Excitation wavelength dependent triple-mode photoluminescence of copper-based halides for advanced anti-counterfeiting

New fluorescent materials with a low cost, hypotoxicity, and concealment are desired for the application of anti-counterfeiting. Herein, we report a CsCu2I3@Cs3Cu2I5 composite with a triple-mode photoluminescence (PL) feature by simply adjusting the excitation wavelengths, which are ascribed to the multiple excited states of different phases in the CsCu2I3@Cs3Cu2I5 composite. The broadband emission and high quantum yield (similar to 51%) of the composite originate from the structure-oriented self-trapped excitons effect of Cs3Cu2I5 and CsCu2I3 phases. Moreover, the incorporation of polyethylene oxide (PEO) into this composite improves the stability of CsCu2I3@Cs3Cu2I5@PEO against harsh environments. The CsCu2I3@Cs3Cu2I5@PEO composite has a slight decay of similar to 5% of its initial PL intensity and only a 3.5% shift of the corresponding color coordinate after 30 days of storage. More importantly, its initial PL intensity shows only 10.3% decay under ultraviolet exposure for 200 h. Our work provides a promising approach to design materials for advanced anti-counterfeiting applications. (c) 2023 Author(s).

Automated summary

We report a new fluorescent material with low cost, hypotoxicity, and concealment for anti-counterfeiting applications. The CsCu2I3@Cs3Cu2I5 composite exhibits triple-mode photoluminescence by adjusting excitation wavelengths due to multiple excited states of different phases. The composite shows broadband emission and high quantum yield from the self-trapped excitons effect of Cs3Cu2I5 and CsCu2I3 phases, and its stability is improved by incorporating polyethylene oxide. The composite only has slight decay in PL intensity and color coordinate after storage, and it maintains its initial PL intensity even after 200 hours of UV exposure.