Researchers at the University of St Andrews have identified advanced organic semiconductor materials that combine two-photon absorption and circularly polarised luminescence, pointing toward precision deep-tissue bioimaging technologies.
University of St Andrews Identifies Chiral Semiconductor Materials for Bioimaging
Scientists working within the Zysman-Colman group in the School of Chemistry at the University of St Andrews have documented the first examples of a new class of advanced organic semiconductor materials. Developed in collaboration with the Pal group at Durham University, these chemical compounds introduce an intersection of optical and electrical capabilities.
The discovery centers on chiral organic multi-resonant thermally activated delayed fluorescent, or MR-TADF, materials that simultaneously support two-photon absorption and emit circularly polarised luminescence, known as CPL. While individual organic materials occasionally display isolated optical traits, combining bright delayed CPL with two-photon absorption within a single organic material is rare.
Chiral Structure Enables Light Polarization and Two-Photon Absorption
Optoelectronic materials function as both optically active and electrically active mediums. Because the newly isolated compounds are chiral, they exist in mirror-image configurations that cannot be superimposed on one another. This structural twist enables the material to emit light carrying a preferred polarization.
Simultaneously, the compounds feature two-photon absorption, a process wherein a molecule absorbs two photons simultaneously. Only a small number of known materials possess this capability. Together, these properties allow the materials to manipulate light in ways that could redefine how scientists probe microscopic environments.
Potential Applications in High-Resolution Deep-Tissue Scans
The practical value of this chemical discovery lies beneath the surface of biological samples. By harnessing simultaneous two-photon absorption alongside circularly polarised luminescence, the research teams see a path toward imaging biological structures below the surface of tissues with greater precision.
“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.”
Professor Eli Zysman-Colman, Professor of Optoelectronic Materials at the University of St Andrews
Detailed results from the collaboration, titled Two-photon excited circularly polarised luminescence of hetero[9]helicene with multiresonant thermally activated delayed fluorescence, are featured in Nature Communications.