UV‐Triggered in Situ‐Formed Excimer‐Sensitized Lanthanide Nanocomposites with Visualization of Photocuring for Multiscale 3D‐Printable Optical Manufacturing

Abstract Printable lanthanide nanocomposites show remarkable promise for high‐throughput manufacturing of active photonic devices. However, the lack of real‐time photocuring monitoring is a critical barrier to the rapid assessment of products in large‐scale manufacturing. Herein, an easy‐to‐prepare and low‐cost printable excimer‐sensitized lanthanide nanocomposites (ESLN) ink based on the common raw‐materials is developed. As photocuring progresses under 365 nm UV light, in situ‐formed isopropylthioxanthone (ITX) excimers synchronously sensitizing neodymium oxide (Nd 2 O 3 ) nanocrystals impart dynamic fluorescence response for real‐time monitoring of photocuring in the printable ESLN inks. Specifically, through interactions with the cross‐linked matrix, the embedded Nd 2 O 3 nanocrystals can achieve photocuring‐dependent control of the spatial proximity to the dopant ITX. The broad emission of ITX excimers overlaps with Nd 3+ absorption bands in VIS, enabling direct emission of visible broadband fluorescence from Nd 3+ . This mechanism yields dynamic color evolution (blue → cyan → yellow), providing visualization of the photocuring degree. Ultimately, scalable active optical manufacturing is demonstrated by fabricating 3D/2D devices via digital light processing (DLP) printing, screen printing, and nanoimprint, achieving millimeter‐to‐micrometer feature sizes. This intriguing printable ESLN system offers a groundbreaking platform for manufacturing active photonic devices exhibiting customizable complex geometries and region‐specific fluorescent patterns.