Research on light-responsive luminescence properties of carbon dots and their applications

Carbon dots (CDs), as zero-dimensional carbon-based nanomaterials, have become a new generation of smart luminescent materials because of their tunable optical properties, excellent biocompatibility and controllable synthesis strategies. On the basis of the difference in their optical response behavior, CDs can be classified into two main systems: photoluminescent and photochromism. Photoluminescent CDs achieve luminescence, including fluorescence, room temperature phosphorescence (RTP), and thermally activated delayed fluorescence (TADF), through the modulation of the carbon core structure, surface state engineering, molecular state jumping, and crosslink-enhanced emission (CEE) mechanisms. On the other hand, photochromic CDs confer dynamic optical response properties to materials through free radical-mediated electron transfer, energy transfer modulation, or molecular isomerization. In this review, we systematically elucidate the underlying luminescence mechanisms of these two types of systems and introduce the unique properties and application prospects of photoresponsive CDs in biomedicine, catalysis, and anticounterfeiting. We summarize the latest research progress on photoresponsive CDs, analyze their material properties, and discuss the key challenges to be addressed in their future development.