MXene in 30 seconds, a hydrogen path under 3 angstroms
A gas-phase process cuts MXene production to seconds, light reveals collective motion in an electron crystal, and a crosslinked polymer builds narrow paths that separate hydrogen from larger gases.
Science··Midday
A short gas step replaces the acid bath
A Rice University team has developed a gas-phase route that cuts the etching step in MXene production from hours to 30 seconds. MXenes are made by removing selected atomic layers from laminated starting materials known as MAX phases. Conventional liquid processing uses hydrofluoric acid, Lewis acids or molten salts, and chemical etching can take 12 to 24 hours. In the new method, flash Joule heating rapidly raises the temperature of a MAX phase before chlorine and tetrafluoromethane gases selectively remove its aluminium layers. Each of nine chemically different MAX phases was converted into a chlorine-terminated MXene within 30 seconds. Computational simulations explain the selective-etching mechanism, while high-resolution transmission electron microscopy images the atomic-scale transition from MAX phase to MXene. The team reports that changing gas composition and exposure time can tune the etching and that damage to the metal layers remains limited. Published in Nature Synthesis, the work demonstrates a sharp reduction in reaction time and names catalysis, electronic devices and aerospace coatings among possible uses. It does not establish the total capacity of a manufacturing line, but it moves the chemical step that forms the material from hours into seconds.[1]
Light catches an electron crystal in motion
Researchers at the University of Basel have measured the collective motion of electrons in a two-dimensional material through hybrid particles made with light. When electrons are confined to one plane and interact strongly, they can settle into a repeating arrangement resembling atoms in a crystal instead of moving independently. The material's atomic lattice does not create this Wigner crystal; repulsion between the electrons does. The team illuminated a single atomic layer of tungsten diselenide cooled to a few degrees above absolute zero and analysed the reflected light. Light-generated excitations called excitons interacted with the ordered electrons and formed hybrid quasiparticles known as Wigner crystal polarons. These particles acted as a probe that carried the collective motion of the electron arrangement into the optical signal. Published in Nature Physics, the result offers a way to investigate what happens inside the crystal rather than merely detecting its presence. The researchers say direct access to the internal behaviour of such electron crystals has been difficult until now. The polarons visible in reflected light make it possible to measure how a crystal order created without an atomic lattice moves.[2]
Narrow pores select hydrogen
A KAIST team has produced a crosslinked polymer membrane that lets hydrogen pass while excluding larger gas molecules. The researchers first defined a metric for the share of crosslinkers bonded at both ends to form a continuous transport path. In the membrane named ms-oDMB-DB50, that share reaches 73 per cent. According to the Nature Communications study, the membrane contains many ultramicropores smaller than 3 angstroms. Hydrogen moves through those narrow openings while larger molecules remain behind. The team reports substantial improvements in both hydrogen permeability and hydrogen-to-nitrogen selectivity compared with the parent material DB50. The membrane operated for 100 hours without losing performance, and its tensile strength was about twice that of previously reported high-performance polymer membranes. Separating high-purity hydrogen from mixed gases produced during manufacture remains a central obstacle to commercialisation. The new membrane addresses it by combining control of pore size with a measure of how completely crosslinks form a transport route. The three materials developments in the midday science news operate at different scales: removing an atomic layer in seconds, reading electron order with light and opening a selective passage for the smallest gas molecule.[3]
