In Situ Confining Citric Acid‐Derived Carbon Dots for Full‐Color Room‐Temperature Phosphorescence

Room‐temperature phosphorescence has received much attention owing to its potential applications in information encryption and bioelectronics. However, the preparation of full‐color single‐component‐derived phosphorescent materials remains a challenge. Herein, a facile in situ confining strategy is proposed to achieve full‐color phosphorescent carbon dots (CDs) through rapid microwave‐assisted carbonization of citric acid in NaOH. By tuning the mass ratio of citric acid and NaOH, the obtained CDs exhibit tunable phosphorescence wavelengths ranging from 483 to 635 nm and alterable lifetimes from 58 to 389 ms with a synthesis yield of up to 83.7% (>30 g per synthesis). Theoretical calculations and experimental results confirm that the formation of high‐density ionic bonds between cations and CDs leads to efficient afterglow emission via the dissociation of CD arrangement, and the evolution of the aggregation state of CDs results in redshifted phosphorescence. These findings provide a strategy for the synthesis of new insights into achieving and manipulating room‐temperature phosphorescent CDs, and prospect their applications in labeling and information encryption. By confining isolated carbon dots (CDs) in ionic crystals, a facile in situ confining strategy has been proposed through rapidly microwave‐assisted carbonizing the only source of citric acid in ionic crystals, endowing the CDs with full‐color phosphoresce emission. There is a maximum productivity of 83.7% with a yield of more than 30 g, which can considerably decrease preparation costs.