The Solid-State Emission of Bilirubin

Bilirubin (BR) is a human-biological compound formed during the haem metabolism that is insoluble in most solvents. BR has shown short emission lifetime with low quantum yield in limited number of solvents, due to the non-radiative ultrafast isomerization process. However, in solid-state, red-shifted emission of long-lived species of BR are detected at room temperature, due to the aggregation-induced emission formed by Frenkel exciton of J-system. This solid-state emission of BR depends on the crystal quality of BR as shown by SEM and XRD. This study allows for better understandings of the photophysics of BR in solid-state, opening opportunities for its applications in luminescent biological sensors.