Imaging breakthrough could aid deep-tissue scans

Researchers at the University of St Andrews have identified the first examples of a new class of advanced organic semiconductor materials that could one day be used as bioimaging agents, opening up new possibilities for deep-tissue imaging.

The breakthrough, published in Nature Communications, was made by the Zysman-Colman group in the School of Chemistry at the University of St Andrews in collaboration with the Pal group at Durham University.

The researchers report the first examples of chiral organic multi-resonant thermally activated delayed fluorescent (MR-TADF) two-photon absorption materials that also emit circularly polarised luminescence (CPL).

The discovery is significant because it is rare for a single organic material to combine bright delayed CPL with two-photon absorption properties. Together, these characteristics make the compounds promising candidates for future applications in advanced optoelectronics and bioimaging.

Optoelectronic materials are both optically and electrically active. The compounds developed by the researchers are also chiral, meaning they exist as mirror-image forms that cannot be superimposed on one another. This chirality enables them to emit light with a preferred polarisation.

The materials also exhibit two-photon absorption, a phenomenon in which a molecule absorbs two photons simultaneously. Only a small number of known materials possess this capability.

The combination of these properties could have important implications for the development of deep-tissue bioimaging technologies, allowing researchers to image biological structures below the surface of tissues with greater precision.

Corresponding author Professor Eli Zysman-Colman, Professor of Optoelectronic Materials at the University of St Andrews, said: “These materials could be used to deliver high-resolution imaging of biological structures by exploiting their distinct combination of optical properties, which is an area that we are currently exploring.”

The findings represent an important step in an emerging area of optoelectronics, with potential applications across imaging and photonic technologies.

The research paper, Two-photon excited circularly polarised luminescence of hetero[9]helicene with multiresonant thermally activated delayed fluorescence, is published in Nature Communications.