Dual-Emission Afterglow of Carbon Dots Induced by an Inorganic Salt for Anticounterfeiting and Temperature Sensing

Afterglow carbon dots (CDs) have been extensively studied for sensing and anticounterfeiting because they can effectively block out the interference of background light. In this work, m-APBA CDs are obtained hydrothermally with m-aminophenylboric acid (m-APBA) and different kinds of inorganic salts (IS). When m-APBA CDs are combined with CaCl₂ and MgCl₂, dual-emission afterglow can be achieved based on CaCl₂ and MgCl₂ having the strongest aggregation ability, high charge density, structural confinement, and defects with respect to m-APBA CDs. The as-obtained CDs@CaCl₂ exhibits a dual mode afterglow with a quantum yield of 4.81% and lifetimes of 352 ms (delayed fluorescence) and 205 ms (phosphorescence). The afterglow of CDs@IS can be excited by both UV and visible light at the same time, which could be recorded for about 8 and 4 s. This unique method of inducing the m-APBA CD afterglow has the advantages of simple synthesis, low cost, and adjustable afterglow emission. Moreover, CDs@IS showed exceptional performance in anticounterfeiting and temperature sensing, further establishing its practical utility.