Ion‐Specific Freezing‐Induced NIR Phosphorescence: Interfacial Synergy Enables Imaging of “Invisible Ice”

at the ice-water interface induces dense aggregation at the freezing front, strengthening molecular interactions to promote intersystem crossing and suppress triplet non-radiative decay. Leveraging this interfacial regulation, PP4P-F enables high-contrast, centimeter-scale ice imaging in diverse frozen media, with a 152-fold increase in signal-to-background ratio (SBR). In wind-tunnel aircraft icing tests, FIP imaging accurately maps the onset, thickness evolution, and downstream propagation of ice along the wing leading edge and correlates with laser-measured ice thickness. Overall, this work establishes a noncontact, in situ, and quantitative approach for "invisible ice" detection and provides a framework for NIR phosphorescent probes in frozen-phase monitoring.