Highly bright solid-state carbon dots for efficient anticounterfeiting.

Carbon dots (C-dots) as promising fluorescent materials have attracted much attention because of their low toxicity and excellent optoelectronic properties. However, the aggregation-caused quenching (ACQ) of the solid-state C-dots has limited their potential applications in anti-counterfeiting and optoelectronic devices. In this work, C-dot powder was prepared by directly dispersing the as-prepared C-dots in a polymer matrix or in situ formation of the C-dot/Ca-complex by vacuum heating in the presence of boric acid. The as-prepared C-dots have high quantum yields (QYs) in the range of 40-67% with temperature-dependent photoluminescent (PL) properties. As a proof of concept, the as-synthesized C-dots were used to produce a flexible anti-counterfeiting code and showed high-level security. This highlights the potential of C-dots in solid-state information, anti-information encryption and anti-counterfeiting.