Recently, a research team led by Professor Sun Mingliang from the School of Materials Science and Engineering at Ocean University of China (OUC) made new progress in the field of organic room-temperature phosphorescent materials. Their outcomes were published online on March 17 in Nature Communications under the title “Isomer design unlocks rainbow phosphorescence”. The study achieves full-spectrum visible room-temperature phosphorescence color tuning through a simple organic molecular isomer design strategy, providing a new approach for the development of full-color organic phosphorescence materials.
Organic room-temperature phosphorescence (RTP) materials are a class of materials that continue to emit light after the removal of the excitation source at room temperature. Owing to their distinctive afterglow characteristics, they hold broad application potential in information anti-counterfeiting, bioimaging, optoelectronic devices, and emergency signage. However, these materials have long faced a key bottleneck: how to achieve stable and predictable multicolor emission, especially color tuning across the full visible spectrum, without relying on complex molecular modification or heavy metal systems. To address this challenge, the research team proposed a concise design strategy based on molecular isomer regulation. By selecting carbazole (Cz) together with its benzindole isomers (Bd[f], Bd[e], and Bd[g]), the researchers established a unified molecular platform and systematically investigated how the position of the nitrogen atom affects phosphorescence while keeping the fused tricyclic molecular framework unchanged. Meanwhile, the team developed a green mechanochemical ball-milling method that enabled the efficient and solvent-free synthesis of key isomers.
The study shows that simply by changing the position of the nitrogen atom, this series of materials can achieve afterglow color tuning from blue, green, yellow, and red, covering the full visible spectrum and exhibiting “rainbow phosphorescence”. Among them, the carbazole-based material shows an ultralong phosphorescence lifetime of up to 4.23 s, demonstrating excellent afterglow performance. Mechanistic analysis revealed that the position of the nitrogen atom regulates the molecular energy level structure, while the strong hydrogen-bonding interactions between carbazole and the polymer matrix effectively suppress energy dissipation, thereby prolonging the emission lifetime. In addition, this material platform exhibits excellent environmental stability: it maintains stable phosphorescence in various polymer matrices, retains its performance under high-temperature and seawater conditions, and can be activated by sunlight to produce persistent afterglow. Based on these advantages, the team demonstrated applications including high-temperature-tolerant anti-counterfeiting patterns, sunlight-activated emergency signage, and marine anti-counterfeiting coatings. Moreover, the emission wavelengths of these materials overlap with the visual sensitivity windows of some marine organisms, providing a new optical tool for related studies. This work proposes a minimalist structural regulation principle, opens up a new pathway for the development of full-color organic phosphorescent materials, and demonstrates broad application prospects in information security, marine engineering, and biomedicine.
