University of Gothenburg
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Karl Börjesson

Professor

Department of Chemistry & Molecular
Biology
Telephone
+46 31-786 90 99
+46 766-22 90 99
Mail
karl.borjesson@gu.se
Visiting address
Kemigården 4
41296 Göteborg
Postal address
Kemivägen 10
41296 Göteborg

About Karl Börjesson

I am leading a group in which we construct molecules or molecular based systems that are able to perform highly specialized functions. The research questions are of fundamental nature, and competence of the group involves both the synthesis of complex molecules and the photophysical/electrical characterization of the molecular based systems. Most often we are working with photoactive organic molecules and even though each molecule is able to perform a task on its own, our aim is not to use the single molecules but ensembles of molecules to create materials for the future. For more information on individual research projects see below (or our group homepage www.molecularmaterials.se), and for the most recent work see my google scholar page.

Research

Strong exciton-photon coupling: Chemistry has had profound impact on society during the last two centuries. From mass production of drugs and pigments, to the invention of plastics, and more recently with the introduction of molecular electronics. However, some basic physical laws govern possible utilizations. It is therefore of great importance to examine how to bend these laws, how to bypass them and by so doing open up new opportunities for novel applications. A common way of envision the creation of molecular orbitals is through the hybridization of atomic orbitals. It is perhaps less known that electronic states in molecules and atoms can hybridize with light or vacuum fields to create hybrid light matter states. So called strong exciton-photon coupling occurs when light-matter interactions are large, and it is manifested through new hybrid light-matter states called cavity polaritons. Our aim is to understand how polaritons interacts with more normal molecular states. For instance, we have shown that strong light-matter coupling enables selective manipulation of energy levels. By so doing allowing for a singlet ground and first excited state, thus challenge Hund’s rule and change how the basic rules of electronic state energetics are envisioned. This enables channelling of all excitation energy, irrespectively of origin, through a singlet pathway, which is of great technological importance in organic electronics.

Resonance energy transfer: Excitation energy transfer through dipole-dipole interactions can efficiently mediate energy between molecules at fairly large distances. In this so called Förster type energy transfer the transition dipole moments on the energy donor and acceptor couple so that excitation energy is transferred between the two molecules. The efficiency of the energy transfer depends not only on the strength of the transition dipole moments, but also on their relative orientation. Our research efforts aim at both studying this process at a fundamental level and also use it to increase the efficiency of molecular electronic devices. Recent advances includes the demonstration that the process works between states of different multiplicity.

Covalent Organic Frameworks: Nanostructured materials made from highly controlled synthetic and supramolecular chemical reactions are becoming increasingly important to solve challenges related to energy storage and clean air. An upcoming material that already has shown a high potential in many of these aspects is the covalent organic framework (COF), which is a metal free, lightweight development from the metal organic framework (MOF). We have developed a platform for synthesizing smooth films of 3D organic covalent frameworks, and by doing so, have opened up a range of new research directions where substrate connection, and film connectivity is a requirement.

Photon Upconversion: Triplet-triplet annihilation photon upconversion (TTA-UC) provides the possibility to convert low to high energy photons at low irradiation conditions. It is thus considered as a promising method to increase the efficiency of solar energy conversion systems like photocatalysis and solar cells. Our research aims at developing concepts for making this, in solution highly efficient, process efficient in the solid state. By doing so, we would bridge academic interest for the fundamental process with real world usability.

Organic Dye Glasses: Materia can be present as gas, liquid, and solids. The ability of a molecule to interact with light depends in which state it is present in. It is specifically important to be able to make materials, where the intrinsic photophysical properties are present even in the solid state. In order to do so, we have introduced a concept where we use entropy to direct the material to form a glass rather than a crystalline state, and by so doing we can create dye glasses, in which the individual molecules retain their intrinsic photophysical properties.

Equipment

My labs are equipped for research through the whole value chain. For synthesis of organic molecules, we have fully equipped synthesis labs, including automated purification systems, dry solvent setups, manifolds, and access to mass spectroscopy and NMR. For processing of molecules into materials, we have a spin coater, a molecular evaporator, and a metal sputterer. For probing molecules, we have UV/Vis/Nir spectrophotometers including a universal reflectance accessory (PE lambda 650 and 950), an optical microscope (Zeiss), a spectrofluorometer (EI FLS1000) including time correlated single photon counting function, a setup for laser flash photolysis (Spectra physics + EI LP980), a cryostat, an integrating sphere, and a probe station.

Funding

Present funding includes ERC Starting grant, Wallenberg Academy Fellow grant, The Swedish Research Council Project grant, and the Göran Gustafsson prize

Group members

PhD students: Clara Schäfer, Rahul Bhuyan

Post Docs: Yizhou Yang, Andrew Carrod, Nicola Peruffo, Krishnapriya Kunnumma, Vishnu Nair Gopalakrishnan

Alumni

PhD students: Manuel Hertzog, Alexei Cravcenco, Martin Ratsch, Jürgen Mony, Yi Yu

Post Docs: Kati Stranius, Khushbu Khushwaha, Pedro Navarro, Suman Mallick, Chen Ye, Mao Wang, Arpita Munkherjee

Teaching

I am responsible and am lecturing in KER230 (organic chemistry for prescriptionists). I am also teaching kinetics in KER220 (basic chemistry) and spectroscopy in KEM040 (physical chemistry).