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.