K 2019 Ausgabe 2

••• 10••• Innovationen Efficient materials for OLED displays For applications such as light- emitting diodes or solar cells, or- ganic materials are nowadays in the focus of research. These or- ganic molecules could be a prom- ising alternative to currently used semiconductors such as silicon or germanium and are used in OLED displays. A major problem is that in many organic semiconductors the flow of electricity is hampered by microscopic defects. Scientists around Dr. Gert-Jan Wetzelaer and Dr. Denis Andrienko of the Max-Planck-Institute for Polymer Research have now investigated how organic semiconductors can be designed such that the electric conduction is not influenced by these defects. In a semiconductor, electrons are moving at a high- er energy level, whereas holes move at a level lower (deeper) in energy. The scientists found that the conduction of both charge types strongly depends on the position of these energy levels. In computer simulations, scientists had a deeper look at the origin of these charge traps. Therefore, the Mainz researchers are able to define how to design highly effi- cient organic semiconductors in the future: The different energy levels of the material should be in a certain range, which strongly re- duces the influence of oxygen and water molecules that are the main cause for charge trapping. Based on this concept, the first highly efficient OLEDs with defect-free electrical conduction have recent- ly been realized. Forscher suchen Alternative für Mikroplastik Die Professur Strömungsmechanik und Strömungsmaschinen der Tech- nischen Universität Bergakademie Freiberg will in den kommenden Jah- ren gemeinsam mit Wissenschaftlern der Johannes-Gutenberg-Universität Mainz und der TU München sowie drei Industriepartnern ein innovati- ves Verdüsungsverfahren für bioba- sierte, bioabbaubare Polymermateri- alien entwickeln. Diese umweltfreundlichen Mikro- partikel sollen umweltschädliches Mikroplastik in Shampoos und ande- ren Kosmetika ersetzen. Im Projekt Bioshampoo wird die vollständige Prozesskette von der Konzeptionie- rung des Verfahrens, der Partikel- entwicklung, der Integration in ein Endprodukt (Shampoo) und der ab- schließenden Untersuchung der Bio- abbaubarkeit nach Einleitung in den Wasserkreislauf untersucht. Material for food coatings Derivatives are non-toxic and have a antibacterial activity Continued from page 1 The article is published in the jour- nal Food Chemistry. Preservatives are widely used in the food industry. They are necessary to extend the shelf life of products. On the other hand, preservatives reduce food quality. Some of them can cause allergies (benzoic acid) or be toxic (nitrates, nitrites). Synthetic waxy substances used to coat fruits can be carcinogenic (biphenyl is pro- hibited in the US and EU). Chitosan is a natural polymer de- rived from chitin, the main com- ponent of insect and crustacean shells. It has antibacterial prop- erties and is already used in the food industry for packaging and coating products with a protec- tive film. However, its activity is much inferior to antibiotics. To obtain non-toxic and highly ac- tive derivatives of chitosan, RUDN University chemists Andreii Kritchenkov and Margarita Kura- sova and their colleagues have modi- fied chitosan with organic azides by “sewing” them to the polymer chain. Azides are derivatives of hydrazoic acid HN3. Both organic and inorganic azides are toxic, but their compounds with chitosan are not poisonous. Antibacte- rial activity of the obtained substances, azido chitosan, was significantly higher than that of chitosan. The experiment showed that samples of polymers based on chitosan had antibacterial activity at the level of antibiotics. The researchers compared this parameter for azido chitosan with the two most common antibiotics – ampicillin and gentamicin. Antibacterial activity was deter- mined by diffusion into the agar (nutrient) layer. A disk of filter paper impregnated with the test substance was placed on the agar layer sown with a bacterial cul- ture. The substance penetrates the agar, killing bacteria or slow- ing their reproduction. As a re- sult, a growth suppression zone is formed around the disk, which dif- fers from the rest of the agar sur- face visually. The value of an anti- bacterial activity is estimated by the diameter of the formed zones. That is, the polymer has almost the same antibacterial activity as antibiotics. This is extremely im- portant, because the use of anti- biotics as components of antibac- terial films is highly unacceptable because it leads to the emergence of resistant strains of bacteria. Chitosan compounds do not have this disadvantage. New chitosan derivatives can be used as harmless and effective preservatives to create protective films for food on their basis. Fruit coatings can be carcinogenic . Photo: Elena Koycheva / Unsplash Vor allem im Meer verbreitet sich Mikroplastik. Foto: Brian Yurasits / Unsplash Impressum K 2019 Verlag: CONNEX Print & Multimedia AG Lavesstraße 3 30159 Hannover Telefon: +49 511 830936 Telefax: +49 511 56364608 E-Mail: connex@die-messe.de Internet: www.die-messe.de Auflage IVW-geprüft. Auflagengruppe: M Redaktion: Claudia Ballhause Verantwortlich für den Anzeigenteil: Tina Wedekind Druck: Rheinische DruckMedien GmbH, 40196 Düsseldorf MESSEJOURNAL DIE MESSE