01-Feb-2017 - Technische Universität Wien

Fluorescence dyes from the pressure cooker

The laboratory of Dr. Miriam M. Unterlass at the Institute of Materials Chemistry at TU Wien has just reported the synthesis of more than 20 different perylene bisimide dyes. This is not impressive per se. The way they prepare these compounds is though: Conventionally, perylene bisimides are generated in highly toxic solvents and employing toxic and expensive catalysts. Moreover, classical reactions towards these dyes require an important excess of the starting compounds. Finally, tedious purification is necessary for obtaining dye products of sufficient purity. All in all, the conventional route is a complex chemical synthesis. "In our approach, we are using the starting compounds in a 1:1 ratio, i.e. without an excess of reactants. The starting compounds are dispersed in water inside a closed reactor. Then the mixture is heated to 200 °C and increased pressure is generated", explains Dr. Unterlass. "In fact, the reactor basically works like a pressure cooker." Such reactions in hot water under pressure are called hydrothermal syntheses. After the reaction has completed, the final perylene bisimide dyes are obtained with high purity, thus removing the necessity for tedious purification. For actual electronic applications, perylene bisimdes are mostly implemented by device engineers and physicists, who often do not have access to chemical laboratories. The novel hydrothermal synthesis bears the potential of enabling an easy access to these materials - an important step towards realistic application.

From big molecules to small molecules

Previously, Miriam Unterlass' team had developed a novel process for high-performance polymers, which equally takes place in hot water. The hydrothermal synthesis of perylene bisimide dyes now shows for the first time that small molecules can also be generated "in the pressure cooker". The order of developments is rather untypical. Normally, novel synthetic pathways are first developed for small molecules - which are often easier to conceive - and later transposed to polymers, i.e. "big molecules". Despite their small size, the hydrothermal synthesis was however very challenging. For perylene bisimides. They are very apolar, which means that they do not like water - at room temperature. By heating the water to increased temperatures, this challenge can however be met. The hydrothermal synthesis of perylene bisimides is highly efficient and environmentally friendly.

Facts, background information, dossiers
  • temperature
More about TU Wien
  • News

    Superconductivity: It’s Hydrogen’s Fault

    Nickel is supposed to herald a new age of superconductivity – but this is proving more difficult than expected. Scientists at TU Wien (Vienna) can now explain why. Last summer, a new age for high-temperature superconductivity was proclaimed - the nickel age. It was discovered that there are ... more

    New preparation processes for super-plastics

    Although organic plastics are not harmful to the environment themselves, toxic substances are often used during their synthesis. TU Wien shows - there is another way. Many materials that we use every day are not sustainable. Some are harmful to plants or animals, others contain rare element ... more

    Neural Hardware for Image Recognition in Nanoseconds

    Automatic image recognition is widely used today: There are computer programs that can reliably diagnose skin cancer, navigate self-driving cars, or control robots. Up to now, all this has been based on the evaluation of image data as delivered by normal cameras - and that is time-consuming ... more

  • Videos

    Epoxy Resin

    A flash of ultraviolet light sets off a chain reaction which hardens the whole object. more

    Noreia

    The coating machine Noreia was built at TU Wien. This time-lapse video shows the construction process. more

    Shaping Drops: Control over Stiction and Wetting

    Some surfaces are wetted by water, others are water-repellent. TU Wien (Vienna), KU Leuven and the University of Zürich have discovered a robust surface whose adhesive and wetting properties can be switched using electricity. This remarkable result is featured on the cover of Nature magazin ... more