Chiral photonic micro-particles enabling circularly polarized luminescence for NIR-II optical anti-counterfeiting

The second near-infrared (NIR-II, 1000–1700 nm) circularly polarized light holds significant untapped potential in areas such as optical anti-counterfeiting and information encryption due to its deeply covert nature. However, the typically low luminescence dissymmetry factor (<i>g</i>_lum) of circularly polarized luminescence (CPL) materials, particularly in NIR CPL materials, limits their practical application. Addressing this challenge, it is crucial to develop NIR CPL materials with enhanced <i>g</i>_lum. In this study, we present a series of chiral photonic micro-particles (CPMPs) with tunable chiral photonic bandgaps in the NIR-II range, capable of modulating NIR-II luminescent quantum dots to produce NIR CPL. These CPMPs not only impart chirality to the quantum dots, but also act as carriers, minimizing luminescence quenching from external environments. The tunable chiral photonic bandgap in CPMPs enables the generation of NIR CPL with a high |<i>g</i>_lum| value of up to 0.81, facilitating the advanced application in covert optical anti-counterfeiting. This work offers a straightforward and viable strategy for the development of NIR CPL materials, broadening their use in invisible information encryption and optical anti-counterfeiting technologies.