Doped Carbon Dots Enable Highly Efficient Multiple‐Color Room Temperature Phosphorescence

Colloidal carbon dots (C-dots) are considered as promising heavy-metal-free materials to achieve room-temperature phosphorescence (RTP) properties for promising applications, such as photoelectronic devices, information encryption, and bio-imaging. However, most of the current obtained RTP C-dots have a short lifetime with a relatively low quantum yield (QY). In this work, the C-dots large-scale synthesized via a vacuum heating approach have multiple RTP emissions (blue, green, and yellow), a long RTP lifetime of as high as 1.92 s, and a high QY of 34.4% by selecting different types of precursors, which is superior to most of reported RTP C-dots. The multiple atoms doping and strong bonding between neighbored C-dots promoted by vacuum heating contributes to the excellent RTP properties. As a proof-of-concept, the as-obtained RTP C-dots are used as optical ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s. This work offers an efficient approach for producing large-scale high-quality RTP C-dots, which can be applied to anti-counterfeiting and information encryption systems. A vacuum-heating approach is demonstrated for large-scale production of over ten grams per batch. The as-prepared carbon dots (C-dots) exhibit multiple room-temperature phosphorescence (RTP) emissions (blue, green, and yellow) and a long RTP lifetime of 1.92 s with a maximum quantum yield of 34.4%. As a proof-of-concept, the as-synthesized RTP C-dots are used as ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s.image