Advanced halide materials provide next-generation anti-counterfeiting

Counterfeiting, whether of bank notes, certificates, or other documents, has caused trillions of dollars in economic losses. To combat this theft, simple fluorescent anti-counterfeiting materials have been used, but these are also increasingly reproducible by counterfeiters.

Liu et al. presented an advanced form of a fluorescent material that could help combat modern-day counterfeiting. Building off previous work with perovskites that showed different fluorescence emission properties, the researchers developed a low-toxicity copper-based halide composite with triple mode emissions. The novel material circumvents the issues of previous perovskites, which contained toxic lead and had challenges producing multiple emission modes.

“Our work provides a promising approach to design fluorescent materials for advanced anti-counterfeiting applications,” said author Dewei Zhao.

The triple mode emission of blue, yellow and white light was confirmed with theoretical calculations and experimental results, showing the properties were due to the structure-oriented self-trapped excitons effect of the materials. Further testing showed the composite is highly stable against heat, oxygen, moisture and ultraviolet light exposure due to the inclusion of polyethylene oxide. The photoluminescence intensity only declined around 10 percent after 200 hours of ultraviolet light exposure.

“I think this new composite could be used for anti-counterfeiting in the near future due to its facile preparation method and high stability,” said Zhao.

The researchers also verified the feasibility of commercial use by testing the composite’s application with different manufacturing techniques, such as spraying, screen printing and sealing. The researchers plan to continue working with copper-based halides to test their potential electroluminescence properties.

Source: “Excitation wavelength dependent triple-mode photoluminescence of copper-based halides for advanced anti-counterfeiting,” by Chengjun Liu, Yuyi Zhang, Manman Luo, Lixi Wang, Xingyu Liu, Jiangyong Pan, Zihan Zhao, Fan Fang, Lei Mao, Yuling Huang, Bingqi Wang, Congyuan Lin, Wei Lei, Qing Li, Zhiwei Zhao, Jun Wu, Zhuoya Zhu, Mehmet Ertugrul, Xiaobing Zhang, Jing Chen, and Dewei Zhao, APL Materials (2023). The article can be accessed at https://doi.org/10.1063/5.0152479 .