“Smart window” keeps heat out, conserves energy

Windows allow brilliant natural light to stream into homes and buildings. Along with light comes heat that, in warm weather, we often counter with energy-consuming air conditioning. Now scientists are developing a new kind of “smart window” that can block out heat when the outside temperatures rise. The advance, reported in ACS’ journal Industrial & Engineering Chemistry Research, could one day help consumers better conserve energy on hot days and reduce electric bills.

Researches Xuhong Guo, Kaimin Chen, Yanfeng Gao and colleagues explained that researchers are pursuing smart windows that can respond to a variety of cues, including electricity, gas, light and heat. Those that are sensitive to heat are particularly useful for cutting down on energy use - when it gets hot outside, the windows turn an opaque white to block unwanted heat from entering a building while still allowing light to pass. They become transparent again as temperatures drop. But current methods for making these windows use jelly-like materials called hydrogels that swell in the heat, which hurts performance. Guo’s and Gao’s teams wanted to address this flaw.

Building on previous advances, the researchers made a version of the hydrogels, but in the form of microscopic soft beads suspended in a liquid. They sandwiched the solution between two pieces of glass and tested it using a model house. When they shined a lamp mimicking solar light on the smart window, it turned opaque and kept the inside of the house cool. The microgel, however, didn’t swell as much as its predecessor. The researchers conclude that their new microgel is a good candidate for use in future smart windows.

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Scientists create ‘artificial chemical evolution’

Scientists have taken an important step towards the possibility of creating synthetic life with the development of a form of artificial evolution in a simple chemistry set without DNA.

A team from the University of Glasgow’s School of Chemistry reported in the journal Nature Communications that they have managed to create an evolving chemical system for the first time. The process uses a robotic ‘aid’ and could be used in the future to ‘evolve’ new chemicals capable of performing specific tasks.

The researchers used a specially-designed open source robot based upon a cheap 3D printer to create and monitor droplets of oil in water-filled Petri dishes in their lab. Each droplet was composed from a slightly different mixture of four chemical compounds.

Droplets of oil move in water like primitive chemical machines, transferring chemical energy to kinetic energy. The researchers’ robot used a video camera to monitor, process and analyse the behaviour of 225 differently-composed droplets, identifying a number of distinct characteristics such as vibration or clustering.

The team picked out three types of droplet behaviour – division, movement and vibration – to focus on in the next stage of the research. They used the robot to deposit populations of droplets of the same composition, then ranked these populations in order of how closely they fit the criteria of behaviour identified by the researchers. The chemical composition of the ‘fittest’ population was then carried over into a second generation of droplets, and the process of robotic selection was begun again.

Over the course of 20 repetitions of the process, the researchers found that the droplets became more stable, mimicking the natural selection of evolution. The research team was led by Professor Lee Cronin, the University of Glasgow’s Regius Chair of Chemistry.

“This is the first time that an evolvable chemical system has existed outside of biology. Biological evolution has given rise to enormously complex and sophisticated forms of life, and our robot-driven form of evolution could have the potential to do something similar for chemical systems,” said Professor Cronin.

“This initial phase of research has shown that the system we’ve designed is capable of facilitating an evolutionary process, so we could in the future create models to perform specific tasks, such as splitting, then seeking out other droplets and fusing with them. We’re also keen to explore in future experiments how the emergence of unexpected features, functions and behaviours might be selected for,” added Professor Cronin.

“In recent years, we’ve learned a great deal about the process of biological evolution through computer simulations. However, this research provides the possibility of new ways of looking at the origins of life as well as creating new simple chemical life forms,” added Professor Cronin.

The project is the latest of the Cronin Group’s efforts to explore evolution outside organic biology. Other projects have included the development of inorganic chemical cells known as iCHELLs, which are built from molecules of metal and exhibit some of the same abilities as living cells.

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Bioplastics production made much greener

Polylactic acid is a degradable plastic used mostly for packaging. To meet the rising demand, ETH researchers have developed an eco-friendly process to make large amounts of lactic acid from glycerol, a waste by-product in the production of biodiesel.

Plastic waste is one of today’s major environmental concerns. Most types of plastic do not biodegrade but break up into ever smaller pieces while remaining a polymer. Also, most types are made from oil, a rapidly dwindling resource. But there are promising alternatives, and one of them is polylactic acid (PLA): it is biodegradable and made from renewable resources. Manufacturers use PLA for disposable cups, bags and other sorts of packaging. The demand for PLA is constantly rising and has been estimated to reach about one megaton per year by 2020.

The research groups of ETH professors Konrad Hungerbühler and Javier Pérez-Ramírez at the Institute for Chemical and Bioengineering are now introducing a new method to produce lactic acid. The process is more productive, cost-effective and climate-friendly than sugar fermentation, which is the technology currently used to produce lactic acid. The new method’s greatest advantage is that it makes use of a waste feedstock: glycerol.

Glycerol is a by-product in the manufacturing of first-generation biofuels and as such is not high-grade but contains residues of ash and methanol. “Nobody knows what to do with this amount of waste glycerol,” said Merten Morales, a PhD student in the Safety and Environmental Technology group of professor Hungerbuhler. This waste substance is becoming more and more abundant, with 3 megatons in 2014 expected to increase to over 4 megatons by 2020. Because of its impurity, glycerol is not suitable for the chemical or pharmaceutical industry. Moreover, it does not burn well and is thus not a good energy source.

“Normally, it should go through waste water treatment, but to save money and because it is not very toxic, some companies dispose of it in rivers or feed it to livestock. But there are concerns about how this affects the animals,” said Morales.

Making use of this waste feedstock by converting it into lactic acid already constitutes an advantage that makes the new method more eco-friendly. In this procedure, glycerol is first converted enzymatically to an intermediate called dihydroxyacetone, which is further processed to produce lactic acid by means of a heterogeneous catalyst.

The researchers of the Advanced Catalysis Engineering group of professor Pérez-Ramírez designed a catalyst with high reactivity and a long life span. It consists of a microporous mineral, a zeolite, whose structure facilitates chemical reactions within the pores. The close collaboration between the two research groups allowed the catalyst to be improved step by step while at the same time performing the life cycle assessment of the procedure as a whole.

“Without the assessment and comparison with the conventional method, we might have been happy with an initial catalyst design used for our study, which turned out to be less eco-friendly than fermentation,” explained Pierre Dapsens, a PhD student in the Pérez-Ramírez group. By improving several aspects of the catalyst design, the researchers were finally able to surpass sugar fermentation both from an environmental and an economic point of view.

Industrial processes are often turned “sustainable” simply by switching to a renewable resource. “However, taking the whole process into account – from the source of the feedstock to the final product and including waste management – you will often find that a supposedly sustainable production method is not necessarily more sustainable than the conventional one,” added Cecilia Mondelli, Senior Scientist in the Advanced Catalysis Engineering group who is also involved in the study.

Taking into account the energy saved by using the waste feedstock glycerol and the improved productivity, the new procedure reduces the overall CO2 emission by 20 per cent compared to fermentation: per kilogram of lactic acid produced, 6 kilograms of CO2 are emitted with the new method compared to 7.5 kilograms with the conventional technology. Also, by lowering the overall cost of the process, the researchers calculated a 17-foldincrease of the profit possible by using the new process. “Our calculations are even rather conservative. We assumed a glycerol feedstock of relatively good quality. But it also works with low-quality glycerol, which is even cheaper,” said Morales. Thus, manufacturers could increase their profit even further.

“Although today’s major bioplastic companies are based in the US, the process is relatively simple and could be implemented in other countries that produce biofuel and the by-product glycerol”, concluded Dapsens.

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Zeolites net new carbon allotropes

Previously unknown carbon allotropes have been predicted by scientists exploring their links with well-known network topologies. The new structures are highly stable and transparent, some with larger optical band gaps than diamond. Advanced computational techniques are leading the search for new forms of carbon and other group 14 elements. Now, Davide Proserpio from the University of Milan, Italy, and co-workers, have shown that fundamental network descriptors known about and catalogued for many years can help predict as well as classify and compare allotropes.

Topology defines a network in terms of its basic elements, such as nodes and links. A network can be deformed, stretched or bent and remain the same topology, but elements cannot be broken or rearranged. Zeolites and metal - organic frameworks are often described and distinguished in this way.

Proserpio’s team took a collection of 600,000 different zeolite topologies and found six new low energy carbon allotropes by applying strict geometrical and stereochemical considerations. “The structures are already out there but you need to feel them out with the correct criteria. A lot of people are doing molecular dynamics but no one has found these structures,” he explained. As well as being very hard, stable and transparent, these predicted allotropes share structural characteristics with physically existing forms of carbon which points to potential fabrication routes.

“What is important about this design work is that it draws beautifully on existing structures from one sub-field of chemistry – zeolites – to come up with possible alternatives for another field,” said allotrope pioneer Roald Hoffmann, from Cornell University in the US. This link is important because scientists can be unaware of relevant developments outside of their immediate research area. “Often people are redoing things that were done in the literature a long time ago … a lot of this [allotrope] work is published in physics journals by physicists, who don’t know the chemistry,” added Proserpio.

Topological labelling could help prevent this duplication of effort by providing a clear system of allotrope classification. Lars Ohrstrom, a metal–organic framework expert at Chalmers University of Technology, Sweden, comments that: “Currently they give them [allotropes] different sorts of names, sometimes space groups … net topology will be a better descriptor than a space group, because the same topology can actually exist in several different space groups, so you can have the same connectivity, the same basic structure, but you can have different space groups.”

And there’s nothing to stop chemists from extending this topological approach to search for other new network forming compounds like water polymorphs and hydrogen bonding systems.

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Newly developed nanoparticle cluster manufacturing technique using DNA binding protein

Researchers at KAIST developed a new manufacturing technique for size-controllable magnetic nanoparticle clusters (NPCs) using the zinc finger protein that specifically binds to target DNA sequence. The research by Hak-Sung Kim, Professor, Department of Biological Sciences, KAIST and doctoral candidate, Yiseul Ryu was published in Angewandte Chemie International Edition online.

NPCs are structures consisting of magnetic nanoparticles, gold nanoparticles, and quantum dots, each of which are smaller than 100 nm (10-9m). NPCs have a distinctive property of collectivity not seen in single nanoparticles. Specifically NPCS differ in physical and optical properties such as plasmon coupling absorbance, energy transfersbetween particles, electron transfers, and conductivity. Therefore, NPCs can be employed in biological and medical research as well as the development of nanoelectric and nanoplasmon devices.

To make use of these novel properties, the size and the composition of the cluster must be exquisitely controlled. However, previous techniques relied on chemical binding which required complex steps, making it difficult to control the size and composition of NPCs.

Professor Kim’s team used Zinc Finger, a DNA binding protein, to develop a NPCs manufacturing technique to create clusters of the desired size easily. The Zinc Finger protein contains a zinc ion and specifically recognizes DNA sequence upon binding, which allows the exquisite control of the size and the cluster composition. The technique is also bio-friendly.

Professor Kim’s team created linear structure of different sizes of NPCs using Zinc Finger proteins and three DNA sequences of different lengths. The NPCs they produced confirmed their ability to control the size and structure of the cluster by using different DNA lengths.

The NPCs showed tripled T2 relaxation rates compared to the existing MRI contrast media (Feridex) and effectively transported to targeted cells. The research findings show the potential use of NPCs in biological and medical fields such as MRI contrast media, fluorescence imaging, and drug transport.

The research used the specific binding property of protein and DNA to develop a new method to create an inorganic nanoparticle’s supramolecular assembly. The technique can be used and applied extensively in other nanoparticles for future research in diagnosis, imaging, and drug and gene delivery.

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Research towards making “artificial leaf” to produce clean hydrogen fuel

For years, scientists have been pursuing “artificial leaf” technology, a green approach to making hydrogen fuel that copies plants’ ability to convert sunlight into a form of energy they can use. Now, one team reports progress toward a stand-alone system that lends itself to large-scale, low-cost production. They described their nanowire mesh design in the journal ACS Nano.

Researchers Peidong Yang, Bin Liu and colleagues noted that harnessing sunlight to split water and harvest hydrogen is one of the most intriguing ways to achieve clean energy. Automakers have started introducing hydrogen fuel cell vehicles, which only emit water when driven. But making hydrogen, which mostly comes from natural gas, requires electricity from conventional carbon dioxide-emitting power plants. Producing hydrogen at low cost from water using the clean energy from the sun would make this form of energy, which could also power homes and businesses, far more environmentally friendly. Building on a decade of work in this area, Yang’s team has taken one more step toward this goal.

The researchers took a page from the paper industry, using one of its processes to make a flat mesh out of light-absorbing semiconductor nanowires that, when immersed in water and exposed to sunlight, produces hydrogen gas. The scientists say that the technique could allow their technology to be scaled up at low cost. Although boosting efficiency remains a challenge, their approach - unlike other artificial leaf systems - is free-standing and doesn’t require any additional wires or other external devices that would add to the environmental footprint.

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Gut bacteria from worm can degrade plastics, finds study

 Plastic is well-known for sticking around in the environment for years without breaking down, contributing significantly to litter and landfills. But scientists have now discovered that bacteria from the guts of a worm known to munch on food packaging can degrade polyethylene, the most common plastic. Reported in the ACS journal Environmental Science & Technology, the finding could lead to new ways to help get rid of the otherwise persistent waste, the scientists say.

Researcher Jun Yang and colleagues point out that the global plastics industry churns out about 140 million tonne of polyethylene every year. Much of it goes into the bags, bottles and boxes that many of us use regularly - and then throw out. Scientists have been trying to figure out for years how to make this plastic trash go away. Some of the most recent studies have tried siccing bacteria on plastic to degrade it, but these required first exposing the plastic to light or heat. Yang’s team wanted to find bacteria that could degrade polyethylene in one step.

The researchers turned to a plastic-eating moth larva, known as a waxworm. They found that at least two strains of the waxworm’s gut microbes could degrade polyethylene without a pretreatment step. They say the results point toward a new, more direct way to biodegrade plastic.

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