QM-FN-SO 3 is a BBB-penetrable near-infrared (NIR) aggregation-induced emission (AIE)-active probe for Aβ plaques. QM-FN-SO 3 can be used for in vivo detection of Aβ plaques. QM-FN-SO 3 has ultra-high S/N ratio, binding affinity, and high-performance NIR emission.