News Source: School of Materials Science and Engineering

Editor: News Agency of BIT

Translator: News Agency of BIT, Zhang Zijun

Beijing Institute of Technology, April 29th, 2021: With the rapid development of society, anti-counterfeiting and secrecy technologies with dual-use functions are receiving more and more attention, and the continuous development of new anti-counterfeiting/ secrecy materials and the breakthrough in the traditional optical anti-counterfeiting/secrecy model are a key prerequisite to promote the development of this field. Prof. Zhang Jiatao and Associate Prof. Xu Meng of Beijing Institute of Technology（BIT） have been working for a long time to achieve controllable preparation and performance regulation of novel complex doped structured semiconductor nanocrystals by innovative approaches. （Angew. Chem. 2015, 54 (12), 3683-3687.，Adv. Mater. 2015, 27 (17), 2753-2761.，Angew. Chem. 2019, 58 (15), 4852-4857.，Chem 2020, 6 (11), 3086-3099.）Based on the established basis of synthesis, the team overcame the challenges from the preparation of micro- and nano-materials to the controlled processing of macro-blocks, and achieved the application of doped nanocrystals in multimode fluorescence anti-counterfeiting and encryption fields.

Ⅰ. The applications of visible doped fluorescence for multimode anti-counterfeiting

Fig 1. The diagram of doped QDs multimode anti-counterfeiting applications

Doped Fluorescent anti-counterfeiting applications are achieved by using common commercial printers to print CdSnanocrystals with water-soluble Ag+ on the flexible and rigid substrates and using ion exchange reaction to create the disappearance and reappearance of doped fluorescence. The anti-counterfeiting method is simple, efficient, which overcomes the drawbacks of low confidentiality of traditional fluorescent anti-counterfeiting materials, and has outstanding cyclic stability. The results were published in the international top journal on materials science Advanced Functional Materials (Adv. Funct. Mater. 2019, 29, 1808762.), at the same time the anti-counterfeiting method was granted a national invention patent (Patent No. ZL 2018 1 0972684.X).

Ⅱ. The applications of invisible doped fluorescence for multi-mode anti-counterfeiting and encrypt

Fig 2. CdSe:Cu@CdS core-shell QDs prepared by a heterogeneous diffusion equilibrium strategy and their confidential applications of near-infrared fluorescence

Fig 3. Diagram of anti-counterfeiting and secrecy applications and actual results

To achieve a higher level of anti-counterfeiting and encryption, the team has recently achieved multimode anti-counterfeiting and encryption application of near-infrared fluorescence for the first time by using Cu@CdS core-shell nanocrystals with invisible near-infrared doped fluorescence Cu based on multimode visible fluorescence security applications. The CdSe@CdS core-shell nanocrystals with only visible intrinsic fluorescence were used to print interference information, and CdSe:Cu@CdS core-shell nanocrystals with near-infrared doped fluorescence were used to print confidential information, which realized the printing of QD inks at the macroscopic scale. As the two nanocrystal inks have the similar optical properties in the visible region, it is impossible to distinguish the interference information from the confidential information by the naked eye only. Moreover, the near-infrared doped fluorescence can be selectively imaged by a mobile phone camera and a filter so that it can achieve fast interpretation of the critical information. The method is different from the traditional visible fluorescence anti-counterfeiting and encryption fields, for it was endowed with stronger concealment and encryption by the near-infrared fluorescence that is invisibility to the naked eye. The method is expected to replace the existing visible light anti-counterfeiting/ encryption materials and has broad application prospects. The work was published in the international top journal on materials science Advanced Functional Materials (DOI: 10.1002/adfm.202100286). At the same time, the preparation method and the anti-counterfeiting/ encryption field have been applied for national invention patents (Application Nos. 2020113212244 and 2020113200548). Not satisfied with 2D planar printing of nanomaterials, the team further used direct-write 3D printing to achieve a controlled processing process of macroscopic size of micro- and nanomaterials at the room temperature, which avoided the deactivation of properties at high temperature, overcame the limitation of moulds so that it could prepare fluorescent aggregators of different shapes, and further achieved a breakthrough from microscopic controlled synthesis to macroscopic bulk processing. The method was granted a national invention patent (Patent No. ZL 2019 1 0401853.9)

The research above was supported by Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications and the Advanced Materials Experimental Centre of the School of Materials Science and Engineering, and funded by the National Natural Science Foundation of China and Innovative Talents Support Program of the Institute of Science and Technology. Bai Bing, a PhD student in the School of Materials Science Engineering of BIT, is the first author of the article. Associate Prof. Xu Meng and Prof. Zhang Jatao of BIT are the co-corresponding authors, and BIT is the first communication unit.

Link to the paper: https://onlinelibrary.wiley.com/doi/10.1002/adfm.202100286