Facile, Quick, and Gram-Scale Synthesis of Ultralong-Lifetime Room-Temperature-Phosphorescent Carbon Dots by Microwave Irradiation

Long-lifetime room-temperature phosphorescence (RTP) materials are important for many applications, but they are highly challenging materials owing to the spin-forbidden nature of triplet exciton transitions. Herein, a facile, quick and gram-scale method for the preparation of ultralong RTP (URTP) carbon dots (CDs) was developed via microwave-assisted heating of ethanolamine and phosphoric acid aqueous solution. The CDs exhibit the longest RTP lifetime, 1.46s (more than 10s to naked eye) for CDs-based materials to date. The doping of N and P elements is critical for the URTP which is considered to be favored by a n ->pi* transition facilitating intersystem crossing (ISC) for effectively populating triplet excitons. In addition, possibilities of formation of hydrogen bonds in the interior of the CDs may also play a significant role in producing RTP. Potential applications of the URTP CDs in the fields of anti-counterfeiting and information protection are proposed and demonstrated.