143 Search Results

The sustainable generation of biodegradable plastics represents an opportunity to capture atmospheric CO2 while reducing plastic waste accumulation in the environment. This study implements an integrated platform for bioelectrocatalytic CO2 conversion to medium-chain-length polyhydroxyalkanoates (mcl-PHAs). Immobilizing cobalt phthalocyanine electrocatalysts on a covalent-organic framework in a gas recirculation electrolyzer enabled CO2-to-methanol conversion with a carbon conversion efficiency of 98%. Integration of polymer biosynthesis pathways enabled Methylotuvimicrobium alcaliphilum 20ZR to produce ~20% mcl-PHA of the dry cell weight with a CO2-to-bioproducts carbon conversion efficiency of 50%. This cell line was adapted to high sodium bicarbonate media, eliminating costly intermediate separation steps whilemore » improving economic potential. Transcriptomic analysis revealed sulfate transporters and peptidoglycan biosynthesis as key pathways involved in sodium bicarbonate halotolerance. Altogether, this research presents a foundation for integrating divergent chemical and biological processes into a transformative electrobiomanufacturing platform, addressing the need for alternative pipelines for generating valuable plastics and chemicals.« less

Recently the topic of altermagnetism has attracted tremendous attention, and RuO₂ has been demonstrated to be one of the most promising altermagnetic candidates. However, disputes still remain on the existence of magnetic order in RuO₂. Here in this work, we employ x-ray linear dichroism (XLD), a widely utilized technique for characterizing antiferromagnets, in conjunction with photoemission electron microscopy and multiple scattering calculation to provide clear evidence of the absence of magnetic order in epitaxial RuO₂ films. The observed XLD signal is nearly invariant with temperature and independent of cooling-field direction, in stark contrast to the substantial magnetic-order-related XLD signal predictedmore » by multiple scattering calculation. This finding strongly suggests a nonmagnetic origin for RuO₂. Furthermore, we observed significantly distinct XLD signals at the Ru M₃ and O K edges in RuO₂ films grown on TiO₂ substrate with different surface orientations, which can be attributed to the low-symmetry crystal field. In conclusion, these results unequivocally demonstrate the absence of magnetic order in RuO₂ and establish XLD measurement as a robust technique for probing the low-symmetry magnetic materials.« less

Alternative catalysts to the industrial Haber Bosch process have been of significant interest in the field of heterogeneous catalysis, yet realizing ammonia synthesis under mild conditions (e.g., 300 °C and 10 bar) is challenging due to the low per-pass conversion. One strategy is to promote the associative ammonia synthesis mechanism which eschews direct N-N bond cleavage. Here, in this work, we use self-pillared pentasil, a self-pillared hierarchical zeolite built by thin MFI zeolite nanosheets, as a support for subnanometric Ru clusters to synthesize ammonia. We show that Ru remains well-dispersed during reaction and further demonstrate that ammonia synthesis rates aremore » higher than Cs-Ru/MgO. Reaction kinetics show a positive order in H₂ providing evidence for the associative mechanism, which then becomes negative in H₂ if Ru is allowed to aggregate into nanoparticles. Operando Density Functional Theory models for Ru speciation in SPP, free energy diagrams, and microkinetic modeling were then applied to develop a reaction mechanism that involves sequential hydrogenation of N₂ from metallic Ru clusters. For this hydrogenation to occur, there are site requirements for N₂ to adopt a bridge-bound configuration that facilitates sequential hydrogenation on single sites and metal clusters. These site requirements in turn inform the design of improved zeolite-supported ammonia synthesis catalysts.« less

Developing advanced catalytic materials for mild-condition ammonia (NH₃) synthesis is essential for improving the energy efficiency of the industrial Haber-Bosch process. Here, in this study, we report a ζ-phase manganese nitride (MnN_0.43) catalyst for low-temperature NH₃ synthesis. The as-synthesized MnN_0.43 catalyst is protected by a carbon shell, allowing for the storage and processing of the air-sensitive metal nitride under ambient conditions. After activation in situ, the MnN_0.43 catalyst exhibits high activity for NH₃ synthesis at 250–350 °C, surpassing the conventional noble metal based Ru/MgO catalyst. A combination of kinetic, chemisorption, isotope labeling and computational studies indicate that a nitrogen vacancy-mediatedmore » associative mechanism accounts for the catalytic enhancements. Our work highlights the great potential of earth-abundant transition metal nitrides for catalyzing mild-condition NH₃ synthesis.« less

In recent years, the paint and coatings industry has shifted away from traditional resin formulations that require high concentrations of volatile organic compounds (VOCs) to achieve the desired rheological performance and sustainability targets. One approach to eliminate or reduce VOCs in paint and coating formulations while maintaining the final performance is to disperse stimuli-responsive polymer latex particles in water. The chemistry and architecture of these particles have been engineered such that the suspension rheology changes in response to the pH changes. The particles can also be swollen with organic solvents to illicit similar rheological changes. To understand how the particlemore » microstructure influences the observed macroscopic properties, we use small-angle neutron scattering and dynamic light scattering to determine that these particles consist of a cross-linked core with long polymer tails that extend into the dispersing medium. Carboxylic acid groups present on the tails deprotonate with increasing pH, and the extension of the polymer chain due to charge repulsion increases the hydrodynamic drag on the particle. Here we find that adjusting the pH alone has a much more significant effect on the shear dependence of the viscosity of the studied resin than adding organic solvent alone. We also find that this resin architecture is more responsive per mole of pH-responsive group than other architectures of pH-responsive latex particles in the literature.« less

End-of-life plastics present a significant challenge to achieving a sustainable economy. It is crucial to develop environmentally friendly technologies to process the waste streams beyond landfilling. This review provides a detailed overview of end-of-life plastics management, covering mechanical recycling, pyrolysis and hydrocracking methods. Mechanical recycling is the predominant technique employed on a large scale in recycling end-of-life plastics, and this review discusses the technoeconomic assessment and life cycle assessment (LCA) of mechanical recycling. This review also summarises key studies concentrating on chemical recycling techniques for handling end-of-life plastics. Among these, pyrolysis and hydrocracking are discussed in depth. Recent advancements andmore » fundamentals of these two techniques are covered, highlighting their significance in tackling the plastic waste challenge. The prospects of scaling up pyrolysis and hydrocracking technologies are interpreted in terms of technical and economic feasibility. The discussion concludes with recommendations for future research to commercialise chemical recycling of end-of-life plastics.« less

Increasing climatic and human pressures are changing the world's water resources and hydrological processes at unprecedented rates. Understanding these changes requires comprehensive monitoring of water resources. Hydrogeodesy, the science that measures the Earth's solid and aquatic surfaces, gravity field, and their changes over time, delivers a range of novel monitoring tools that are complementary to traditional hydrological methods. It encompasses geodetic technologies such as Altimetry, Interferometric Synthetic Aperture Radar (InSAR), Gravimetry, and Global Navigation Satellite Systems (GNSS). Beyond quantifying these changes, there is a need to understand how hydrogeodesy can contribute to more ambitious goals dealing with water-related and sustainabilitymore » sciences. Addressing this need, we combine a meta-analysis of over 3,000 articles to chart the range, trends, and applications of satellite-based hydrogeodesy with an expert elicitation that systematically assesses the potential of hydrogeodesy. We find a growing body of literature relating to the advancements in hydrogeodetic methods, their accuracy and precision, and their inclusion in hydrological modeling, with a considerably smaller portion related to understanding hydrological processes, water management, and sustainability sciences. The meta-analysis also shows that while lakes, groundwater and glaciers are commonly monitored by these technologies, wetlands or permafrost could benefit from a wider range of applications. In turn, the expert elicitation envisages the potential of hydrogeodesy to help solve the 23 Unsolved Questions of the International Association of Hydrological Sciences and advance knowledge as guidance toward a safe operating space for humanity. It also highlights how this potential can be maximized by combining hydrogeodetic technologies simultaneously, exploiting artificial intelligence, and accurately integrating other Earth science disciplines. Finally, we call for a coordinated way forward to include hydrogeodesy in tertiary education and broaden its application to water-related and sustainability sciences in order to exploit its full potential.« less

Optical metasurfaces, consisting of subwavelength-scale meta-atom arrays, hold great promise of overcoming the fundamental limitations of conventional optics. Due to their structural complexity, metasurfaces usually require high-resolution yet slow and expensive fabrication processes. Here, using a metasurface polarimetric imaging device as an example, the photonic structures and the Nanoimprint lithography (NIL) processes are designed, creating two separate NIL molds over a patterning area of > 20 mm2 with designed Moiré alignment markers by electron-beam writing, and further subsequently integrate silicon and aluminum metasurface structures on a chip. Uniquely, the silicon and aluminum metasurfaces are fabricated by using the nanolithography andmore » 3D pattern-transfer capabilities of NIL, respectively, achieving nanometer-scale linewidth uniformity, sub-200 nm translational overlay accuracy, and <0.017 rotational alignment error while significantly reducing fabrication complexity and surface roughness. Here, the micro-sized multilayer metasurfaces have high circular polarization extinction ratios as large as ≈20 and ≈80 in blue and red wavelengths. Further, the metasurface chip-integrated CMOS imager demonstrates high accuracy in broad-band, full Stokes parameter analysis in the visible wavelength ranges and single-shot polarimetric imaging. This novel, NIL-based, multilayered nanomanufacturing approach is applicable to the scalable production of large-area functional structures for ultra-compact optic, electronic, and quantum devices.« less