Dual-Functional Photonic Metacoating Integrating Fluorescence Thermometry and High-Performance Space Radiative...

Fluorescence thermometry offers a non-contact strategy for early detection of thermal instabilities on complex spacecraft surfaces, enabling reliable in-orbit temperature mapping. However, simultaneously achieving high-sensitivity fluorescence thermometry and efficient space radiative cooling remains challenging, as enhanced visible absorption improves thermometric response but increases solar heating. Here, we address this trade-off through a material-structure co-design strategy by developing an Eu-doped ZrO₂ submicrosphere metacoating that integrates space radiative cooling with fluorescence-based temperature sensing. Guided by photonic-structure optimization using a constrained-gradient optimizer combined with grid-search mapping, the optimized metacoating, featuring a submicrosphere diameter of 0.756 µm and a volume fraction of 35%, achieves an ultralow solar absorptance (α_s = 0.076) and a high thermal emittance (ε = 0.931). In parallel, bandgap-driven compositional optimization identifies an optimal Eu content of 8.48%, enabling outstanding thermometric performance. The metacoating delivers a net cooling power of 323.69 W m^-2 and a 77 °C temperature reduction relative to an Al sheet, outperforming representative oxide-based inorganic coatings. It allows temperature sensing over 173-433 K with a maximum relative sensitivity of 0.797% K^-1, surpassing fluorescent oxides with comparable absorption edges. Moreover, the metacoating maintains the lowest α_s and reliable irradiation resistance under proton, electron, atomic oxygen and ultraviolet exposures, outperforming reported counterparts. Together with its scalable fabrication, this work establishes a dual-functional metacoating platform for intelligent spacecraft thermal management that combines efficient radiative cooling with high-sensitivity fluorescence thermometry.