Carbogenic π-conjugated domains as the origin of afterglow emissions in carbon dot-based organic composite films

The development of carbon dot (CD)-based pure organic materials displaying afterglow emissions under ambient conditions with readily tunable emissions is highly desirable. Herein, a facile solid-phase synthesis approach at ambient pressure is proposed for the production of CDs with yellow fluorescence emissions, which are further embedded in the polyvinyl alcohol (PVA) matrix to generate composite films with activated afterglow emissions. Studies show that the incorporation of an aromatic precursor in the CD fabrication process can enlarge the carbogenic π-conjugated domains of CDs, which are suggested as the main origin of the afterglow emissions. More importantly, the simple achievement of tunable fluorescence and afterglow emissions can be accompanied by either pre-treatment of the CDs or post-treatment of the composite film with an alkaline solution where a pure blue afterglow emission film of CD2-OH/PVA with CIE coordinates of (0.14, 0.07), a lifetime up to 338.4 ms and a quantum yield up to 6.88% under ambient conditions is achieved.