Ultra-stable dual-color phosphorescence Carbon-Dot@Silica material for advanced anti-counterfeiting

Room temperature phosphorescence (RTP) materials have motivated massive attention due to their great ad-vantages in anti-counterfeiting and optical encryption. However, the commonly used carbon-based RTP mate-rials suffer from drawbacks of photobleaching, quenching and single phosphorescence color outputs, which obstruct their performance in high-level anti-counterfeiting techniques. Herein, we present a universal method for the fabrication of a carbon-dot@silica (CDs@SiO2) composite that possesses ultralong lifetime, high phos-phorescence quantum efficiency (PQE), excellent luminescence stability, and dual-color phosphorescence emission. Taking advantage of the restriction by rigid network of SiO2 and stable covalent bonding between CDs and SiO2, the triplet excited states of CDs are stabilized. As a result, the CDs@SiO2 exhibit ultralong lifetime of 1.33 s and 0.38 s under excitation at 254 nm and 365 nm, respectively. Furthermore, the phosphorescence color of CDs@SiO2 can change from cyan to yellow when the exciting wavelength switches from 254 nm to 365 nm. The obtained CDs@SiO2 also exhibit outstanding characteristics of anti-photobleaching and phosphorescence stability in an aqueous solution. Based on the unique phosphorescent properties of the CDs@SiO2, a stable and dual-color phosphorescence security label is designed for advanced information encryption.