Afterglow luminescent probes with high signal-to-background ratio show promise for in vivo imaging; however, such probes that can be selectively delivered into target sites and switch on afterglow luminescence remain limited. We optimize an organic electrochromic material and integrate it into near-infrared (NIR) photosensitizer (silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) and (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) containing nanoparticles, developing an H₂S-activatable NIR afterglow probe (F1²⁺-ANP). F1²⁺-ANP displays a fast reaction rate (1563 ± 141 M⁻¹ s⁻¹) and large afterglow turn-on ratio (~122-fold) toward H₂S, enabling high-sensitivity and -specificity measurement of H₂S concentration in bloods from healthy persons, hepatic or colorectal cancer patients. We further construct a hepatic-tumor-targeting and H₂S-activatable afterglow probe (F1²⁺-ANP-Gal) for noninvasive, real-time imaging of tiny subcutaneous HepG2 tumors (<3 mm in diameter) and orthotopic liver tumors in mice. Strikingly, F1²⁺-ANP-Gal accurately delineates tumor margins in excised hepatic cancer specimens, which may facilitate intraoperative guidance of hepatic cancer surgery.

Tumor response to radiotherapy or ferroptosis is closely related to hydroxyl radical (•OH) production. Noninvasive imaging of •OH fluctuation in tumors can allow early monitoring of response to therapy, but is challenging. Here, we report the optimization of a diene electrochromic material (1-Br-Et) as a •OH-responsive chromophore, and use it to develop a near-infrared ratiometric fluorescent and photoacoustic (FL/PA) bimodal probe for in vivo imaging of •OH. The probe displays a large FL ratio between 780 and 1113 nm (FL₇₈₀/FL₁₁₁₃), but a small PA ratio between 755 and 905 nm (PA₇₅₅/PA₉₀₅). Oxidation of 1-Br-Et by •OH decreases the FL₇₈₀/FL₁₁₁₃while concurrently increasing the PA₇₅₅/PA₉₀₅, allowing the reliable monitoring of •OH production in tumors undergoing erastin-induced ferroptosis or radiotherapy.