A sunlight-powered breakthroughPlastic waste, notably microplastics, has been found across many of the planet’s ecosystems, raising concerns about threats to terrestrial and marine life and to human health as well. To tackle this problem, researchers at the University of Waterloo, Ontario, Canada, developed a way, using sunlight, to turn plastic waste into acetic acid, the main ingredient of vinegar. White rot fungus (Phanerochaete chrysosporium) is known for its ability to break down lignin, one of the toughest polymers found in wood. It uses enzymes that generate highly reactive chemical species capable of dismantling complex carbon structures. Yimin Wu and his colleagues at the university wondered if a synthetic material could mimic this strategy. The team developed a bio-inspired cascade photocatalysis using iron-doped carbon nitride as the catalyst. Carbon nitride is a semiconductor that absorbs visible light.“Rather than forming nanoparticles, each iron atom is isolated and embedded within the carbon nitride structure. This atomic precision is crucial. Each iron atom behaves like an active site in a natural enzyme, maximizing efficiency while maintaining stability,” Wu wrote in The Conversation, a magazine, describing the work. The system works through a cascade of light-driven reactions, he explained. Under sunlight, and in the presence of hydrogen peroxide, the iron sites activate the peroxide to generate hydroxyl radicals. A radical is an atom, molecule, or ion that has at least one unpaired electron, which makes it highly chemically reactive.These radicals attack the long carbon chains that make up plastics, like polyethylene (used in plastic bags), polypropylene (food containers), PET (drink bottles), and even PVC (pipes and packaging). The polymers are progressively oxidised and broken down into smaller molecules, eventually forming carbon dioxide (CO2). Rather than allowing this CO2 to escape, the same catalyst then uses sunlight to reduce the CO2 into acetic acid.In other words, the carbon in plastic waste is first oxidised and then reassembled into a new, valuable molecule. “Essentially, this approach breaks down plastic and converts the resulting carbon into a commodity chemical in a single system. This distinguishes it from most existing recycling technologies,” Wu said.Since the reaction takes place in water, it makes the process particularly relevant for plastic pollution in aquatic environments. The researchers also tested the process with real world waste streams containing polluted plastic and mixtures of different types. Significantly, compared with many chemical recycling methods that require heating plastic to several hundred degrees Celsius, this reaction proceeds at room temperature and normal atmospheric pressure.Acetic acid is widely used in food production, chemical manufacturing, and energy applications. Currently, most acetic acid is produced through an energy-intensive process process called methanol carbonylation, whereby methanol is reacted with carbon monoxide at high temperatures. “By mimicking the way enzymes control reactivity at precise metal centres, we can achieve complex chemical transformations under mild conditions using sunlight as the energy source,” Wu stated.While this approach is still at the laboratory stage, the team envisions that it could be adapted for scalable, solar-driven recycling and environmental clean-up and the photocatalytic upcycling system can be further enhanced through strategic materials engineering and manufacturing processes. A patient undergoing CT scan. A study by the International Atomic Energy Agency found significant variation in the radiation dosage received by patients from diagnostic tests for coronary artery disease. | Photo Credit: K.R. DeepakIAEA flags worldwide variation in radiation doses from diagnostic imagingA study by the International Atomic Energy Agency (IAEA) has found significant variation in the radiation dosage received by patients from diagnostic tests for coronary artery disease. The study, which was funded and conducted under the IAEA-coordinated research project IAEA Noninvasive Cardiology Protocols Study (INCAPS4) was carried out in association with Columbia University, New York City.The findings underscore an urgent need for improved training, standardised protocols, and updated equipment, particularly in low- and middle-income countries, where the data suggest that radiation doses could be lowered without compromising test results. The results were published recently in The Journal of the American Medical Association.The study analysed data from more than 19,000 patients at 742 centres in 101 countries, gathered over a 9-week period in 2023, making it the largest and most comprehensive global assessment of radiation exposure from non-invasive cardiac imaging.Researchers examined radiation doses from widely used imaging techniques, including nuclear cardiology tests and computed tomography (CT) scans of the heart. While many centres could keep radiation exposure within recommended limits, the study found marked variations between countries, regions, and income levels, with some people receiving higher doses than others for the same test.The study found that median radiation doses varied widely by imaging modality, income levels, and geography. Optimised protocols and use of newer technology, which often deliver clearer images, were consistently associated with lower patient exposure. Patients in low- and middle-income countries often received significantly higher doses, particularly for coronary CT angiography, a test that is increasingly used because of CT’s availability and technological improvements.“These differences are not inevitable,” said Andrew J. Einstein, the study’s principal investigator and corresponding author. “In many cases, the technology and knowledge to reduce dose already exist. The challenge is ensuring that they are applied consistently and equitably across the world.” The authors emphasised that reducing radiation doses does not mean reducing diagnostic quality.“This research provides critical evidence that can inform national policies and international action,” said Diana Paez of the IAEA, the senior investigator and co-lead of the study. The study points to the importance of peer-to-peer knowledge sharing, development of regional and global dose reference levels, and closer collaboration between regulators, professional societies, and industry, an IAEA release said.W.E. Moerner (an undated photograph). He won the Nobel Prize in Chemistry Prize in 2014 along with Eric Betzig and Stefan Hell “for the development of super-resolved fluorescence microscopy”. | Photo Credit: Linda A. Cicero/Stanford News/Handout via ReutersLabel-free microscope for nanoscale view inside living cellsBy combining two microscopy techniques, researchers at Stanford University have developed a one-of-a-kind instrument that can reveal cell structures interacting in real time at an unprecedented resolution of 120 nanometres, the highest achieved without the use of fluorescent labels.This new “label-free” technology, called Interferometric Image Scanning Microscopy (iISM), enables observation of cellular structures in their wider context, including their responses to intrusions, such as pathogens or drugs. The advance was published in the journal Light: Science and Applications.iISM’s capabilities open up new avenues in a range of life science fields, from understanding disease mechanisms and developing drugs to investigating relationships between plants and microbes.Even though the resolution is not as fine as other types of specialised microscopes, iISM allows the viewing of many structures at once for a long duration. In contrast, methods that rely on fluorescence to label structures typically can highlight only a few target structures at a time. Also, fluorescence can eventually “bleach” or wear off. These labels can also be difficult to introduce and, in some cases, may change the behaviour of the structures they tag.The difference between earlier high-contrast label-free approaches and iISM is that it can operate at a substantially lower illumination (less than a microwatt), which reduces the risk of photodamage to living cells and makes it less likely to disturb the tiny, delicate structures.iISM manages to achieve higher resolution and sensitivity by combining the advantages of two different microscopy methods that are the respective areas of expertise of the two scientists who created the technique and authored the paper on it. W.E. Moerner won the 2014 Nobel Prize in Chemistry for his work on super-resolution fluorescence microscopy and Michelle Kueppers’ doctoral work focussed on “interferometric scattering (iSCAT) microscopy”.In iSCAT microscopy, a laser shines on a cell, and the tiny structures inside scatter some of the light. A second laser beam is then used to amplify the weaker scattered light and make it strong enough to be detected so that the small structures can be viewed.The key advance in iISM is the combination of the iSCAT method with an adapted concept from next-generation confocal microscopes. While traditional confocal microscopes use a pinhole and a single detector to focus on target structures, advanced versions of these microscopes use camera-based array detectors, which capture many views of the same area.iISM uses a type of array detector that collects more light than the pinhole and single detector model. This provides increased depth and precision. It works similar to the way two human eyes both take in information to distinguish the foreground from background except that iISM uses tens to hundreds of views from an array detector. The researchers then developed a method to combine these measurements into sharper, higher-contrast images.iISM will, of course, not replace the use of fluorescence microscopy, which has yielded insights into the life sciences for decades. “Every method has its advantages and disadvantages, and we believe in a complementary implementation in the future,” said Kueppers. “If we use the strengths of fluorescence for molecular specificity and the strength of iISM for label-free context and dynamics, we can really start tackling questions that have been difficult to address before.”Also Read | Plastic pollution is surging. What are governments doing?Also Read | Atoms in industryCONTRIBUTE YOUR COMMENTS