Metal oxide hybridization enhances room temperature phosphorescence of carbon dots–SiO2 matrix for information encryption and anti-counterfeiting

Room temperature phosphorescent (RTP) carbon dot (CD) materials have been widely used in various fields, but it is difficult to achieve a long lifetime, high stability and easy synthesis. In particular, realizing the phosphorescence emission of CDs using a metal oxide (MO) matrix is a challenge. Here, solid gels are synthesized via in situ hydrolysis, and then RTP CDs are synthesized based on a SiO₂ matrix (CDs@SiO₂) and hybridized with a MO matrix (CDs@SiO₂-MO) by high-temperature calcination. Among the materials synthesized, Al₂O₃ matrix RTP CDs (CDs@SiO₂-Al₂O₃) have a long phosphorescence lifetime of 689 ms and can exhibit yellow-green light visible to the naked eye for 9 s after the UV light (365 nm) is turned off. Compared with the green phosphorescence of CDs@SiO₂, the yellow-green phosphorescence lifetime of CDs@SiO₂-Al₂O₃ is enhanced by 420 ms. In addition, CDs@SiO₂-Al₂O₃ maintains good stability of phosphorescence emission in water, strongly oxidizing solutions and organic solvents. As a result, CDs@SiO₂-Al₂O₃ can be applied to the field of information encryption and security anti-counterfeiting, and this work provides a new, easy and efficient synthesis method for MO as an RTP CD matrix.