Prof. LIU Bin (NUS) reveals how trace impurities unlock breakthroughs in ultralong organic phosphorescence

On 25 March 2026, Professor LIU Bin, Deputy President (Research and Technology) of National University of Singapore (NUS), delivered a PAIR Distinguished Lecture titled “Iso-structure Induced Ultralong Organic Phosphorescence” at the PolyU campus.  The event attracted nearly 100 in-person participants and over 15,700 online viewers across various social media platforms.

Prof. Liu began the lecture by highlighting a long-standing challenge in organic photophysics: the inherent difficulty of achieving efficient triplet state emission. She then presented her team’s breakthrough discovery in carbazole, a ubiquitous organic building block.  Their research revealed that trace impurities—notably the isomer 1H-benz[f]indole (Bd) commonly found in commercial carbazole—are actually the hidden drivers of ultralong phosphorescence. This insight has fundamentally shifted the field’s focus from intrinsic molecular properties toward understanding the critical role of “iso-structural doping” in generating phosphorescence.

The lecture further explored the diverse origins of these influential impurities, including variability in raw starting materials, side reactions during synthesis, and previously unidentified by-products. By regulating the doping process, Prof. Liu’s team has moved beyond “serendipitous observations” toward “rational design”, leading to the development of high-performance “multi-functional phosphorescent materials”, such as organic persistent mechanoluminescence and colour-tunable room-temperature phosphorescence.

A significant portion of the presentation was dedicated to translating these insights into practical materials engineering.  One key advancement is the development of the “Matrigel-Alginate Granular-Interstitial Composite (MAGIC) matrix”, which supports the bottom-up nanofabrication of organic phosphorescent nanocrystals.  The MAGIC matrix is a “sandwich-like” composite structure that combines particle support and matrix nutrition: optically transparent, bio‑inert alginate is processed into cell‑sized microgel particles, assembled into a granular scaffold, and infused with Matrigel to form a robust, cell‑compatible composite.  Prof. Liu emphasised that these organic phosphorescent nanocrystals show immense promise for biomedical applications, with preliminary in-vivo evaluations demonstrating their effectiveness for high-contrast lymph node imaging.  Other cutting-edge applications discussed included data encryption, anti-counterfeiting, and optical waveguides.

The lecture concluded with an engaging Q&A session moderated by Prof. XING Bengang, Chair Professor of Chemical Biology.  Both onsite and online audiences actively participated, raising questions on topics such as the distinctions between iso-structure induced effects and other aggregation-induced phosphorescence strategies, the structure-property relationship between spin-orbit coupling strength and ultralong phosphorescence performance, and biomimetic approaches to designing next-generation devices, leaving the audience inspired by the future possibilities of molecular engineering.