Frequency resonance amplification in ultrasound-induced long-lasting afterglow.

Ultrasound-induced afterglow has emerged as a promising modality for in vivo imaging, yet achieving sufficient afterglow brightness remains a challenge. Here, we report the inaugural realization of ultrasound-induced afterglow from carbon nanodots using engineered carbon nanodots, the elucidation of the resonance amplification mechanism during the ultrasound process, and the facilitation of high-contrast tumor imaging and precise resection. Through ultrasound frequency matching, we achieved up to 51-fold enhancement in sonoluminescence from carbon nanodots as fluorophore matrice, far surpassing the ultrasound-induced conventional organic polymer-based afterglow materials. Experimental and finite element analyses reveal an inverse monotonic relationship between ultrasound frequency and matrix dimensions, where resonant ultrasound enhances reactive oxygen species generation, leading to intermediate oxidation-derived near-infrared afterglow lasting over 240 min following a single 2-min ultrasound pulse. With significant amplification in afterglow brightness via precise frequency decoding, this approach evokes a 2.5 cm tissue penetration enabling high-contrast tumor imaging and precise resection in animal models, outperforming conventional optical-excited afterglow agents and fluorescence imaging. Our work elucidates the mutual size-frequency selection mechanism in ultrasound-induced afterglow and establishes a non-invasive, sensitive platform for advanced bioimaging and therapeutic monitoring.