Constructing matrix-free solid-state carbon dots with efficient room-temperature phosphorescence

Efficient solid-state room-temperature phosphorescence (RTP) carbon dots (CDs) usually need to be embedded by a matrix to suppress the vibration dissipation between triplet and singlet states. However, selecting a suitable matrix is time-consuming, and the preparation process is often complicated. Here, we adopted a simple one-step hydrothermal method to obtain matrix-free solid-state RTP CDs with a long lifetime (1.22 s) and high fluorescence quantum yield (21.6%) by selecting suitable chain-like structure molecules for dehydration condensation and carbonization. The main source of RTP is the n-pi* transition of C=O/C=N on the surface of CDs. The polymer chain structure effectively avoids the disordered collision of CDs during curing. The formed cross-linked network structure helps stabilize the excited triplet state and provides a rigid environment to prevent the triplet state excitons from being quenched by ambient oxygen. The facile preparation process and efficient RTP properties provide a new idea for researching and developing matrix-free CDs.