Na + : the key to ultra-long afterglow lifetimes of CDs in dense SiO 2 matrices

Carbon dot-based room-temperature phosphorescence materials have emerged as a shining new star in the carbon nanomaterial family in recent years due to their excellent optical properties. However, there still exists a significant challenge in obtaining carbon dots (CDs) with ultra-long phosphorescence lifetimes. In this study, tetraethyl orthosilicate (TEOS) was used to achieve in situ growth and encapsulation of CDs in a 3D SiO 2 network using a one-pot hydrothermal method. It was demonstrated that Na + is the key factor to achieve ultra-long afterglow lifetimes of CDs in dense SiO 2 matrices, and the introduction of Na + has a significant effect on extending the afterglow lifetime of various CDs. The designed Na/CDs@SiO 2 nanomaterial exhibited an ultra-long afterglow lifetime of 6.69 s, which surpassed most reported CD-based afterglow lifetimes. This work provides a design principle and general strategy for achieving ultra-long afterglow lifetimes of CDs in dense SiO 2 matrices. Due to the stable photoluminescence (PL) properties, low biotoxicity, and ultra-long afterglow lifetime of the Na/CDs@SiO 2 nanomaterial, it was successfully applied in HeLa cell imaging.