrid Solar Cells In Space' (OHSCIS) in their hands. Credit: Wei Chen, Chair of Functional Materials, Technical University of Munich "This is a good hint and confirms that the technology can go into what is called deep space missions, where you would send them far out in space, far away from the sun, where standard solar cells wouldn't work in," says Müller-Buschbaum. "There's really exciting future for this sort of technology, bringing these solar cells into more space missions in the future." But before launching more new solar cells into space, Müller-Buschbaum says one of the limitations of the study is the short time the rocket spent in space, where the total time was 7 minutes. The next step is to employ long-term applications in space, such as satellites, to understand the cells' lifetime, long-term stability, and full potential. "It's the very first time these perovskite and organic solar cells ever were in space, and that's really a milestone," says Müller-Buschbaum. "The really cool thing is that this is now paving the way for bringing these types of solar cells to more applications in space. On the long run, this might also help to bring these technologies for broader use in our terrestrial environment." Reference Reb et al., Perovskite and Organic Solar Cells on a Rocket Flight, Joule (2020), https://doi.org/10.1016/j.joule.2020.07.004 Source Cell Press

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  • Molecular additives enhance mechanical properties of organic solar cell material

    Ganesh Balasubramanian, P.C. Rossin assistant professor of Mechanical Engineering & Mechanics at Lehigh University, and his graduate student Joydeep Munshi demonstrated that adding small molecules to a semiconducting polymer blend enhances the performance and stability of material used in organic solar cells. The study is described in an article, 'Elasto-morphology of P3HT:PCBM bulk heterojunction organic solar cells' featured on the back cover of Soft Matter. Organic solar cells are ideal for use in flexible electronics because of the inherently malleable nature of semiconducting polymers. Recent research on the interplay between processing, thermodynamics and mechanical stability of typical photoactive layers in organic cells is providing a deeper understanding of these high-potential materials. Ganesh Balasubramanian, P.C. Rossin assistant professor of Mechanical Engineering & Mechanics at Lehigh University, and his graduate student Joydeep Munshi recently set out to understand how stable these materials are when deformed, and whether the promising properties can be realized under harsh loading conditions when the solar cells may be subject to stretching and compression. Through computational experiments using the leadership class computing resources in Frontera, the team demonstrated that adding small molecules to the semiconducting polymer blend enhances the performance and stability of material used in organic solar cells. They predict this is also true for organic solar cell material more generally. Showcasing research from Professor Ganesh Balasubramanian's laboratory (Group for Interfacial and Nanoengineering), Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, USA. Despite the recent advances in the power conversion efficiency of organic solar cells, an insight into the processing-driven thermo-mechanical stability of bulk heterojunction active layers is still warranted. Correlating the elasto-morphology with device performance requires a deeper understanding of the molecular-level physics, as presented in this research on the interplay between processing, thermodynamics and mechanical stability of typical photoactive layers in organic solar cells. Credit: Professor Ganesh Balasubramanian's laboratory (Group for Interfacial and Nanoengineering), Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, USA. "Based on previous literature, we anticipated that variations in the materials processing parameters would influence the structure as well as the thermal and mechanical properties of these solar cells," says Balasubramanian. "However, the finding that presence of small molecular additives can augment the mechanical properties is new knowledge gained from this work." The team demonstrated that, in addition to the solar-to-electrical power conversion efficiency, the mechanical stability and flexibility of typical organic solar cells is significantly impacted by the presence of molecular additives. "This could prove crucial towards the commercialization of organic solar cells," says Balasubramanian. The results were achieved by performing large scale molecular simulations in the supercomputer Frontera, located at the Texas Advanced Computing Center (TACC) at the University of Texas at Austin), which is the world's fastest academic supercomputer. The predictions consisted of the deformation mechanisms of the polymer blend under straining conditions as well as examining the structure/morphology of the material upon loading. Balasubramanian's team has been among the first to utilize Frontera. While similar approaches have been considered for interrogating the properties of organic photovoltaic materials, the correlation between the material structure and elastic properties had not been done before, according to Balasubramanian. By adding molecular additives to the polymeric blends, advanced solar power materials and devices can be fabricated that sustain extreme operational stress-strain conditions while delivering superior performance. He adds: "The research has the potential to provide new directions for scientific practices in this field of materials and energy research." Reference Joydeep Munshi, TeYu Chien, Wei Chen and Ganesh Balasubramanian, Elasto-morphology of P3HT:PCBM bulk heterojunction organic solar cells, Soft Matters 29 (2020), http://dx.doi.org/10.1039/D0SM00849D

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  • Masks, PPE materials should be hydrophilic

    Drying time of a 5-nanoliter droplet as a function of the contact angle on the surface. Credit: R. Bhardwaj and A. Agrawal Since the COVID-19 virus spreads through respiratory droplets, researchers in India set out to explore how droplets deposited on face masks or frequently touched surfaces, like door handles or smartphone touch screens, dry. Droplets can be expelled via the mouth or nose while coughing, sneezing or simply talking. These droplets are tiny, around twice the width of a human hair, and studies have shown a substantially reduced chance of infection once they dry. In Physics of Fluids, from AIP Publishing, Rajneesh Bhardwaj and Amit Agrawal, professors at IIT Bombay, publish findings that surface wetting properties to reduce the drying time of droplets could help lessen the risk of infection from coronaviruses. "We wanted to quantify the droplet drying time on various surfaces and make a recommendation for the ideal types of surfaces for masks and personal protective equipment (PPE) based on the drying time," said Bhardwaj. By studying the drying time of a droplet for different contact angles, the expected chances of survival of the coronavirus on a surface can be estimated by using a mathematical physics model. "Our calculations of the drying time as a function of contact angle show that the droplet dries roughly four times faster on the hydrophilic surface that attracts water than on the one that repels water. This will drastically reduce the chances of virus survival," Bhardwaj said. Their work also shows that, by tailoring the surface wettability and drying time, the chances of infection can be reduced. "Making a surface more hydrophilic reduces the drying time, and it is advisable to use it for masks, PPE and frequently touched surfaces where outbreaks are most likely to occur, such as the common areas within hospitals," said Agrawal. In the case of N95 respirators, surgical masks and PPE bodywear, a reduction to a contact angle of a hydrophilic surface implies that the chances of infection of COVID-19 will be cut in half. "We recommend reducing the contact angle of the surface of face masks and frequently touched surfaces," Agrawal said. The biggest surprise was their finding that the maximum drying time occurs at an intermediate contact angle value of 148 degrees. "This implies that a superhydrophobic surface needs to be made even more superhydrophobic to reduce the drying time," Agrawal said. "This is counterintuitive, because we normally think of making a surface more hydrophilic, reducing the contact angle, to reduce the drying time." This work provides a better understanding of coronavirus survival within a drying droplet, which may be helpful for predicting the survival of other transmissible diseases spread through respiratory droplets, such as the flu. Reference Rajneesh Bhaardwaj and Amit Agrawal, Tailoring surface wettability to reduce chances of infection of COVID-19 by a respiratory droplet and to improve the effectiveness of personal protection equipment, AIP Physics of Fluids 32 (2020), http://dx.doi.org/10.1063/5.0020249

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  • UBC helps Arc'teryx stay green and dry with next-generation water-repellent fabrics

    UBC Okanagan researchers Sadaf Shabanian (left) and Kevin Golovin (right) test water-repellent fabric treatment. Credit: UBC Okanagan A sustainable, non-toxic and high-performance water-repellent fabric has long been the holy grail of outdoor enthusiasts and clothing companies alike. New research from UBC Okanagan and outdoor apparel giant Arc'teryx is making that goal one step closer to reality with one of the world's first non-toxic oil and water-repellent performance textile finishes. The research was published this week in the journal Nature Sustainability. Outdoor fabrics are typically treated with perfluorinated compounds (PFCs) to repel oil and water. But according to Sadaf Shabanian, doctoral student at UBC Okanagan's School of Engineering and study lead author, PFCs come with a number of problems. "PFCs have long been the standard for stain repellents, from clothing to non-stick frying pans, but we know these chemicals have a detrimental impact on human health and the environment," explains Shabanian. "They pose a persistent, long-term risk to health and the environment because they take hundreds of years to breakdown and linger both in the environment and our bodies." According to Mary Glasper, materials developer at Arc'teryx and collaborator on the project, these lasting impacts are one of the major motivations for clothing companies to seek out new methods to achieve the same or better repellent properties in their products. To solve the problem, Shabanian and the research team added a nanoscopic layer of silicone to each fibre in a woven fabric, creating an oil-repellent jacket fabric that repels water, sweat and oils. By understanding how the textile weave and fibre roughness affect the liquid interactions, Shabanian says she was able to design a fabric finish that did not use any PFCs. "The best part of the new design is that the fabric finish can be made from biodegradable materials and can be recyclable," she says. "It addresses many of the issues related to PFC-based repellent products and remains highly suitable for the kind of technical apparel consumers and manufacturers are looking for." Arc'teryx is excited about the potential of this solution. "An oil- and water-repellent finish that doesn't rely on PFCs is enormously important in the world of textiles and is something the whole outdoor apparel industry has been working on for years," says Glasper. "Now that we have a proof-of-concept, we'll look to expand its application to other DWR-treated textiles used in our products and to improve the durability of the treatment." "Working to lessen material impacts on the environment is crucial for Arc'teryx to meet our goal of reducing our greenhouse gas emissions by 65 per cent in intensity by 2030," she adds. Kevin Golovin, principal investigator of the Okanagan Polymer Engineering Research & Applications Lab where the research was done, says the new research is important because it opens up a new area of green textile manufacturing. He explains that while the new technology has immense potential, there are still several more years of development and testing needed before people will see fabrics with this treatment in stores. "Demonstrating oil repellency without the use of PFCs is a critical first step towards a truly sustainable fabric finish," says Golovin. "And it's something previously thought impossible." Reference Sadaf Shabanian, Behrooz Khatir, Ambreen Nisar and Kevin Golovin, Rational design of perfluorocarbon-free oleophobic textiles, Nature Sustainability (2020), http://dx.doi.org/10.1038/s41893-020-0591-9

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  • Breakthrough technology purifies water using the power of sunlight

    A research team, led by Australia's Monash University, has been able to transform brackish water and seawater into safe, clean drinking water in less than 30 minutes using metal-organic frameworks (MOFs) and sunlight. Credit: Monash University A research team, led by Australia's Monash University, has been able to transform brackish water and seawater into safe, clean drinking water in less than 30 minutes using metal-organic frameworks (MOFs) and sunlight. A global research team has been able to transform brackish water and seawater into safe, clean drinking water in less than 30 minutes using metal-organic frameworks (MOFs) and sunlight. In a discovery that could provide potable water for millions of people across the world, researchers were not only able to filter harmful particles from water and generate 139.5L of clean water per kilogram of MOF per day, but also perform this task in a more energy-efficient manner than current desalination practices. The World Health Organization suggests good quality drinking water should have a total dissolved solid (TDS) of <600 parts per million (ppm). Researchers were able to achieve a TDS of <500 ppm in just 30 minutes and regenerate the MOF for reuse in four minutes under sunlight. This world-first research was published in the prestigious journal Nature Sustainability. Lead author Professor Huanting Wang from the Department of Chemical Engineering at Monash University in Australia, said this work opened up a new direction for designing stimuli-responsive materials for energy-efficient and sustainable desalination and water purification. "Desalination has been used to address escalating water shortages globally. Due to the availability of brackish water and seawater, and because desalination processes are reliable, treated water can be integrated within existing aquatic systems with minimal health risks," Professor Wang said. "But, thermal desalination processes by evaporation are energy-intensive, and other technologies, such as reverse osmosis, has a number of drawbacks, including high energy consumption and chemical usage in membrane cleaning and dechlorination. "Sunlight is the most abundant and renewable source of energy on Earth. Our development of a new adsorbent-based desalination process through the use of sunlight for regeneration provides an energy-efficient and environmentally-sustainable solution for desalination." Metal-organic frameworks are a class of compounds consisting of metal ions that form a crystalline material with the largest surface area of any material known. In fact, MOFs are so porous that they can fit the entire surface of a football field in a teaspoon. The research team created a dedicated MOF called PSP-MIL-53. This was synthesised by introducing poly(spiropyran acrylate) (PSP) into the pores of MIL-53 - a specialised MOF well-known for its breathing effects and transitions upon the adsorption of molecules such as water and carbon dioxide. Researchers demonstrated that PSP-MIL-53 was able to yield 139.5L of fresh water per kilogram of MOF per day, with a low energy consumption. This was from desalinating 2,233 ppm water sourced from a river, lake or aquifer. Professor Wang said this highlights the durability and sustainability of using this MOF for future clean water solutions. "This study has successfully demonstrated that the photoresponsive MOFs are a promising, energy-efficient, and sustainable adsorbent for desalination," Professor Wang said. "Our work provides an exciting new route for the design of functional materials for using solar energy to reduce the energy demand and improve the sustainability of water desalination. "These sunlight-responsive MOFs can potentially be further functionalised for low-energy and environmentally-friendly means of extracting minerals for sustainable mining and other related applications." Reference Ou et al., A sunlight-responsive metal–organic framework system for sustainable water desalination, Nature Sustainabilty (2020), http://dx.doi.org/10.1038/s41893-020-0590-x

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  • New-generation CO2 gas separation system using gate-type adsorbents

    Scientists in Japan designed a gate-type adsorbent tower system that captures and separates mixed gases, CO2, to enable lowering greenhouse gas emissions from industrial sources. Credit: Shotaro Hiraide Ph.D., Department of Chemical Engineering, Kyoto University The Paris Agreement of 2015 set a goal of reducing CO2 emissions, a greenhouse gas that causes global warming to levels less than 2°C more than before the Industrial Revolution. In order to achieve this goal, it is necessary to reduce industrial energy consumption, half of which is used in separation processes for purifying, distilling and drying chemicals. It takes a lot of energy and is costly to separate a mixture of molecules. In other words, the development of a highly efficient and energy-saving separation technology is one of the most important challenges facing the world today, of which CO2 separation and capture is a high priority for lowering greenhouse gases. The adsorption separation method for separating a mixture of molecules makes use of the property that specific molecules are adsorbed in a porous material. This is how water purifier filters and deodorizing charcoal in refrigerators work. When a gas mixture is poured from one end of an adsorption tower filled with a porous material (adsorbent), molecules that strongly interact with the adsorbent are captured into the pores. Some molecules with a weak interaction with the adsorbent are also adsorbed in the pores, but most pass through and flow out of the adsorption tower. The molecules taken into the pores are recovered or desorbed by heating or depressurizing the content of the adsorption tower. In order to selectively adsorb molecules into an adsorbent, there is a need for a stronger interaction, but the energy required for desorption increases accordingly. The key to greatly improving the adsorption separation efficiency is to find adsorbents with certain contradictory properties that can selectively adsorb large amounts of molecules and easily desorb them. The pressure vacuum swing adsorption (PVSA) and temperature swing adsorption (TSA) processes, which are both gas separation methods using porous materials, can be more energy efficient than distillation, which requires selective boiling and condensation. However, PVSA and TSA aren't without their limitations. It is difficult to achieve high-throughput separation with these techniques because pressure loss is caused due to necessary system enlargement as well as the crushing of adsorbents at the bottom of the adsorption column. Previous efforts to resolve these issues have caused other problems such as heat generated by adsorption, which results in a decrease of adsorption capacity, so there is a need to find a novel adsorption material that exhibits a large loading capacity, high selectivity and minimal heat of adsorption, which are actually conflicting characteristics with known materials. Therefore, the focus of this research was on "gate-type adsorbents". The greatest feature of this material is that it has a flexible structure. The researchers worked with ELM-11, a flexible metal-organic framework (MOF), which is a porous material with "gate-opening" and "gate-closing" properties exhibited at specific gas pressures. ELM-11's pores are closed and does not adsorb CO2 when the concentration of CO2 contained in the gas mixture is low, but rapidly expands when the CO2 concentration exceeds a certain threshold value, and opens the pores to capture CO2 molecules. Since the opening and closing behavior of the pores is like a gate, it is called a gate type adsorbent. ELM-11 deforms its structure to encapsulate CO2 molecules, and thus exhibits high CO2 selectivity. Furthermore, ELM-11 contracts its structure and releases all the adsorbed CO2 molecules when the CO2 concentration in the gas mixture falls below a threshold value. In other words, ELM-11 has properties that are highly suitable for CO2 adsorption and separation. It selectively adsorbs CO2 and easily desorbs CO2. For the real world application of the adsorption separation of CO2 contained in exhaust gas, a large amount of gas must be processed at high speed. The problem is the generation of heat associated with CO2 adsorption. In traditional "hard" adsorbents, the heat of adsorption raises the temperature, resulting in reduced CO2 adsorption and reduced CO2 selectivity. ELM-11, which has a flexible structure, expands when it takes in CO2 molecules. The research group focused on the possibility that the expansion of ELM-11 may generate cold heat and effectively suppress the temperature rise due to CO2 adsorption. First, they conducted a gas adsorption experiment on ELM-11 and conducted a variety of computational studies to quantify the CO2 separation capacity of ELM-11. They compared performance data with HKUST-1, a conventional adsorbent which is considered to be the most promising for separating CH4and CO2 gas mixtures. The data showed that ELM-11 has a CO2 selectivity 9.7 times that of HKUST-1. The CO2 recovery amount per adsorbent weight is 2.1 times that of HKUST-1, which has no intrinsic thermal management capability. ELM-11 proved to be extremely suitable for high-speed adsorption separation systems. The researchers designed a high-speed adsorption separation system consisting of two-stage adsorption towers, one packed with HKUST-1. When the CO2 concentration contained in the gas mixture exceeds a certain threshold value, ELM-11 expands rapidly and opens pores, adsorbing CO2 molecules. This means that when the CO2 concentration in the gas falls to the threshold due to CO2 adsorption on ELM-11, the remaining CO2 is not adsorbed at all and flows out with CH4, which means that high-purity CH4 gas is not obtained. Therefore, to prevent this problem the researchers installed a small adsorption column filled with HKUST-1 that has excellent adsorption characteristics for low-concentration CO2 gas, in the latter stage of the adsorption column filled with ELM-11. They conducted a breakthrough measurement for a mixed gas of CH4 and CO2 using a small two-stage adsorption column, and was able to confirm that high-purity CH4 gas was obtained. The two-stage adsorption tower system enables the reduction of the total tower volume, reduces the amount of adsorbent used, and reduces energy consumed. At first glance, the system is based on a simple idea, but it was possible to reduce the system size significantly in this way by designing the first-stage adsorption tower so that the characteristics of ELM-11 can be fully exhibited. The hybridization system utilizing the characteristics of ELM-11 and HKUST-1 worked extremely effectively. The researchers needed to clarify three issues to see if ELM-11 possessed the necessary qualities needed for a real-life high-throughput separation process. First, it was necessary that the host framework response for the gate-opening needed to be very fast. Secondly, the separation properties must work for non-isothermal conditions, which has not been previously reported to the knowledge of the researchers. Thirdly, the "slipping-off" phenomenon caused by a decrease in the partial gas pressure below the gate-opening pressure, which makes the flexible MOF unable to adsorb molecules needed to be addressed. ELM-11 showed that the researchers are able to overcome these three issues, the "slipping-off" problem can be managed with the two-stage adsorption tower. In addition, this system can be applied to the exhaust gas treatment of CO2 emission sources such as thermal power plants. In order to put this high-speed adsorption/separation system that uses a gate-type adsorbent into practical use, the hinderance of gate-opening due to the pelletization of flexible MOFs, and the pressure drop due to the volume expansion of pellets need to be addressed. The team have already started tackling these issues. The accomplishments of this present research has opened the doors to a new era in gas separation. Corresponding author Hideki Tanaka of Shinshu University states that, "the study took 3 years to publish, which we are very grateful for because the multiple feedback from reviewers was very insightful and the subsequent re-writes made the study more innovative and better, which eventually led to the paper being published in Nature Communications. I'm very happy that the hard work of first author Shotaro Hiraide of Kyoto University was finally rewarded." Reference Hiraide et al., High-throughput gas separation by flexible metal–organic frameworks with fast gating and thermal management capabilities, Nature Communications (2020), http://dx.doi.org/10.1038/s41467-020-17625-3

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  • New science behind algae-based flip-flops

    Commerical-quality biodegradable flip-flops. Photo: Stephen Mayfield, UC San Diego. Sustainable flip-flops: A team of UC San Diego researchers has formulated polyurethane foams made from algae oil to meet commercial specifications for midsole shoes and the foot-bed of flip-flops. The results of their study are published in Bioresource Technology Reports and describe the team's successful development of these sustainable, consumer-ready and biodegradable materials. As the world's most popular shoe, flip-flops account for a troubling percentage of plastic waste that ends up in landfills, on seashores and in our oceans. Scientists at the University of California San Diego have spent years working to resolve this problem, and now they have taken a step farther toward accomplishing this mission. Sticking with their chemistry, the team of researchers formulated polyurethane foams, made from algae oil, to meet commercial specifications for midsole shoes and the foot-bed of flip-flops. The results of their study are published in Bioresource Technology Reports and describe the team's successful development of these sustainable, consumer-ready and biodegradable materials. The research was a collaboration between UC San Diego and startup company Algenesis Materials - a materials science and technology company. The project was co-led by graduate student Natasha Gunawan from the labs of professors Michael Burkart (Division of Physical Sciences) and Stephen Mayfield (Division of Biological Sciences), and by Marissa Tessman from Algenesis. It is the latest in a series of recent research publications that collectively, according to Burkart, offer a complete solution to the plastics problem - at least for polyurethanes. "The paper shows that we have commercial-quality foams that biodegrade in the natural environment," said Mayfield. "After hundreds of formulations, we finally achieved one that met commercial specifications. These foams are 52 percent biocontent - eventually we'll get to 100 percent." In addition to devising the right formulation for the commercial-quality foams, the researchers worked with Algenesis to not only make the shoes, but to degrade them as well. Mayfield noted that scientists have shown that commercial products like polyesters, bioplastics (PLA) and fossil-fuel plastics (PET) can biodegrade, but only in the context of lab tests or industrial composting. "We redeveloped polyurethanes with bio-based monomers from scratch to meet the high material specifications for shoes, while keeping the chemistry suitable, in theory, so the shoes would be able to biodegrade," Mayfield explained. Putting their customized foams to the test by immersing them in traditional compost and soil, the team discovered the materials degraded after just 16 weeks. During the decomposition period, to account for any toxicity, the scientists, led by UC San Diego's Skip Pomeroy, measured every molecule shed from the biodegradable materials. They also identified the organisms that degraded the foams. Grafic (r.): Biodegradation of PU cubes over 12 weeks. Degradation was analyzed through A) Change in appearance, B) Cube mass and C) Maximum force at 50% compression force deflection (CFD). Error bars indicate sample standard deviations of the triplicate measurements. For compost and soil mass loss, p<0.01 and for compost and soil CFD, p<0.01 (Table 2 in published paper). (Source: Stephen Mayfield, UC San Diego) Foot-bed of flip-flops being pulled from a mold. Photo: Stephen Mayfield, UC San Diego. "We took the enzymes from the organisms degrading the foams and showed that we could use them to depolymerize these polyurethane products, and then identified the intermediate steps that take place in the process," said Mayfield, adding, "We then showed that we could isolate the depolymerized products and use those to synthesize new polyurethane monomers, completing a 'bioloop.'" This full recyclability of commercial products is the next step in the scientist's ongoing mission to address the current production and waste management problems we face with plastics - which if not addressed, will result in 96 billion tons of plastic in landfills or the natural environment by 2050. According to Pomeroy, this environmentally unfriendly practice began about 60 years ago with the development of plastics. "If you could turn back the clock and re-envision how you could make the petroleum polymer industry, would you do it the same today that we did it years ago? There's a bunch of plastic floating in every ocean on this planet that suggests we shouldn't have done it that way," noted Pomeroy. While commercially on track for production, doing so economically is a matter of scale that the scientists are working out with their manufacturing partners. "People are coming around on plastic ocean pollution and starting to demand products that can address what has become an environmental disaster," said Tom Cooke, president of Algenesis. "We happen to be at the right place at the right time." The team's efforts are also manifested in the establishment of the Center for Renewable Materials at UC San Diego. Begun by Burkart, Mayfield, Pomeroy and their co-founders Brian Palenik (Scripps Institution of Oceanography) and Larissa Podust (Skaggs School of Pharmacy and Pharmaceutical Sciences), the center focuses on three major goals: the development of renewable and sustainable monomers made from algae and other biological sources; their formulation into polymers for diverse applications, the creation of synthetic biology platforms for the production of monomers and crosslinking components; and the development and understanding of biodegradation of renewable polymers. "The life of material should be proportional to the life of the product," said Mayfield. "We don't need material that sits around for 500 years on a product that you will only use for a year or two." Reference Gunawan et al., Rapid biodegradation of renewable polyurethane foams with identification of associated microorganisms and decomposition products, Bioresource Technology Reports 11 (2020), http://dx.doi.org/10.1016/j.biteb.2020.100513

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  • A closer look at water-splitting's solar fuel potential

    Scientists at Berkeley Lab and the Joint Center for Artificial Photosynthesis (JCAP) have gained important new insight into how the performance of a promising semiconducting thin film can be optimized at the nanoscale for renewable energy technologies such as solar fuels. In the fight against climate change, scientists have searched for ways to replace fossil fuels with carbon-free alternatives such as hydrogen fuel. A device known as a photoelectrical chemical cell (PEC) has the potential to produce hydrogen fuel through artificial photosynthesis, an emerging renewable energy technology that uses energy from sunlight to drive chemical reactions such as splitting water into hydrogen and oxygen. The key to a PEC's success lies not only in how well its photoelectrode reacts with light to produce hydrogen, but also oxygen. Few materials can do this well, and according to theory, an inorganic material called bismuth vanadate (BiVO4) is a good candidate. Yet this technology is still young, and researchers in the field have struggled to make a BiVO4 photoelectrode that lives up to its potential in a PEC device. Now, as reported in the journal Small, a research team led by scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub, have gained important new insight into what might be happening at the nanoscale (billionths of a meter) to hold BiVO4 back. "When you make a material, such as an inorganic material like bismuth vanadate, you might assume, just by looking at it with the naked eye, that the material is homogeneous and uniform throughout," said senior author Francesca Toma, a staff scientist at JCAP in Berkeley Lab's Chemical Sciences Division. "But when you can see details in a material at the nanoscale, suddenly what you assumed was homogeneous is actually heterogeneous - with an ensemble of different properties and chemical compositions. And if you want to improve a photoelectrode material's efficiency, you need to know more about what's happening at the nanoscale." Photo: Francesca Toma (right) and Johanna Eichhorn developed a special technique using an atomic force microscope at Berkeley Lab's JCAP laboratory to capture images of thin-film bismuth vanadate at the nanoscale to understand how a material's properties can affect its performance in an artificial photosynthesis device. (Source: Marilyn Sargent/ Berkeley Lab) X-rays and simulations bring a clearer picture into focus In a previous study supported by the Laboratory Directed Research and Development program, Toma and lead author Johanna Eichhorn developed a special technique using an atomic force microscope at Berkeley Lab's JCAP laboratory to capture images of thin-film bismuth vanadate at the nanoscale to understand how a material's properties can affect its performance in an artificial photosynthesis device. (Eichhorn, who is currently at the Walter Schottky Institute of the Technical University of Munich in Germany was a researcher in Berkeley Lab's Chemical Sciences Division at the time of the study.) The current study builds on that pioneering work by using a scanning transmission X-ray microscope (STXM) at Berkeley Lab's Advanced Light Source (ALS) (https://als.lbl.gov/), a synchrotron user facility, to map out changes in a thin-film semiconducting material made of molybdenum bismuth vanadate (Mo-BiVO4). The researchers used bismuth vanadate as a case example of a photoelectrode because the material can absorb light in the visible range in the solar spectrum, and when combined with a catalyst, its physical properties allow it to make oxygen in the water-splitting reaction. Bismuth vanadate is one of the few materials that can do this, and in this case, the addition of a small quantity of molybdenum to BiVO4 somehow improves its performance, Toma explained. When water is split into H2 and O2, hydrogen-hydrogen and oxygen-oxygen bonds need to form. But if any step in water-splitting is out of sync, unwanted reactions will happen, which could lead to corrosion. "And if you want to scale up a material into a commercial water-splitting device, no one wants something that degrades. So we wanted to develop a technique that maps out which regions at the nanoscale are the best at making oxygen," Toma explained. Working with ALS staff scientist David Shapiro, Toma and her team used STXM to take high-resolution nanoscale measurements of grains in a thin film of Mo-BiVO4 as the material degraded in response to the water-splitting reaction triggered by light and the electrolyte. "Chemical heterogeneity at the nanoscale in a material can often lead to interesting and useful properties, and few microscopy techniques can probe the molecular structure of a material at this scale," Shapiro said. "The STXM instruments at the Advanced Light Source are very sensitive probes that can nondestructively quantify this heterogeneity at high spatial resolution and can therefore provide a deeper understanding of these properties." David Prendergast, interim division director of the Molecular Foundry, and Sebastian Reyes-Lillo, a former postdoctoral researcher at the Foundry, helped the team understand how Mo-BiVO4 responds to light by developing computational tools to analyze each molecule's spectral "fingerprint." Reyes-Lillo is currently a professor at Andres Bello University in Chile and a Molecular Foundry user. The Molecular Foundry is a Nanoscale Science Research Center national user facility. "Prendergast's technique is really powerful," Toma said. "Often when you have complex heterogeneous materials made of different atoms, the experimental data you get is not easy to understand. This approach tells you how to interpret those data. And if we have a better understanding of the data, we can create better strategies for making Mo-BiVO4 photoelectrodes less vulnerable to corrosion during water-splitting." Reyes-Lillo added that Toma's use of this technique and the work at JCAP enabled a deeper understanding of Mo-BiVO4 that would otherwise not be possible. "The approach reveals element-specific chemical fingerprints of a material's local electronic structure, making it especially suited for the study of phenomena at the nanoscale. Our study represents a step toward improving the performance of semiconducting BiVO4-based materials for solar fuel technologies," he said. Next steps The researchers next plan to further develop the technique by taking STXM images while the material is operating so that they can understand how the material changes chemically as a photoelectrode in a model PEC system. "I'm very proud of this work. We need to find alternative solutions to fossil fuels, and we need renewable alternatives. Even if this technology isn't ready for the marketplace tomorrow, our technique - along with the powerful instruments available to users at the Advanced Light Source and the Molecular Foundry - will open up new routes for renewable energy technologies to make a difference." Reference Eichhorn et al., Revealing Nanoscale Chemical Heterogeneities in Polycrystalline Mo‐BiVO4 Thin Films, Small (2020), https://doi.org/10.1002/smll.202001600

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  • Chemists create the brightest-ever fluorescent materials

    This image shows glowing 3D-printed gyroids made with bright SMILES materials. Photo: Amar Flood By formulating positively charged fluorescent dyes into a new class of materials called small-molecule ionic isolation lattices (SMILES), a compound's brilliant glow can be seamlessly transferred to a solid, crystalline state, researchers report August 6 in the journal Chem. The advance overcomes a long-standing barrier to developing fluorescent solids, resulting in the brightest known materials in existence. "These materials have potential applications in any technology that needs bright fluorescence or calls for designing optical properties, including solar energy harvesting, bioimaging, and lasers," says Amar Flood, a chemist at Indiana University and co-senior author on the study along with Bo Laursen of the University of Copenhagen. "Beyond these, there are interesting applications that include upconverting light to capture more of the solar spectrum in solar cells, light-switchable materials used for information storage and photochromic glass, and circularly polarized luminescence that may be used in 3D display technology," Flood says. While there are currently more than 100,000 different fluorescent dyes available, almost none of these can be mixed and matched in predictable ways to create solid optical materials. Dyes tend to undergo "quenching" when they enter a solid state due to how they behave when packed close together, decreasing the intensity of their fluorescence to produce a more subdued glow. "The problem of quenching and inter-dye coupling emerges when the dyes stand shoulder-to-shoulder inside solids," says Flood. "They cannot help but 'touch' each other. Like young children sitting at story time, they interfere with each other and stop behaving as individuals." To overcome this problem, Flood and colleagues mixed a colored dye with a colorless solution of cyanostar, a star-shaped macrocycle molecule that prevents the fluorescent molecules from interacting as the mixture solidified, keeping their optical properties intact. As the mixture became a solid, SMILES formed, which the researchers then grew into crystals, precipitated into dry powders, and finally spun into a thin film or incorporated directly into polymers. Since the cyanostar macrocycles form building blocks that generate a lattice-like checkerboard, the researchers could simply plug a dye into the lattice and, without any further adjustments, the structure would take on its color and appearance. This image shows how 3D printed gyroids made with SMILES materials are colored under white light and fluoresce brightly under UV. Photo: Amar Flood While previous research had already developed an approach to spacing the dyes apart using macrocycle molecules, it relied on colored macrocycles to do the job. Flood and colleagues found that colorless macrocycles were key. "Some people think that colorless macrocycles are unattractive, but they allowed the isolation lattice to fully express the bright fluorescence of the dyes unencumbered by the colors of the macrocycles," says Flood. Next, the researchers plan to explore the properties of fluorescent materials formed using this novel technique, enabling them to work with dye makers in the future to realize the materials' full potential in a variety of different applications. "These materials are totally new, so we do not know which of their innate properties are actually going to offer superior functionality," says Flood. "We also do not know the materials' limits. So, we will develop a fundamental understanding of how they work, providing a robust set of design rules for making new properties. This is critical for putting these materials into the hands of others--we want to pursue crowd sourcing and to work with others in this effort." Reference Benson et al., Plug-and-Play Optical Materials from Fluorescent Dyes and Macrocycles, Chem (2020), https://doi.org/10.1016/j.chempr.2020.06.029

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  • Developing new smart soft materials

    The research team directed by H. Shimomoto and E. Ihara in Ehime University synthesized pH-responsive dendronized polymers by C1 polymerization of dendron-containing diazoacetates, and demonstrated a unique pH-responsive behavior of the resulting polymers. These achievements will contribute to progress in the field of polymer chemistry and will allow us to develop new types of smart soft materials. Image: The research team directed by H. Shimomoto and E. Ihara in Ehime University synthesized pH-responsive dendronized polymers by C1 polymerization of dendron-containing diazoacetates, and demonstrated a unique pH-responsive behavior of the resulting polymers. These achievements will contribute to progress in the field of polymer chemistry and will allow us to develop new types of smart soft materials. Source: Ehime University C1 polymerization is a useful technique for preparing polymers with a carbon-carbon main chain. This technique constructs a polymer backbone from "one carbon unit", in contrast to conventional vinyl polymerization, which produces polymers from a "two carbon unit" derived from vinyl groups. The representative characteristic of C1 polymerization is that it can yield carbon-carbon main polymers having a substituent on each main chain carbon atom [poly(substituted methylene)s]. For the C1 polymerization system, diazoacetates are suitable monomers, yielding polymers with an alkoxycarbonyl group (ester) on each main chain carbon atom. pH-responsive dendronized poly(substituted methylene)s prepared by C1 polymerization of dendron-containing diazoacetates. Image: Ehime University Stimuli-responsive polymers or smart polymers are macromolecules that undergo a change in properties in response to external stimuli, such as temperature, pH, light, and additives. Their stimuli-responsive behavior strongly depends on the primary structure of the polymer, and thus precise synthesis is necessary to develop smart materials with superior properties. Precise C1 polymerization for diazoacetates is still a challenge, whereas various controlled/living polymerization techniques of vinyl monomers have been achieved to give well-defined stimuli-responsive vinyl polymers. In this context, with the results reported in this report, we have demonstrated that diazoacetates with a sterically bulky substituent can be polymerized in a controlled manner with the π-allylPdCl/borate systems to yield polymers with narrow molecular weight distribution. In addition, we have successfully synthesized carboxy-functionalized dendronized polymers and demonstrated the characteristic pH-responsive behavior derived from the dense accumulation of the side chains in comparison to the corresponding vinyl polymers bearing the same side chains. The introduction of functional groups, other than a carboxy group, in the peripheral phenyl groups should result in a high density of the functional groups around the rigid main chain. These structural characteristics will lead to development of a variety of new functional poly(substituted methylene)s in the near future. Reference Shimomoto et al., Pd-Initiated Polymerization of Dendron-Containing Diazoacetates to Afford Dendronized Poly(substituted methylene)s with Narrow Molecular Weight Distribution and Its Application to Synthesis of pH-Responsive Dendronized Polymers, Macromolecules (2020), https://doi.org/10.1021/acs.macromol.0c01029

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  • Machine learning methods provide new insights into organic-inorganic interfaces

    By combining two new machine-learning methods, TU Graz physicist Oliver Hofmann was able to refute theories on long-range charge transfer between organic and inorganic materials. Photo: Baustädter - TU Graz Oliver Hofmann and his research group at the Institute of Solid State Physics at TU Graz are working on the optimization of modern electronics. A key role in their research is played by interface properties of hybrid materials consisting of organic and inorganic components, which are used, for example, in OLED displays or organic solar cells. The team simulates these interface properties with machine-learning-based methods. The results are used in the development of new materials to improve the efficiency of electronic components. The researchers have now taken up the phenomenon of long-range charge transfer. A transfer of electrons from one material to another already occurs in the switched-off state if there are energetically more favourable states for the electrons in the neighbouring material. This raises the fundamental question of how far this transfer of electrons can extend in organic material, i.e. how many layers it encompasses. Many studies report that for organic-inorganic interfaces this effect is limited to the first layer, i.e. the layer where the (organic) molecules are in direct contact with the (inorganic) metal surface. On the other hand, some reports assume that the effect also extends over longer distances, to the second layer or beyond. "If this is the case, the effect could be used to reduce the electrical resistance of the hybrid material, making it more energy efficient," says Hofmann, explaining why it is so interesting. New examination method combines two machine learning methods In order to demonstrate long-range charge transport in organic-inorganic interfaces, the researchers used the new machine learning methods SAMPLE and BOSS to investigate a copper-tetracyanoethylene interface (TCNE/Cu(111)), "since there are particularly strong experimental data available here that indicate long-range charge transport," said Hofmann. There is no clear theory why some systems show this effect. Hofmann and his team wanted to "solve this mystery in order to create a basis for how to produce materials with the same property." By combining both methods, the researchers were able to identify over two million potential interface structures for the TCNE-Cu interfaces and predict the behaviour of the molecules under various experimental conditions. Surprisingly, the results showed that there is no long-range charge transfer, but instead the molecules in the system change their structure. Molecules change their atomic arrangement When molecules are applied, usually they retain their general arrangement and pack more closely until, at a certain density, they finally start growing the second layer. In the TCNE/Cu(111) system, however, the adsorbed molecules change from the original lying position to a standing one after a certain amount has been deposited. They thus straighten up in order to be able to crowd even closer together. "However, standing molecules have a completely different charge transfer than lying molecules. The structural transformation is difficult to detect experimentally, but the measurement results are similar to those of long-range charge transport," explains Hofmann. The investigations refute the hypothesis of long-range charge transfer. The use of the combined machine learning methods SAMPLE and BOSS is intended to support future experiments in material development in such a way that such misinterpretations no longer occur. By taking a deeper look into the physical processes, the new processes help to ensure that materials are no longer designed to chase an effect that does not exist in this form. Hofmann underlines the advantage of the new method: "Thanks to the two methods, millions of different structures can be simulated in the future." The TU Graz researchers recently published details of the study in Advanced Science. Reference Egger et al., Charge Transfer into Organic Thin Films: A Deeper Insight through Machine‐Learning‐Assisted Structure Search, Advanced Science (2020), https://doi.org/10.1002/advs.202000992

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