Ultrasmall green-emitting carbon nanodots with 80% photoluminescence quantum yield for lysosome imaging

Carbon-based fluorescent nanomaterials have gained much attention in recent years. In this work, greenphotoluminescent carbon nanodots (CNDs; also termed carbon dots, CDs) with amine termination were synthesized via the hydrothermal treatment of amine-containing spermine and rose bengal (RB) molecules. The CNDs have an ultrasmall size of-2.2 nm and present bright photoluminescence with a high quantum yield of-80% which is possibly attributed to the loss of halogen atoms (Cl and I) during the hydrothermal reaction. Different from most CNDs which have multicolor fluorescence emission, the as prepared CNDs possess excitation-independent emission property, which can avoid fluorescence overlap with other fluorescent dyes. Moreover, the weakly basic amine-terminated surface endows the CNDs with the acidotropic effect. As a result, the CNDs can accumulate in the acidic lysosomes after cellular internalization and can serve as a favorable agent for lysosome imaging. Besides, the CNDs have a negligible impact on the lysosomal morphology even after 48 h incubation and exhibit excellent biocompatibility in the used cell models. (c) 2021 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.