Laser-induced surface restructuring of carbon dots enables tunable multicolor photoluminescence via microcavity confinement

Photochromic carbon dots (CDs) with high-contrast and tunable multicolor emission in solution hold great promise for the development of versatile light emitters. However, achieving such properties through a convenient and controllable synthesis method remains a significant challenge. Here, we introduce an innovative approach utilizing laser irradiation of CDs confined within a microcavity, enabling the synthesis of multicolored photoluminescent CDs. The laser-irradiated CDs exhibit time-dependent dynamic photochromic emission, transitioning from yellow to blue as a function of irradiation time. Notably, upon exceeding 450 s of irradiation, the CDs stabilize into a time-independent blue emission. The resulting CDs, with their diverse emission colors, demonstrate excellent stability and quenching resistance under ambient conditions. Mechanistic investigations reveal that the laser-induced modulation of electronic transitions within surface states, coupled with radiative recombination involving multiple surface functional groups, underpins the tunable emission properties. This work provides a robust and scalable strategy for the synthesis of photochromic CDs, opening avenues for their application in advanced optoelectronic devices and beyond.