Low‐Power‐Activated Afterglow Nanoprobes With Naked‐Eye Visibility for High‐Contrast Imaging of Brain Inflammation

Afterglow luminescence imaging ingeniously circumvents the need for real‐time excitation, thereby substantially eliminating background interference. Nevertheless, its application in brain imaging has been hindered by low afterglow brightness under aqueous conditions. Here, we present naked‐eye‐visible afterglow nanoprobes excited by low‐power light for high‐contrast imaging of brain inflammation. By strategically integrating highly efficient donor–acceptor–donor (D–A–D) luminescent molecules into photochemical afterglow systems, we developed a series of ultrabright afterglow materials emitting in the yellow, orange, and red spectral regions. The resulting afterglow nanoparticles remain naked‐eye detectable even under ultralow excitation power (0.73 mW cm −2 ). Their afterglow brightness is over 1300 times higher than that of commonly used afterglow nanoparticles, and they still maintain a 3‐fold advantage compared to previously developed blue‐emitting nanoparticles based on molecular fusion strategies. Leveraging this exceptional performance, we accomplished real‐time naked‐eye observation of freely moving mice. Moreover, macrophage‐encapsulated nanoparticles enabled blood–brain barrier (BBB) penetration and high‐contrast imaging of brain inflammation. This work introduces a new paradigm for constructing high‐brightness afterglow materials and opens transformative avenues for real‐time visualization of brain disorders.