In a groundbreaking achievement, researchers from CNR – Istituto Officina dei Materiali (CNR-IOM), the University of Trieste, Italy, and Innsbruck, Austria, and Elettra Sincrotrone Trieste have successfully synthesized a novel two-dimensional crystalline form of diboron trioxide. This new crystal, composed entirely of structural units previously seen only in its disordered, glassy state, marks a significant scientific milestone. Published in the prestigious journal Science, the study confirms the existence of a structure previously predicted only in theory, and opening exciting possibilities for future applications of this innovative material.

Boron oxide is a critical component in the production of ultra-durable glasses, such as Pyrex, and high-performance enamels. The addition of boron trioxide enhances glass’s resistance to thermal shock and chemical reactions, making it ideal for demanding industrial and scientific applications. However, the vitrification process of boron oxide remains poorly understood, exhibiting unique anomalies compared to other oxides, like silica, which can exist in both crystalline and amorphous forms.

“The key distinction between a crystal and a glass lies in the ordered arrangement of atoms in the former, which is absent in the latter,” explains Alessandro Sala, a CNR-IOM researcher and the project’s lead designer. “Both materials typically share a basic structural unit of a few atoms, repeated throughout. In crystals, this “building block” is arranged in a precise, repeating pattern, while in glass, it is disordered. Boron oxide is an exception: its glassy phase contains a structural unit called boroxine – a ring of three boron and three oxygen atoms – that have never been observed in a crystalline form until now. Our team has achieved a world-first by creating a two-dimensional crystalline phase made entirely of these boroxine units.”

The international research team not only devised a method to synthesize this material, using platinum as a substrate, but also conducted detailed analyses of its physical properties. Maria Peressi, a professor at the University of Trieste, elaborates: “Our numerical simulations reveal that this porous material, formed by a lattice of boroxine rings, is extraordinary flexible – ten times more elastic than graphene, making it the most elastic single-layer material ever reported. This remarkable flexibility arises because the rigid boroxine rings are connected by a single oxygen atom, acting as a hinge that allows them to rotate in the plane. Experimental and simulation results also show that the material interacts weakly with its platinum substrate, suggesting it could be easily separated using conventional techniques for using in cutting-edge devices.”

Laerte Patera, a professor of University of Innsbruck, adds: “using advanced scanning tunneling microscopy in Trieste and Innsbruck, we visualized the crystalline structure of this two-dimensional material down to its individual atoms. This unprecedented resolution enables us to pinpoint the position of each atom in the lattice, offering valuable insights into how atoms reorganize during the transition from crystalline to glassy states. This capability will be transformative for future studies of material transformations.”

Andrea Locatelli, head of the Nanospectroscopy beamline at Elettra Sincrotrone Trieste, emphasizes the mix of advanced technology: “Synchrotron light was instrumental in confirming the material’s elemental composition, purity and crystallinity. We can now produce homogeneous crystals spanning tens of square microns. The synergy between experimental techniques and numerical simulations was pivotal to this project’s success. With its unique properties – a wide-bandgap semiconductor that is both highly flexible and porous – this material holds immense potential for application in fields ranging from electronics and catalysis to quantum technologies.”

Adding to the significance of this achievement, the study’s first authors, Teresa Zio and Marco Dirindin, are PhD students from the University of Trieste, specializing in experimental and theoretical research, respectively. Their contribution highlights the University’s commitment to fostering excellence in advanced research training.