Scientists have developed a new way to change the internal structure of glass while it is being made, potentially paving the way for advanced materials with precisely controlled magnetic, optical and chemical properties.
Researchers from TU Dortmund University, Paderborn University, the University of Duisburg-Essen and the University of Oxford developed the technique for glasses made from materials known as metal-organic frameworks, or MOFs.
Their findings were published in Nature Materials.
MOFs are unusual materials built from metal atoms connected by organic molecules. Some types can be melted and rapidly cooled to form glass.
These glasses have attracted interest for applications ranging from gas storage and batteries to sensors, optics and catalysis.
However, producing them can be difficult. High temperatures may cause some MOFs to break down before they melt, creating unwanted impurities and limiting the properties scientists can build into the resulting glass.
The researchers found a way around this problem using an organic molecule called 1,10-phenanthroline. They mixed the molecule with the starting material before heating it.
The molecule performs two important jobs. First, it acts like a flux, lowering the temperature needed to melt the material. This allows researchers to produce glass without exposing it to potentially damaging levels of heat.
More importantly, the molecule actively changes the chemical structure of the material while it is molten.
Rather than simply becoming trapped inside the glass as an additive, phenanthroline binds strongly to the metal atoms. In doing so, it changes the arrangement of chemical bonds surrounding them and restructures the glass network from within.
By changing how much phenanthroline they add, researchers can control the extent of this restructuring. This could allow scientists to design glasses with particular magnetic or light-emitting properties.
Experiments with cobalt-containing glasses showed another major advantage. Because the materials could be processed at lower temperatures, harmful decomposition products were avoided. This allowed researchers to study the glass’s true magnetic properties without interference from impurities.
The team used advanced techniques, including X-ray absorption spectroscopy, to examine the surroundings of individual cobalt atoms. The measurements confirmed that although the atoms maintained the same oxidation state, the arrangement of their neighboring molecules changed significantly.
The researchers also demonstrated that the approach works with another group of materials known as carboxylate-based frameworks, suggesting the technique could have broader applications.
The discovery changes the way scientists can think about the glass-making process. Instead of treating the molten state simply as a temporary stage between a solid starting material and finished glass, researchers can use it as an opportunity to actively redesign the material’s chemistry.
In the future, this approach could lead to new organometallic glasses for sensors, optoelectronics, catalysis and other technologies that require precise control over light, magnetism or chemical reactions.
