Structure changes function: mirror-image perovskites and fungal-chitin hydrogels
Mirror-image perovskite films produced different electrical responses to circularly polarized light, while chitin particles milled from fungi stiffened a hydrogel and offered another route around shellfish processing.
Science··Night
Right- and left-handed crystals answer light differently
Researchers at the Hebrew University of Jerusalem read the electrical response of mirror-image two-dimensional perovskite films to circularly polarized light without placing a metal contact on top of the film. These chiral structures come in two forms that do not fully overlap, much like right and left hands. The R form responded more strongly to right-circularly polarized light, while the S form favored left-circularly polarized light. Phys.org reports that the electrical difference was far more pronounced than the difference explained simply by how much of each polarization the materials absorbed. Study leads Joanna Dehnel and Igal Levine connect the response to a twisted crystal structure passing electrons of one spin more readily than the other. They link the persistence of the electrical difference to charges becoming trapped and recombining within the material. The present result describes the behavior of films rather than a finished device. Even so, the link between the direction of light polarization and charge separation makes visible a material property that could matter for spintronic and optoelectronic devices.[1]
Chitin from fungi instead of shells
A team at Oak Ridge National Laboratory and the University of Tennessee, Knoxville extracted chitin from fungi and used it to reinforce polyvinyl alcohol hydrogels. Chitin usually comes from shrimp and crab shells. That source can bring allergens with it and requires harsh chemistry to strip away contaminants and heavy metals. The fungal route reduces the material to submicron- and nanoscale particles through mechanical milling, with the team emphasizing that the resulting properties come from mechanochemistry instead of severe reactions or high temperatures. Electron microscopy was used to confirm the structure of the particles. When they were added to the polyvinyl alcohol network, the hydrogel became stiffer. The researchers list contact lenses, water-cleaning systems, and wound dressings among possible targets, and point to soft robotics and protective coatings as further areas of use. The report does not present those applications as finished products. Its concrete development is a source of chitin independent of shellfish processing that can enter a hydrogel structure and change its stiffness.[2]
Material properties are built from two different directions
The perovskite and hydrogel reports do not improve the same material. In the first, function appears in the electrical difference produced when right- and left-handed crystal structures meet polarized light. In the second, chitin particles from fungi enter a polyvinyl alcohol network and create a stiffer composite. One reads charge movement inside an existing thin film; the other changes the material input and the structure of a gel. Their shared direction is that a material's name alone cannot describe its expected function. The mirror-image form of a crystal, the source of a particle, and the way a component sits inside a network all become part of the observed behavior. Possible uses follow from those structures: light- and spin-based devices for the perovskites, and water cleaning, wound dressings, or soft robotics for fungal chitin. Those targets require separate development paths. Read together, the reports show material function emerging not only from discovering a new substance, but also from changing the orientation, source, and arrangement of familiar components.[1], [2]
