Engineering strategy for achieving transparent aqueous multicolor long lifetime room temperature phosphorescent carbon dots

Abstract

Carbon dot-based room-temperature phosphorescent (RTP) materials are attracting more and more attention due to the exceptional optical properties. However, achieving stable afterglow emission in aqueous solution is a great challenge since high concentrations of dissolved oxygen in water severely quench triplet excitons. In this work, we report a multiple confinement structure strategy to realize multicolor tunable (blue to orange) and transparent aqueous phosphorescent carbon dots (CDs) for the first time. This approach synergistically restricts molecular motion of CDs through surface coordination and confinement within a three-dimensional nanosilica network, effectively suppressing nonradiative transitions. At the same time, phosphorescence emission can be amplified by tailored modification of abundant functional groups on surface of CDs. Thus, carbon dot-based silica nanocomposites (CDs@SiO₂) not only exhibit high transparency (> 95%) and a long lifetime (1.5 s) in aqueous solution, but also have the ability to maintain a stable afterglow emission in harsh environments. Based on the advantages, novel multimodal anti-counterfeiting technologies, including Morse code and QR code encryption systems have been developed. This work proposes an engineering strategy for achieving multicolor transparent aqueous afterglow of CDs, laying a foundation for emerging applications in optical encryption and intelligent sensing.