Examples of projects offered during the summer school
Luminescent solar concentrators (LSCs) have the potential to act as solar energy generators in area snot appropriate for silicon-based solar panels, such as in a city setting. LSCs are plastic sheets that contain a fluorescent dye that absorbs direct and indirect incident sunlight, and re-emit this light at a lower energy. The re-emitted light is trapped in the plastic lightguide, exiting at the edges where it can be converted into electricity by an attached solar cell. The devices are colorful, can be any shape, which makes it easier to integrate in an urban environment. The devices have not found commercial use because their efficiency remains limited. By better control of the direction of light emission by the dyes we can limit losses through the surface and in the interior of the device. In this project we will make use of liquid crystals to bring order to the dye molecules and direct the light where we want it to go. These materials can in this way be applied to form switchable, energy generating windows as well.
Chemistry accelerated by light
You cannot imagine life without sunlight. In nature, many chemical processes occur under the influence of light. Processes like photosynthesis in plants. Surprisingly the chemical industry hardly uses the abundant and free solar energy. This is due to the absorption of light in a reaction medium. All light is typically absorbed within submillimeter scale. Which causes inefficient processing on larger scale or a limited throughput. Microreactor technology is a solution to overcome these issues. The reaction rates can be boosted enormously by going to lower scale reactors and throughput issues can be overcome by production via continuous flow.
Microreactors possess multiple benefits, like high mass and heat transfer, excellent mixing properties and enhanced safety. This means that mass and/or heat limited reactions could be conducted in a microreactor, where in a conventional reactor these reactions would be very slow or possibly not even work. This is especially true for multiphase reactions, which are often mass transfer limited. Furthermore, unsafe reaction (e.g. explosive reactions) could be applied in microreactor technology where the reaction volume is orders of magnitude lower than in conventional reactors. This diminishes the risk on an unwanted and dangerous outcome.
Different types of reactions can be applied to microreactors, such as polymerizations, cross-coupling via transition metals, fluorinations and oxidations via photocatalysis. Cross-coupling can be used to link different building blocks. Fluorinated compounds have a much longer lifetime in the human body than the non-fluorinated versions of these molecules. This is a great advantage for pharmaceutical compounds, as medicines then can work slower, but longer. In such, better control of dosing medicines to patients can be achieved. The disulfide bond (that you can below), created via an oxidation strategy involving photocatalysis, is widely used in the rubber industry. But it is also found in biomedical compounds where it can strengthen helix structures. This you can also see in people with curly hair.
In this project you will show that microreactors can be applied to overcome drawbacks that occur in conventional reactors. Also you will build your own reactor and compare different reactor types and systems using commercially available light sources.