Flexible multicolor-emitting lanthanide-alginate hybrid fibers with multi-stimuli responsiveness for anti-counterfeiting

Information leakage and counterfeiting are critical global issues threatening human security and social stability. Advanced flexible anti-counterfeiting technologies are urgently needed, as flexible wearables are becoming more and more significant. In this study, we report a straightforward and efficient wet spinning technique to prepare lanthanide-alginate hybrid fibers with multicolor-emitting capabilities for flexible anti-counterfeiting. Lanthanide ions are able to coordinate with sodium alginate to endow the hybrid fibers with good molding properties, thermal stability, and homogenicity. These hybrid fibers can emit red, orange, and green fluorescence depending on the ratios of doped lanthanide elements under 254 nm UV light. The fluorescence lifetime of these hybrid fibers is longer than that of commonly used organic dyes. Notably, their fluorescence can be quenched in acidic environments or by Fe3+ ions, which is ascribed to the weakened coordination strength between 2,2 '-bipyridine with the lanthanide elements. More importantly, the hybrid fibers can be woven into various flexible anti-counterfeiting patterns. Our study demonstrates the significant flexible anti-counterfeiting potential of lanthanide-doped fibers due to their low cost, ease of fabrication, and flexibility.Graphical AbstractThe multicolor-emitting lanthanide-alginate hybrid fibers with multi-stimuli responsiveness are produced through a simple wet spinning process and can be woven into various patterns for flexible anti-counterfeiting.